PRODUCTIVE BIOFILMS FROM MESOPHILIC TO THERMOPHILIC ENDOSPORE-FORMING BACILLI FOR INDUSTRIAL APPLICATIONS

Abstract

The basic biofilm characteristics and extracellular polymeric substances (EPSs) production of Bacillus licheniformis E114 (mesophile), Bacillus pumilus D75b, Brevibacillus thermoruber B93 (facultative thermophile) and Anoxybacillus caldiproteolyticus D621 (thermophile) isolates were evaluated in this study. They were initially investigated in terms of their pellicle formation at the air-liquid interface, complex carbohydrate production in TSA (Tryptic Soy Agar) medium supplemented with calcofluor dye, and also colony morphologies in TSA medium supplemented with Congo Red dye. Their biofilm productions on abiotic surfaces such as polystyrene and stainless steel were also quantified by crystal violet binding assay and viable cell enumerations. The ideal way for the mechanical removal of the adherent cells from the steel surface such as bead vortexing or scraping were also tested for each isolate. The optimal growth and biofilm production parameters of E114, D75b, B93, and D621 in terms of pH, NaCl, and temperature were determined. Under optimal conditions, their EPSs components such as carbohydrate, protein, and eDNA were also measured quantitatively. The isolates evaluated in this study presented colony morphotypes in different characteristics on Congo Red agar that display also unique biofilm forming capacities for each isolate. Also, useful optimization approaches were determined that might be adapted to potential industrial applications for the biofilm and EPSs producers. According to these findings, four different endospore-forming bacilli exhibiting mesophilic to thermophilic growth, and biofilm production, possessing various EPSs contents which may be novel were elucidated that could be important in many industrial processes.