Abstract
Several products of industrial interest are produced by Bacillus, including enzymes, antibiotics, amino acids, insecticides, biosurfactants and bacteriocins. This study aimed to investigate the potential of two bacterial isolates (P5 and C3) from puba, a regional fermentation product from cassava, to produce multiple substances with antimicrobial and surface active properties. Phylogenetic analyses showed close relation of isolates P5 and C3 with Bacillus amyloliquefaciens and Bacillus thuringiensis, respectively. Notably, Bacillus sp. P5 showed antimicrobial activity against pathogens such as Listeria monocytogenes and Bacillus cereus, in addition to antifungal activity. The presence of genes encoding pre-subtilosin (sboA), malonyl CoA transacylase (ituD), and the putative transcriptional terminator of surfactin (sfp) were detected in Bacillus sp. P5, suggesting the production of the bacteriocin subtilosin A and the lipopeptides iturin A and surfactin by this strain. For Bacillus sp. C3 the presence of sboA and spas (subtilin) genes was observed by the first time in members of B. cereus cluster. Bacillus sp. P5 showed emulsifying capability on mineral oil, soybean biodiesel and toluene, while Bacillus sp. C3 showed emulsifying capability only on mineral oil. The reduction of the surface tension in culture medium was also observed for strain P5, confirming the production of surface-active compounds by this bacterium. Monoprotonated molecular species and adducts of sodium and potassium ions of surfactin, iturin, and fengycin were detected in the P5 culture medium. Comparative MS/MS spectra of the peak m/z 1030 (C14 surfactin A or C15 surfactin B [M+Na]+) and peak m/z 1079 (C15 iturin [M+Na]+) showed the same fragmentation profile of standards, confirming the molecular identification. In conclusion, Bacillus sp. P5 showed the best potential for the production of antifungal, antibacterial, and biosurfactant substances.
Highlights
Spontaneous fermented foods are sources of microorganisms that frequently produce antimicrobial molecules
Two bacterial strains isolated from a fermented cassava product were initially identified as Bacillus sp
On the basis of biochemical and physiological tests, the strain C3 was found to be closely related to species of the B. cereus group while strain P5 shown to be associated with the B. subtilis/amyloliquefaciens group
Summary
Spontaneous fermented foods are sources of microorganisms that frequently produce antimicrobial molecules. Traditional fermentation of cassava is dominated by lactic acid bacteria, but yeast and Bacillus spp. were described Lacerda et al (2005). Bacillus spp. are known as cassava endophytic bacteria (Melo et al, 2009). Among the useful metabolites produced by Bacillus spp., a diversity of peptide antibiotics has been described by Stein (2005). These include well known substances such as bacitracin, bacteriocins and antimicrobial lipopeptides produced by multiple-step enzymatic processes (Stein, 2008; Abriouel et al, 2011). Some lipopeptides produced by Bacillus are biosurfactants of great interest, given that they may be explored as an alternative to synthetic surfactants, providing advantages such as biodegradability and low toxicity to humans, animals, and plants (Angelini et al, 2009)
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