Abstract:Chronic wounds are characterized by complicated pathogenesis, easy recurrence, long treatment time, great difficulty, high cost and high disability rate which have serious negative impacts on the life quality of patients. The treatment of chronic wounds is one of the difficult problems of wound treatment today. Wound dressings play a key role in wound treatment, especially the functional dressings with biomacromolecules as matrix components. Because of good biocompatibility, biodegradability, low toxicity and other biological characteristics, biomacromolecules can be made into various biological dressings for chronic wound repair, and can be modified or compounded with enhanced performance as a dressing. This article reviewed the research progresses of biomacromolecule-related properties and the applications of biomacromolecule dressings in chronic wound repair. It indicates that biomacromolecule dressings have great application prospects in chronic wound repair, providing ideas and help for clinical research of biomacromolecule dressings.

Abstract:Antimicrobial peptides(AMPs) are small molecules of natural innate immune system against the exogenous pathogenic microorganisms. AMPs are found in a variety of organisms and possess broad-spectrum activity, capacity of inhibiting the proliferation of multidrug-resistant bacteria, stable activity, low immunogenicity, green pollution-free characteristics and so on. AMPs show great potential in food storage and preservation. The functions, preparation, antibacterial mechanism and application of AMPs in food storage and preservation were summarized and analyzed in order to provide ideas for the development of targeted new food preservatives.

Abstract:Pyruvate is widely used in pharmaceutical, agrochemical and chemical industries. Two strategies were used to improve the efficiency of bioconversion to pyruvate. First, the efficiency of adenine dinucleotide(FAD) synthesis was improved by expressing cytochrome b562, reducing the reaction time from 27 h to 21 h and increasing the productivity by 28.5%. Secondly, the directional evolution of L-amino acid deaminase(pm1) was achieved by site-saturation mutagenesis to improve its catalytic ability, and the yield of pyruvate in the triple mutant E418A/V438I/L278I was 25.58 g/L, which was 44.60% higher than that of the control strain. All the results showed that the efficiency of pyruvate produced by E. coli whole-cell biocatalyst could be effectively increased by the improvement of pm1 catalytic ability and FAD synthesis efficiency using site-saturation mutagenesis and expressing pm1 chaperone (cytochrome b562).

Abstract:4-Hydroxyisoleucine(4-HIL) is a promising drug that promotes insulin secretion, improves peripheral tissue resistance to insulin, and regulates dyslipidemia. L-isoleucine hydroxylase (IDO) is commonly used in the production of 4-HIL. First, the L-isoleucine hydroxylase derived from Bacillus thuringiensis was cloned, and successfully expressed in E. coli BL21(DE3). Secondly, the site-directed mutation of I156 locus was achieved through homology modeling and protein structure analysis based on the principle of changing the amino acid residue bound to the supstrate side chain from the hydrophilic or long-chain hydrophobic structure to Ala. The mutation aimed at increasing the supstrate binding pocket and widening the supstrate channel to increase the yield of 4-HIL. Finally, the biochemical properties of wild-type and mutated enzymes were studied. The hydroxylation reaction system of mutated enzyme was studied. Under the optimal catalytic conditions, the supstrate was fed in batches to produce 4-HIL. The results of enzymatic properties showed that the optimum temperature and pH of wild-type enzyme and mutated enzyme I156A were 25 ℃ and pH 7.0, and the I156A mutated enzyme activity was 1.9 times higher than that of the wild-type enzyme with 28% increased L-ILe conversion rate. The optimal conversion conditions for the hydroxylation reaction system were: 20 mmol/L L-ILe, 20 mmol/L α-ketoglutarate, 8 mmol/L Fe²⁺, 30 mmol/L ascorbic acid, and HEPES (50 mmol/L, pH 7.0) buffer. Under the optimal transformation conditions, the recombinant E. coli BL21/pET28a-ido^I156A was fed in batches for a time interval of 4 h. After 32 h, 77.3 mmol/L 4-HIL was obtained, and the highest conversion rate of supstrate was 98.35%.

Abstract:With people's attention to nutrition and health care functions, the prediction of grain protein function has become a research hotspot. Faced with large amounts of sequenced cereal protein genome data, the use of computational methods to predict grain protein function has become the mainstream. For the first time, the MIMLRBF algorithm was applied to protein function prediction from the grain protein domain sequence. Based on this algorithm, several improved grain protein function prediction models were proposed. Among them, an automatic adjustment coefficient for the average Hausdorff distance was introduced to calculate the similarity between proteins aiming to solve the problem that the average Hausdorff distance weakened the shortest domain distance between two proteins. At the same time, in order to improve the prediction effect, the improved MIMLRBF algorithm model was obtained using the improved hybrid radial basis kernel function to activate. Finally, the improved MIMLRBF was confirmed to be better than the traditional prediction based on the evaluation of prediction results using mainstream evaluation criteria, which proved the superiority of the proposed model.

Abstract:Lysine, as a primary metabolite, is normally produced by Corynebacterium glutamicum, and its synthesis is closely related to intracellular NADPH levels. However, the regulatory mechanisms between L-lysine biosynthesis and the cofactor NADPH in C. glutamicum are still poorly understood. In this paper, the lysine-producing strain C. glutamicum XQ-5 was used as the starting strain, and the recombinant strain C. glutamicum XQ-5Δzwf::pgi with low NADPH levels was constructed by blocking the pentose phosphate pathway, reducing the intracellular NADPH level in each 10⁴ cells from 3.57×10^-8 μmol to 1.12×10^-8 μmol. In addition, the recombinant strain C. glutamicum XQ-5Δpgi::(zwf-gnd) with high NADPH level was constructed by enhancing the pentose phosphate pathway. It increased the intracellular NADPH level in each 10⁴ cells from 3.57×10^-8 μmol to 1.8×10^-7 μmol. Cell growth, bacterial mass and intracellular by-product accumulation of strains under different NADPH levels were significantly different through shake-flask fermentation. Based on the results of transcriptomics and other experiments, the expression level of the panD gene in the recombinant strain C. glutamicum XQ-5Δpgi::(zwf-gnd) was significantly increased. The lysine production of recombinant strain C. glutamicum XQ-5ΔpanDΔpgi::(zwf-gnd) with inactivated panD gene increased to 55 g/L, an increase of 14.3% to the original strain C. glutamicum XQ-5, which suggested that the increased expression level of panD gene was one of the reasons for the decline in lysine levels based on the over-expression of pentose phosphate pathway. This study provides a solid theoretical basis for further studies on the regulation mechanism of cofactor NADPH on L-lysine biosynthesis.

Abstract:The sterilizing effect of individual sodium hypochlorite (NaClO), chlorine dioxide (ClO2) and peracetic acid(PA) on fresh-cut coriander were investigated. The results showed that the most effective disinfectant agent for fresh-cut coriander was ClO2 with the aerobic plate count in the range of (2.08~2.79) lg(CFU/g). NaClO took second place with the range of (1.43~2.29) lg(CFU/g), and peracetic acid(PA) was the weakest disinfectant agent. The results based on single-factor and orthogonal experiments indicated that the optimum conditions for treating fresh-cut coriander with chlorine dioxide were concentration of 60 mg/L, time of 10 min and solution to fresh-cut product ratio of 8 mL : 1 g. Based on 16S rDNA high-throughput sequencing technology, seven bacterial species were isolated and identified from fresh-cut coriander, which were <>iErwinia, Pseudomonas, Aeromonas, Acinetobacter, Rahnella, Rhizobium and Enterobacter. ClO² could effectively reduce three bacterial species, which were Rhizobium, Acinetobacter, and Aeromonas.

Abstract:To make up a defect of current food safety testing technology, gas chromatography-mass spectrometry technology (GC-MS) combined with headspace solid phase microextraction (HS/SPME) was established to explore the volatile metabolites of Aspergillus flavus. Then the differential metabolites and their metabolic pathways of Aspergillus flavus in dried bean curd were analyzed by metabonomics and genomics approaches. The results showed that the differential metabolites of Aspergillus flavus contained 1,2,3-trimethyl-benzene, mesitylene, ethanol, methyl hexadecanoate, 2,4-ditert-butylphenol, acetic acid, trichloromethane, 1-butanol and 1-methyl-3-(1-methylethyl)-benzene. Particularly, acetic acid, ethanol and 1-butanol played key roles in the metabolic network of Aspergillus flavus.