Classification, application, multifarious activities and production improvement of lipopeptides produced by Bacillus

Production-optimized fermentation of antifungal compounds by bacillus velezensis LZN01 and transcriptome analysis

Fusarium wilt is one of the major constraints on global watermelon production, and Fusarium oxysporum f. sp. niveum (Fon) is the causative agent of Fusarium wilt in watermelon and results in severe yield and quality losses worldwide. The enhancement of antifungal activity from antagonistic bacteria against Fon is highly practical for managing Fusarium wilt in watermelon. The aim of this study was to maximize the antifungal activity of Bacillus velezensis LZN01 by optimizing fermentation conditions and analysing its regulatory mechanism via transcriptome sequencing. The culture and fermentation conditions for strain LZN01 were optimized by single-factor and response surface experiments. The optimum culture conditions for this strain were as follows: the addition of D-fructose at 35 g/L and NH4Cl at 5 g/L in LB medium, pH 7, and incubation at 30°C for 72 h. The fungal inhibition rate for strain LZN01 reached 71.1%. The improvement of inhibition rate for strain LZN01 in optimization fermentation was supported by transcriptomic analysis; a total of 491 genes were upregulated, while 736 genes were downregulated. Transcriptome analysis revealed that some differentially expressed genes involved in carbon and nitrogen metabolism, oxidation-reduction, fatty acid and secondary metabolism; This optimization process could potentially lead to significant alterations in the production levels and types of antimicrobial compounds by the strain. Metabolomics and UPLC/Q-Exactive Orbitrap MS analysis revealed that the production yields of antimicrobial compounds, such as surfactin, fengycin, shikimic acid, and myriocin, increased or were detected in the cell-free supernatant (CFS) after the fermentation optimization process. Our results indicate that fermentation optimization enhances the antifungal activity of the LZN01 strain by influencing the expression of genes responsible for the synthesis of antimicrobial compounds.

Transcriptomic and Biochemical Analysis of the Antimicrobial Mechanism of Lipopeptide Iturin W against Staphylococcus aureus

Staphylococcus aureus is one of the most serious pathogens threatening food safety and public health. We have previously showed that iturin W exhibited obvious antifungal activity on plant pathogens. In the present study, we found iturin W, especially C14 iturin W, showed strong antimicrobial activity against S. aureus, and the antimicrobial mechanism of C14 iturin W was further investigated by transcriptomic analysis and a related biochemical experiment. The results showed that C14 iturin W can reduce the expression levels of genes associated with the reactive oxygen species (ROS) scavenging enzyme and genes involved in arginine biosynthesis, thus leading to the increase in ROS levels of S. aureus. Furthermore, C14 iturin W can also interfere with proton dynamics, which is crucial for cells to regulate various biological possesses. Therefore, ROS accumulation and change in proton motive force are import ways for C14 iturin W to exert the antimicrobial activity. In addition, C14 iturin W can also reduce the expression levels of genes related to virulence factors and decrease the production of enterotoxins and hemolysins in S. aureus, indicating that C14 iturin W has a good potential in food and pharmaceutical fields to reduce the harm caused by S. aureus in the future.

Production, characterization, and potential applications of lipopeptides in food systems: A comprehensive review

Lipopeptides are a class of lipid-peptide-conjugated compounds with differing structural features. This structural diversity is responsible for their diverse range of biological properties, including antimicrobial, antioxidant, and anti-inflammatory activities. Lipopeptides have been attracting the attention of food scientists due to their potential as food additives and preservatives. This review provides a comprehensive overview of lipopeptides, their production, structural characteristics, and functional properties. First, the classes, chemical features, structure-activity relationships, and sources of lipopeptides are summarized. Then, the gene expression and biosynthesis of lipopeptides in microbial cell factories and strategies to optimize lipopeptide production are discussed. In addition, the main methods of purification and characterization of lipopeptides have been described. Finally, some biological activities of the lipopeptides, especially those relevant to food systems along with their mechanism of action, are critically examined.

Lipopeptide C17 Fengycin B Exhibits a Novel Antifungal Mechanism by Triggering Metacaspase-Dependent Apoptosis in Fusarium oxysporum

Fusarium wilt is a worldwide soil-borne fungal disease caused by Fusarium oxysporum that causes serious damage to agricultural products. Therefore, preventing and treating fusarium wilt is of great significance. In this study, we purified ten single lipopeptide fengycin components from Bacillus subtilis FAJT-4 and found that C17 fengycin B inhibited the growth of F. oxysporum FJAT-31362. We observed early apoptosis hallmarks, including reactive oxygen species accumulation, mitochondrial dysfunction, and phosphatidylserine externalization in C17 fengycin B-treated F. oxysporum cells. Further data showed that C17 fengycin B induces cell apoptosis in a metacaspase-dependent manner. Importantly, we found that the expression of autophagy-related genes in the TOR signaling pathway was significantly upregulated; simultaneously, the accumulation of acidic autophagy vacuoles in F. oxysporum cell indicated that the autophagy pathway was activated during apoptosis induced by C17 fengycin B. Therefore, this study provides new insights into the antifungal mechanism of fengycin.

Lipopeptides from Bacillus: unveiling biotechnological prospects-sources, properties, and diverse applications

Bacillus sp. has proven to be a goldmine of diverse bioactive lipopeptides, finding wide-range of industrial applications. This review highlights the importance of three major families of lipopeptides (iturin, fengycin, and surfactin) produced by Bacillus sp. and their diverse activities against plant pathogens. This review also emphasizes the role of non-ribosomal peptide synthetases (NRPS) as significant enzymes responsible for synthesizing these lipopeptides, contributing to their peptide diversity. Literature showed that these lipopeptides exhibit potent antifungal activity against various plant pathogens and highlight their specific mechanisms, such as siderophore activity, pore-forming properties, biofilm inhibition, and dislodging activity. The novelty of this review comes from its comprehensive coverage of Bacillus sp. lipopeptides, their production, classification, mechanisms of action, and potential applications in plant protection. It also emphasizes the importance of ongoing research for developing new and enhanced antimicrobial agents. Furthermore, this review article highlights the need for future research to improve the production efficiency of these lipopeptides for commercial applications. It recognizes the potential for these lipopeptides to expand the field of biological pest management for both existing and emerging plant diseases.