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In order to investigate the effect of salt addition on the fermentation of shrimp paste, the physicochemical indexes, sensory attributes and bacterial communities of shrimp paste (noted as C10, C15, C20 and C25, respectively) with four salt concentrations (10%, 15%, 20% and 25%) were analyzed. The results showed that C15 had the highest sensory scores for smell, taste and overall acceptability. As fermentation proceeded, the increasing trend of total volatile basic nitrogen (TVB-N) and amino acid nitrogen (AAN) contents in shrimp paste was negatively correlated with salt addition. Malondialdehyde (MDA) content showed a fluctuating upward trend, and at the end of fermentation, C15 had the lowest MDA value. The pH of shrimp paste did not change significantly during the fermentation process, and no significant difference was observed among the four shrimp pastes (P > 0.05). Bacterial diversity and abundance were significantly lower in C10 and C15 than in C20 and C25 (P < 0.05). The dominant bacterial genera in C10 were Tetragenococcus and Staphylococcus. Tetragenococcus was the dominant genus in C15. Unclassified_f__Rhodobacteraceae, Planktotalea and Pandoraea were the dominant genera in unfermented shrimp paste, C20, and C25. Using Kruskal-Wallis H Test, 10 significant differential bacterial genera were selected among unfermented shrimp paste and the four fermented samples. Pearson correlation analysis showed that in C10, the relative abundance of Acinetobacter, Virgibacillus and unclassified_f__Bacillaceae was positively correlated with TVB-N. In C15, the relative abundance of Persicirhabdus showed a significant negative and positive correlation with TVB-N and AAN, respectively. In C20, the relative abundance of Sulfitobacter, Rubritalea, Ruegeria and Planktotalea showed a positive correlation with both TVB-N and MDA. In C25, the relative abundance of Sulfitobacter, Ruegeria, Ruegeria, Ascidiaceihabitans and Planktotalea was positively correlated with all AAN, TVB-N, and MDA. Overall, the key microorganisms responsible for the differences in physicochemical properties between low- (C10 and C15) and high-salt (C20 and C25) shrimp pastes were Acinetobacter, Mycobacterium, Rubritalea, Planktotalea, Sulfitobacter and Ascidiaceihabitans. This study provides a theoretical basis for the development and industrial production of salt-reduced shrimp paste.

In order to study the effect of fermentation temperature on the flavor substances in low-salt shrimp paste, the natural fermentation of shrimp paste was carried out at 10, 15, 20 or 25 ℃. The contents of free amino acids, free fatty acids and volatile compounds in shrimp paste were determined by high performance liquid chromatography (HPLC), gas chromatography (GC) and gas chromatography-ion mobility spectrometry (GC-IMS), respectively. The results showed that 17 free amino acids and 26 free fatty acids were detected in each shrimp paste sample. The content of flavor amino acids was highest in shrimp paste fermented at 10 ℃, and the content of free fatty acids was highest in shrimp paste fermented at 20 ℃. A total of 69 volatile compounds were identified in all samples, including 19 alcohols, 13 aldehydes, 13 ketones, 12 esters, 2 alkenes, 2 ethers, 1 acid and 7 other compounds. The relative contents of alcohols and ketones were higher in shrimp paste fermented at 10 ℃ and 15 ℃. The relative contents of ammonia were higher in shrimp paste fermented at 20 or 25 ℃. Principal component analysis (PCA) showed that volatile compounds were significantly distinguishable in low-salt shrimp pastes fermented at different temperatures. A total of six differential volatile compounds (variable importance in projection (VIP) >1, P < 0.05) were identified by orthogonal partial least squares-discriminant analysis (OPLS-DA), namely 3-methyl-1-butanol (monomer and dimer), ethyl acetate dimer, ethyl acrylate, 2-methylbutanal dimer and ammonia. Cluster heatmap analysis showed that the flavor of low-salt shrimp paste fermented at 10 and 15 ℃ was similar, and the flavor of low-salt shrimp paste fermented at 20 and 25 ℃ was similar. The results of this study may provide a theoretical basis for promoting the thermostatic fermentation of commercialized low-salt shrimp paste.

Summary: Ball‐milling is increasingly recognised as an efficient and environmentally friendly physical modification method in food processing. In this study, natural Litopenaeus vannamei protein (LVP) was subjected to ball‐milling treatment for 0, 5, 10, 15 and 20 min, respectively. Then, its structure and functional properties were investigated. Results indicated that proper ball‐milling treatment significantly enhanced the quality of LVP by influencing its structure. Specifically, ball‐milled LVP (BLVP) powder exhibited finer and brighter. BLVP subjected to 10 min demonstrated the highest solubility (22.80%), digestibility (64.50%) and foaming stability (93.69%), which were attributed to particle size and structure. BLVP processed for 15 min exhibited the highest oil holding capacity (1042.67%) and foaming capacity (17.11%), positively related to its surface hydrophobicity and sulfhydryl content. And its allergenicity decreased by 4.35%. These results provide a foundational framework for utilising ball‐milling to modify LVP, suggesting that this method may enhance the industrial applications of LVP. [ABSTRACT FROM AUTHOR]

Aims: Brevilaterin B is a natural antimicrobial lipopeptide produced by Brevibacillus laterosporus S62‐9. However, its antifungal spectrum and modes of action are still unclear. Herein, we investigated the detailed antifungal activity of brevilaterin B against 33 pathogenic fungi and the antifungal effects against two sensitive fungi in vitro and in vivo. Methods and Results: Brevilaterin B exhibited inhibitory activity against 33 pathogenic fungi involved in plant disease and food spoilage at the minimum inhibitory concentrations (MICs) range of 16–128 μg ml−1. The antifungal effects were further studied by Fusarium oxysporum and Penicillium chrysogenum. Both spore germination and mycelium growth were inhibited by brevilaterin B at sub‐MIC. Transmission electron microscopy and fluorescent dye staining assays indicated brevilaterin B damaged cell integrity and induced apoptosis. In vivo tests, brevilaterin B inhibited the infection of F. oxysporum to Dendrobium officinale and P. chrysogenum to mandarin (Citrus reticulata) at 500 μg ml−1, respectively. Conclusions: Brevilaterin B showed broad‐spectrum antifungal activity against 33 pathogenic fungi. And its antifungal modes of action were proposed as damaging cell integrity and inducing cell apoptosis. The lipopeptide is promising to control F. oxysporum in the D. officinale and P. chrysogenum in the mandarin. Significance and Impact of Study: The research provided insights into antifungal modes of action of brevilaterin B. The lipopeptide brevilaterin B is potential to be developed as a broad‐spectrum antifungal agent for agricultural biocontrol and postharvest storage. [ABSTRACT FROM AUTHOR]

Aspergillus flavus has been regarded as a potential candidate for its production of industrial enzymes, but the details of β-glucosidase from this strain is very limited. In herein, we first reported a novel β-glucosidase (AfBglA) with the molecular mass of 94.2 kDa from A. flavus. AfBglA was optimally active at pH 4.5 and 60 °C and is stable between pH 3.5 and 9.0 and at a temperature of up to 55 °C for 30 min remaining more than 90% of its initial activity. It showed an excellent tolerance to Trypsin, Pepsin, Compound Protease, and Flavourzyme and its activity was not inhibited by specific certain cations. AfBglA displayed broad substrate specificity, it acted on all tested pNP-glycosides and barley glucan, indicating this novel β-glucosidase exhibited a β-1, 3-1, 4-glucanase activity. Moreover, the AfBglA could effectively hydrolyze the soybean meal suspension into glucose and exhibit a strong tolerance to the inhibition of glucose at a concentration of 20.0 g/L during the saccharification. The maximum amount of the glucose obtained by AfBglA corresponded to 67.0 g/kg soybean meal. All of these properties mentioned above indicated that the AfBglA possibly attractive for food and feed industry and saccharification of cellulolytic materials. [ABSTRACT FROM AUTHOR]

A novel xylanase from the filamentous fungus Aspergillus flavus was purified and characterized as the β‐1, 4‐endoxylanase (designed as AfXynB) with a molecular mass (32.2 kDa), which is different from all of the previously reported xylanases from the same strain. AfXynB was optimally active at pH 7.5 and 55 °C, respectively. It was stable up to 50 °C within range of pH 4.0–9.5, and displayed an excellent tolerance to various cations, reagents, and proteases. AfXynB showed specific activity toward beechwood xylan but no detected activity toward CMC and pNP‐β‐D‐xylopyranoside. The xylanase is a typical endo‐xylanase; it could hydrolyze beechwood xylan to only yield xylobiose (X2) and xylopentaose (X5). Actually, this may be the first report for the endo‐xylanases that displayed such a unique hydrolytic property. These findings in the present study have great implications for its future applications of the novel xylanase. [ABSTRACT FROM AUTHOR]