[Objective] Long-term and excessive application of chemical fertilizers leads to soil degradation and an imbalanced microbial community structure in soil. The combination of organic active substances with chemical fertilizers is considered an important approach for controlling soil degradation and maintaining microbial community stability. [Methods] Metagenomics was employed to study the effects of combining the bioactive substance γ-polyglutamic acid (γ-PGA) with chemical fertilizer on soil microbial community and function in cotton fields. Four fertilization groups were designed: chemical fertilizer (NK), chemical fertilizer combined with γ-PGA aqueous solution (YT), chemical fertilizer combined with γ-PGA granules (GT), and no fertilizer (CK). [Results] GT and YT groups outperformed NK and CK groups in terms of cotton growth and soil nutrient content. The combination of γ-PGA with chemical fertilizer significantly increased the microbial abundance and diversity in soil, while chemical fertilizer alone did not improve soil microbial diversity. In addition, the application of γ-PGA changed soil microbial community composition. Compared with the NK group, YT and GT groups showed a 9.70%–12.72% decrease in the relative abundance of Proteobacteria and 13.33%–20.90% and 8.09%–13.01% increases in the relative abundance of Bacteroidetes and Actinobacteria, respectively. In addition, the relative abundance of Rhizophagus (a genus of mycorrhiza fungi) increased by 19.71% in the YT group. The functional gene analysis showed that GT and YT significantly increased the abundance of functional genes related to amino acid biosynthesis, secondary metabolite biosynthesis, and ABC transporters. [Conclusion] The application of γ-PGA has the potential of improving soil microbial diversity and ecosystem stability in Xinjiang cotton fields.

The aquaculture industry has rapidly expanded in recent years in China, whereas it faces the challenge brought by bacterial diseases. Antibacterial agents have been the primary tools to combat these diseases. However, prolonged and haphazard usage of antibacterial agents in aquaculture has exacerbated antimicrobial resistance and led to severe antimicrobial residues. Considering these challenges, scholars worldwide have been exploring natural alternatives, such as Chinese herbal medicines. Among them, Pithecellobium clypearia stands out due to its antibacterial, antiviral, and anti-inflammatory properties, coupled with its safety and lack of antimicrobial resistance. Nonetheless, the potential of P. clypearia in the prevention and control of aquatic diseases remains underexplored. [Objective] This study evaluated the in vitro inhibitory activity of P. clypearia aqueous extract against aquatic pathogenic bacteria, including an artificially induced antimicrobial-resistant strain. Additionally, we investigated changes in bacterial cell membrane permeability and observed cellular alterations by transmission electron microscopy to elucidate the mechanism of the extract. Our findings are expected to pave the way for developing P. clypearia as an environmentally friendly antibacterial agent, reducing antibacterial agent dependency, and mitigating pathogen resistance in aquaculture. [Methods] We employed the microbroth method to assess the antimicrobial resistance of 107 pathogen strains attacking aquatic animals and analyzed the inhibitory activity of P. clypearia aqueous extract against aquatic pathogenic bacteria, including an artificially induced antimicrobial-resistant bacterial strain. Furthermore, we determined the extracellular K⁺ content and ultrastructural changes in Streptococcus agalactiae and Vibrio parahaemolyticus after treatment with the extract. [Results] The resistance rate of 107 pathogen strains to sulfonamides was as high as 67.29%, and 46.73% of the strains showed multidrug resistance, among which Aeromonas sp. showed the most severe resistance. The aqueous extract (12.50 mg/mL) of P. clypearia exerted inhibitory effects on all the pathogenic bacteria, especially on Aeromonas sp. with the minimum inhibitory concentration (MIC) as low as 0.39 mg/mL. The MICs of the extract were similar for the strains belonging to the same genus but with different antimicrobial resistance characteristics. The aqueous extract of P. clypearia showed stronger inhibitory effect on the artificially induced enrofloxacin-resistant strain of A. schubertii than on the original strain, with the MICs of 0.78 mg/mL on the original strain and 0.20 mg/mL on the resistant strain. In addition, the treatment with P. clypearia aqueous extract significantly increased the extracellular K⁺ concentration, leading to damage to the bacterial cell membrane structure, leakage of intracellular contents, and vacuolation of cytoplasm, which suggested that P. clypearia exerted the antibacterial effect by destroying the bacterial membrane structure. [Conclusion] P. clypearia exerts in vitro inhibitory effects on aquatic pathogenic bacteria and demonstrates great potential for further research and development in the prevention and treatment of bacterial diseases in aquatic animals. The antibacterial mechanism of P. clypearia appears to involve disrupting bacterial cell membranes. The application of P. clypearia in aquaculture promises to reduce antibiotic dependency and pathogen resistance, paving the way for a healthy and sustainable aquaculture industry.

The widely used trypsin is mainly extracted from animal pancreas, which has the disadvantages of limited raw materials, high costs, and low purity. In addition, the autolysis of trypsin affects its stability in storage and application. [Objective] To obtain an anti-autolysis recombinant trypsin by heterologous expression and methylation. [Methods] We employed gene recombination to realize the heterologous expression of porcine trypsinogen in Pichia pastoris. Furthermore, we conducted single factor experiments to investigate and optimize the temperature, pH, and time of enzyme activation and improved the anti-autolysis performance of the recombinant trypsin by methylation. [Results] The engineered strain of P. pastoris expressing trypsinogen was successfully constructed. Under the trypsin concentration of 10 mg/mL, methylation reagent addition of 30 μL, and reaction time of 3 h, the methylated trypsin showed the activity loss of only 22% and the relative activity of 79% after autolysis for 6 h, which was about 3.4 times higher than that of the control, suggesting that the anti-autolysis performance of the recombinant trypsin was greatly improved. [Conclusion] This study successfully produced a novel anti-autolysis recombinant trypsin by heterologous expression and methylation, which can improve the production and application of trypsin in China.

β-glucosidases have been widely used in food, medicine, bioenergy and other fields, and thus it is necessary to explore new and efficient β-glucosidases.[Objective] To realize the prokaryotic expression of a GH1 glucosidase derived from Devosia psychrophila and characterize the enzymatic properties of the expressed protein. [Methods] The gene encoding the β-glucosidase derived from D. psychrophila was synthesized, named bgl59, and then transformed into Escherichia coli BL21(DE3). After the gene expression was induced, and the obtained protein was purified and characterized for the enzymatic properties. [Results] Bgl59 had a molecular weight of 48.8 kDa, with the highest activity at 55 ℃ and pH 6.0. After treatment for 1 h within the range of pH 5.0–8.5, Bgl59 maintained the relative activity over 80%. Bgl59 had the highest hydrolysis ability for 4-nitrophenyl-β-D-glucopyranoside (pNPG) among the eight substrates tested, with the K_m of 3.090 mmol/L, V_max of 194 μmol/(min·mg), and k_cat of 159 s⁻¹. The presence of 1 mmol/L of Ca²⁺ and Co²⁺ had a significant activating effect on Bgl59, while the presence of 0.1% SDS resulted in a complete loss of enzyme activity. The presence of 0.10 mol/L glucose and 0.30 mol/L xylose increased the activity of Bgl59 by 74% and 91%, respectively. Moreover, the enzyme remained the relative activity above 50% even when being cultured with 1.25 mol/L glucose or 2.00 mol/L xylose. [Conclusion] Bgl59 exhibits outstanding enzymatic properties, robust pH stability, and tolerance to metal ions and chemical reagents. It is a rare glucose-activated β-glucosidase with exceptional tolerance to glucose, holding significant potential for future industrial production and application.

[Objective] To study the effects of adding different concentrations of garlic juice on the fermentation of pickled Chinese cabbage. [Methods] The physicochemical indicators and OD₆₀₀ during the fermentation process were measured, and the effects of garlic juice concentration on the richness, community structure, and abundance of bacteria during the fermentation were studied with natural fermentation as the control. The 16S rRNA gene high-throughput sequencing was carried out in the late fermentation stage for the pickled Chinese cabbage samples with the addition of garlic juice at different concentrations. Fuzzy mathematics-based evaluation was conducted for the sensory quality of garlic-flavored samples to select the lactic acid bacterial strains with excellent fermentation performance. [Results] Different concentrations of garlic juice had minor effects on the pH and OD₆₀₀ but significantly reduced the peak value of nitrite. Adding 0.2%–0.4% garlic juice was beneficial for the growth of Lactiplantibacillus, and the species richness of the product fermented with the addition of garlic juice was higher than that of the naturally fermented product. The fermentation liquid with the addition of 0.3% garlic juice had the highest species richness, with much higher number of genera than other concentration groups. The product from fermentation with 0.3% garlic juice showcased the best quality, presenting better sensory quality and appearance. The product with high species richness and a large number of genera had good sensory quality. A strain of lactic acid bacteria with excellent fermentation performance was screened out and identified as Lactiplantibacillus pentosus, which produced the most acids during fermentation, had the highest nitrite degradation rate, and exhibited tolerance to garlic. [Conclusion] This study provides a strain for the development of lactic acid bacteria fermentation agents and lays a theoretical foundation for the industrialization of garlic-flavored pickled Chinese cabbage.

Parkinson's disease is a common neurodegenerative disorder that seriously threatens the health of middle-aged and elderly individuals. However, the pathogenesis of Parkinson's disease is not fully understood. Recent studies have shown that gut microbiota plays an important role in the occurrence and development of Parkinson's disease. Gut microbiota and its metabolites influence the intestinal mucosal barrier, neuroinflammation, endocrine system, and other aspects through the microbiota-gut-brain axis, thereby participating in the occurrence and development of Parkinson's disease. Gut microbiota can be regulated by various methods such as probiotic supplementation, fecal microbiota transplantation, dietary adjustments, and traditional Chinese medicine interventions, being an important target for the prevention and treatment of Parkinson's disease. This article reviews the possible mechanisms of gut microbiota being involved in the occurrence of Parkinson's disease and further discusses the current status of prevention and treatment of gut microbiota dysbiosis.

[Objective] Bovine bones contain a large amount of beneficial nutrients such as proteins, mineral salts, and vitamins for human health. With the calcium-to-phosphorus ratio meeting the optimal absorption ratio for the human body, bovine bones serve as a valuable nutrient source. [Methods] Lactic acid bacteria with high yields of L-lactic acid were screened by the calcium-dissolving ring method and the performance of strains in L-lactic acid production was then determined via fermentation of bovine bone meal. Metabolomics was employed to explore the differential metabolites and main pathways during the fermentation. [Results] One strain LP15, identified as Lactobacillus plantarum, was isolated from the liquid sample in the production of sour bamboo shoots for its strong ability to produce L-lactic acid. After fermentation of bone meal for 96 h, the strain produced 3.89 g/L L-lactic acid and 69.82 mg/100 mL free calcium, which represented a 32.6-fold increase compared with that in the control group. The metabolomic analysis revealed ABC transporters, metabolic pathway, and biosynthesis of secondary metabolites as the most important differential metabolic pathways during the fermentation of bovine bone meal. Meanwhile, a huge number of physiological active substances, such as cyclocreatine and 2-hydroxy-2-methylbutyric acid, were detected in the fermented bone meal. [Conclusion] Fermentation of bovine bone meal by L. plantarum LP15 is an effective strategy to promote calcium dissolution and produce beneficial active substances. This study lays a practical foundation for developing health food products by microbial fermentation of bovine bone meal.

Microalgae are rich in lipids, proteins, and exopolysaccharides, serving as potential producers of high-value by-products. Compared with monoculture, microalgal co-culture offers advantages such as fast growth rates and strong resistance, increasing the microalgal biomass and lipid production. Biomass production by microalgae co-culture is influenced by environmental conditions, nutrient composition, and external stress, and the produced biomass can be utilized for biofuel production and food processing. This article introduces the types of microalgal co-culture systems and reviews the related studies on the production of high-value by-products. It summarizes the factors influencing biomass production in microalgal co-culture systems and highlights the potential of microalgal co-culture for resource utilization. Furthermore, this article discusses the prospects and challenges of microalgal co-culture.

[Objective] Microplastics (particle size < 5 mm) with hydrophobic surface, strong adsorption capacity, and difficult degradation can be retained in the environment for a long time and easily colonized by microorganisms, which poses a potential risk to the ecosystem. To study the distribution characteristics of microorganisms on the surface of microplastics in the wetland of Poyang Lake in wet and dry seasons. [Methods] Samples of water, sediments, and microplastics in sediments were collected from the wetland during the wet and dry seasons. The bacterial diversity and community structure in the samples were analyzed by high-throughput sequencing of the 16S rRNA gene. [Results] The richness and diversity of bacteria in the environment were higher than those on the microplastic surface in wet and dry seasons. During the wet season, the bacterial community structure was similar between the water and sediment samples and had large differences between the environment and the microplastic surface. During the dry season, the bacterial community structure was different among different samples. At the phylum level, the bacteria in the environment were dominated by Proteobacteria, Bacteroidetes, and Actinobacteria, while the bacteria on the microplastic surface during the wet season mainly included Proteobacteria, Bacteroidetes, and Firmicutes. The dominant bacterial phyla on the microplastic surface were similar to those in the environment during the dry season. The relative abundance of Pseudomonas on the microplastic surface was higher than that in the environment. Most of the keystone bacterial species in the wet and dry seasons belonged to Proteobacteria, including Sphingomonas. [Conclusion] This study reveals the differences in the bacterial community structure in the environment and on the microplastic surface in the Poyang Lake wetland in wet and dry seasons. The findings can enrich the knowledge about microplastics in lake wetlands in China and provide a theoretical basis for the management of lake environments including the Poyang Lake wetland.

Glucose-1-phosphate is a key precursor for starch biosynthesis of photoautotrophs. Phosphoglucomutases (PGMs) belonging to the phosphohexomutase family have a high conserved characteristic and perform the interconversion between glucose-6-phosphate and glucose-1-phosphate to regulate the starch biosynthesis. Compared with the higher plants, microalgae possess unique photosynthetic systems. Additionally, some microalgae strains can utilize organic carbon sources to produce valuable biomass by heterotrophic or mixotrophic cultivation, which might endow PGMs with specific structural features and biological functions in starch metabolism to regulate the levels of carbon fixation by photosynthesis, carbohydrate metabolism, and other pathways in microalgae. This article summarizes the molecular characteristics, functions, and activity regulation of PGMs for microalgae. Moreover, this article elucidates the potential mechanisms by which PGMs regulate microalgae starch synthesis to influence intracellular protein and lipid metabolic pathways. This review lays a theoretical foundation for microalgae carbon sequestration and the value-added utilization of microalgae resources, contributing to the achievement of China's "dual-carbon" goals.