In this work, an anti-deoxynivalenol nanobody isolated from a naive phage display library was adopted to investigate the relationship between bioactivity and the composition of amino acid residues using error prone polymerase chain reaction (epPCR) and phage display. The epPCR was firstly optimized to produce a phage display library with balanced distribution of mutation. After six rounds of panning of the mutant library, 30 out of 96 picked clones exhibited 8 different mutations, whose signal was 2.1 folds higher than that of the wild-type clone. Multi-sequence alignment analysis showed that mutant sites were prone to be found in the junction region between complementarity determining regions (CDRs) and framework regions (FRs). Three-dimensional structure modeling results indicated that some mutants were capable of forming an intramolecular disulphide bond, which benefits to stabilize the molecular structure. These data can provide a clue for further mutation and modification of anti-deoxynivalenol nanobody and also provide a guideline for the design of nanobody recognizing other low molecular weight compounds.

Lactobacillus paracasei HD1.7, isolated from spent brine from pickled Chinese cabbage, was used as a starter culture to establish and investigate a microbial ecosystem model for pickled Chinese cabbage fermentation, i.e., HD1.7 fermentation in comparison with natural fermentation as control. High performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) were adopted to detect organic acid, acidity, nitrite, VC, glycerol, ethanol, mannitol, 2,3-butanedilol and volatile flavor compounds in the model and control groups and eight commercial products. It was found that the organic acid content and acidity were positively correlated in all samples. The organic acids contents of Heida branded pickled Chinese cabbage, HD1.7 fermented Chinese cabbage and Yuanziyuanwei branded pickled Chinese cabbage were (13.21 ± 0.13), (13.20 ± 0.17) and (13.13 ± 0.13) g/L, respectively, which were higher than those of other samples. Furthermore, Heida branded pickled Chinese cabbage, HD1.7 fermented Chinese cabbage and Bianfuji branded pickled Chinese cabbage showed a significantly lower nitrite concentration and a significantly higher VC concentration (P < 0.05) and therefore had better safety and nutritional value than did other samples in addition to higher contents of flavor compounds and better sensory quality. In conclusion, these results may help to monitor the production process of pickled Chinese cabbage and establish quality standard for pickled Chinese cabbage and they are of great practical significance to enhance the quality stability of pickled Chinese cabbage and the level of industrial development.In addition, these results also indicate the promising application potential of L. paracasei HD1.7 as a starter culture in industrial production of pickled Chinese cabbage.

Among the known Listeria strains, only Listeria monocytogenes (Lm) can cause human disease. The expression of most virulence genes is regulated fully or partially by positive regulatory factor A (PrfA) protein encoded by prfA gene. In this study, we adopted homologous recombination method to knock out the prfA gene of the wild strain EGDe, and investigated the biological characteristics of EGDe-ΔprfA by testing growth state, virulence gene expression and Caco-2 cell invasion. There was no difference in the growth status of EGDe-ΔprfA and EGDe as demonstrated by the growth curves. Real time quantitative PCR results showed that the expression levels of plcA and plcB genes increased by 2.5 times and twice, respectively, while the expression levels of inlA, inlB, inlC, actA and vip declined. The expression level of prfA gene was nearly zero. The invasion of Caco-2 cells by EGDe-ΔprfA was one fifth as high as that by the wild strain. The gene-deleted strain can provide an important tool for studying the pathogenic mechanism of the foodborne pathogen Listeria monocytogenes.

library of Pseudoalteromonas carrageenovora arylsulfatase mutants was constructed by random mutagenesis using error-prone PCR. After screening, one mutant strain named 4-153 was obtained whose arylsulfatase had improved thermal stability. It was found that there were two amino acid substitutions in the mutant, including D84A and H260L. When p-nitrophenyl sulfate was used as a substrate, the optimal reaction temperature for the mutant enzyme was 55 ℃. Mutant arylsulfatase 4-153 (M4-153) retained 85%, 83%, 48%, and 13% of its initial activity after incubation at 45, 50, 55 and 60 ℃ for 30 min, respectively. Meanwhile, wild-type arylsulfatase (WT) retained 79%, 68%, 21%, and 1% of its initial activity after incubation at 45, 50, 55 and 60 ℃ for 30 min, respectively. These results showed that M4-153 had a better thermal stability than WT. M4-153 had an optimum pH of 8.0, and it was stable over the pH range of 5.0–9.0. Inhibition assay with EDTA indicated that metal ions played an important role in the catalytic process of the mutant enzyme. The recombinant arylsulfatase 4-153 showed a relatively strong tolerance to some detected detergents including Triton X-100, Tween 20, Tween 80, and Chaps. The desulfuration ratio of the crude polysaccharides from Gracilaria lemaneiformis by M4-153 was 79.5%.

The fermentation conditions for the production of exopolysaccharides (EPS) by Lactobacillus plantarum YM-2, isolated from traditional fermented tempeh in Yunnan province, were optimized. Firstly, the carbon and nitrogen sources in the medium were screened. Secondly, the effects of carbon source concentration, nitrogen source concentration, culture time and culture temperature on EPS yield were studied through one-factor-at-a-time analysis. Finally, response surface methodology (RSM) based on a four-variable, three-level Box-Behnken design was used to determine the optimal culture conditions as follows: carbon source concentration, 30 g/L; nitrogen source concentration, 30 g/L; culture time, 30.05 h; and culture temperature, 36.36 ℃. Under these conditions, the yield of EPS was 257.362 mg/L.

Aim: To obtain an engineered bacterial strain able to express cellulose-degrading enzymes through constructing an integration vector using Bacillus subtilis as the host. Methods: The homologous fragments M1 and M2 were cloned by polymerase chain reaction (PCR) from the genome of B. subtilis LN. The glucosidase gene CelKg, homologous fragments M1 and M2 and the strong promoter P43 were ligated to the pGEM-T vector by T4 DNA Ligase to construct the integrated vector pGEM-Kmpgmt. The vector was then transformed to B. subtilis LN by double crossover homologous recombination method. Results: The integration vector was successfully constructed and integrated into the genome of B. subtilis LN, as verified by PCR. Congo red staining indicated that the recombinant B. subtilis could obviously degrade sodium carboxymethyl cellulose in the medium. The cellulase activity from the culture supernatant harvested after 18 h culture of the recombinant strain in a modified medium at 37 ℃ with shaking was increased by 115% as compared with the wild-type B. subtilis LN.

We explored the effects of low-frequency magnetic field (LF-MF) on the production of ergosterol by fermentation with Monascus purpurcus and further determined the optimal LF-MF treatment conditions such as LF-MF intensity, time treatment time and the fermentation stage when M. purpurcus was treated with LF-MF on ergosterol production by liquid-state fermentation of M. purpurcus. We also investigated the effects of LF-MF on the metabolism of ergosterol by M. purpurcus, and examined the change in M. purpurcus biomass throughout the fermentation period and the effects on other main metabolites of M. purpurcus under optimal treatment conditions. Results showed that ergosterol yield was 7.08 mg/g and the biomass of M. purpurcus was 3.2 g/L on the 12th day of fermentation, which were respectively increased by 62.5% and 31.68% as compared to that of the control when M. purpurcus was treated by LF-MF at an intensity of 1.2 mT during the first two days of fermentation. Consequently, LF-MF was an effective method to enhance ergosterol yield. This result may provide evidence supporting the use of LF-MF to improve the production of beneficial microbial metabolites by fermentation.

Brown rot disease caused by Monilinia fructicola is one of the major postharvest diseases of flat peach, which causes serious postharvest loss. Meanwhile, the pathogenicities of M. fructicola for different fruit hosts are different. In this investigation, we studied the biological characteristics of M. fructicola under different culture conditions including temperature, pH, and light, and we also examined the impacts of culture temperature, pH and time on the activities of cell wall degrading enzymes. The results showed that the optimum pH for spore germination and germ tube extension of M. fructicola was 5.0 and it grew well in a weak acidic environment, while the spore germination rate was significantly lower in an excessively acidic environment. The optimum temperature for colony growth was in the range of 20?28 ℃, and the pathogen could not grow normally at a temperature above 36 ℃. Temperature affected colony morphology, and at different temperatures, the colony morphology characteristics were different. Light had little effect on the hyphal growth. The activities of the cell wall degrading enzymes endoglucanase (EG), β-glucosidase (BG), polymethylgalacturonase (PMG), and polygalacturonase (PG) were the highest at 28 ℃. The activities of EG and BG reached the highest values at pH 6.0, while the activities of PMG and PG reached the highest values at pH 7.0. The activities of these four enzymes were the highest after cultivation for 5 days. Regardless of changes in pH, temperature and incubation time, BG activity was higher than EG activity and PG activity was higher than PMG activity.

Objective: The purpose of this study was to explore whether the sigB gene palyed a regulatory role in Listeria monocytogenes (Lm) exposed to sodium hypochlorite stress. Methods: We studied the phenotypic changes and compared the percent increases in reactive oxygen species (ROS) levels in the wild-type Lm WaX12 and its sigB deletion mutant under sodium hypochlorite stress at the median lethal concentration (3 mmol/L). The changes in the transcriptional levels of lmo1433, lmo0906, lmo2344, ohrR and lmo2770 genes were investigated during sodium hypochlorite stress. Results: The wild-type strain presented a stronger tolerance to sodium hypochlorite stress than the mutant, especailly during the stationary growth phase. The percent increase in ROS levels in the wild-type strain was 19.97% higher than that in the mutant after 30 min of sodium hypochlorite stress, confirming the regulatory role of the sigB gene in Lm under sodium hypochlorite stress. Moreover, the relative expression levels of lmo1433, lmo2344 and ohrR genes in the wild-type strain were much higher than those in the mutant (P < 0.01), as revealed by RT-PCR. No significant differences in the expression levels of lmo0906 and lmo2770 were found between the wild-type and mutant strains. Conclusion: The sigB gene plays an important regulatory role in Lm exposed to NaClO stress, which may be partially achieved by directly or indirectly activating some genes regulating the redox balance in the body.

This study aimed to optimize the culture conditions for Carnobacterium spp. LB1, isolated from the ribbonfish intestine, to produce anti-Pseudomonas fluorescens metabolites. By using one-factor-at-a-time method, three of the five factors were selected for their significant influences on the antibacterial activity. A Box-Behnken design was applied to evaluate the effects of interaction among the chosen variables and optimize them. The optimum culture conditions obtained were as follows: initial pH, 6.22; temperature, 28.6 ℃; and glucose concentration, 3%, where the percentage inhibition of concentrated fermentation broth harvested after 15 and 18 h against Pseudomonas fluorescens were 80.7% and 86.3%, respectively. The antibacterial mechanism was due to increased cell wall permeability and leakage of a large amount of alkaline phosphatase (AKP) after the destruction of the cell wall of Pseudomonas fluorescens, leading to metabolic disorders. Finally, the experimental results obtained under the optimized fermentation conditions were in good agreement with the model predictions, indicating that the established model in this study was feasible.

The natural fermentation of millet is difficult to control. This study aimed to compare the physicochemical properties of naturally fermented millet starch and those fermented by the dominant microbes lactic acid bacteria and yeasts isolated from naturally fermented millet for the purpose of better understanding the mechanism of the natural fermentation of millet and providing a theoretical guideline for controlling the process. Starches were extracted from three different fermented millet samples with 0.2 g/100 mL NaOH and measured for solubility, swelling power, transparency, thermal properties and viscosity characteristics. The results demonstrated that, the solubility, swelling power and transparency of all three millet starches were decreased with fermentation time, and the transparency of millet starch fermented by lactic acid bacteria and yeasts were decreased by 1.4% and 1.0% compared with natural fermentation. The gelatinization temperature of millet starch subjected to lactic acid bacterial fermentation and yeast fermentation for 96 h were decreased by 1.84 ℃ and 1.13 ℃, respectively compared with natural fermentation, the peak temperatures were decreased by 1.04 ℃ and 0.43 ℃, respectively, the final temperatures were reduced by 3.69 ℃ and 2.85 ℃, respectively, and the enthalpies were increased by 1.00 J/g and 0.78 J/g. respectively. In addition, lactic acid bacterial fermentation and yeast fermentation resulted in a decrease in breakdown viscosity of millet starch of 978 and 743 mPa·s and a decrease in setback of 400 and 471 mPa·s as well as an increase in peak viscosity of 185 and 103 mPa·s, respectively in comparison with natural fermentation. In conclusion, fermentation with the dominant microorganisms of lactic acid bacteria and yeasts isolated from naturally fermented millet could significantly modify the physicochemical properties of millet starch compared with natural fermentation.

In order to improve the utilization rate of millet bran as a protein source and to provide references for the intensive processing of millet bran, solid state fermentation of millet bran by Bacillus natto was optimized for increased production of antioxidant peptides. Firstly, one-factor-at-a-time experiments were carried out. Secondly, the fermentation conditions with a significant effect on the total antioxidant capacity (T-AOC) of aqueous extracts from fermented millet bran were selected using Plackett-Burman design for further optimization using response surface methodology (RSM). The polypeptide content and 1,1-diphenyl-2-trinitrobenzene hydrazine (DPPH) radical scavenging ability of the aqueous extract from millet bran fermented under optimized conditions were determined. Results showed that the optimum fermentation conditions were as follows: average particle diameter of millet bran, 0.22 mm (between 60 and 80 mesh); inoculum size, 0.4 mL; initial pH, 6.7; fermentation time, 26 h; and fermentation temperature, 35 ℃. Experiments conducted under these conditions yielded an extract with a T-AOC of (344.51 ± 8.02) U/g, and a polypeptide yield of (68.37 ± 0.92) mg/g millet bran. The results also showed that the bioactive peptides had strong DPPH free radical scavenging activity with an IC50 value of 0.12 mg/mL. Therefore, this study proves that bioactive peptides obtained from fermented millet bran have a high antioxidant capacity.

Plant growth promoting rhizobacteria (PGPR) can decompose and transform organic substances and minerals in soil, prevent and control plant diseases and reduce the use of pesticides and fertilizers. Thus, PGPR are considered to be used as a new strategy to improve agricultural production. Bacillus amyloliquefaciens L-H15 is an excellent plant growth promoting rhizobacterium. Based on the results of previous studies of its full-length genomic sequence, we investigated the plant growth promoting properties of B. amyloliquefaciens L-H15 and optimized its culture conditions in order to develop a highly active solid starter culture. Our results indicated that B. amyloliquefaciens L-H15 produced a high level of siderophore (65.53%) and strong activity of 1-aminocyclopropane-1-carboxylate (ACC) deaminase showing a specific activity of 0.401 U/mg. This strain could also produce indole-3-acetic (IAA) and cytokinins (CTK). The ability to produce CTK was particularly significant, which was as high as 2.157 7 × 10-10 mol/L. Acetyl methyl alcohol, which can promote plant growth, was also detected in the volatiles generated by L-H15. These factors were able to effectively stimulate plant growth. We used response surface methodology based on Box-Behnken design to optimize the culture conditions of B. amyloliquefaciens L-H15 as follows: an inoculum size of 8%, a proportion of medium in a 500-mL volumetric flask of 67.8%, a culture temperature of 32 ℃, a culture time of 11.5 h, and a rotational speed of 196 r/min. Under these conditions, the viable cell count of B. amyloliquefaciens L-H15 was 1.21 × 109 CFU/mL. In conclusion, B. amyloliquefaciens L-H15 is an excellent PGPR, which has a broad prospect of development and utilization as a biofertilizer.

In order to investigate the effect of microorganisms present in rice milk on the production and quality of yellow rice wine, Illumina high-throughput sequencing technology was used to comprehensively analyze the bacterial community structure in rice milk for yellow rice wine. The results showed that Lactobacillus was the dominant bacterial genus in rice milk, and its abundance was 60.67%, with Lactobacillus plantarum and Lactobacillus brevis being the most predominant, accounting for 57.4% and 21.1% of the total Lactobacillus isolates, respectively. Seven bacterial species, such as Lactobacillus plantarum and Lactobacillus brevis, were selected from a bacterial library for yellow rice wine, and then ion chromatography and gas chromatography-mass spectrometry (GC-MS) were used to determine acidic substances in their fermentation broth. It was found that Lactobacillus plantarum L4 had the strongest acid-producing capacity (9.96 g/L), and the main products were organic acids with light and fresh taste, such as lactic acid, malic acid, and citric acid. In addition, it also produced low contents of strong acid (acetic acid) and acid with bad odor (butyric acid, isovaleric acid and heptanoic acid). In the L-4 fermentation broth, the ratio of non-volatile acid to volatile acid was as high as 11.89, and the taste and odor were obviously superior to those of other strains.

The purpose of this study was to investigate the bacterial diversity and its influencing factors in bottom pit mud from artificial cellars used for the production of Maotai-flavor liquor. A high-throughput sequencing technique was used to analyze the bacterial diversity of four pit mud samples from different liquor producing regions and its correlations with physicochemical factors. The results showed that there was a significant difference in physicochemical characteristics and bacterial community among bottom pit muds from different regions and the longer the geographic distance was, the greater the difference in bacterial community structure was, the greater in differences was. Cluster analysis showed that the bacterial community structure of bottom pit muds from Erlang, Xijiu and Maotai, which were closer to each other, was similar, with Aminicenantes, Chloroflexi, and Proteobacteria being predominant. However, the bacterial flora of bottom pit mud from a liquor producer in Luzhou was dominated by Firmicutes, which was significantly different from that of bottom pit mud from the above three regions. Correlation analysis showed that available K, pH, and moisture content were the main factors that had significant effects on the structure and diversity of bacterial community in bottom pit muds, especially for Aminicenantes, Firmicutes, Actinobacteria, and Armatimonadetes.

The main microbes which could form pellicle in spoiled vegetable were isolated and identified. The growth characteristics of these microbes were also analyzed. Tryptone soy agar (TSA) medium was used to isolate the pellicleforming microorganisms. Fifty isolates were selected randomly from TSA medium and inoculated into tryptone soy broth medium supplemented with fermented brine (TFB). Six isolates which could form pellicle on the surface of the medium were subjected to 16S rDNA or 18S rDNA identification. The results showed that the pellicle-forming agents were all bacteria, which were identified as Bacillus subtilis, Citrobacter freundii, Staphylococcus cohnii subsp. cohnii, Providencia vermicola, Klebsiella sp. and Enterobacter cloacae. The pellicle-forming abilities of each isolate in different model media were different. Bacillus subtilis and Staphylococcus cohnii subsp. cohnii could also increase the pH value of the medium and had lower nitrogen requirement. Klebsiella sp. and Providencia vermicola could form pellicle only in TFB and TSA supplemented with squeezed juice from fermented vegetable (TFVJ). The bacteria described above might be the key agents for pellicle formation and pose a potential risk for fermented vegetable quality.

A total of 113 strains of lactic acid bacteria (LAB) were isolated from yak milk dreg in Tibet. Out of these, four dominant LAB stains were screened and compared for their exopolysaccharide (EPS)-producing ability, acid, bile and osmotic pressure tolerance, and antimicrobial activity. Results demonstrated that the EPS-producing abilities were different for the 4 selected strains, with strain GY-L003 producing the highest yield of EPS (379.94 mg/L). The LAB strains exhibited different levels of tolerance to three environmental factors and strains GY-L003 and GY-L004 could survive at extremely acidic pH of 1.5. At a bile concentration of higher than 0.4%, GY-L003 and GY-L004 could grow while GY-L055 and GY-L112 were inhibited. In terms of osmotic tolerance, GY-L003 and GY-L004 were superior, being able to grow when NaCl concentration was up to 9%. All four LAB strains had strong antimicrobial activity, among which GY-L004 had the strongest inhibitory effect against Staphylococcus aureus, with an inhibition zone diameter of (15.94 ± 0.31) mm, GY-L003 had the strongest inhibitory effect against both E. coli and Salmonella, with an inhibition zone circle of (18.21 ± 0.65) and (16.27 ± 0.50) mm, respectively, and GY-L112 exhibited the strongest inhibitory effect against Listeria monocytogenes with an inhibition zone diameter of (15.24 ± 0.35) mm. Taken collectively, our results suggested that both GY-L003 and GY-L004 had high EPS-producing ability, good tolerance to acid, bile and osmotic pressure, and strong antimicrobial activity. Accordingly, these strains have a good application potential and can provide a reference basis for application in the production of fermented dairy products.

The microbial community of lactic acid bacteria isolated from Chinese Paocai prepared with different salt concentrations (2%, moderate 5% and 8%), was assessed by cultivable methods and various molecular biology methods. The results showed that lactic acid bacteria in Paocai brine exhibited faster growth rate at lower salt concentration during the fermentation process. A total of 563 lactic acid bacteria were isolated from Paocai brines fermented with different salt concentrations and identified by 16S rDNA sequencing analysis, multiplex-PCR method, and PCR-FRLP analyses. The isolates were identified to belong to 11 species of 5 genera respectively. Lactococcus lactis, Lactobacillus pentosus and Leuconostoc were found to be the dominant flora in Paocai samples during the early stage of fermentation with lower salt concentration (2%) while Lactobacillus pentosus dominated the late fermentation stage. Furthermore, Lactobacillus pentosus and Weissella were the most abundant isolates from Paocai brine during the early stage of fermentation with 5% and 8% salt concentrations, but the major microbes involved in the late fermentation stage were still Lactobacillus pentosus.

A strain capable of producing α-glucosidase inhibitor as a potential antidiabetic agent from mulberry leaf was isolated. Subsequently, atmospheric and room temperature plasma (ARTP) was applied to mutagenize the isolated strain for improved production of α-glucosidase inhibitors. At the same time, the physicochemical properties and stability were investigated preliminarily. Out of the 188 isolated strains, a bacterial strain named XuW-LB-188 was selected after examination of α-glucosidase inhibitory activity using 4-nitrophenyl-α-D-glucopyranoside (PNPG) as a substrate, giving an inhibition percentage of 52.67% in the fermentation supernatant. On the basis of its morphological characteristics and 16S rDNA gene sequence, the strain was preliminarily identified as Bacillus atrophaeus. After ARTP mutation breeding and subsequent high-throughput screening, T-690 was selected out of 880 mutant strains, whose inhibition rate (73.25%) against α-glucosidase was increased by 40.61% compared with that of the original strain. The experiment results indicated that the α-glucosidase inhibitor mainly existed in the fermentation broth. Consequently, the inhibitor was an extracellular product. Moreover, it had high polarity and good thermostability.

This study was undertaken to analyze the microbial communities in Pixian soybean paste during the postfermentation process by high-throughput sequencing method. The results revealed that at the taxonomic levels of microbes including phylum, class, order, family, and genus, high-throughput sequencing could detect a total of 57 phyla, 174 classes, 321 orders, 535 families and 921 genera. Post-fermentation time had a significant effect on the bacterial community composition of Pixian soybean paste. During post-fermentation, the quantities of Enterobacteriaceae and Streptophyta continued to decrease whereas Sphingomonadaceae, Bacillaceae, Clostridiaceae and Peptostreptococcaceae increased first and then decreased, most of which reached their peak values during 1 to 3 years. However, after 6 years of fermentation, the bacterial community of Pixian soybean paste was significantly lower than that of other samples. With this method, a large number of non-cultureable bacteria and unclassified bacteria were detected. The results of bacterial diversity analysis were close to the microecology of the samples, which were helpful to better understand the bacterial diversity of Pixian soybean paste and might provide a scientific support for the modernization of the traditional industry and the control of food quality and safety.

Chitosan-halloysites nanotube (CTS-HNTs) composite microspheres were successfully prepared by crosslinkingadsorption method, and used to immobilize papain. The successful immobilization of papain on CTS-HNTs composite microspheres was confirmed through infrared spectroscopy, scanning electron microscopy, and fluorescent labeling. The microspheres prepared with 2% CTS and 1% HNTs displayed the highest immobilization efficiency for papain. The optimal immobilization conditions were determined as 1 mg/mL and 10 h for papain concentration and immobilization time, respectively. The optimal pH and temperature for the immobilized enzyme were 6.8 and 60 ℃, respectively, while those for the free enzyme were 7.2 and 50 ℃, respectively. After 30 days of storage, the relative activity of the immobilized and free papain was 62% and 27%, respectively. The immobilized enzyme retained 26.26% of the initial activity after fourth repeated use. The immobilized papain had good storage stability and operational stability, enhancing the utility efficiency of the enzyme, cutting down the cost of enzymatic hydrolysis and enhancing the production efficiency.

A nicotinic acid hydroxylase- producing strain from spoiled fish from Bohai Bay in Yantai, designated H9, was rapidly and directionally screened using a 96-well microplate and ultraviolet imaging. Strain H9 was identified as Pseudomonas putida based on its morphological, physiological and biochemical characteristics, and 16S rDNA sequence. Our results showed that the highest activity of nicotinic acid hydroxylase of 0.37 U/mL was obtained by culturing strain H9 with 50 mL of a medium consisting of 15 g/L soluble starch, 15 g/L corn steep liquor, 10 g/L nicotinic acid and, 1.0 g/L K2HPO4 at an initial pH of 7.0 in a 500-mL flask at 25 ℃ with an inoculum amount of 7%, which was increased by 68% as compared to that before optimization. The yield of 6-hydroxynicotinic acid (6-HNA) produced by resting cell biotransformation reached 124.77 g/L. Accordingly, strain H9 had a promising application potential in the industrial production of 6-hydroxynicotinic acid.

Changes in the composition and bioactivities of a mixture of Chinese yam pulp, apple juice and tomato juice during fermentation by lactic acid bacteria were assessed through the determination of its physicochemical and microbial properties, enzyme activities, and antioxidant and antibacterial activities. Results showed that pH and total acid content changed fast from the second day to the fourth day of fermentation, and then remained stable after 8 days. Total sugar content declined firstly, then increased, and finally declined again, reaching and maintaining a minimum level after 12 days. Nitrite content reached the highest value on the fourth day but reduced to a minimum level 10 days later. The microbial growth mainly occurred during the first 6 days, and lactic acid bacteria gradually became the dominant bacteria during the fermentation, inhibiting the growth of other bacteria. The activities of superoxide dismutase, amylase, protease and lipase were increased gradually with fermentation time. Superoxide dismutase activity was highest whereas lipase activity was lowest. DPPH radical scavenging, hydroxyl radical scavenging, superoxide anion radical scavenging and total antioxidant activity were increased gradually during fermentation until reaching a plateau after 10 days. The inhibition percentages against Escherichia coli and Staphylococcus aureus were increased gradually during fermentation, reaching the highest value after 12 days of fermentation. This study may provide a theoretical basis for the development of functional products based on lactic acid fermentation of fruit and vegetable blends.

The effects of ethylene on α-amylase activity, kinetics and microenvironment were investigated. Compared with the control group, α-amylase activity was enhanced by ethylene at low concentration but inhibited at high concentration. However, ethylene hardly affected the optimum pH (6.0) for α-amylase, whereas it resulted in an increase in the optimum temperature by 5 ℃. The hydrolysis kinetics of α-amylase in the presence of low and high concentrations of ethylene followed a first-order kinetic equation (Michaelis-Menten), and the Lineweaver-Burk double-reciprocal curves were well fitted. The mechanism of action of ethylene in this respect was investigated. The ultraviolet (UV) absorption and fluorescence emission intensity of α-amylase were obviously enhanced with increasing ethylene concentration, and the absorption peak of α-amylase at 229 nm showed a red shift by 1 nm. After ethylene was added, the viscosity of α-amylase solution declined obviously compared with the control group, leading to a change in the microenvironment of α-amylase. This research is of great significance for supporting the safe application of ethylene in fruits and vegetables.

Candida utilis CL1501 was mutagenized with a combination of UV irradiation and nitrosoguanidine treatment. An excellent mutant with high ability to produce nucleic acid, named as CL15013, was obtained. Its nucleic acid content was 16.8% on a dry cell weight basis, which was 47.8% higher than that of CL1501. The dry biomass yield of the mutant was 16.9 g/L in fed-batch culture, which was 94.3% higher than that from batch culture. Under optimized fed-batch culture conditions obtained by orthogonal array design, the biomass yield was up to 21.3 g/L, which was 144.8% higher than that from batch cultivation. These results indicated that mutant CL15013 has a great application potential in industrial production.

Sweet potato puree was obtained from sweet potato by peeling, pulping and liquefaction, and saccharified after addition of gelatinized malt for wine production. By one-factor-at-a-time method, fermentation temperature, inoculum size of yeast and initial pH were chosen as the major factors for further optimization by mathematical modeling using Box- Behnken design and response surface analysis. The contents of alcohol and total esters were selected as response variables. The optimal fermentation conditions were determined as follows: initial sugar content, 24%; inoculum size of active dry yeast, 0.15%; and initial pH, 4.0. Under these optimal conditions, the contents of alcohol and total esters were 14.25% and 372.41 mg/L, respectively. Fifty-four aroma compounds were identified from sweet potato wine, mainly including alcohols and esters. The wine had a uniform golden color and its flavor was identical to that of both sweet potato and wheat malt.

In the present study, Sep-Pak C18 and porous graphitized carbon column chromatographies were sequentially used to separate and purify oligosaccharides from defatted and deproteinated milk. After derivatization with phenyl-3- methyl-5-pyrazolone (PMP) or 2-aminoacridone (AMAC), the oligosaccharides were analyzed by high-performance liquid chromatography ion trap time of flight tandem mass spectrometry (HPLC-IT-TOF-MS). AMAC was a better derivatization agent than PMP, since they produced about 67 and 20 chromatographic peaks, respectively. Finally, seven lacto-oligosaccharides were identified under optimized HPLC conditions, and their monosaccharide compositions were determined.

A new method was developed for the determination of trace selenium (Se) in enzymatic hydrolysates of rice by direct injection-inductively coupled plasma-mass spectrometry (ICP-MS), and applied to evaluate the Se bioaccessibility during in vitro gastrointestinal digestion. After filtration and centrifugation, the prepared samples were determined by direct injection-ICP-MS. The proposed method showed a good linearity in the concentration range of 0–160 μg/L with correlation coefficient above 0.999 5 and a limit of detection (LOD) of 0.009 μg/L. The recoveries of spiked samples were between 95.3% and 102.8%, and the relative standard deviations (RSDs) were in the range of 0.87% to 4.48%. Furthermore, the direct injection-ICP-MS method was successfully applied to determine trace Se in in vitro gastrointestinal digestion products of cooked rice with short analysis time and environmental friendliness. In conclusion, this method can be used in nutritional evaluation in vitro of Se-enriched grain materials.

The volatile flavor compounds of raw whole milk (RWM), pasteurized whole milk (PWM) and ultra-hightemperature whole milk (UWM) were extracted by headspace solid-phase micro-extraction, and then analyzed by gas chromatography-mass spectrometry (HS-SPME-GC-MS). A total of 12 volatiles were identified from RWM, mainly including acids and hydrocarbons; 17 volatiles were identified from PWM, mainly including acids, esters, ketones and hydrocarbons; and 17 volatiles were identified from UWM, mainly including acids, ketones and hydrocarbons. According to the statistical analysis of the data, there was a significant variability among the volatiles of 3 milk samples.

The triglyceride composition of Pseudosciaena crocea lipids was analyzed by ultra performance liquid chromatography-electrospray ionization/quadrupole/electrostatic field orbit trap high resolution mass spectrometry (UPLCESI/ Orbitrap-MS). The chromatographic separation was performed on a Hypersil Gold C18 column (150 mm × 4.6 mm, 2.1 μm) using a mobile phase consisting of methanol (including 0.1% formic acid)-isopropyl alcohol (82:18, V/V) and 0.05% ammonium acetate. The analytes were detected by ESI/Orbitrap-MS in the positive ion mode to obtain mass and tandem mass spectra together and then the results obtained were compared with those from the Lipidblast database. A total of 28 triacylglycerols were identified by UPLC-ESI/Orbitrap-MS). Among these, PoOL was the most abundant (35.261%), and PoOL, PoSO, PPO, PPoO, PSO, MPO, POL and PoSA together accounted for 87.87% of the total triacylglycerols.

The volatile flavor components in Beijing spiced beef during 4 different cooking times were extracted and identified by purge and trap thermal desorption (P&T-TD) combined with gas chromatography-mass spectrometry (GC-MS) in an effort to determine the optimal cooking time to achieve the best flavor. A total of 93 volatile compounds were identified in Beijing spiced beef during cooking for 1, 2, 3 and 4 h. The numbers of volatile compounds identified at 4 cooking times were 60, 60, 69 and 60, respectively, and 36 compounds were common to four samples. Ketones and esters reached a peak at 1 h, alcohols, phenols and heterocyclic compounds reached a peak at 2 h, hydrocarbons exhibited the highest value at 3 h, and aldehydes and ethers reached the highest value at 4 h. At the same time, the composition of volatile flavor compounds in the samples was analyzed with e principal component analysis and comprehensive factor scores. The results showed that the 2 h-cook sample gained the highest comprehensive score. In term of volatile flavor analysis, Beijing spiced beef had better flavor in two-hour cooking.

To understand the changes in the fatty acid profile of Pyropia haitanensis under heat shock stress, the fatty acids (FAs) and volatile organic compounds (VOCs) of P. haitanensis under heat shock stress at different temperatures were analyzed by gas chromatography-mass spectrometry (GC-MS). The results showed that after subjecting P. haitanensis to heat shock at 20 (control), 25, 28 and 35 ℃, a total of 13 total fatty acids (TFAs), 14 free fatty acids (FFAs) and 32 VOCs were identified. The contents of saturated fatty acids (SFAs) and VOCs were increased with increasing heat shock temperature up to 28 ℃, whereas the contents of unsaturated fatty acids (UFAs) and FFAs were decreased. As the heat shock temperature further rose to 35 ℃, the contents of TFAs, FFAs and VOCs were decreased. This study may be helpful to understand the mechanism of heat resistance of P. haitanensis and its cultivation.

The extraction and gas chromatography-mass spectrometry (GC-MS) conditions for analysis of volatile flavor compounds in Allium tenuissimum flowers were systematically studied. An HP-5MS chromatographic column was chosen and the optimal conditions were determined. In this investigation, 1.0 g of sample was extracted at 100 ℃ for 40 min in a 20-mL headspace vial. Under these conditions, a total of 52 compounds were isolated by headspace-gas chromatographyolfactometry- mass spectrometry (HS-GC-O-MS), of which 46 accounting for 99.15% of the total volatile substances, were structurally identified. These compounds included 17 sulfurs, 10 aldehydes, 4 hydrocarbons, 4 ketones, 3 furans, 4 alcohols, 2 acids, 1 aromatic compound, and 1 terpenoid compound. According to the result of olfactometry and relative odor activity value (ROAV), the main flavor volatile components were identified as dimethyl sulfide, 2-methyl-,disulfide, dimethyl trisulfide, 3-methyl-,butanal, 2-methyl,butanal, and 1,3-dithiane.

A solid phase extraction method coupled with hydride generation-atomic fluorescence spectrometry (HGAFS) method was developed for the determination of Se in various food and water samples. The method was based on the retention of the trace metal ions on Dowex Marathon A ion exchange resin for eliminating the interference from co-existing metal ions. The limits of detection (LOD) for Se (Ⅳ) was 0.013 μg/L, while the limit of quantification (LOQ) was 0.043 μg/L. The linear range was in the range of 0.1–10.0 μg/L (R2 = 0.999 9). The relative standard derivation was less than 3% for 11 parallel determinations. The recovery was more than 95%. The method was rapid, accurate and precise, and its accuracy was satisfactorily verified by using it to analyze certified reference materials.

Ethyl ester type tuna oil, a high-quality oil obtained after multi-stage molecular distillation of crude tuna oil, is rich in polyunsaturated fatty acids, being colorless and tasteless. During the process, a series of changes may occur. In this paper, gas chromatography-mass spectrometry (GC-MS), electronic nose, and Fourier transform infrared (FTIR) spectroscopy were used to detect tuna oil fractions from different stages of molecular distillation for differences in composition, flavor and properties as well as identification of the main volatile substances. The results showed that the contents of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in fish oil were increased at first, reaching a maximum of 74.10% and 31.41%, respectively and then decreased during the distillation process. The second distillation stage yielded ethyl ester type tuna oil having a total content DHA and EPA of up to 84.26%, which was significantly higher than that of the third, fourth and fifth distillation stage. Electronic nose detection indicated significant differences in the volatile composition of crude fish oil and its distillation fractions. The major flavor components of the different distillation fractions were hexanal, octanal, heptanal and nonanal, 1-octen-3-ol demonstrated, 2-11 ketone, 2-pentyl-furan, which together contributed to the fishy, earth/ muddy and greasy odors, fatty flavor, grassy, vegetable and mushroom aromas. The results of infrared spectroscopy showed that the contents of the main components of the distillation fractions of tuna oil were different. The fractions from the first and second stages contained the largest number of lipid components, showing the highest enrichment effect, which was significantly higher than that of the third, fourth and fifth distillation stage.

This study aimed to reduce the waste of wheat germ resource and simultaneously achieve its value-added utilization for the purpose of solving the problem of calcium deficiency in some populations. Wheat germ protein hydrolysates was prepared by enzymatic hydrolysis using alkaline protease and then chelated with calcium ions to obtain calcium-chelating polypeptides. One-factor-at-a-time and orthogonal array experiments were devised to investigate the influence of reaction temperature, molar ratio between polypeptides and calcium ions, reaction time and pH on the chelation efficiency. The optimal conditions that provided maximum chelation efficiency (86.21%) were determined as follows: reaction at 65 ℃ and pH 9.5 for 60 min with a molar ratio of polypeptide to calcium of 3:1. Infrared spectroscopic analysis confirmed the coordination reaction between calcium and carboxyl/amino groups in the polypeptides. Circular dichroism spectra indicated that the calcium-chelating polypeptides lost their disordered secondary structure and formed compact and ordered conformations compared to the control group. Scanning electron microscopy observation con?rmed significant aggregation of calcium-chelating polypeptides.

The inactivation kinetics of Escherichia coli in mango juice by high pressure homogenization (HPH) was fitted with the Weibull model to predict the inactivation effect in this study. E. coli was subjected to HPH treatments (inlet temperature: 20–60 ℃; pressure: 40–190 MPa, and passes: 1–5). The reduction in E. coli was enhanced with increasing pressure, inlet temperature or number of passes. The reduction in E. coli in the sample after one pass at 50 ℃ was enhanced from 0.46 to 5.16 (lg(CFU/mL)) with pressure increasing from 40 to 190 MPa, which reached the hygienic requirements for non-thermally processed food claimed by the US food and drug administration. The reduction in E. coli after one pass at 70 MPa was enhanced from 0.34 to 5.02 (lg(CFU/mL)) with inlet temperature rising from 20 to 60 ℃. The reduction in E. coli at 190 MPa and 20 ℃ was enhanced from 1.73 to 5.15 (lg(CFU/mL)) with increasing number of passes from 1 to 4. The Weibull model provided a good fit to the inactivation curves of E. coli at different HPH treatments, with R2 > 0.90. The simplified Weibull models were fitted well under 20–50 ℃/40–190 MPa for one pass and 20–40 ℃/190 MPa for 1–5 passes (R2 > 0.92). The simplified Weibull models to predict HPH inactivation kinetics of E. coli could provide a theoretical basis for microbial safety control in the HPH processing of mango juice.

The conditions for solvent extraction of Chaenomeles speciosa (Sweet) Nakai seed oil (CSNSO) were optimized using one-factor-at-a-time and orthogonal array design methods. A solid-to-liquid ratio of 1:4 (g/mL); an extraction temperature of 60 ℃ and an extraction time of 150 min were found to be optimal for the maximum oil yield (28.48%). Both the acid value and peroxide value of CSNSO met the quality standard for edible oils and fats. After methyl esterification, 12 fatty acids were identified by gas chromatography-mass spectrometry (GC-MS), and the major fatty acid in the oil was oleic acid, which accounted for 42.69% of the total fatty acids, followed by linoleic acid (32.46%), palmitic acid (12.92%), stearic acid (4.82%) and arachic acid (3.27%). The relative content of unsaturated fatty acids was as high as 77.42%. The antioxidant activity of CSNSO was estimated by testing DPPH free radical and ·OH scavenging ability, and the 50% inhibitory concentration (IC50) values were determined to be 8.51 and 0.396 mg/mL, respectively.

In this study, our objective was to quantify the capacity of a ceramic microfiltration (MF) membrane with a pore size of 200 nm to remove whey proteins, lactose, ash and calcium from skim milk. Skim milk was concentrated three times by microfiltration at 50 ℃, and then the resulting retentate was diluted to the original volume followed by three-fold concentration under the same conditions as for skim milk. The same treatment was performed on the retennate obtained from the second microfiltration. During the whole process, the cumulative removal percentages of α-lactalbuminn, β-lactoglobulin, lactose, ash and calcium calculated from the three filtrates obtained were 79.27%, 71.64%, 85.81%, 62.16%, and 35.64%, respectively. After the second filtration, the pure water flux of the membrane was reduced 89.27%, and the membrane flux was recovered to 99.07% of the initial level after cleaning the membrane with 2% NaOH and 0.5% nitric acid solution.

To explore an efficient and feasible extraction procedure for the removal of tannins in Quercus acutissima acorns for comprehensive exploitation of Quercus acutissima acorns, the factors affecting the removal rate of tannins from Quercus acutissima acorns collected from Qiaoshan Mountains by ultrasonic-assisted extraction using ethanol as extraction solvent were firstly investigated by one-factor-at-a-time method and then the significant ones were selected and further optimized by response surface methodology. Besides, the antioxidant activity of the tannins extracted was determined by testing 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and hydroxyl radical (·OH) scavenging capacity. Our results demonstrated that liquid-to-solid ratio, ethanol concentration, extraction temperature and ultrasonic power were found to be the factors with a significant effect on the removal efficiency of tannins. The proposed model showed good fitness. An ethanol concentration of 53%, a liquid-to-solid ratio of 42:1 (mL/g), an extraction temperature of 65 ℃ and an ultrasonic power of 240 W were found to be optimal for maximum removal rate of tannins (37.27%). The antioxidant activity of the tannins extracted was positively linearly correlated with their concentration, and the scavenging percentages for DPPH and hydroxyl radical radicals were respectively 75.56% and 62.74% at a tannin concentration of 80 mg/L. Hence, the tannins can be used a new antioxidant.

The first purpose of this research was to study the properties of ultra-fine eggshell powder in comparison with those of coarse eggshell powder. A second purpose was to optimize the preparation of calcium-chelating glutamate from ultra-fine eggshell powder using combination of one-factor-at-a-time method and response surface methodology. Results showed that the filling property, water solubility and electric conductivity of ultra-fine eggshell powder were better than those of coarse powder and a pulverization time of 4 min was found to be optimal to achieve the best quality of ultra-fine eggshell powder. Calcium-chelating glutamate prepared from ultra-fine eggshell powder demonstrated an increase in chelating rate of 12.57% compared with that prepared from coarse powder. Ultra-fine pulverization improved the utilization rate of glutamic acid and simultaneously cut down energy consumption. The optimal conditions for producing calcium-chelating glutamate were determined as follows: molar ratio of eggshell powder to glutamic acid, 1:2.0; pH, 7; chelating time, 59 min; and chelating temperature, 60 ℃. Under these optimal conditions, the chelating rate of calcium-chelating glutamate was 81.12%.

The fruits of Vitis amurensis cv. ‘Shuanghong’ were extracted using ultra-high pressure technique to obtain anthocyanins. The extraction process was optimized by response surface methodology. High performance liquid chromatography (HPLC) was applied to analyze the types and contents of anthocyanidins. The optimal extraction parameters that provided maximum yield of anthocyanins of (0.304±0.007) g/100 g were determined as follows: liquid/material ratio of 8.5:1 (mL/g), extraction pressure of 200 MPa and pressure-holding time of 2 min, which was 26.7% higher than that ((0.24±0.005) g/100 g) obtained with the traditional heat extraction method. The anthocyanins in Amur grapes mainly included delphinidin, cyanidin, petunidin, peonidin and malvidin. Their contents were 51.03, 19.30, 13.54, 3.00, and 99.91 mg/100 g, respectively. The HPLC analysis of anthocyanins components provided a theoretical basis for further development and utilization of pigment from Vitis amurensis.

In this investigation, the response surface methodology was employed to optimize the ionic liquid [BMIM]PF6- assisted enzymatic extraction of curcuma oil from turmeric powder. For this purpose, a regression model was developed to describe the yield of curcuma oil as a function of 4 independent variables including ionic liquid concentration, cellulase concentration, liquid-to-solid ratio and hydrolysis temperature. The optimum extraction parameters were determined as follows: ionic liquids concentration, 18% (V/V); cellulase concentration, 1.4% (m/m); liquid-to-solid ratio, 10:1 (mL/g); and hydrolysis temperature, 50 ℃. Under these conditions, the yield of curcuma oil was 5.0 mL/g. The essential oils obtained from SD and ILSE were analyzed by gas chromatography-mass spectrometry (GC-MS). A total of 48 and 53 components were identified, respectively, which were mainly sesquiterpenes substance and its total relative content reached 74.49% and 84.57%, respectively. Compared with the steam distillation method, the volatile oil component of turmeric powder was increased. The volatile oil of turmeric had the same components, but their relative contents were different. The major components and their relative contents from SD and ILSE methods were ar-turmerone (42.86%, 39.37%), curlone (13.71%, 15.02%), and benzene,1-(1,5-dimethyl-4-hexen-1-yl)-4-methyl- (7.22%, 9.12%), respectively.

In this paper, hyperspectral technology was used to detect the moisture content in rice. Hyperspectral images of 120 rice samples were collected and preprocessed by multiple scatter correction (MSC). Due to the large amount of original spectral data and their strong redundancy, a stepwise regression (SWR) analysis method was adopted for feature extraction after preprocessing. Finally, a quantitative prediction model for rice moisture content was built based on BP neural network with and without optimization of weight and threshold optimized using genetic algorithm (GA) and mind evolutionary algorithm (MEA), respectively. A comparison was made among BP, GA-BP and MEA-BP prediction models, of which the determination coefficients for the prediction set were all above 0.86. The results showed that the prediction performance of MEA-BP model was the best among these three models with a determination coefficient for the validation set of 0.966 3, and a root mean square error of 0.81%.

Primer specificity is one of the key figures of merit for the identification of meat adulteration by polymerase chain reaction (PCR). In this study, the pattern of occurrence of non-specific amplification in real-time quantitative polymerase chain reaction (RT-qPCR) was evaluated in terms of the ΔCt value between base pair matches and mismatches. Three independent variables including the type, position and number of base pair mismatches were investigated for building a quadratic polynomial to predict the ΔCt value. Results showed that the type, location, and number of base pair mismatches had a significant impact on non-specific RT-qPCR amplification in a very regular pattern. As far as different types of base pair mismatches were concerned, nonspecific amplification between purine and pyrimidine, but not between different purines or between different pyrimidines, occurred easily, with a significant difference being observed between two types of base pair mismatches. For base position, the first base of the 3’ end of the primer had the greatest impact on the ΔCt value; the mismatch position gradually far away from the 3’ end had a decreased effect on the Ct value, making nonspecific amplification occur more easily. The greater the number of base pair mismatches was, the more significant the influence on the ΔCt value was, leading to reduced occurrence of nonspecific amplification. The prediction model for ΔCt was fitted using a stepwise method with correlation coefficient of more than 0.80, which could provide a useful and accurate method to predict the ΔCt value within certain limits.

Graphene nanosheets (GNs), which were prepared by liquid-phase exfoliation method, were directly casted onto the surface of a glassy carbon electrode to obtain a graphene-modified electrode (GN/GCE). Then, the polypyrimidine/ graphene composite film modified electrode (pAMP/GN/GCE) was fabricated by electrodeposition method. The surface morphology of the modified electrode was characterized by scanning electron microscope. Electrochemcial behaviors of sunset yellow (SY) and tartrazine (TT) on pAMP/GN/GCE were investigated with cyclic voltammetry (CV) and square wave voltammetry (SWV). The experimental results showed that the as-prepared electrode exhibited remarkable catalytic ability for both SY and TT. Under the optimized experimental conditions, the linear ranges for detecting SY and TT were 0.002–2 mmol/L and 0.003–6 mmol/L, respectively. The limits of detection (LODs) were as low as 0.5 and 0.9 nmol/L (RSN = 3), respectively. This developed method can be used for the simultaneous determination of SY and TT in food samples.

The quality of fresh Tan sheep meat is closely related to the metabolites produced by microbes during chilled storage. Metabolomics can systematically determine the profiles of intracellular and extracellular metabolites systematically and therefore contribute to qualitative and quantitative analysis. This study focused on the metabolomic analysis of microorganisms in tray-packaged Tan sheep meat during chilled storage by gas chromatography-mass spectrometry (GCMS) and on the discrimination of the differences among biological samples with different storage times in order to find out the variables or molecules contributing to these differences. The variable metabolites were mapped to the corresponding metabolic pathways in the major spoilage bacteria Pseudomonas for analyzing the relative intensity of metabolism. The use of pattern recognition mode of orthogonal partial least squares analysis could complete distinguish different storage time groups. The results showed that the metabolism intensity of citric acid cycle, arginine metabolism, alanine, aspartic acid and glutamic acid metabolism and pentose phosphate pathway were relatively high. It is feasible to find out and determine the variable metabolites of microorganisms using GC-MS.

A high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed for the simultaneous detection of 13 mycotoxins including aflatoxins, zearalenone, and trichothecenes in peanut and corn oils. Samples were extracted with acetonitrile-water, followed by clean-up with a MultiSep 226 multifunctional column. The positive electrospray ionization mode (ESI+) and negative electrospray ionization mode (ESI-) were respectively employed to acquire signals. The mobile phase for ESI+ was composed of 0.1% formic acid containing 2 mmol/L ammonium formate (solvent A) and methanol (solvent B), while that for ESI- consisted of 0.1% ammonia water (solvent A) and acetonitrile (solvent B). The limits of detections (LODs) for 13 mycotoxins in peanut and corn oils ranged from 0.05 to 3.00 μg/kg and the limits of quantification (LOQ) ranged from 0.10 to 10.00 μg/kg. The mean recoveries ranged from 66.6% to 114.9%. The method developed in the present study had the advantages of simple operation, high sensitivity and good reproducibility, and so it could be used for the detection of multi-mycotoxins in peanut and corn oils.

A chemiluminescent enzyme immunoassay based on magnetic beads was developed for quantitative determination of chloramphenicol (CAP) residues in pork samples. Sample, anti-chloramphenicol antibody, and magnetic beads coated with goat anti-mouse antibody were mixed on the microwell plate. After reacting for a certain period of time, CAP-horseradish peroxidase (HRP) was added and incubated. Then chemiluminescence substrate solution was added after washing the magnetic beads three times. Ten minutes later, the results were recorded by a microplate reader. Besides, the amount of magnetic beads coated with goat anti-mouse antibody, CAP-HRP, antibody concentration and reaction pattern were optimized. A sensitive and accurate magnetic bead-based chemiluminescent enzyme immunoassay for CAP was successfully developed. The limit of detection was 0.013 μg/kg, and good linear relationship was observed in the concentration range between 0.060 and 2.421 μg/kg. The recoveries of spiked pork samples varied from 85.24% to 93.57%, with relative standard deviation of less than 11.5%.