The reason why lactic acid bacteria and its fermented food are helpful for health in most situations may be due to the production of lactate. The metabolic role of lactate has gained extensive attentions from physiologists and biochemists. However, during the first half of the last century, lactate has been designated as a waste product, especially for the controversial role in muscle fatigue. Currently, more and more publications are exploring and unveiling the critical roles of lactate in multicellular organisms. Lactate has been described as modulation enzymes with catalytic properties to affect hormonal release and responsiveness, and control body homeostasis. Moreover, these properties are directly related to the genesis and sustainability of pathological conditions such as diabetes and cancer. Lactate should not be regarded simply as an anaerobic metabolite, but should be considered as a regulatory molecule that modulates the integration of metabolism. Although lactate is not a redox product, it is an important intermediate metabolite for glycolysis, biological oxidation and biosynthesis. Lactate is produced in the cytosol by the fermentative branch of glycolytic pathway through the reduction of pyruvate with the concomitant oxidation of NADH to NAD+, a reaction catalyzed by lactate dehydrogenase (LDH). Therefore, lactate plays key roles in maintaining the dynamic equilibrium of NADH/NAD+, pH, ATP and biological oxidation/biosynthesis. Due to its multiple bioactivities, lactate is widely used in fermented and functional food, meat quality and color protection, and cancer prevention and resistance so that it is an ideal marker for evaluating physiological alteration, stress and pathology.
Objectives: To rapidly separate and identify antioxidant constituents from the whole plant of Taxillus delavayi, a Yi ethnomedicinal material, and assess their antioxidant activity. Methods: The antioxidant activity of the methanol extract of the medicinal material and its different solvent fractions obtained by repeated extractions sequentially with dichloromethane, n-butanol and water was assessed by DPPH free radical scavenging assay. The dichloromethane-soluble fraction was further separated by silica gel column chromatography, and a high antioxidant component named as TDD8 was obtained and analyzed by bioassay-linked HPLC and 1H-NMR. Results: An individual compound named as TDD8-2 was separated from TDD8 by semi-preparative HPLC and identified by 1H-NMR as pinoresinol. Conclusion: The bioassay-linked HPLC method allows the rapid separation and identification of antioxidant components from medicinal materials.
Crude ethanol extract from the leaves of E. grandis×E. urophylla Guanglin No. 9 was fractionated by repeated extractions sequentially with solvents of different polarity into petroleum ether-soluble, chloroform-soluble, ethyl acetate-soluble, n-butanol-soluble fractions and residue. Total phenolic contents in the six samples were determined by Folin-Ciocalteu method. Meanwhile, their antioxidant activity was tested by in vitro ABTS, DPPH and FRAP assays. The results indicated that among the samples, the ethyl acetate-soluble fraction showed the highest total phenolic content, 502.67 mg/g, and the strongest ABTS and DPPH scavenging activity and reducing power activity, which were better than those of VC. The IC50 values of the fraction against DPPH and ABTS radicals were 0.097 mg/mL and 0.034 mg/mL, respectively. Moreover, a positive correlation between total phenolic content and antioxidant activity was observed for all the samples. This indicates that polypehnolics are mainly responsible for their antioxidant activity. The crude ethanol extract exhibited a total phenloic content (over 30%) similar to that of its counterpart from tea. This study demonstrates that the crude ethanol extract has a high exploitation potential.
This paper deals with the effect of lipid oxidation on protein structure. Oxidized lipid products were prepared by oxidizing linoleic acid under different conditions and allowed to react with bovine serum albumin (BSA) under the same conditions (25 ℃, 4 h). Changes in various properties of BSA were determined during the reaction with oxidized lipid products. The results showed that oxidized lipid products revealed a decrease in thiobarbituric acid value (TBA) after reaction with BSA, while the oxidation value (carbonyl group content) and surface hydrophobicity of BSA increased. Meanwhile, the maximum emission wavelength of the protein showed a red shift and the secondary structure varied obviously. Therefore, lipid oxidation has a significant impact on protein structure.
The in vitro antioxidant activity of polyphenolic extract from Shanxi aged vinegar was investigated using different antioxidant evaluation systems and compared with that of gallic acid and vitamin C. The results showed that the polyphenolic extract possessed antioxidant activity in a dosage-dependent manner which varied with the type of model systems. The reducing power and hydroxyl free radical scavenging activity of the samples under investigation were found to decrease in the following order: the polyphenolic extract ＞ gallic acid ＞ vitamin C. The decreasing order of superoxide anion radical scavenging activity among the samples was the polyphenolic extract ＞ vitamin C ＞gallic acid. The DPPH radial scavenging activity was in the decreasing order of gallic acid ＞ the polyphenolic extract ＞ vitamin C. The nitrite scavenging activity of the extract was poorer than that of vitamin C. The samples decreased in total antioxidant capacity (at the same concentration) in the order of gallic acid ＞ vitamin C ＞ the polyphenolic extract.
Two hyaluronic acid fractions with different relative molecular mass isolated from squid eyes, named as HA-1 and HA-2, respectively and the degradation products of HA-2 separated by ultrafiltration were determined for their moisture retention capacity and antioxidant properties such as ferric ion reducing power and scavenging activity against DPPH and hydroxyl radicals. The results showed that the moisture retention capacity of hyaluronic acid and its degradation products was superior to that of glycerol and increased with increasing relative molecular mass. Fraction HA-2 exhibited the highest water retention rate, 92.66%. All the HA samples investigated possessed antioxidant activity, which increased with decreasing relative molecular mass. Stronger free radical scavenging activity was observed for hyaluronic acid with relative molecular mass below 6000, while HA-1 and HA-2 had weaker antioxidant activity.
Titanium dioxide was prepared and used to explore its synergistic effect with ultrasonic on degradation of acephate aqueous solution at low concentration. The degradation rate of acephate was investigated with respect to temperature, pH, ultrasonic intensity, titanium dioxide amount and various combinations of ultrasonic intensity and titanium dioxide amount. The degradation rate of acephate increased as the ultrasonic treatment time increased up to 1 h and the temperature increased from 5 ℃ to 20 ℃. An acidic environment of pH 3 was favorable to the degradation of acephate. Within a certain range, titanium dioxide amount was positively related to the degradation rate of acephate. An ultrasonic intensity of 40 W/cm2 was conducive to increasing the degradation rate of acephate. Moreover, ultrasonic and titanium dioxide could synergistically degrade acephate. A degradation rate of 78.3% was observed for 2 mg/L acephate aqueous solution at 20 ℃ and pH 3.0 with the addition of titanium dioxide at 0.6 g/L after 50 min ultrasonic treatment at a frequency of 25 kHz and an intensity of 40 W/cm2.
The present study aimed to characterize physicochemical properties and stability of pigments extracted from the spine and shell of sea urchin (Glyptocidaris crenularis). Our results showed that the pigments had relatively high solubility in polar solvents such as water and methanol but had relatively low solubility in non-polar solvents such as light petroleum and hexane. The pigments showed orange color in acidic conditions but yellowish brown color in basic conditions. The pigments were relatively stable to heat but unstable to light. Na2SO3 and potassium sorbate could not only cause changes in the color but also decrease the stability of the pigments. H2O2 and NaCl could not cause any changes in the color but decrease the stability of the pigments. High concentrations of cane sugar could enhance the stability of the pigments. Vitamin C could protect and enhance the color of the pigments.
In this study, the effects of oat starch-based fat substitutes (OSFS) as a partial substitute for fat on texture and the physico-chemical characteristics of high-ratio cake were investigated. OSFS could well simulate the role of fat in high-ratio cake. The additions of 25% OSFS with a DE value of 2.39, 2.93 and 3.73, respectively were all good substitutes for fat and OSFS with a DE value of 2.39 was the best among them. A fat content below 40% in high-ratio cake was successfully replaced by adding the best fat substitute at a concentration of 25%. When 20% of fat was substituted by OSFS, OSFS brought no detectable changes in texture and physico-chemical properties of high-ratio cake, suggesting that the optimum level of fat substitution in high-ratio cake was 20%.
Maillard reaction products (MRPs) were prepared using xylose and glycine by model Maillard reaction. The pH value, absorbance and color parameters of the MRPs were determined. Meanwhile, the antioxidant effect was evaluated in terms of DPPH free radical scavenging activity, ferrous ion-chelating activity and lipid peroxidation inhibitory activity. The results showed that the colorless reaction system became blue and finally showed brown color as the reaction proceeded. Moreover, the pH and L* value gradually decreased. The a* value increased, while the b* value revealed an opposite change. However, the two color parameters changed little during the later part of the reaction. The MRPs exhibited good ferrous ion-chelating activity, and resulted in a lower peroxide value, but possessed weak DPPH free radical scavenging activity. In general, the products had strong antioxidant properties.
Broken rice was used to make rice tea after soaking and roasting. In the process, the occurrence of Maillard reaction and caramelization could produce pigment materials that make rice tea infusion colorful. The effects of making parameters and infusing time on the color parameters of rice tea: lightness (L*), redness (a*), yellowness (b*) and chroma (c*) were investigated. The results showed that the orange color turned to pure yellowness and tea lightness decreased with prolonged infusing time. The process of color formation followed an exponential model. Furthermore, rice soaking could influence the color of rice tea. Rice tea resulting from 10 min soaking at a material-to-water ratio of 1:20 (m/V) could quickly show stable color with high lightness, yellowness and chroma.
Carboxymethyl thiourea chitosan (CMTCS) was prepared and characterized by infrared spectrometry (FT-IR), ultraviolet spectrometry (UV) and differential thermal and thermogravimetry analysis (TG-DTA) methods. The antibacterial activity of CMTCS against E.coli and St.aureus were investigated in vitro. The results showed that the antibacterial activity of CMTCS was obviously higher than that of chitosan with an MIC of 0.20 mg/mL against both E.coli and St.aureus.
A homogeneous polysaccharide named as TC-1 was obtained from kelp by DEAE-cellulose and gel filtration chromatography. Its chemical structure was characterized by means of monosaccharide composition analysis, methylation analysis and IR spectroscopic analysis. TC-1 was a complex sulfated polysaccharide with a weight-average molecular weight of 3.7 × 105. TC-1 mainly consisted of fucose and small amounts of xylose, mannose, glucose and galactose were also found. The chain of TC-1 included 1,4-linked or 1,3-linked fucose, 1,3-linked xylose, 1,3-linked or 1,6-linked mannose, 1,3,4-linked or 1,2,4,6-linked glucose, and 1,6- linked,1,3,6- linked, or 1,3,4,6- linked galactose.
In order to explore the phytochemical profile of three adlay varieties, the levels of total, free and bound phenols and flavonoids were determined using a microplate reader. Meanwhile, the oxygen radical absorbance capacity (ORAC) was measured as an indicator for total antioxidant capacity using a multifunctional fluorescence microplate reader. The contents of free ((45.19 ± 0.91) mg of gallic acid equivalent/100 g of dried samples) and bound ((30.86 ± 1.18) mg of gallic acid equivalent/100 g samples) phenols in Longyi I were significantly higher than those in Liaoning V and Guizhou Heigu (P ＜ 0.05). For all these adlay varieties, bound phenols averagely accounted for 45.28% of total phenols. The content of free flavonoids in Liaoning V showed a significant increase as compared with Longyi I and Guizhou Heigu, and the content of bound flavonoids in Longyi I was higher than that of Liaoning V and Guizhou Heigu. The highest content of total flavonoids was found in Liaoning V. The adlay varieties were ranked in decreasing order of ORAC as follows: Longyi I ((668.0 ± 32.7) mg of Trolox equivalent/100 g of dried samples), Liaoning V and Guizhou Heigu. The average percentage of bound ORAC in total ORAC was 48.08%. A correlation coefficient (r2) of 0.933 was observed for the significant correlation (P ＜ 0.05) between the total phenol content and total antioxidant capacity of each adlay variety.
Bovine colostrum was extracted to obtain bioactive proline-rich polypeptides (PRP). The molecular weight and amino acid composition of PRP were analyzed by means of SDS-PAGE and an automated amino acid analyzer, respectively. Reversed-phase high performance liquid chromatography (RP-HPLC) was employed to purify PRP. The results showed that the proline content in PRP was as high as 20%. The molecular weights of principal components were in the range of 5－25 kD as determined by SDS-PAGE. RP-HPLC showed that major spectral peaks were eluted by 37%－45% acetonitrile. As a result, PRP with a purity of 96.7% was obtained.
Wuzhumuqin sheep aged 1－18 months were tested for the structural change of intramuscular connective tissues by a histological method. Meanwhile, the contents of pyridinoline and proteglycans in intramuscular connective tissues were determined during the development of Wuzhumuqin sheep. The thickness of endomysium increased with increased age and no significant difference was observed between 6 and 9 months and between 12 and 18 months (P＞ 0.05). The thickness of perimysium showed an obvious increase during the first 6 months and then a significant decrease (P ＜ 0.05). The diameter of endomysial honeycomb structure gradually increased, and collagen fibrils in endomysium became more tightly bounded to each other. Moreover, the wavy pattern of collagen fibres in perimysium became more regular during the growth of sheep. Furthermore, the contents of pyridinoline and uronic acid in connective tissue revealed a significant increase during the growth process of sheep (P ＜ 0.05).
A self-made online testing device for microwave drying was used to dry lees for exploring its batch drying properties. The effects of microwave power, lees layer thickness and intermittent time on moisture content, drying rate and temperature were investigated. The dehydrating law of lees was achieved during intermittent microwave drying. A kinetic model for intermittent microwave drying was established based on experimental data as follows: ln (－lnMR)＝ －3.9977＋0.0038P－0.6427H－ 0.4118R ＋(1.7216 ＋ 0.0001P ＋0.0200H－0.0403R) lnt. The kinetic model could accurately describe drying process of lees and predict water content and drying rate.
Restructured beef is made from smaller pieces of beef fused together by a binding agent. In order to improve the quality of restructured beef, a mixture of transglutaminase (TG) and sodium caseinate (SC) at a ratio of 1:4 (m/m) was used to bind beef pieces. The effects of time (1, 2, 3, 4, 5 or 6 h), temperature (1, 4, 7 or 10 ℃) and pressure (2, 3, 4, 5 or 6 N/m2) on physical properties of restructured beef were studied by one-factor-at-a-time method. The results showed that the optimal time, temperature and pressure were 3 h, 4 ℃ and 4 N/m2, respectively. Under these conditions, the binding strength of restructured beef was reinforced, the thawing loss and cooking loss were decreased, and the texture and color were improved.
A rapid and efficient method to analyze the amino acid sequence of casein was presented using LTQ-Orbitrap mass spectroscopy coupled with liquid chromatography. In order to understand the amino acid sequence and substitution of cow, water buffalo and goat caseins, LTQ-Orbitrap mass spectroscopy coupled with liquid chromatography was used to analyze 4 major casein components, and their complete amino acid sequences were acquired by database searching. The amino acid substitutions of cow milk caseins were markedly lower than those of goat milk caseins. Thus, this study demonstrates that the amino acid sequences of cow milk caseins are more stable than those of goat milk caseins.
The objective of the present study was to investigate the mechanisms for the inhibition of Bacillus cereus by Fructus Mume extract. The effect of Fructus Mume extract on the integrity of cell wall was studied by determining the content of alkaline phosphatase (AKP). The contents of extracellular proteins were assayed by Bradford method. Cell membrane permeability was examined based on changes in electrical conductivity. The effect of Fructus Mume extract on the synthesis of bacterial proteins was analyzed by SDS-PAGE. The results indicated that Fructus Mume extract could damage the structures of cell wall and cell membrane, causing an increase in cell membrane permeability and the release of intracellular contents. Fructus Mume extract could also affect the synthesis of bacterial proteins and block protein expression in bacteria.
In order to achieve selenium enrichment in Spirulina maxima, the effects of different amounts and strategies for selenium addition on the growth of S. maxima as indicated by biomass and selenium concentration were explored. The addition of 100μL of 100 μg/mL Na2SeO3 at the same time each day for 8 consecutive days after 1 day of growth in Se-free environment was found optimal, resulting in a biomass of 0.903g/L and an organic Se content of 1413.168 μg/g dry S . maxima.
The microbial community structure of Bozaa, a traditional Kyrgyz fermented beverage, was analyzed by the PCRDGGE technique. PCR amplification of 16S rRNA gene V6－V8 region and 26S rDNA D1 region were performed for bacteria and yeast in the beverage, respectively. The main DNA bands in the DGGE profiles of the PCR products obtained were subjected to sequence analysis. The results showed that the microbial flora of Bozaa was composed of Lactobacterium plantarum, Lactobacillus brevis, Bacillus cereus, Acetobacer pasteurianus, and Saccharomyces cerevisiae, which was a successful primary elucidation of the microbial diversity of Bozaa.
Alcalase 2.4L FG was used to hydrolyze soybean protein isolate (SPI) to prepare soybean protein hydrolysates with the highest antioxidant activity, which showed a degree of hydrolysis of 14.0% and an ABTS+ radical scavenging rate of 43.6%. The prepared hydrolysates were modified with Alcalase 2.4L FG by plastein reaction and the optimal enzyme dosage, substrate concentration and temperature to maximize the reduction of free amino groups were determined by response surface methodology to be 1037 U/g protein, 30 g/100 mL, and 20 ℃, respectively. The maximum degree of reaction and antioxidant activity were obtained after reaction for 6 h under these conditions. Moreover, the antioxidant activity of the SPI hydrolysates and their modification products obtained after reaction for 1, 3 h and 6 h was better than that of SPI. The DPPH and superoxide anion radical scavenging activity and reducing power of the hydrolysates and modification products showed no significant difference, while a significant difference was observed in their hydroxyl radical scavenging activity.
A high-yield neutral phytase-producing strain with an enzymatic activity of 12.52 U/mL was isolated from soil and initially identified as Agrobacterium radiobacter based on its morphological, physiological and biochemical characteristics as and 16S rDNA sequence. The optimum reaction temperature and pH of neutral phytase produced by the strain were 45 ℃ and 7.0, respectively. The relative activity of the enzyme was 80% after heating at 65 ℃ for 60 min, revealing that it was thermostable to some extent. The enzyme was stable at pH values in the range of 5.5－8.0. Its activity could be activated by Ba2+ but inhibited by Fe2+ , Mg2+, Zn2+ and Cu2+ .
Spent mushroom compost (SMC) was used to prepare industrial grade cellulase by solvent extraction, membrane filtration and salting out and high-purity cellulase by further aqueous two-phase extraction. The results showed that crude cellulase solution with an enzymatic activity of 102.64 U/mL was obtained after 3 h of extraction at 25 ℃ with an extraction solvent composed of 0.2 mol/L acetic-acetate sodium buffer at pH 5.0 and 0.2% Triton X-100. Subsequent salting out at 60% (NH4)2SO4 saturation could recover 65.54% of the total cellulase activity, and industrial grade cellulase with an enzymatic activity of 2865.47 U/mL was obtained. After further aqueous two-phase extraction with a system made up of 22% polyethylene glycol 6000 (PEG6000) and 20% (NH4)2SO4 under the conditions of 7 mmol/L NaCl, pH 5.5 and normal temperature, the cellulase activity and specific activity were 10208.46 U/mL and 106.62 U/mg, respectively and a total activity yield of 51.22% was achieve, revealing a 12.85-fold increase when compared with that of crude enzyme solution. As a result, high-purity cellulase was obtained.
A strain of non-starter lactic acid bacteria capable of accelerating cheese ripening were screened and isolated and its effect on cheddar cheese slurry proteolysis during ripening was also explored. Rogosa agar medium was used for primary strain isolation from Chinese northeastern traditional fermented food Suancai,, and the isolates obtained were screened further by multivariate statistical analysis. Strain identification was conducted by 16S rDNA gene sequencing and Blast searches against the public database. The results showed that a non-starter lactic acid bacterium was successfully isolated and named as S-1. The strain was identified as Lactobacillus plantarum subsp. plantarum ST-III. Moreover, the strain displayed high aminopeptidase activity and autolytic capacity although it had low acid-producing capacity. Furthermore, the strain revealed high proteolytic capacity during cheese slurry ripening.
This paper deals with the separation, purification and cytotoxicity of C-phycocyanin (C-PC) from Spirulina platensis and its tryptic peptides. Repeated freezing and thawing coupled with ultrasonic treatment was used for disrupting the cell wall of Spirulina platensis. The purity (A620nm/A280nm) of C-PC was 2.19 after fractional precipitation by 28－55 g/100 mL (NH4)2SO4 and could reach 3.89 after further purification by sequential chromatography on hydroxylapatite (HA) column and Sephacryl S-200 HR gel column. The purified C-PC was hydrolyzed by trypsin at 40 ℃ for 60 min. Four peptides were obtained from the hydrolysate of C-PC by DEAE-Sepharose Fast Flow column chromatography. The cytotoxicity of C-PC and its hydrolysate as well as the 4 peptides on HeLa and 293T cells was evaluated by MTT assay. The results showed that the inhibition rates of peptide fractions I and IV, C-PC hydrolysate and C-PC on the growth of HeLa cells were 37.71%, 47.04%, 34.02% and 26.03%, respectively. Therefore, peptide fractions I and IV revealed obvious suppressive effect on the proliferation of cancer cells, while neither of them had cytotoxicity on 293T cells. Moreover, peptide fraction IV had the strongest tumor suppression activity, indicating a great potential to be developed as health-care products.
