Abstract:With the development of people's living standard, requirement for food quality has improved continuously. New technologies and concepts should be introduced to food industry, so as to fulfill the modern commercial markets. Bioengineering is the key technology of food industry, showing great effects on food raw material processing, development of food additives, and technical innovation of food antisepsis. With the implementation of the 'Healthy China 2030' plan, bioengineering will play a more important role in future. This paper summarized recent research advances in food bioengineering, which might shed light on relevant industrial upgrading in this field.

Abstract:The gut is a complex ecosystem of host cells, available nutrients and microbiota. The microbiota have close relationship to the host nutrition, metabolism, physiology and immunity, and their disorder will lead to various diseases. Clinical tests indicate that lactic acid bacteria (LAB) with probiotic function can cure or relieve many diseases. This review described three methods for quantifying homeostasis of gut microbiota and their application and elaborated the effect of LAB with probiotic function on the gut microbiota homeostasis of obese and healthy hosts. This literature also pointed out the possible beneficial mechanisms: 1) competing with the pathogenic bacteria in the intestinal tract to bind the site or secreting substance to inhibit the growth of pathogenic bacteria; 2) secreting metabolites to provide livable environment for growth and reproduction of beneficial symbiotic bacteria in the intestinal tract; 3) creating imaginary enemies to stimulate the host immune response. The significance of balancing the host gut microbiota homeostasis was also discussed. Finally, perspectives for probiotic LAB were summarized, and in the future research of probiotic LAB should be personalized, considering not only the individual difference of test population but also the difference among the strains.

Abstract:The acid accumulation caused by carbon metabolism seriously affects the metabolic activity of microbial cells. In order to improve acid tolerance of cells, the acid tolerance of recombinant strain was studied by overexpression of the thiamine transporter ThiT. Based on this, comparative and recombinant strains were studied by comparative transcriptomics. We found that the survival rate of recombinant strain was 2.4 times higher than that of the control strain after 3 h of treatment with acid stress (pH 4.0). Transcriptomic analysis found that overexpression of the ThiT transporter increases the ability of cells to transport carbohydrates, thereby providing more energy for the cells against acid stress tolerance. In addition, significant upregulation of oligopeptides, betaine and other related transporters can help cells resist the damage of acid stress. The authors explored the specific mechanism of ThiT transporter in Lactococcus lactis to increasee tolerance of cellular acid stress. This study provided a theoretical basis for the application of ThiT protein in other industrial microorganisms.

Abstract:The study aimed to investigate the uric acid lowering activity of chicken breast hydrolysate enriched with anserine in mice with hyperuricemia. Different sources of hydrolysates enriched with anserine were administrated with different doses to hyperuricemia mice induced by potassium oxonate. The effects of anserine on organ index, serum levels of uric acid (UA), creatinine (CRE) and urea nitrogenand (UN), activities of hepatic xanthine oxidase (XOD) , adenosine deaminase (ADA), aspartate transaminase (AST) and alanine transaminase (ALT), and the content of triglyceride were studied in hyperuricemia mice. Results showed that anserine could effectively alleviate the liver and kidney index. The medium dosage in sample 1 and sample 2 had the most obvious effect, and could effectively reduce the levels of UA, UN and CRE in serum, and the effect was better than allopurinol. Both sample 1 and 2 could inhibit the liver ADA activity in mice, and the effect was not significantly different from allopurinol. However, only the low dosage in sample 1 could significantly reduce XOD activity. Sample 1 could significantly reduce ALT activity, and low dose reduced enzyme activity more than allopurinol, high dose could significantly reduce AST activity. The effect of chicken breast hydrolysate on liver TG content was consistent with the trend of XOD, which confirmed the correlation between TG content and XOD activity. Therefore, chicken breast hydrolysate enriched with anserine can effectively reduce uric acid levels and alleviate hyperuricemia in mice.

Abstract:New recoverable antibacterial microspheres were fabricated by chitin, and the antibacterial effect of microsphere was studied to extend the application of chitin in fields such as food bacteriostatic preservation. Silver-magnetic chitin microspheres (Ag-Fe _{3 O 4 -NMs) were prepared by sol-gel and in-situ synthesis methods. The microspheres were characterized and the antibacterial effect was studied on Escherichia coli and Staphylococcus aureus. The results showed that the antibacterial agent was 3D-porous nanofibrous spheres with magnetic beads and AgNP being embedded in the fiber structure. The AgNP in the microspheres could be released quickly and continuously, which showed a concentration-dependent antibacterial activity by destroying the structural integrity of the two test bacteria.}

Abstract:In order to improve the quality of frozen large yellow croaker, breeding large yellow croaker was selected for the project. Based on unpackaged air circulation freezing (UAF-0), vacuum film packaging air circulation freezing (PAF-1), the study compared the differences of freezing rate, physical and chemical properties of large yellow croaker between vacuum film packaging cold storage cycle freezing(PLF-1) and unpackaged refrigerant circulating freezing(ULF-0). The results showed that although the time for maximum ice crystal formation in the PLF-1 mode was 44 minutes longer than that in the ULF-0 mode, the myofibril microstructure of large yellow croaker was relatively clear, the muscle tissue damage and chromatic aberration change were relatively small, and hardness, elasticity, chewiness and recovery were only decreased by 6.8%, 1.2%, 1.2% and 1.9%, respectively. Neither the change of pH nor the decrease of salt soluble protein content was obvious( P >0.05), the rising rate of TVB-N was the slowest. Comparing the large yellow croaker quality of four freezing methods, the following was the order from good to bad: PLF-1>ULF-0>PAF-1>UAF-0.

Abstract:Particle size is a critical factor for capture efficiency (CE) of immunomagnetic beads (IMBs). IMBs were prepared by conjugating micrometer size (1 μm) or submicrometer size (300 nm)of superparamagnetic beads with anti- Salmonella polyclonal antibody. The amount of coupled antibody and the recovery rate were measured by flow cytometer and spectrophotometer, respectively. The results showed that compared with micron-IMBs, submicron-IMBs had a higher amount of coupled antibody and a higher recovery rate in buffer, and the CE was higher (300 nm: 55%, 1 μm: 41%). However, submicron-IMBs had a lower recovery rate in milk, which led to asignificant reduction of the CE of submicron-IMBs(300 nm: 15%, 1 μm: 26%). Therefore, the particle size of IMBs should be determined according to the volume and viscosity of samples.

Abstract:The study aimed to investigate the decolorization and detoxification abilities of laccase from Pycnoporus sp.SYBC-L3 for azo dyes and optimize decolorization reaction conditions.The effect of different reaction conditions on the decolorization of three azo dyes catalyzed by Lac-L was studied by single factor analysis, and the toxicity change was investigated by comparing the effect of dyes before and after degradations on the germination and the growth of roots and buds of wheat and rice. The results showed that the optimum treatment conditions were as follow： HBT as mediator, reaction temperature at 50 ℃ and pH at 4.0（AR1,RV5R）or 5.0（RB5）, 1 U/mL of laccase dosage, initial dye concentration at 30 mg/L（AR1）or 50 mg/L（RB5、RV5R）. Under the optimized conditions, AR1 and RV5R were almost completely degraded with decolorization rates of 96.1% and 97.8%, while RB5 also had a decolorization rate of 83.8%. Plant toxicological experiments showed that the three azo dyes had no effect on the germination rate of wheat and rice after degraded by laccase, and the inhibition on the growth of germ and root was also reduced.

Abstract:In order to improve the quality of Luzhou-flavor liquor, the yeasts were isolated by traditional microbial separation from the distiller's grains. The strain with high yield of ester was screened by liquid fermentation and identified by physiological biochemical tests and 26S rDNA homology analysis. Finally, the Box-Behnken center combination method was used to optimize the culture conditions for the strain. The results showed an aroma-producing yeast, numbered S5, was isolated from the distiller's grains and identified as Wickerhamomyces anomalus. The optimal fermentation was obtained under the following conditions: initial pH 4.95, fermentation time 3 d, the initial sugar content 6 g/dL. Under the conditions, the total ester content was 7.67 g/L, which was more than 64.2% than that before optimization. Thus the strain can be used to improve the quality of Luzhou-flavor liquor.

Abstract:To prepare high sesaminol sesame oil, a screening was performed to select an enzyme having the strongest ability to yield sesaminol by aqueous enzymatic method. Based on single factor test and response surface methodology, the optimal aqueous enzymatic extraction conditions of high sesaminol sesame oil were obtained as following: Aromase H2, reaction temperature 55 ℃, pH 4.5, time 9.2 h, enzyme dosage 1% and the ratio of solid to liquid 1∶1.3. Under the optimized condition, the content of sesaminol in sesame oil was increased up to 3 000 mg/kg. The total amount of lignans was increased by nearly 23%.

Abstract:Aroma-producing yeasts play an important role in the flavor formation of Pixian bean paste. In the study, yeast strains were screened from traditional Pixian bean paste and a strain with prominent alcohol and aroma-producing abilities was selected for further investigation of its growth characteristics under different salt concentrations, pH and temperatures. The results showed that most yeast strains screened from Pixian bean paste were Zygosaccharomyces rouxii while Kodamaea ohmeri, Pichia kudriavzevii, Saccharomyces cerevisiae and Hyphopichia burtonii also existed. Zygosaccharomyces rouxii BP02, the selected aroma-producing strain, was able to grow in the pH 3~8, temperature 10~37 ℃ and endured salt concentration up to 20%. The optimum growing condition for strain BP02 was 5% NaCl, pH 4~6 and 37 ℃. It was concluded that the obtained aroma-producing yeast BP02 grew well under the condition of high-salt, subacidity and moderate temperature that resembles the environment for Pixian bean paste fermentation. Therefore, strain BP02 can be inocualted into Pixian bean paste during moromi or post fermentation period to improve the flavor quality of the final product.

Abstract:Cinnamon essential oil has antibacterial and antibacterial functions, but its application is limited due to its poor water solubility, volatilization and poor stability. The oil-in-water emulsion was prepared by dissolving cinnamon essential oil in the medium chain fatty acid and using emulsifiers of Span 20 and Tween 80. By changing the mass fraction (0%~2.5%) of cinnamon oil, an emulsion with particle size distribution of 50~280 nm could be obtained. Centrifugation experiments showed that the emulsion was stable and suitable for utilization at temperatures below 40 ℃.After storage at 25 ℃ for 10 d, the particle size and dispersion coefficient of the emulsion were almost unchanged.In addition, the bacteriostatic effect of emulsions with different particle sizes was determined by turbidimetry. It was found that the cinnamon oil emulsion with a particle size of 150 nm had the best inhibitory effect on Escherichia coli and Staphylococcus aureus.

Abstract:The enzymatic hydrolysis conditions of ovalbumin from duck eggs were investigated through orthogonal test, and the optimal hydrolysis conditions were determined by taking the hydrolysis degree as the index: the amount of papain 4.5×104 U/（g·min）, hydrolysis time 5.5 h, temperature 55 ℃, pH 6.40. With the optimal conditions, the hydrolysis degree was 27.91%. The molecular weight distribution ranges of hydrolysate were determined by HPLC: 0w<300(33.71%), 300w<450(29.21%), 450w<1 450(20.42%), 1 450w<6 500(0.49%), 6 50012 500(11.12%). Its biological activity was further studied. Hydrolysate (250 μg/mL) significantly increased the secretion of NO, cytokines TNF-α and IL-6 in RAW 264.7 cells (P<0.05), showing a certain immunological activity. Meanwhile, the inhibition rate of 1 000 μg/mL hydrolysate for AAPH induced erythrocyte hemolysis was （53.95±1.82）%(P<0.05), the scavenging rates of DPPH and ABTS+·free radical were （31.92±0.54）% and （86.46±2.12）%, and the ORAC value was 0.357 4 μmol/mg, indicating that the hydrolysate also had a good antioxidant activity in vitro.

Abstract:L-asparaginase II (EC 3.5.1.1), which can convert L-asparagine, the precursor of carcinogenic acrylamide, to L-aspartic acid, is attracting much attention in food industry. The use of L-asparaginase II can reduce the formation of acrylamide during the pretreatment of foods. However, the application of this enzyme is limited due to variant requirements of commercial use, especially for its activity and thermostability. In this study, by sequence aligning and homology modeling,three mutants of PyAsnase gene from the thermophilus Pyrococcus yayanosii CH1was constructed and over-expressed in Bacillus subtilis. According to the results, the specific activities of the mutants E22K and R111L were increased by 37.3% and 31.1%, respectively, and the half-life of the mutant obtained by the mutant M92A was extended by 30 min at 85 ℃. This work provides references for studying the interrelationship between function and structure of L-asparaginase, and also develops the application of L-asparaginase in food industry.

Abstract:A visualized microarray for rapid detection of nucleic acid of three food-borne pathogenic bacteria was developed. Substrate and detection probes which were complementary to both ends of Salmonella invA, Staphylococcus aureus nuc and Shigella ipaH genes were designed, respectively. Specific target sequences of three genes were also designed. One end of the specific target sequence or genomic DNA was hybridized with the amination probe fixed on the slide, and the other end was complementary to the sulfhydrylation probe to form a complex. The detection probe was connected with colloidal gold, and the signal was amplified by silver staining for the detection of food-borne pathogenic bacteria. Through comparative analysis of hybridization silver staining with genomic DNA, PCR products and specific target sequences, all results were positive, which demonstrated that the method could directly use genomic DNA to detect food-borne microorganisms rapidly and efficiently. The detection limit of genomic DNA of three foodborne pathogenic bacteria was 1 pmol/L, and clear results could be observed by naked eyes in the concentration range of 1 mmol/L ~1 pmol/L. The results of hybridization between probe and genomic DNA indicated that visual microarray had good specificity for the detection of microorganisms. Therefore, this method can detect food-borne microorganisms quickly and easily, and has broad market prospects.