Degradation of dual-species biofilms using hydrolytic enzymes produced by Bacillus subtilis 170 strain

I. Ganchev*, G. Dzhelebov

Department of Food Technologies, Faculty of Technics and Technologies, Trakia University Stara Zagora, Bulgaria

(Manuscript received 18 May 2022; accepted for publication 14 November 2023)

Abstract. Biofilms, that are the community of microorganisms attached on biotic or abiotic surfaces coated with a self-produced matrix, composed by exopolymeric substances, dominate in all habitats on the surface of the Earth, except in the oceans, accounting for ~80% of bacterial and archaeal cells. Hydrolytic enzymes have a number of industrial applications and have been indicated as an alternative to the traditional chemical methods that are used to eradicate microbial biofilms. In this study, we evaluated the ability of enzymatic extracts produced by Bacillus subtilis 170 to remove multispecies biofilms, formed by the interaction of Bacillus subtilis and Escherichia coli strains. After culture in liquid medium, containing inorganic nitrogen sources, the bacterial hydrolytic extracts showed protease (250 U/mL) activity. Cell-free supernatants of B. subtilis 170 strain with proteolytic activity were the most effective, and promoted the complete removal of Bacillus subtilis and Escherichia coli dual-species biofilms. Of the treatments using cell-free supernatants of B.subtilis 170 with proteolytic enzyme activities with 250 U/mL, total biofilm degradation was observed for both dual-species biofilms in this study. Thus, the hydrolases produced by Bacillus subtilis 170 strains evaluated here are highlighted as an interesting tool in the fight against microbial biofilms.