Objective: The aims of this study were to investigate mathematical relationships of pork tenderness with muscle fibre diameter, density and intramuscular fatty area (IFA). Method: Six varieties of cross-bred pigs (N=36) were taken as study objects, and meat or muscle samples were all from M. longissimus dorsi (ld, n=36×2 or ×3) and M. psoas major (pm, n=36 × 2 or × 3), respectively. Two-dimensional microscopy images of histomorphology characteristics of skeletal muscle were reconstruted, and mathematical relationships of pork tenderness with histomorphology characteristics were fitted. Results: The muscle fibre diameter and density in pm are thinner and denser than those in ld. However, the IFA in pm is less than that in ld. The muscle fibre diameter is the most significant factor affecting the pork tenderness with the linear coefficient (r) of 0.966 (p <0.01). It means that the thicker the muscle fibre is, the worse the pork tenderness is. Otherwise, the muscle fibre density varies with its diameter. The muscle fibre density decreases, when its diameter increases. So the linear relationship between the muscle fibre density and pork tenderness is significantly negative (r=0.905, p<0.05). The tenderer the muscle fibre is, the denser the muscle fibre is. But, the effect of muscle fibre density on pork tenderness is less than muscle fibre diameter. In this study, IFA is only about 3% of total muscle area, so it is not enough to carry weight on pork tenderness. Conclusion: Muscle fibre diameter and density have remarkable effect on muscle tenderness, whereas IFA mostly affects the smack but not tenderness. In five vatieties of Shennong, their muscle fibre is thinner with the better pork quality (tenderness) because these pigs are bred from Taihu swine.
Request for the mechanical properties of natural casing in various cases is different. Some of mechanical properties of natural casings could be changed with the application of ultrahigh pressure in casing process. In this study, the shearing strength and tensile strength of natural hog casing under 100 to 600 MPa, at 20 to 45 ℃ and 5 to 30 min pressure-holding time were investigated by using single factor test method. The results showed that the shearing strength and tensile strength of pressurized casing are markedly enhanced under 300 to 600 MPa at 20℃ (p ＜ 0.05). However, both of the strengths are decreased obviously under 300 MPa at 45℃ (p ＜ 0.05). The effect of pressure on them is barely marked during 5 to 30 min under 300 MPa, and 20℃ (p＞0.05). In conlusion, the decrease of both of the strengths in pressurized casing is beneficial to improve the texture properties of casings and the increase of tensile strength is also advantageous to enhance the possibility of applying casing to tissue engineering.
Objective: To optimize process conditions of separation and purification of total flavonoids from Lycium ruthenicum Murr. with macroreticular resin. Methods: Siginal factor and orthogonal tests were done. Results: Using AB-8 resin to adsorb and purify total flavonoids from Lycium ruthenicum Murr, the optimal purification conditions are as follows: concentration of sample solution 0.200 mg/ml,velocity of sample solution 2 ml/min, pH 5, velocity of 95% ethanol taken as eluent 4 ml/min, and volume of 95% ethanol 5 BV (bed volume). The saturated adsorption capacity of AB-8 is 0.64691 mg/g resin, and after used 9 times repeatedly, adsorption capacity of AB-8 is still good. With these paramaters, the purity of product is 28.0%. Conclusion: AB-8 resin is effective in the adsorption and purification of the total flavonoids form Lycium ruthenicum Murr. with good repetition and stability. Therefore, the above technice is suitable to industrial production.
By means of periodate oxidation , Smith degradation , methylation, GC, GC-MS, the structure of low molecular weight polysaccharide, LWPP-Ia isolated from pumpkin was analyzed. Monosaccharide composition analysis of LWPP-Ia indicated hat it is a low branched molecule composed of glucose, fructose and galactose in the molar ratio of 3.6:1:1.2. The main chain is made up of (1 → 4)-linked-Glu and (1 → 4)-linked-Gal1 Some of (1 → 4)-linked-Glus were substituted at 2-O. The (1 → 2)- linked Glu is on the position 1 of side chain and the branch end is (1→)-Glu and (2→)- Fru.
Essential oil was extracted from Cuminum cyminum L. fruit with steam distillation extraction method in 2.6% yield. The chemical components of the essential oil were analyzed with gas chromatography-mass (GC-MS). Twenty-eight components were detected and twenty-six components among them (99.801% of the total essential oil) were identified. Cuminal (39.511%) is the main component, followed by 2-caren-10-al (17.707%) and 3-caren-10-al (17.542%). The sodium nitrite scavenging effect of the essential oil was studied. It was found that the essential oil has considerable sodium nitrite scavenging effect with the maximum scavenging rate 92.5%. The extracts from residue after steam distillation extraction with different organic solvents also show significant sodium nitrite scavenging effects, and the maximum scavenging rates of acetone, methanol and ethanol extracts are 71.1%, 58.7% and 45.5%, respectively.
Starch graft copolymer microspheres were synthesized by inverse suspension polymerization with N,N'- methylenebisacrylamide and soluble starch, using K2S2O8-NaHSO3 as initiator. The adsorption behavior of starch graft copolymer microspheres to Cd2+ was investigated. The starch graft copolymer microspheres and their adsorption products were characterized with scan electron microscope (SEM), FT-IR spectroscopy, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The results showed that the adsorption behavior of the copolymer microspheres to Cd2+ is adapted to Langmiur and Freundlich adsorption isotherm equation. Furthermore, the adsorption of Cd2+ on microspheres not only decreases their crystallinity but promotes the rupture of bonds among their main chains.
Newhall navel orange [Citrus sinenisis (L.) Newhall] fruit was used to study the changes of flavonoids and antioxidant activity and the relationship between them during its growth. The results showed that flavonoids content, antioxidant activity in vitro, H2O2 -scavenging capacity and O2·-scavenging capacity in peel decrease during the fruit growth. But the changes of all these parameters in pulp display single-peak patterns and most peaks are found on 15th of September. According to correlation analysis, there is a significant positive relationship between flavonoid content and antioxidant activity or H2O2 -scavenging capacity or O2·-scavenging capacity, and their correlation coefficients are 0.9664 (p＜0.01), 0.7723 (p＜0.01) and 0.9144 (p＜0.01), respectively.
The antimicrobial effects of different extracts from Pinus massoniana Lamb, Pinus elliottii Engelm, Pinus thunbergii Parl with different solvents were investigated respetively. Result showed that all the pine needle crude extracts inhibit the growth of Escherichia coli, Bacillus subtilis, Staphylococcus aureus,Saccharorngces cerevisiae, Penicillium sp. and Aspergillus in different degrees. Especially, they have remarkable antimicrobial effects on Bacillus subtilis and Aspergillus. Furthermore, the antimicrobial activities of water and enthanol extracts of these three cultivars of pine needles have wider pH range (5 to 9).
In this study, barley malts were processed by complete experiment, considering the eddects of initial languish temperature and kilning temperature on malt quality. It was found that β-Glucanase activity in dried malt has significant positive relationship (p＜0.01) with α-amylase activity, proteinase activity, extract yield, α-N or Kolbach Index, but it has significant negative (p＜0.01) relationship with saccharification time, wort viscosity or content of β-glucan. With β-glucanase activity increasing, the wort viscosity reduces but the content of β-glucan inreases and qualities of malts are improved. Both of the initial languish temperature and kilning temperature have effects on β-glucanase activity, but kilning temperature is more significant than initial languish temperature. The highest β-glucanase activity in dried malt is obtained when initial languish temperature is controlled at 48℃, and kilning temperature is controlled at 78℃.
The antioxidant activities of ethanol or water extracts from eleven species of natural plants were measured with DPPH (2,2-dipheny1-1-picrylhydrazyl) method, respectively. The results indicated that all of them have antioxidant activities， especially some flavonoids-rich extracts, which show stronger antioxidant activities with dose-effect relationship. Furthermore, the antioxidant activities of bee pollen and propolis extracts are the strongest among all the extract samples.
The SCF-CO2 extraction process and GC analysis of fatty acid of “Xiaobai” apricot almond oil were investigated in this study. The results showed that the parameters for extracting apricot almond oil with SCF-CO2 are determied as following: extraction press 30 MPa, temperature 35 ℃, extraction time3.0 h, CO2 flow rate 15 to 20 kg/h, and using absolute C2H5OH as cosolvent with amount of 10% (accounting for the total raw material). “Xiaobai” apricot almond oil is rich in unsaturated fatty acids, especially oleic acid and linoleic acid，accounting for 91.65% and 91.75%, respectively.
Effect of ultra-high pressure sterilization technology on the qualities of fresh raw milk was studied. Fresh raw milk was subjected to UHP treatment (continuous, alternative pressure treatment and hurdle technology) at selected pressure (350 to 600 MPa) for various holding times. Pressure treated samples were enumerated to determine the residual microbial population and initial counts were obtained from the control samples. The changes of nutrition in milk treated with different technologies are also deterimined. Resilts showed that:(1) Higher pressure, longer holding time and more alternative times favour a larger destruction of microorganisms; (2) The combined effect of barrier (fence) technology and pressure on the destruction of microorganisms in fresh raw milk is more effective than that of only pressure treatment, and the effect of ε -polylysine on inactivation of microorganism in fresh raw milk is more effective than that of Nisin at the same concentration of 100 mg/L; (3) Compared with the SDS-PAGE electrophoretogram of whole proteins in fresh raw milk, the first bands near the negative pole of those in milk treated with different sterilization ways disappear and the colour of the second bands has slight loss, which suggests that subunits of some proteins are dissociated, but the 400 MPa-treated milk shows the similar eletrophoretogram with the fresh raw milk; (4) The loss of threonine, VA and VC in high pressure-treated milk is much less than those in pasteurism-treated milk, in particular threonine and VA are almost retained, and the contents of VB1 and VB2 in the former also more than that in the latter; (5) High pressure-treated milk has longer shelf life than pasteurism-treated milk, extending the sale semidiameter of products.
Effects of height of chicken sauage sample and degree of compression on TPA results were investigated. The results indicated that height of sample has little effects on hardness and resilience, but has significant effects on cohesiveness and springiness；However the degree of compression has extremely significant effects on hardness, cohesiveness and resilience, expect significant effect on springiness. Quadratic models were fitted for resilience and cohesiveness, which had statistical significance. It was found that hardness increases basically linearly with testing rate, cohesiveness shows little change, and chewiness and springiness have extremely similar change tendency. Meanwhile, TPA test conditions were chosen primarily, and the ideal conditions were estimated, including height of sample (2.0 cm), degree of compression (70%), and test rate (2 mm/s).
The production of Douchi, a Chinese traditional fermented soybean product, was replicated in the laboratory on a small scale in order to study the biochemical changes associated with the ripening process. Douchi was made by mucor SP. fermenting uncracked, undehulled and cooked soybean seeds and followed by a 42-d ripening at 45 to 48 ℃. Changes in proximate compositions (moisture, ash, crude lipid, dietary fiber, carbohydrate and energy), total nitrogen, non-protein nitrogen, nitrogen soluble index, amino nitrogen, water soluble nitrogen, free amino acid concentration, in vitro digestibility of protein, total titratable acid, and browning index of Douchi with different length of ripening time were analyzed. Results showed that ash content increases over the ripening process, while dietary fiber and carbohydrate significantly diminish. A sharp increase and a slight decline in total titratable acid are detected at the beginning (0 to 8 d) and end (32 to 42 d) of ripening, respectively. Total nitrogen keeps stable, while non-protein nitrogen, nitrogen soluble index, amino nitrogen, water-soluble nitrogen, free amino acid concentration, and in vitro digestibility of protein increase throughout the ripening process, which results in enhancemant of nutritional value of product.
The extraction of Sapium sebiferum Roxb epidermis oil was carried out with supercritical fluid carbon dioxide technique, and the effects of extraction pressure, temperature and CO2 flow rate on extraction rate of Sapium sebiferum Roxb epidermis oil were investigated through orthogonal design．The results showed that the optimal extraction pressure, temperature, CO2 flow rate and time for the maximum extraction rate are 40 MPa, 36 ℃, 20 L/h and 1 h, respectively. Meanwhile the components of Sapium sebiferum Roxb epidermis oil were analyzed with gas chromatography (GC).
The fruit quality and juice-making suitability of there different guava (Psidium guajava L．) cultivars were evaluated, and their sugar and acid compositions and antioxidant activities were analyzed. The results showed that“Zhenzhu”has the highest content of total soluble solids (TSS) (9.11%) and its titratable acids is also high (0.36 g/100 ml); “Xinshiji” has the highest contents of VC (4.96 g/L), total phenolics (2.13 g/L) and TAC (67.26 mmol/L). A comprehensive evaluation showed that “Xinshiji” scores the highest in fruit quality, while “Zhenzhu” scores the highest in juice-making suitability. Fructose, glucose and sucrose are the predominant sugars in guava. The three guava cultivars are all monosaccharide-prevalent, with higher fructose content. Different cultivars contain different acid compositions. The main acids in“ Xinshiji” are citric acid, succinic acid and propionic acid, while those in“ Zhenzhu” and“ Shuijing” are citric acid, succinic acid, α-ketoglutaric acid, propionic acid, tartaric acid and pyruvic acid. Among them, citric acid and succinic acid are the two dominant organic acids“. Xinshiji” is the highest in antioxidant activity.
Artichoke is a vegetable rich in active polyphenols (mainly chlorogenic acid). Polyphenolic compositions in different parts of artichoke are different, and they vary with season. The order of polyphenols content is as follows (from most to least): leaf ＞stem＞ flower bud and the older leaves＞ new leaves. Treatments such as high temperature, alkaline condition and damp environment should be avoided, otherwise, the polyphenols, especially chlorogenic acid would be lost. Microwave pretreatment， ethanol immersion and shade drying could reduce the polyphenols losses.
This study focused on citral which is the main component of essential oils such as Litsea cubeba oil and lemongrass oil, and explored a experimental approach of MTT assay in the selection of antitumor essential oils. It compared the effects of different wavelengths on absorbance, taking citral as experimental drug and non-volatile adriamycin (ADM) as control, investigated their volatility and diffusibility according to morphological changes of human K562 cells, and explored the effect of stockage temperature and time on the repetition of MTT assay. It was found that the results followed the same trend at different detection wavelengths as 492 nm, 570 nm and 630 nm. The volatility and diffusibility affect both control and citral treated wells, and make the well that adjoined high concentration well show higher cell toxicity than its actual value. The results also proved the low temperature stockage of volatile essential oils to be not only advisable but also a key point for good experimental repetitions.
To confirm the feasibility of nitrosohemoglobin made from blood for the application to industry, its effect on the quality of red sausage was studied. The results showed that the addition of nitrosohemoglobin significantly increases the a* value of red sausage (p＜0.05) and decreases the value of TBARS. Also, nitrosohemoglobin reduces the residue of sodium nitrite and total plate counts of red sausage. Furthermore, sensory evaluation showed that the optimum addition of nitrosohemoglobin is 0.15%. In conclusion, nitrosohemoglobin plays a role of antioxidant and colorant and could be used to substitute nitrite in the processing of red sausage to improve its sensory quality.
Beaded chitosan resins were prepared, which show good thermostability when temperature is lower than 172 ℃. Tea polyphenols (TP) was separated from green tea via the absorption of the beaded chitosan resins. The conditions and the mechanism of adsorption and desorption of TP were discussed. The results showed that the optimum adsorption conditions of TP (1.573 mg/ ml) in 25 ml tea soup are as follows: the beaded chitosan resin 4.0 g ( dry weight 0.22 g ), adsorption time 2 h, pH of tea soup 7.06 and adsorption temperature 30 ℃. The extraction rate can reach 74.1% under the above conditions and the absorption capacity is 136.1 mg/g. Furthermore, the experimental results showed that the adsorption kinetics of the beaded chitosan resins to TP accords with the Langmuir formula, and the saturated adsorption capacity is 1116 mg/g.
This study aimed to investigate the effects of tea polyphenols or the monomers (ECG, EGCG, and so on) on foaming property of egg alblumen protein by using electric beating machine and through direct measurement. It was found that 0.2% to 0.4% content of tea polyphenols is appropriate content to improve the foaming property of egg alblumen protein and that the active hydroxyl is the main reason for the improvement. Meanwhile, the effects of processing environmental factors affecting the interaction between tea polyphenols and protein were explored preliminarily.
The content of triterpenes extracted from sclerotia of Poria cocos was determined by colorimetry with vanillin-glacial acetic acid and perchloric acid, and the in vitro antibacterial activity of triterpenes was tested by plate growth rate method. The positive results of chemical reactions indicated that methanol extract of sclerotia of Poria cocos contains triterpenes and the content is 1.58%. Its lowest antibacterial concentrations are 0.47, 0.47, 0.95 μg/ml against Escherichia coli, Staphylococcus aureusm, and Pseudomonas aeruginosa respectively. The results also showed that the inhibitory activities of this sclerotia extract against Escherichia coli and Staphylococcus aureusm are relatively stable and hardly affected by time. In conclusion, the triterpenes extracted from sclerotia of Poria cocos have good antimicrobial activity and could be further developed as drug of treating suppurative infection and natural cosmetic of dispelling blain.
Particle size and hygroscopicity of KAC, MCC and SiO2 were measured, and anticaking functions of these three substances added into chicken flavor powder were compared at different amounts and environmental conditions. The results showed that the smaller particle size has the better anticaking function, and when the particle size is 20 to 30 μm, the anticaking function is excellent. Furthermore, the flowing and anticaking property of chicken flavor powder added with 3‰ KAC are obviously better than those of chicken flavor power added with 1% MCC or 1% SiO2 at relative humidity 90%±3% and 25± 1℃, relative humidity 75% ± 3% and 25 ± 1℃, and relative humidity 30% ± 3% and 25 ± 1℃, respectively.
Freeze-drying is a major way to produce lactic acid bacteria and probiotic powders, and both freezing and drying can influence the cell survival. In order to evaluate the damage of Bifidobacterium infantis caused by freeze-drying, microstructure, β-galactosidase activity and concentrations of Na+ and K+ were determined in this experiment. The results showed that the changes of microstructure, β-galactosidase activity and concentrations of Na+ and K+ increase during freezing and drying processes, which include concentration of cytoplasm, separation between cytoplasm and cellular wall, shrinking and damage of cell, increase of cell membrane permeability, decrease and disparity between Na+ and K+ concentrations.
Gelatin was cross-linked with tannic acid as cross-linking agent. Gel properties and degradation characters of crosslinked gelatin were evaluated. Microcapsules were prepared with cross-linked gelatin as wall material and vitamin B1 as core material. Release characters of core material in microcapsules were analyzed. The results showed that the minimum concentration of cross-linked gelatin to form gel is identical to raw gelatin at about 0.6%. However, the gel strength of cross-linked gelatin is lower than that of raw gelatin at the same concentration. Degradation study in vitro showed that the raw gelatin and cross-linked gelatin are hardly degraded in simulated gastric fluid, but both of them are degraded in simulated intestinal fluid, and the cross-linked gelatin is degraded slower than the raw gelatin. The microcapsules with cross-linked gelatin as wall material show certain slowrelease property in simulated gastric and intestinal fluids.
Taking emulsion forming in the aqueous-enzymatic extraction of peanut oil as study object, the amino acid composition, emulsion ability index, emulsion stability, secondary structure of adsorbing protein in emulsion surface, protein in continuous phase and peanut protein were compared respectively. The results indicated that the content of hydrophobic amino acid, emulsion ability index and emulsion stability of adsorbing protein in emulsion surface are higher than those of the protein in continuous phase and peanut protein. The rheological characteristics of the emulsion showed that the emulsion is a typical elasticity system, and the emulsion stability could be reduced by increasing temperature and shear rate.
The active proteins from Dasyatis akajei liver were isolated by precipitating with ammonium sulfate, chromatographing with Sephadex G-150. Then the activities of scavenging superoxide radical and hydroxyl radical and inhibiting lipid peroxidation were determined. The results showed that the isolated three protein peaks (P1, P2 and P3) could effectively scavenge superoxide radical and hydroxyl radical and inhibit lipid peroxidation. The inhibiting ability of P3 is the highest, while that of P1 is the lowest. In conclusion, the active proteins from Dasyatis akajei liver have antioxidation.
Silica gel column chromatography was used to separate and purify total alkaloids from Fritillaria ussuriensis Maxim. The solid phase was thin layer chromatography silica gel G and the mobile phase was ethyl acetate-methanol-ammonia (17:2:1). The purities of the separated products, pemine and peinine were determined using HPLC-ELSD. They are 93.19% and 92.09%, respectively. In conclusion, the separation method of silica gel column chromatography applied in this experiment can be used to gain highly purified products.
Mung bean, potato, sweet potato, rice and corn starches were isolated and their physico-chemical properties were compared respectively. Amylose leaching and setback (SB) are the highest for mung bean starch, and they are both highly correlated to apparent and total amylose content. Though mung bean starch has the highest amylose content, yet it does not show thermalpaste stability. The results showed thatduring heating sweet potato starch granules swell rather freely with bad thermal-instability and low retrogradation, indicating hign swelling power, peak viscosity (PV) and breakdown (BD), and low syneresis of the sweet potato starch, while rice starch shows the inverse. The gel consistency is also different among various starches, with potato starch the highest, and rice starch the lowest. The syneresis shows no obvious correlationship with amylose content and seems to be affecfed by other factors.
The change of scavenging activity on hydroxyl free radical of antioxidant peptide from Decapterus maruadsi was selected as the index to investigate the effects of temperature, pH, food materials, preservative, metal ions and different drying ways on the antioxidation stability of the peptide. The results showed that the antioxidant peptide from Decapterus maruadsi has a strong heat-resistant ability; It can keep high activity in the acidity environment, but loses its activity in the alkali environment; Some food materials, such as sucrose, NaCl, etc have little effects on its antioxdation stability while glucose and sodium benzoate can reduce its activity; All of K+, Ca2+, Mg2+, Zn2+ and Cu2+ can affect the stability, and the order is Cu2+＞Zn2+＞Ca2+ ＞K+＞Mg2+; And freeze-drying is better to keep the antioxdant activity of peptide from Decapterus maruadsi than spray-drying.
Analysis of contents and bioavailability of minerals in food is one of the important research points in the field of food processing and food nutrition in recent years. Contents of iron, zinc and calcium in baked foods such as bread, biscuit and cake, which were collected at supermarkets in Beijing, were analyzed, and the bioavailability of these minerals was evaluated by in vitro model as well. It was shown that among the three types of baked food, bread contains the highest contents of iron and zinc, and higher calcium than cake. Bread is a potential source for dietary minerals, while biscuit is a good source for calcium. However, bioavailability of minerals in bread is the lowest. Bioavailability of iron and zinc in cake, and that of calcium in biscuit is the highest.
Rheological properties of xanthan and welan gums were studied, and their viscosity affected by concentration, temperature, shearing rate, pH, freezing-thawing and cold store was compared in this study. A novel kind of microbial exopolysaccharides, welan gum shows wide application future due to its high temperature stability, pH tolerance and good environment-friendly properties.
Antioxidative Activity of Extracts from Viola tianshanica Maxim. was measured by Na2S2O3-I2 titrimetric method. The results showed that the antioxidative activities decreased in the order of 85% ethanol solution extracts ＞ acetone extracts ＞ chloroform extracts ＞ ethyl acetates extracts＞ methanol anhydrous extracts ＞n-hexane extracts.The amount of extracts used is directly inproportion to the anti-oxidative effect.When the control experiment was performed by using VC and VE, it is showed that 85% ethanol solution extracts of Viola tianshanica Maxim.(0.5%W/V) have stronger antioxidant activity than 0.02%VC(W/ V), but 0.02%VE(W/V) have no antioxidant activity.
Objective: To clone, express and identify the gene of Gal d 3 in eggs. Methods: The total RNA was extracted from eggs, and the gene of Gal d 3 was amplified by RT-PCR and cloned into pMD18-T for sequencing. Then the interesting gene was subcloned into pET-28a for expression. After purification of the recombinant protein, its IgE-binding capacity was determined by Western blotting. Results: The gene of Gal d 3 in eggs is obtained by clone, which has 2118 bp and encodes 705 amino acids. This isoelectric point of the encoded protein is 6.5 with a molecular weight of 76000. Conclusion: The main allergen gene Gal d 3 in eggs is successfully cloned and expressed in this study, and this recombinant protein shows good IgE-binding capacity.
L-lactic acid is increasingly used as feedstock for potential biodegradable plastics. With the aim to achieve efficient production and high productivity, it is important to optimize the fermentation process for an industrial strain, genome shuffled strain Lc-F34. Temperature and pH play important roles in the lactic acid batch fermentation process. Their effects on L-lactic acid production were studied using central composite design. According to the regression model, the maximum L-lactic acid yield can be obtained at pH 5.5 and 40.2 ℃.
This study aimed to optimize the fermentation conditions for nattokinase production by Bacillus subtilis Natto with response surface methodology. Firstly, Plackett-Burman design was used to evaluate the effects of related factors on nattokinase production. It was found that soybean powder concentration is the most signficant positive factor, followed by concentrations of glucose and CaCl2 (negative factor). And then, the concentrations of soybean powder, glucose and CaCl2 were further optimized using response surface analysis. Results revealed that the optimal medium constituents for liquid fermentation are as follows: glucose 1%, soybean powder 3%, KH2PO4 0.2%, K2HPO4·3H2O 0.26%, MgSO4·7H2O 0.1% and CaCl2 0.12%. The optimized conditions allow nattokinase production to increase from 1800 U/ml to 2226.06 U/ml.
Lactobacillus acidophilus and traditional lactic acid bacteria were adopted to make fermented soybean milk. Effects of adding ascorbic acid in culture medium on the survival of probiotics were studied in fermented soybean milk. The results showed that adding ascorbic acid could keep the best survival of probiotics. Under the conditions of 39 ℃, fermentation starter amount 6% and ascorbic acid amount 0.01%, the flavor of the obtained fermented soybean milk is better, and its nutritive value is also higher. The survival number of probiotics is 6.3×108 CFU/ml.
Two strains of fungi (C4 and G1) producing high activity xylanase were isolated by soil dilution coating method and through primary and repeated screening. Furthermore, the optimum carbon source for their growth and enzymological properties of xylanases produced by them were studied. The results showed that the best carbon source for strain C4 producing xylanase is the mixture of corncob and bran. The xylanse activity produced by strain G4 reaches the peak after cultivation for 24h, 6582. 29 U/ml. The optimum reaction temperature of the xylanse is 40 ℃ and it is relatively stable below 50 ℃. Its optimum reaction pH is 5.0 and it shows good pH stability; The best carbon source for strain G1 producing xylanase is corncob. The xylanase activity produced by strain G1 reaches the peak after 96 hours of cultivation, 6301.04 U/ml. The optimum reaction temperature of xylanase produced by strain G1 is 40 ℃ and it is stable below 40 ℃. The optimum reaction pH is 5.0, but its stability is less than that of xylanase produced by strain G4.
The comparison among the activities of isoflavone-glucosidases isolated from 32 species of plants showed that chickpea (Cicer arietinum)β-glucosidase activity is the highest. Then the chickpea β-glucosidase was purified by 10.1 folds with the yield of 7.2% after ammonium sulphate precipitation, DEAE-Cellocuse -52 ion exchange and Sephadex G-100 gel filtration chromatography. This purified enzyme has a molecular weight of about 73.2 kD and two subunits. The optimum temperature, pH and Km towards genistin and daidzin of this enzyme are 45 ℃, 6.0, 11.0 μg/ml and 19.0 μg/ml, respectively. This β- glucosidase is stable at pH and temperature range of 4.0 to 6.5 and 30 to 45 ℃ respectively. Furthermore, this enzyme can effectively hydrolyse genistin and daidzin, but be strongly inhibited by Ag+, Hg2+ and D-glucono-δ-lactone at a concentration of 1 mmol/L.
α-Amylase was immobilized on five 3-aminopropyl silica gels with glutaraldehyde as crosslinking agent. Some factors that affect the activity of immobilized α-amylase were investigated, such as the mesh of silica gel, concentration of glutaraldehyde, reaction temperature and pH. The properties of imm obilized and free α-amylases were also compared. The results indicated that the optimum temperature of the immobilized enzyme is 75℃, which is 10℃ higher than that of the free α-amylase, and its thermal stability is better than that of free enzyme. Compared with free α-amylase, the immobilized α-amylase is also markedly improved in acid and alkaline stability, storage stability and operation stability. Furthermore, the Michealis constant (Km) of immobilized α-amylase is 2.13 mg/ml, while that of free α-amylase is 1.02 mg/ml.
