Microalgae are photosynthetic autotrophic single-celled aquatic organisms, which can synthesize lipids, proteins, astaxanthin, and other bioactive components. Microalgae are rich in protein with high nutritional properties that can regulate body health, prevent and treat diseases, etc., and have broad development prospects in food, medicine, cosmetics, and other fields. The key to protein extraction from microalgae is the efficient lysis of its cell wall, aiming at releasing the protein in the microalgae cell fully. Therefore, based on the common microalgae cell wall disruption technology, the extraction methods of microalgae protein were compared and analyzed systematically. The purpose of this study was to explore the extraction methods of microalgae protein, which were easier to industrialize, had higher wall-breaking efficiency and more economical process, and obtained protein with better quality. It is expected to guide the further development and utilization of microalgae protein, as well as increase its commercial value.

L-alanine is an important natural amino acid, which is widely used in medicine, food and feed industries. At present, L-alanine is mainly produced by Escherichia coli. It is of great significance to develop safe and industrially robust Corynebacterium glutamicum production strains. In this study, exogenous alanine dehydrogenase was optimized to synthesize L-alanine efficiently without using other amino acids as an amino donor. The non-phosphotransferase system glucose uptake pathway was strengthened by the simultaneous inactivation of the transcriptional repressor IolR and overexpression of the glucose kinase, which drastically promote the cell growth and L-alanine synthesis. The introduction of exogenous Entner-Doudoroff pathway that supply pyruvate only through 4-step reactions, an alternative to the 10-step Embden-Meyerhof-Parnas (EMP) pathway, further increased the production of L-alanine. In addition, in order to avoid the use of antibiotics and guarantee the genetic stability of the producer, essential genes were integrated into the genome of the strain. The final engineered strain produced 104 g/L L-alanine after 48 h fermentation in a 5 L fermenter. The study lays a solid foundation for the industrial production of L-alanine by C. glutamicum, and provides a reference for the metabolic engineering of other microbes to produce products derived from pyruvate.

Improving stress tolerance by functional genes is very important for efficient utilization of cellulose hydrolysate to produce ethanol. Candida glycerinogenes is an industrial strain with multiple stress tolerance. The rRNA methyltransferase gene CgBmt5 was obtained by screening of the genomic library. Overexpression of CgBmt5 in Saccharomyces cerevisiae improved acetic acid tolerance, and the ethanol yield of the recombinant bacteria reached 60.5 g/L with an increase of 17.7% under acetic acid stress. In C. glycerinogenes, overexpression of CgBmt5 also enhanced ethanol yield by 17.6% under acetic acid stress. Besides, the ethanol yield per cell, glucose conversion, and production intensity of both recombinant strains were improved. The ethanol yield, glucose conversion rate, and production intensity were improved by 71.7%, 65.0%, and 155.7%, respectively, using cellulose hydrolysate as substrate. Under acetic acid stress, the lipid peroxidation level of overexpressed strain was decreased, and the activities of superoxide dismutase (SOD) and catalase (CAT) were increased. Transcriptional analysis showed that Pfk1 and Arg3 genes were up-regulated, and Gpd1 and Cox3 genes were down-regulated in the C. glycerinogenes CgBmt5, suggesting that CgBmt5 may promote acetic acid tolerance and fermentation performance by reducing lipid peroxidation levels, increasing SOD and CAT activities, and affecting glucose metabolism and arginine synthesis. This study provides new information for the stress tolerance of yeast and the development of cellulosic ethanol technology.

D-tagatose, the isomer of D-galactose, the C-3 epimer of D-sorbitol, and the C-4 epimer of D-fructose, is a natural low-calorie functional sweetener, with sweetness of 92%, and calories of 33.3% of sucrose (the caloric value is 1.5 kcal/g). D-tagatose protects against dental cavities and obesity, lowers blood sugar, and is good for gut health. In this paper, the physiological functions and applications of D-tagatose are briefly described, the biological enzyme L-arabinose isomerase mainly required for the biosynthesis of D-tagatose is introduced, the research progress of D-tagatose biosynthesis in recent years were summarized, and the future for D-tagatose biosynthesis are prospected.

The changes of microbial community structure and biomass of different layers of Daqu for the production of special-flavor Baijiu (Te-Daqu) and its correction with flavor compounds are not well understood. In this study, the absolute quantitative and relative quantitative amplification sequencing techniques were used to determine the microbial compositions as well as their changes of different layers of Te-Daqu. Moreover, microbial source tracking was used to analyze the origins of dominant bacteria and fungi. Headspace solid phase micro-extraction combined with gas chromatography-mass spectrometry was used to analyze the content of flavor compounds in different layers of Te-Daqu. The results showed that the total bacterial biomass in core of Te-Daqu was significantly lower than that of surface-layer and middle-layer, i.e, was 55% of that of surface-layer and 53% of that of middle-layer. Weissella, Lactobacillus, and Enterobacter were the dominant bacteria within the surface-layer. Thermoactinomyces was the specific bacteria of the core-layer, whereas Saccharopolyspora only dominated in the middle- and core-layer rather the surface-layer. Isatchenkia and Pichia were the main yeasts within the surface-layer, while Aspergillus was the dominant mold within the core-layer. The total contents of alcohols, aldehydes and ketones, pyrazines, ethers, and phenols in the core-layer were higher than that in the surface- and the middle-layers, while the total contents of esters in the surface-layer were higher than that in the core-layer. These results provided an essential reference to optimize the Te-Daqu making process and to improve the quality of Te-Daqu by using ecological fermentation technology.

Seasonings have an important effect on the quality of Fengdu spicy chicken. To evaluate the flavor characteristics of Fengdu spicy chicken seasonings, the numbing and spicy intensity, aroma components, and sensory characteristics were analyzed by HPLC, electronic nose, GC-MS, and sensory evaluation. Results showed that the contents of sanshool and capsaicinoids in Fengdu spicy chicken seasonings from different manufacturers were 0.023-4.053 mg/g and 0.123-0.471 g/kg, respectively. Their intensity of numbing and spicy difference was significant. An electronic nose combined with principal component analysis could be used to quickly distinguish Fengdu spicy chicken seasonings from different manufacturers. A total of 81 volatile components were detected in Fengdu spicy chicken seasoning. The difference in composition and proportion resulted in different flavor of Fengdu spicy chicken products from different manufacturers. 13 main aroma components were screened out by odor activity value (OAV) analysis, including myrcene, linalool, (Z)-2-decenal, D-limonene, and linalyl acetate. The sensory scores of S4, S8, and S9 were significantly higher than those of other samples, and their spicy taste was more coordinated and palatable. On the whole, the numbing and spicy intensity and aroma of Fengdu spicy chicken seasonings from different manufacturers were different. Combined with the results of the numbing and spicy intensity analysis and sensory evaluation, the intensity of numbing (1.512-4.053 mg/g) and spicy (0.184-0.200 g/kg) may be the more suitable range for Fengdu spicy chicken seasoning. The overall flavor of Fengdu spicy chicken seasoning was mainly fatty, floral, and spicy.

To compare the effects of different types of rapid descriptive analysis methods for sensory evaluation, Napping combined with ultra-flash profiling (Napping-UFP), free choice profiling (FCP), and polarized sensory positioning (PSP) were performed on Douchi samples from different origins. The results showed that the same samples were located close to each other on the sample loading diagrams, revealing the high accuracy of the methods. The distributions of sample plots of the three methods were similar, and Douchi from different origins could be distinguished by three methods. Meanwhile, the adjusted RV coefficient (ARV) were all above 0.750, further indicating the three methods were relatively well correlated. The best agreement was obtained between PSP and FCP, but PSP could not provide descriptors. The Napping-UFP and FCP methods could provide sensory characteristics of the products. In summary, the rapid descriptive analysis methods represented by Napping-UFP, FCP and PSP can quickly distinguish samples, as well as obtain the differences of sensory characteristics among products effectively and accurately, which have broad application prospects in the field of food sensory evaluation.

Taro is the staple food of residents in Africa and parts of Asia, and also an important source of carbohydrates. It has a long history of cultivation and consumption in China. Modern pharmacological research shows that non-starch polysaccharide is an important active ingredient in taro, which has the effects of immune regulation, anti-oxidation, hypoglycemia, and hyperlipidemia, which could stimulate the application potential of taro polysaccharides in food, medicine, and other fields. This paper reviewed the extraction, purification, structure characterization, functional activity, and application of taro polysaccharides in China and abroad in recent years, providing a reference for further research, development, and application of taro polysaccharides.

Ribosome binding site (RBS) is an important biological control element for fine-regulation of genes expression, which has been widely applied in microbial metabolic engineering and synthetic biology. Corynebacterium glutamicum is an important industrial microorganism for industrial fermentation of several amino acids and organic acids. However, there were few researches on the RBS element for C. glutamicum. In this study, a random RBS library was designed and constructed based on the common RBS characteristics in C. glutamicum. Then, a high-throughput screening technology was developed by coupling flow cytometry and 96-well plate screening technology for screening of the artificial RBS library. After two-step screening, an artificial RBS element library with wide range of regulation and uniform coverage was constructed, and the regulation strength range of the library was 29.04-fold. Next, the artificial RBS library was further characterized by α-amylase expression system, and the results showed that the RBS library had high stability and versatility. Subsequently, the artificial library was applied for the regulation and optimization of the L-homoserine biosynthetic pathway. The expressions of LysC^r and Hom^r, the key enzymes in L-homoserine synthesis pathway, were fine-regulated using RBS elements with different intensities. Finally, the best combination of LysC^r and Hom^r for L-homoserine synthesis was obtained, and the resulted strain accumulated 12.7 g/L of L-homoserine, which was 3.6 times higher than that of the wild-type strain. Therefore, an artificial RBS library was constructed and exhibited wide regulation range and high stability in this study, which provided the effective control elements for metabolic engineering and gene expression regulation in C. glutamicum.

L-serine is widely used in medicine, food and cosmetic industry, however, the industrial production of L-serine by microbial fermentation has not yet been realized. In previous studies, we found that there had a significant difference in L-serine titer by Corynebacterium glutamicum A using sucrose and glucose. In this paper, comparative metabolomics analysis method was used to study the differences of intracellular metabolites of C. glutamicum A in different carbon sources, revealed the key metabolites of L-serine synthesis, and then investigated the influence of the addition of key metabolites on L-serine production. Through GC-MS, principal component analysis, and partial least squares discriminant analysis, 15 kinds of intracellular metabolites were found to be closely related to L-serine synthesis, including glucose, glucose 6-phosphate, 3-phosphoglycerate, pyruvate, fructose 6-phosphate, alanine, succinic acid, fumaric acid, citric acid, malic acid, phenylalanine, tryptophan, proline, glycine and methionine, among which fumaric acid, succinic acid, α-ketoglutaric acid, malic acid, and citric acid in the tricarboxylic acid cycle had great influence on the synthesis of L-serine. The fermentation results showed that the addition of 2.5 g/L fumaric acid had the significant inhibition on the cell growth, and the biomass (OD₅₆₂) decreased by 33.9%. Although fumaric acid was added to inhibit the cell growth, it was significantly beneficial to L-serine production. When 2 g/L fumaric acid was added, L-serine titer increased by 29.8%. These results showed that the optimal medium based on comparative metabolomics analysis could improve the L-serine production.

β-nicotinamide mononucleotide (NMN) as the direct precursor of the important coenzyme NAD⁺ in the human body has received widespread attention, and the current industry mainly uses chemical method or chemical-enzyme catalytic method for synthesis, and the fermentation method has not yet made a breakthrough. In order to obtain an engineered strain with high NMN yield, the metabolic pathway of Escherichia coli was modified. Firstly, nicotinamide phosphoribosyl transferase from Chitinophaga pinensis was expressed heterologous in E. coli, and a remedial synthesis pathway for NMN was constructed. In order to enhance the supply of the precursor 5-phosphate ribose-1-pyrophosphate (PRPP), multiple pathway enzymes originating from glucose were expressed, which promoted the flow of glucose to the pentose phosphate pathway; Further, in order to facilitate the accumulation of NMN, by knocking out the NMN downstream metabolic catalysis pathway genes pncC and ushA and regulating the NAD⁺ derivative gene nadR, the yield of recombinant strain obtained reached 60 mg/L, notably, which was 4.95 times over the initial level, and the fermentation was further performed on a 5 L fermenter, and the yield reached 390.1 mg/L. The strain exhibits significant potential for fermentation production of NMN.

In this study, the patented Isaria cicadae Y.R.L-3 was used for rice fermentation to develop raw materials for beautifying food. The fermentation culture was extracted by heating reflux method, and the extraction process was optimized by orthogonal experimental design to study antioxidant activity. The results showed that the rice fermentation extract had a DPPH scavenging rate of 95.24% (IC₅₀ value of 0.352 mg/mL), an ABTS cation radical scavenging rate of 89.51% (IC₅₀ value of 0.302 mg/mL), and a ·OH scavenging rate of 89.51% (IC₅₀ value of 0.302 mg/mL) under the conditions of optimal extraction process of 40 mesh sieve, 1∶12(g∶mL) material-liquid ratio, ethanol-free (95%), and reflux extraction for 2 h. Moreover, rice fermentation extract could improve the survival rate of HaCaT cells induced by H₂O₂, reduce its malondialdehyde content, and enhance the superoxide dismutase and glutathione peroxidase activity. In conclusion, rice fermentation culture has a certain antioxidant effect, which has potential value in developing natural antioxidant raw materials of beatifying food.

In order to explore the alleviating effects of two strains of Lactobacillus plantarum on muscle injury and decreased muscle energy metabolism ability in mice after high-intensity exercise and its relationship with the changes in intestinal environment, a high-intensity exercise mouse model was established through 6-week weight-bearing swimming, during which L. plantarum strains were used to treat these model mice. After 30 min of non-weight-bearing swimming, the changes of relevant biochemical indexes and gut microbiota in mice with the intervention of L. plantarum (6-week, 2×10⁸ CFU/d) were checked. The results showed that the content of lactate in muscle and the activities of lactate dehydrogenase and creatine kinase in serum of mice were significantly increased by high-intensity exercise. L. plantarum 73L1 significantly reversed this change, suggesting that this strain can relieve lactic acid accumulation and injury of gastrocnemius muscle under high-intensity exercise. In addition, the intervention of this strain significantly increased the relative abundance of Oscillibacter, and decreased the relative abundance of Candidatus Saccharimonas and Ruminococcaceae UCG-005. Correlation analysis results showed that the relative abundance of Candidatus Saccharimona was significantly positively correlated with lactate dehydrogenase activity (P<0.001). In conclusion, L. plantarum 73L1 has a good ability to relieve muscle injury caused by high-intensity exercise in mice. This ability is significantly related to its specific regulation on gut microbiota. These results suggest that reducing the relative abundance of intestinal Candidatus Saccharimonas may be a potential mechanism by which L. plantarum 73L1 alleviates muscle injury caused by high-intensity exercise in mice.

D-allulose has been a hot research topic in recent years, which is a food additive with multiple physiological functions. To investigate the bioconversion of D-allulose, three different microbial sources of D-allulose 3-epimerases (DAEase) were selected for heterologous expression in E. coli BL21(DE3). Through the exploration of the whole-cell bioconversion and the analysis of the catalytic capacity of different recombinant strains, it was concluded that DAEase from Dorea sp. CAG317 was shown to have a more promising industrial potential with a conversion rate of 32.60%. Based on this, we carried out chromatographic separation of the reaction solution to obtain a high-purity D-allulose stock solution. We took the cooling crystallization method for D-allulose stock solution to precipitate crystals, and the results showed that the optimized cooling crystallization processes achieved a 77.43% crystallization rate and a 98.70% purity of the product. This study provides an important reference for the upstream and downstream processes for the industrial production of D-allulose.

To investigate the hypolipidemic effect of flaxseed oil krill oil with different proportions, 80 male rats were randomly divided into 8 groups, including the blank group, model control group, and flaxseed oil and krill oil (46:50, 62:34, and 78:18) with different ratios in high and low dose groups. The rats were fed a high-fat diet for 7 days and orally treated with different doses of flaxseed oil and krill oil with different ratios for 30 days. The serum triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) in each group were detected to evaluate the efficacy of flaxseed oil krill oil in alleviating hyperlipidemia and optimal ratio of different functional components. Results indicated that compared with the blank control group, the serum TC, TG, and LDL-C contents in the model group were significantly increased (P<0.01), indicating that the model was established. Compared with the model control group, the contents of TC, TG, and LDL-C in different dosage groups were significantly decreased (P<0.05 and P<0.01), and there were no significant differences in body weight and HDL-C in different dosage groups, which showed that flaxseed oil krill oil with different ratios had assistant hypolipidemic effect. When the ratio of flaxseed oil to krill oil was 62:34, the decrease of TG and LDL-C in hyperlipidemia rats was the most significant.

Isoprene is the simplest terpene and an important raw material for the rubber, food, pharmaceutical, and cosmetic industries. The construction of the mevalonate metabolic pathway in microorganisms is currently an effective way to produce isoprene and its derived terpenes, however, it can be limited by the activity and expression levels of key enzymes. Aiming at the low activity of isopentenyl pyrophosphate isomerase (IDI) and other problems, in this study, the expression of IDI was optimized from three aspects: enzyme engineering, promoter engineering and ribosome binding site (RBS) engineering. Firstly, an isoprene production system was established in Escherichia coli. IDI from Streptococcus pneumoniae was then selected for protein modeling and structural analysis, and the functional hotspot Met146 was computationally obtained and subjected to site-directed mutagenesis. The modification resulted in a mutant strain Met146His, which enhanced isoprene production to 820.46 mg/L and was 2.45 times higher than of the wild type. Next, the promoter optimization and the RBS optimization were performed for this mutant, and a final optimized strain obtained enhanced isoprene production to 862.79 mg/L, which was 2.58 times higher than that of the starting strain. The results demonstrate it is an efficient strategy to improve isoprene production by performing enzyme molecular modification and expression optimization for IDI to improve enzyme activity and regulate expression levels. The modification of IDI can also be applied to the biosynthesis of downstream products such as sesquiterpenes and diterpenes.

Isomaltulose is an isomer of sucrose and has many excellent physiological functions, so it is widely used in the food industry. Sucrose isomerase can isomerize sucrose into isomaltulose. Compared with sucrose isomerase derived from other microorganisms, the sucrose isomerase derived from Pantoea dispersa UQ68J can obtain higher yield of isomaltulose and fewer by-products when converting sucrose. In order to better apply isomaltulose to the food field, P. dispersa sucrose isomerase was recombinantly expressed in food safety microorganism Bacillus subtilis, the enzymatic properties of recombinant sucrose isomerase were studied and the reaction conditions for preparing isomaltulose were optimized in this study. The results showed that the optimal pH and temperature of recombinant sucrose isomerase were 6.0 and 30 ℃, respectively. The recombinant sucrose isomerase had good stability in the range of pH 5.0-8.0, and its half-life at 45 ℃ was 68 min. Using this recombinant sucrose isomerase to prepare isomaltulose, the yield was 90.61% with 400 g/L sucrose as the substrate, when the amount of enzyme was 20 U/g, at 30 ℃ and pH 8.0 for 10 h. When the sucrose concentration increased to 700 g/L, the yield of isomaltulose still reached 89.20%. This research improves the safety characteristics of sucrose isomerase, realizes the high yield of isomaltulose, and lays the foundation for the industrial production of isomaltulose.

Thin film solid-phase microextraction and gas chromatography-mass spectrometry were used to analyze and compare the volatile flavor components of four beef tallow hotpot seasoning brands with high market share for business (B end) and consumers (C end) and established a mathematical model to evaluate their difference. Results showed that 154 kinds of flavor substances were detected in B-end products and 158 kinds of flavor substances were detected in C-end products, while the same 25 flavor compounds were detected in all eight samples. By comparing products of the same brand, it was found that the proportion of hydrocarbons in the C-end product had dropped significantly. Principal component analysis was used to analyze the flavor composition of hotpot seasoning products, and the results showed that the cumulative variance contribution rate of the first seven principal component factors reached 100%, which could effectively characterize the flavor information of hotpot seasoning materials. Finally, a principal component analysis model was constructed. The comprehensive evaluation index was calculated and the flavor was evaluated and ranked. The Pearson correlation analysis found that the correlation between the comprehensive score of the principal component and the sensory evaluation results was extremely significant (P<0.01), and the correlation coefficient was 0.908, indicating that the constructed model could effectively evaluate the flavor of hotpot seasoning.

Wine processing produces a large amount of waste, which is rich in bioenergy and bioactive substances. In recent years, disposal capacity of wine processing waste has been improving rapidly in our country, but the reuse rate of biological resources is low, and a comprehensive utilization and large-scale production system has not been formed. This paper provides a comprehensive overview on utilization of wine wastes from these four aspects: sources of wine processing wastes, material composition of wastes, industrial application, and graded utilization of waste. This paper aims to turn waste into treasure of wineries and to improve the added value of waste. It will provide a reference for the resource utilization of wine processing waste, and promote the low-carbon and sustainable development of wine industry.

Streptomyces albulus is an industrial strain for ε-poly-L-lysine (ε-PL) production. ε-PL is a homopoly (amino acids) produced by S. albulus,which is currently used as an excellent natural food preservative in many countries due to its eminent antibacterial activity. It often suffers low-pH stress during fermentation, which easily cause a decrease in the capacity of ε-PL biosynthesis. As a result, the adaptive evolution strategy with increasing the selection pressure step by step was introduced to improve the low-pH tolerance of S. albulus GS114 in this study. We first determine the initial transfer pH (pH 4.0) and transfer time (36 h) in adaptive evolution strategy. After 93 days of adaptive evolution, the tolerance pH value of S. albulus GS114 is reduced from 4.0 to 3.6. After a lot of strain screening in each selection pH (i.e. pH 4.0, 3.8, 3.6) in acid tolerance and ε-PL yield, we obtained S. albulus ALE4.0, S. albulus ALE3.8 and S. albulus ALE3.6. We chose spore plate coating and ε-PL shake flask fermentation to evaluate the characteristics of the strains after adaptive evolution. Combined with low pH tolerance and shaker fermentation experiments, it was determined that the optimal adaptive evolutionary strain is S. albulus ALE3.6. Further study investigated the influence of pH on the production of ε-PL by S. albulus ALE3.6. Results showed that S. albulus ALE3.6 had significant fermentation advantages under different pH values compared with parent strain S. albulus GS114. In terms of ε-PL production, dry cell weight, ε-PL yield, and ε-PL productivity, S. albulus ALE3.6 had different degrees of advantages. The ε-PL production of S. albulus ALE3.6 in batch fermentation at pH 4.0, 3.8, and 3.6 were reached 4.63, 6.14, and 7.2 g/L, respectively, which were enhanced by 13.5%, 8.9% and decreased by 7.7%, compared with the original strain S. albulus GS114. Meanwhile, the dry cell weight of S. albulus ALE3.6 was achieved by 16.8, 11.8, and 14.7 g/L, respectively, which were decreased to varying degrees compared to the original strain. After comparing the fermentation processes of different pH, we chose pH 4.0 for follow-up study from the point of view of the average specific synthesis rate of the product. Finally, the ε-PL production of S. albulus ALE3.6 in fed-batch fermentation at pH 4.0 were investigated. In a 5 L scale fermentor, ε-PL production of S. albulus ALE3.6 was reached by 43.7 g/L in 192 h, which is 63% higher than the original strain S. albulus GS114. The dry cell weight was attained by 39.8 g/L, which was 30% lower than the original strain. S. albulus ALE3.6 had higher ability of cell synthesis per unit and average specific synthesis rate of products in this fermentation process than the original strain. The acquisition of the S. albulus ALE3.6 provided an object for the analysis of the mechanism of acid tolerance. Furthermore, this result showed that the low-pH tolerance of S. albulus can be significantly improved through the adaptive evolution method, and enhancing the low-pH tolerance of S. albulus is an effective way to improve its ε-PL production.