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Nitrile-converting enzymes, including nitrilase and nitrile hydratase (NHase), have received increasing attention from researchers of industrial biocatalysis because of their critical role as a tool in organic synthesis of carboxylic acids and amides from nitriles. To date, these bioconversion approaches are considered as one of the most potential industrial processes using resting cells or purified enzymes as catalysts for production of food additives, pharmaceutical, and agrochemical precursors. This review focuses on the distribution and catalytic mechanism research of nitrile-converting enzymes in recent years. Molecular biology aspects to improve the biocatalytic performance of microbial nitrilase and NHase are demonstrated. The process developments of microbial nitrilase and NHase for organic synthesis are also discussed. [ABSTRACT FROM AUTHOR]

Antrodia cinnamomea is a medicinal mushroom producing potent bioactive triterpenoids. However, triterpenoids of A. cinnamomea in submerged culture are much less than those in fruiting bodies. Here we evaluated effects of different extracts from a host-related species, Cinnamomum camphora, on the mycelial growth and triterpenoid production of A. cinnamomea in submerged culture. The hot water extract of the stem showed the strongest promotion of the mycelial growth. The petroleum ether extract of the stem ( PES) (0.05 g L−1) showed the greatest stimulatory effect on content and production of triterpenoids. A total of 39 compounds including terpenoids, phenolic and aromatic compounds were identified in the PES by GC - MS analysis. Furthermore, the effects of seven compounds contained in the PES on the mycelial growth and triterpenoid production of A. cinnamomea were evaluated. Among them, α-terpineol (0.5 mg L−1) showed the greatest stimulatory effect on the triterpenoid content (23.31 mg g−1) and triterpenoid production (91.33 mg L−1) of A. cinnamomea. Results of LC- MS analysis showed that α-terpineol (0.5 mg L−1) stimulated the syntheses of six triterpenoids in the mycelia of A. cinnamomea. This indicates that α-terpineol can act as an elicitor for triterpenoid biosynthesis in A. cinnamomea. [ABSTRACT FROM AUTHOR]

The energy dissipation capacities and fragments distribution of concrete exposed to high temperature under impact loading are studied. Dynamic compressive tests of concrete at room temperature and after exposure to elevated temperatures ranging from 200 to 800 °C are conducted by using a split Hopkinson pressure bar with 100 mm in diameter. The effects of high temperature and impact velocity on dissipated energy,failure mode and fractal dimension of fragments are analyzed. The results indicate that the dissipated energy grows with the increase in impact velocity and strain rate at the same temperature; and at fixed impact velocity,the dissipated energy decreases with the increase in the exposure temperature. The fragment-size distribution of concrete fragments statistically has fractal property subjected to impact loading. An increase in temperature and impact velocity results in a greater crushing degree and a larger fractal dimension value. There is a positive correlation between dissipated energy and fractal dimension at the same temperature. As a result,the impact crushing of concrete at various temperatures and impact velocities is a fractal evolution process driven by external energy. [ABSTRACT FROM AUTHOR]

Many traditional fermented foods and beverages industries around the world request the addition of multi‐species starter cultures. However, the microbial community in starter cultures is subject to fluctuations due to their exposure to an open environment during fermentation. A rapid detection approach to identify the microbial composition of starter culture is essential to ensure the quality of the final products. Here, we applied single‐cell Raman spectroscopy (SCRS) combined with machine learning to monitor Oceanobacillus species in Daqu starter, which plays crucial roles in the process of Chinese baijiu. First, a total of six Oceanobacillus species (O. caeni, O. kimchii, O. iheyensis, O. sojae, O. oncorhynchi subsp. Oncorhynchi and O. profundus) were detected in 44 Daqu samples by amplicon sequencing and isolated by pure culture. Then, we created a reference database of these Oceanobacillus strains which correlated their taxonomic data and single‐cell Raman spectra (SCRS). Based on the SCRS dataset, five machine‐learning algorithms were used to classify Oceanobacillus strains, among which support vector machine (SVM) showed the highest rate of accuracy. For validation of SVM‐based model, we employed a synthetic microbial community composed of varying proportions of Oceanobacillus species and demonstrated a remarkable accuracy, with a mean error was less than 1% between the predicted result and the expected value. The relative abundance of six different Oceanobacillus species during Daqu fermentation was predicted within 60 min using this method, and the reliability of the method was proved by correlating the Raman spectrum with the amplicon sequencing profiles by partial least squares regression. Our study provides a rapid, non‐destructive and label‐free approach for rapid identification of Oceanobacillus species in Daqu starter culture, contributing to real‐time monitoring of fermentation process and ensuring high‐quality products. [ABSTRACT FROM AUTHOR]

Hyaluronidases catalyze the degradation of hyaluronan (HA), which is finding rising applications in medicine, cosmetic, and food industries. Recombinant expression of hyaluronidases in microbial hosts has been given special attention as a sustainable way to substitute animal tissue–derived hyaluronidases. In this study, we focused on optimizing the secretion of hyaluronidase from Homo sapiens in Pichia pastoris by secretion pathway engineering. The recombinant hyaluronidase was first expressed under the control of a constitutive promoter PGCW14. Then, two endoplasmic reticulum–related secretory pathways were engineered to improve the secretion capability of the recombinant strain. Signal peptide optimization suggested redirecting the protein into co-translational translocation using the ost1-proα signal sequence improved the secretion level by 20%. Enhancing the co-translational translocation by overexpressing signal recognition particle components further enhanced the secretory capability by 48%. Then, activating the unfolded protein response by overexpressing a transcriptional factor ScHac1p led to a secreted hyaluronidase activity of 4.06 U/mL, which was 2.1-fold higher than the original strain. Finally, fed-batch fermentation elevated the production to 19.82 U/mL. The combined engineering strategy described here could be applied to enhance the secretion capability of other proteins in yeast hosts. Key points: • Improving protein secretion by enhancing co-translational translocation in P. pastoris was reported for the first time. • Overexpressing Hac1p homologous from different origins improved the rhPH-20 secretion. • A 4.9-fold increase in rhPH-20 secretion was achieved after fermentation optimization and fed-batch fermentation. [ABSTRACT FROM AUTHOR]

Nicotinamide mononucleotide (NMN), a naturally occurring biologically active nucleotide, mainly functions via mediating the biosynthesis of NAD+. In recent years, its excellent pharmacological activities including anti-aging, treating neurodegenerative diseases, and protecting the heart have attracted increasing attention from scholars and entrepreneurs for production of a wide range of formulations, including functional food ingredients, health care products, active pharmaceuticals, and pharmaceutical intermediates. Presently, the synthesis methods of NMN mainly include two categories: chemical synthesis and biosynthesis. With the development of biocatalyst engineering and synthetic biology strategies, bio-preparation has proven to be efficient, economical, and sustainable methods. This review summarizes the chemical synthesis and biosynthetic pathways of NMN and provides an in-depth investigation on the mining and modification of enzyme resources during NMN biosynthesis, as well as the screening of hosts and optimization of chassis cells via metabolic engineering, which provide effective strategies for efficient production of NMN. In addition, an overview of the significant physiological functions and activities of NMN is elaborated. Finally, future research on technical approaches to further enhance NMN synthesis and strengthen clinical studies of NMN are prospected, which would lay the foundation for further promoting the application of NMN in nutrition, healthy food, and medicine in the future. Key points: • NMN supplementation effectively increases the level of NAD+. • The chemical and biological synthesis of NMN are comprehensively reviewed. • The impact of NMN on the treatment of various diseases is summarized. [ABSTRACT FROM AUTHOR]

Liver fibrosis is associated with gut dysbiosis. Metformin administration has emerged as a promising method for the treatment of organ fibrosis. We aimed to investigate whether metformin ameliorates liver fibrosis by enhancing the gut microbiota in mice with carbon tetrachloride (CCl 4)-induced liver fibrosis and the underlying mechanism. A liver fibrosis mouse model was established, and the therapeutic effects of metformin were observed. We administered antibiotic treatment and performed fecal microbiota transplantation (FMT), and 16S rRNA-based microbiome analysis to evaluate the effects of the gut microbiome on metformin-treated liver fibrosis. We isolated the bacterial strain preferably enriched by metformin and assessed its antifibrotic effects. Metformin treatment repaired the gut integrity of the CCl 4 -treated mice. It reduced the number of bacteria in colon tissues and reduced the portal vein lipopolysaccharide (LPS) levels. The FMT performed on the metformin-treated CCl 4 mice alleviated their liver fibrosis and reduced their portal vein LPS levels. The markedly changed gut microbiota was screened out from the feces and named Lactobacillus sp. MF-1 (L. sp. MF-1). In the CCl 4 -treated mice, daily gavage of L. sp. MF-1 maintained gut integrity, inhibited bacterial translocation, and reduced liver fibrosis. Mechanistically, metformin or L. sp. MF-1 inhibited the apoptosis of intestinal epithelial cells and restored CD3+ intestinal intraepithelial lymphocytes in the ileum and CD4+Foxp3+ lamina propria lymphocytes in the colon. Metformin and its enriched L. sp. MF-1 can reinforce the intestinal barrier to alleviate liver fibrosis by restoring immune function. • Metformin treatment repaired gut integrity of CCl4-induced mice and restored the expressions of tight junction proteins. • The markedly changed gut microbiota (MF-1) was screened out from feces of the metformin-treated CCl4 mice. • In CCl4-treated mice, the daily gavage of MF-1 maintained gut integrity, inhibited BT, and reduced fibrosis in the liver. • Metformin and its enriched MF-1 can reinforce the intestinal barrier to alleviate liver fibrosis by restoring immune function. [ABSTRACT FROM AUTHOR]

Solubility and folding stability are key concerns for difficult-to-express proteins (DEPs) restricted by amino acid sequences and superarchitecture, resolved by the precise distribution of amino acids and molecular interactions as well as the assistance of the expression system. Therefore, an increasing number of tools are available to achieve efficient expression of DEPs, including directed evolution, solubilization partners, chaperones, and affluent expression hosts, among others. Furthermore, genome editing tools, such as transposons and CRISPR Cas9/dCas9, have been developed and expanded to construct engineered expression hosts capable of efficient expression ability of soluble proteins. Accounting for the accumulated knowledge of the pivotal factors in the solubility and folding stability of proteins, this review focuses on advanced technologies and tools of protein engineering, protein quality control systems, and the redesign of expression platforms in prokaryotic expression systems, as well as advances of the cell-free expression technologies for membrane proteins production. [ABSTRACT FROM AUTHOR]

Hyaluronate lyases (HA lyases) have been proved to distribute widely among microorganisms, with large potential in hyaluronan processing. Here, a highly active HA lyase HylC from Citrobacter freundii strain Cf1 is reported. HylC was expressed in Escherichia coli BL21(DE3) under the regulation of T7 promoter, and purified to electrophoretic homogeneity for enzymatic characterization, which suggested its suitable thermo- and pH stability under 45 °C and pH rang of 4–8, and high halotolerancy in 1.5 M NaCl. The enzyme exhibited the optimal activity under 37 °C and pH 5.5, and was activated by Ca2+, K+, Zn2+, Ni2+ and Li+. Analysis of degradation product proved it cleave HA in endolytic manner, releasing unsaturated disaccharides as final product. Then, through optimization of promoter and construction of dual promoter, expression level of HylC improved from 1.10 × 104 U/mL to 2.64 × 104 U/mL on shake-flask level. Finally, through batch fermentation, a highest activity of 2.65 × 10 5 U/mL was achieved in a 5-L fermenter. Taken together, this work demonstrates the potential of HylC and its recombinant strain in industrial applications. To our knowledge, the HA lyase production reported in this study was the highest level in literatures to date. • A highly active hyaluronate lyase was found, cloned and characterized. • Promoter engineering enhanced recombinant expression of hyaluronate lyase by 2.4-fold. • (3)The highest level of recombinant hyaluronate lyase reached up to 2.65 × 105 U/mL. [ABSTRACT FROM AUTHOR]

[Display omitted] • The richness and diversity of yeast community increased throughout fermentation. • The vast majority of yeasts in the fermentation sourced from the brewing environment. • Wickerhamomyces (29.6 %), Saccharomycopsis (25.0 %), and Torulaspora (14.9 %) were the predominant genera. • These predominant genera showed distinct spatial distributions throughout the fermentation stack. • T. delbrueckii ME22, S. fibuligera ME8, and W. anomalus ME57 drove the formation of floral, fruity, and sweet flavor compounds. Yeasts play a crucial role in determining the quality and yield of sauce-flavor Baijiu, yet the source, succession, and metabolic functions of the yeast community in fermented grains during stacking fermentation remains unclear. In this study, amplicon sequencing combined with solid-state fermentation was used to investigate the structure and function of yeast community during the first-round fermentation of sauce-flavor Baijiu. The richness and diversity of yeast community increased throughout fermentation, with 83.05 % of yeast ASV sourced from the fermentation environment. Fourteen yeast genera were identified, with Wickerhamomyces (29.6 %), Saccharomycopsis (25.0 %), and Torulaspora (14.9 %) being the predominant genera. These genera showed distinct spatial distributions throughout the fermentation stack. Spearman correlation analysis indicated positive correlations between the three genera and multiple volatiles in fermented grains alcohols and esters. After solid-state fermentation in pure culture, T. delbrueckii ME22, S. fibuligera ME8, and W. anomalus ME57 produced distinct floral, fruity, and sweet flavor compounds, such as phenylethyl alcohol, isoamyl alcohol, ethyl acetate, phenethyl acetate, and isoamyl acetate. T. delbrueckii ME22 demonstrated a great capacity for cellulose degradation, whereas S. fibuligera ME8 exhibited enhanced capabilities for protein and starch degradation. This study provides a theoretical reference for the application of yeast in the fermentation of sauce-flavor Baijiu. [ABSTRACT FROM AUTHOR]

[Display omitted] • A high-efficiency expression system of PLD in B. subtilis was constructed. • Optimized culture strategy achieved a high PLD activity of 4055.9 U/mL and a production efficiency of 52.0 U/mL/h. • An optimal phosphatidic acid production of 219.1 g/L was achieved. Although Bacillus subtilis shows promise as a potential microbial cell factory for phospholipase D (PLD) expression, its production capacity remains insufficient. In this study, a secretory expression system, by co-optimization the promoter and signal peptides and employing a fed-batch fermentation strategy, was constructed to enhance expression of PLD from separate sources. The highest PLD production of 4056.9 U/mL was observed using this system, with a PLD production efficiency of 52.0 U/mL/h. Finally, a phosphatidic acid (PA) biosynthesis system was established using the constructed PLD as a catalyst, which achieved a PA yield of 219.1 g/L. This is the highest PLD production and PA yield reported globally to date. The protocol has significant potential for application for industrial PLD production as well as enzymatic phospholipids modification and also provides a valuable reference for overexpressing proteins in B. subtilis. [ABSTRACT FROM AUTHOR]

Excessive UVB exposure increased the production of reactive oxygen species (ROS), leading to oxidative damage and epidermal inflammation. To enhance UVB protection effect, a strong phenolic antioxidant, ferulic acid (FA) was designed onto HA via a free radical mediated method. Our previous work has confirmed its structural characterization and in vitro antioxidant. The aim of this study was to evaluate its protective effects against UVB-induced damage in human HaCaT cells. We observed a significant reduction in cell viability to 57.43 % following UVB exposure at a dose of 80 mJ/cm2. However, pretreatment with FA-HA (250 to 2000 μg·mL−1) significantly attenuated cytotoxicity in a dose-dependent manner. Furthermore, FA-HA was found to suppress the intracellular generation of ROS and up-regulated the expression of the antioxidant enzyme superoxide dismutase (SOD). The elevated levels of pro-inflammatory cytokines, including interleukin-1 beta (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8) and tumor necrosis factor-alpha (TNF-α) as well as the mRNA expression of matrix metalloproteinase-1/9 (MMP-1/9) induced by UVB irradiation, were also effectively reduced by FA-HA. Additionally, FA-HA treatment decreases the phosphorylation of mitogen-activated protein kinase (MAPK) and activator protein-1 (AP-1), ultimately preventing apoptosis. These findings suggest that FA-HA is a promising candidate for UVB protection in skincare formulations. [ABSTRACT FROM AUTHOR]

Qu -aroma is of great significance for evaluation the quality of Daqu starter. This study aimed to decode the Qu -aroma of medium-temperature Daqu (MT- Daqu) via "top-down" and "bottom-up" approaches. Firstly, 52 aroma descriptors were defined to describe the MT- Daqu aroma by quantitative descriptive analysis. Secondly, 193 volatile organic compounds (VOCs) were identified from 42 MT- Daqu samples by HS-SPME-GC–MS, and 43 dominant VOCs were screened out by frequence of occurrence or abundance. By Thin Film (TF)-SPME-GC-O-MS, 27 odors and 90 VOCs were detected in MT- Daqu mixture, and 14 odor-active VOCs were screened out by odor intensity. Thirdly, a five-level MT- Daqu aroma wheel was constructed by matching 52 aroma descriptors and 37 aroma-active VOCs. Finally, Qu -aroma of MT- Daqu was reconstructed with 37 aroma-active VOCs and evaluated by omission experiments. Hereinto, 26 key aroma-active VOCs were determined by OAV value ≥1, including isovaleric acid, 1-hexanol, isovaleraldehyde, 2-octanone, trimethylpyrazine, γ-nonalactone, 4-vinylguaiacol, etc. • 52 descriptors were determined through a "Top-down" approach. • 37 aroma-active compounds were identified via "Bottom-up" approach. • A five-level aroma wheel of MT- Daqu was established. • Qu -aroma of MT- Daqu was reconstructed using 37 aroma-active VOCs. • 26 key aroma-active VOCs were confirmed by OAV, reconstitution, and omission. [ABSTRACT FROM AUTHOR]