Characterization of dual bacteriocins producing Bacillus subtilis SC3.7 isolated from fermented food

Probiotic Bacillus as fermentation agents: Status, potential insights, and future perspectives

Probiotic Bacillus strains can solve the problems of single flavor and long fermentation time of fermented products caused by the lack of certain functional genes and insufficient metabolism ability of fermenter strains (Lactobacillus and Bifidobacterium) at the present stage. There is a lack of systematic evaluation and review of probiotic Bacillus as food fermentation agents. In this paper, it is observed that probiotic Bacillus strains are involved to varying degrees in liquid-state, semi-solid state, and solid-state fermentation and are widely present in solid-state fermented foods. Probiotic Bacillus strains not only produce abundant proteases and lipases, but also effective antifungal lipopeptides and extracellular polymers, thus enhancing the flavor, nutritional value and safety of fermented foods. Bacillus with probiotic qualities is an underutilized group of probiotic food fermentation agents, which give a potential for the development of fermentation technology in the food business and the integration of ancient traditional fermentation techniques.

Anti-listerial peptides from a marine Bacillus velezensis FTL7: production optimization, characterizations and molecular docking studies

Antimicrobial peptides (AMPs) with potent anti-listerial activity were characterized from a novel marine Bacillus velezensis FTL7. A Box-Behnken statistical experimental design was used to study the combined impact of culture conditions on the production of AMPs by B. velezensis FTL7. The conditions optimized by statistical experimental design were 34.5 °C incubation temperature, 23 h incubation time, and 7.6 initial pH of the medium. AMP purification was performed by ammonium sulphate fractionation and butanol extraction followed by reversed-phase C18 solid-phase extraction. Tricine-SDS-PAGE analysis revealed a peptide with a molecular mass of ~ 6.5 kDa in an active AMPs fraction, whereas the mass spectrometry (MS) analysis showed the presence of AMPs in the mass range of 1-1.6 kDa, along with a 6.5 kDa peptide. Both MS and MS/MS analysis confirmed the AMPs as lipopeptides including surfactin, fengycins and iturin A and a circular bacteriocin amylocyclicin. The minimum inhibitory concentration of these AMPs against L. monocytogenes Scott A was 2.5 µg/mL. Further, the in-silico docking studies showed that the AMPs from B. velezensis FTL7 have high binding energy and stable binding patterns towards L. monocytogenes target proteins. Thus, this new combination of AMPs can serve as an effective food bio-preservative.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-03944-5.

Complete Genome Sequence Analysis of Bacillus subtilis MC4-2 Strain That against Tobacco Black Shank Disease

The MC4-2 bacterium strain was isolated and purified from the Periplaneta americana intestine as a biocontrol agent with good antagonistic effect against the pathogens of a soil-borne disease called tobacco black shank. The MC4-2 strain was found to have good broad-spectrum inhibition by plate stand-off test. Based on 16S rRNA and gyrB genes, ANI analysis, and other comparative genomics methods, it was determined that the MC4-2 strain was Bacillus subtilis. The complete genome sequence showed that the genome size was 4,076,630 bp, the average GC content was 43.78%, and the total number of CDSs was 4,207. Genomic prediction analysis revealed that a total of 145 genes were annotated by the CAZy, containing mainly GH and CE enzymes that break down carbohydrates such as glucose, chitin, starch, and alginate, and a large number of enzymes involved in glycosylation were present. A total of ten secondary metabolite clusters were predicted, six clusters of which were annotated as surfactin, bacillaene, fengycin, bacillibactin, subtilosin A, and bacilysin. The present investigation found the biological control mechanism of B. subtilis MC4-2, which provides a strong theoretical basis for the best use of this strain in biological control methods and provides a reference for the subsequent development of agents of this bacterium.

Multispecies biofilms in fermentation: Biofilm formation, microbial interactions, and communication

Food fermentation is driven by microorganisms, which usually coexist as multispecies biofilms. The activities and interactions of functional microorganisms and pathogenic bacteria in biofilms have important implications for the quality and safety of fermented foods. It was verified that the biofilm lifestyle benefited the fitness of microorganisms in harsh environments and intensified the cooperation and competition between biofilm members. This review focuses on multispecies biofilm formation, microbial interactions and communication in biofilms, and the application of multispecies biofilms in food fermentation. Microbial aggregation and adhesion are important steps in the early stage of multispecies biofilm formation. Different biofilm-forming abilities and strategies among microorganisms lead to several types of multispecies biofilm formation. The spatial distribution of multispecies biofilms reflects microbial interactions and biofilm function. Then, we discuss the intrinsic factors and external manifestations of multispecies biofilm system succession. Several typical interspecies cooperation and competition modes and mechanisms of microbial communication were reviewed in this review. The main limitations of the studies included in this review are the relatively small number of studies of biofilms formed by functional microorganisms during fermentation and the lack of direct evidence for the formation process of multispecies biofilms and microbial interactions and communication within biofilms. This review aims to provide the food industry with a sufficient understanding of multispecies biofilms in food fermentation. Practical Application: Meanwhile, it offers a reference value for better controlling and utilizing biofilms during food fermentation process, and the improvement of the yield, quality, and safety of fermented products including Chinese Baijiu, cheeese,kefir, soy sauce, kombucha, and fermented olive.