Abstract:The green biomanufacturing of nutritional chemicals is an important guarantee for sustainable development. The technological development and application of this field are expected to bring disruptive technological changes in food, pharmaceutical, chemical and agricultural industries. In this paper, we summarized the progress of bioinformatics, genome editing technology, system metabolic engineering strategy and enzyme engineering technology in the field of biomanufacturing of nutritional chemicals. Furthermore, the biological manufacturing methods of functional sugars, amino acids, functional lipids, vitamins and flavonoids were briefly described. Finally, the possible challenges in the future of biomanufacturing of nutrient chemicals were prospected. It is expected to provide a reference and support for promoting the competitiveness of green biomanufacturing.

Abstract:The research progress of Saccharomyces cerevisiae as a chassis cell for metabolic regulation and synthesis of functional nutrients was summarized in this review. Firstly, a series of metabolic regulation strategies related to the promoter regulation, terminator regulation, cofactor regulation, transporter regulation and dynamic regulation of Saccharomyces cerevisiae as a cell factory were introduced, and the related genetic transformation tools and metabolic analysis techniques to enhance product synthesis were also introduced. Secondly, the research progress on synthesis of functional nutrients, such as oligosaccharides, vitamins and terpenoids, short chain organic acids and fatty acids, by Saccharomyces cerevisiae was summarized. Lastly, the current challenges were put forward, and the future development trend of metabolic regulation of Saccharomyces cerevisiae was prospected in combination with the emerging technologies of metabolic engineering, in order to provide a reference for the efficient synthesis of functional nutrients in Saccharomyces cerevisiae.

Abstract:The seaweed resources are extremely abundant in China, but currently it is mainly used in a few areas, such as food, feed and health goods manufacture. Hence, the high-value utilization of seaweed resources needs to be further developed. Algal polysaccharides are important components of seaweed cell wall and possess various biological activities. However, it is difficult to be absorbed and utilized by the body due to its high polymerization, high viscosity and poor solubility. Algal polysaccharides can be degraded into oligosaccharides through physical, chemical and biological methods, resulting in significantly increased solubility and physiological activity, which makes them suitable for use in a variety of fields including food, health goods, feed and agriculture. The development of green preparation technology of algal oligosaccharides based on enzymatic process has superior advantages over traditional methods in terms of efficiency, cost and pollution. This paper reviews the research progress on the physiological activities and enzymatic conversion of marine oligosaccharides, such as alginate oligosaccharides, agar oligosaccharides, carrageenan oligosaccharides and fucoidan oligosaccharides, which could provide the basis for the high-value utilization of seaweed resources.

Abstract:Meat and meat products may have food quality degradation, nutritional function reduction, and other problems during processing and storage. It is of great significance and economic value to seek green and healthy improvers to improve meat quality. Basic amino acids have become more popular in industrial production and application, which can be as substitutes for traditional food improvers such as NaCl and NaNO₂. The effects of basic amino acids on the texture, color and tenderness of meat were summarized in this paper, and the mechanism of basic amino acids affecting meat quality was highlighted from the aspects of protein solubility, heat aggregation, gelation, oxidative stability and regulation of protease activity, providing a reference for the application and promotion of basic amino acids in meat.

Abstract:Ergothioneine(Ergothioneine, ERG) has various physiological functions such as antioxidant, anti-inflammatory and radiation protection, widely applied in food, medicine and cosmetic industries. Microbial fermentation of ergothioneine is of great potential, but engineered strains often have problems such as insufficient precursor supply, resulting in low fermentation concentration and production performance. This study aimed to explore the precursor limitation in different stages of ergothioneine synthesis, and to improve the ergothioneine synthesis capacity of Escherichia coli by optimizing precursor supply and removing the limitation. On the basis of proving that histidine was the key factor limiting the synthesis of ergothioneine, the fermentation concentration of ergothioneine at shake flask level reached 175.81 mg/L by optimizing the supply of histidine. On this basis, additions of cysteine, ammonium ferric citrate and vitamin B6 were orthogonally optimized, and the fermentation concentration was increased to 182.61 mg/L. By further optimizing the additions of methyl donors (1.5 g/L methionine and 0.6 g/L betaine) and by adding 0.2 g/dL CaCl2 to improve the permeability of the cell membrane，the final fermentation concentration of ergothioneine at shake flask level was further increased to 243.06 mg/L. Through fed-batch fermentation for 108 h, the fermentation level of ergothioneine reached 2.01 g/L in a 3 L fermenter, and the titer reached 18.61 mg/L/h. This study could lay a foundation for the large-scale industrial production of ergothioneine.

Abstract:To well understand the current research status on the relationship between food and depression, the authors determined the optimal search terms for Web of Science Database Topic retrieval. The general characteristics of literature was analyzed online, and the network clustering and co-occurrence analysis were conducted using CiteSpace software. A narrative review of key literature was carried out. The literature volume increased significantly in 2020. Most articles have been published in journals of food, and from the United States, the United Kingdom, Australia, Canada, and China with the disciplines of psychiatry, nutrition, and food science. Frontier keywords include food addiction, gut microbiota, food insecurity, etc., showing a phenomenon of 'ebb and flow' against the different citation clusters. Factors contributing to depression include dietary inflammation, eating disorders, overweight, metabolic syndrome and COVID-19. The overwhelming conclusion is that healthy eating patterns have a positive effect on depression. Developed countries are leading the research, and major traumatic events are promoting research progress. The research frontiers include food addiction, food insecurity, and gut bacteria. The research paradigm has shifted from narrow perspectives to macroscopic view, and diet is expected to become an important intervention for depression.

Abstract:L-glutamine is the most abundant semi-essential amino acid in human fluids. It has a variety of nutritional and pharmacological functions and is widely used in medicine, food additives, nutritional health products, feed and other fields. At present, microbial fermentation is the main method to produce L-Gln, but its industrial application is seriously limited by the problems of low fermentation acid production efficiency, many by-products, and lack of bacterial performance. In order to solve those problems, the L-Gln production strain CGQ03 constructed early in our laboratory was used as the starting strain in this study. The synthesis of precursor L-glutamate was promoted by enhancing the expression of glutamate dehydrogenase and the supply of cofactor NADPH. The yield of L-Gln production was increased by enhancing the intracellular content of cofactor ATP, overexpressing the dissolved oxygen-related protein VHb to improve the oxygen carrying capacity of cells, enhancing the catalytic activity of key enzyme glutamine synthetase, and optimizing the fermentation process. The final genetically engineered strain CGQ08/pDXW10-glnA^Sc-gdh^Cg was fed-batch fermented in a 5 L fermenter for 66 h, and the yield of L-Gln was up to (94.5±1.8) g/L, with the sugar-acid conversion rate of 34.8% and the production intensity of 1.43 g/(L·h). This study could provide an important reference for the industrial production ofL-Gln and its related compounds.

Abstract:Currently, the heterologous synthesis of pyrroloquinoline quinone (PQQ) in Escherichia coli is mainly achieved via plasmid vector, which is difficult to systematically optimize the synthesis pathway of multiple gene expression, and easy to cause fermentation instability. In this study, E. coli was used as the chassis organism to systematically optimize the PQQ synthesis at the genome-scale using CRISPR/Cas9 gene editing technology. The operon pqqABCDE from Gluconobacter oxydans 621H was introduced into the chassis E. coli. An engineered strain for highly-efficient synthesis of PQQ was obtained by further optimizing the gene expression strength in the synthesis pathway, knocking out the native inhibitor gene in E. coli, and enhancing the intracellular demand and extracellular transport of PQQ. A total of 86.3 mg/L PQQ was produced after 72 h fermentation in shake-flask. In this study, the construction of efficient PQQ synthesis pathway in the chassis E. coli could provide a reference for future production of PQQ or related metabolites in other chassis.

Abstract:Menaquinone-7 (MK-7) has a promising application prospect in the fields of health food and pharmaceutical manufacturing as an important vitamin of the K family. In this work, the yield of MK-7 fermentation was improved by using Bacillus subtilis 168 as the starting strain, knocking out the genes from metabolic branch pathways, screening and optimizing the mutant of speed-limited gene menA of the MK-7 synthesis pathway, and enhancing the expression of several MK-7 biosynthesis pathway genes through an artificial operon. Finally, a high-yield strain MK7-13 was developed with the yield of （73.73±1.86） mg/L, which was 9.71 times higher than that of the original strain. In summary, a high-yield MK-7 strain was successfully constructed by a combinatorial metabolic engineering strategy, which laid a foundation for the subsequent industrial production of MK-7 by microbial fermentation.

Abstract:To investigate the effect of lactic acid bacteria fermentation on the antioxidant activity of elderberry juice, the changes of antioxidant activity of elderberry juice before and after fermentation were compared by measuring the scavenging rate of DPPH, hydroxyl and superoxide anion radicals and cellular antioxidant assay. The experimental results showed that the fermentation of elderberry juice improved the scavenging ability of DPPH, hydroxyl and superoxide anion radicals, and increased the inhibitory ability of α-glucosidase and α-amylase, which proved the hypoglycemic activity of fermented juice. HepG2 cells were pretreated with phenolic substances before and after fermentation for 24 h, respectively, and then stimulated with H₂O₂. It was found that the total antioxidant capacity (T-AOC) and catalase (CAT) activity in the cells were higher than those of the control group. The relative release rate of lactate dehydrogenase (LDH) was higher than that of the blank group but much lower than that of the control group. The accumulation of reactive oxygen species in the cells was reduced. Moreover, the gene expression levels of heme oxygenase 1 (HO-1), quinone oxidoreductase 1 (NQO1), and glutamate cysteine ligase catalytic subunit (GCLC)-related antioxidant enzymes was decreased in HepG2 cells treated with H2O2 only, however, they were significantly increased in HepG2 cells pretreated with phenolics before and after fermentation at mass concentrations of 200 μg/mL and 300 μg/mL, respectively, indicating that the phenolic compounds in elderberry juice reduced the degree of oxidative damage of HepG2 cells induced by H2O2. Therefore, the changes in antioxidant capacity of elderberry juice before and after fermentation might be due to the increased gene expression levels of HO-1, NQO1 and GCLC in HepG2 cells in the presence of phenolic compounds. Thus, it could be suggested that the juice fermentation could improve the protective effect on cells.

Abstract:As the main by-products of coffee production, coffee cherry husks are rich in polyphenols. However, its comprehensive development and utilization are limited. In this study, polyphenols in coffee cherry husks were extracted, purified and characterized. The antioxidant activity was determined. The inflammatory model of Caco-2 cell induced by lipopolysacchride (LPS) was established to explore the anti-inflammatory properties of polyphenols. The results showed that the purification effect of LX-17 macroporous resin was excellent. The main components of purified coffee cherry husks polyphenols were 3, 4-dihydroxybenzoic acid (15.78 μg/mg), chlorogenic acid (37.85 μg/mg) and alkaloid caffeine (55.82 μg/mg). The antioxidant assay showed that the extracted polyphenols exhibited good antioxidant activity and showed strong scavenging activity on DPPH, ABTS+ and hydroxyl free radicals. In the inflammatory cell model, 5~200 μg/mL of purified polyphenols could inhibit the expression of proinflammatory factors (IL-6, IL-10, IL-1β and TNF-α) induced by LPS. In conclusion, this study provided a good theoretical basis for the extraction, purification and comprehensive utilization of polyphenols from coffee cherry husks.