Biodiversity of thermotolerant Bacillus sp. producing biosurfactants, biocatalysts, and antimicrobial agents

Abstract

Thermotolerant bacteria isolated from soil and water samples taken from 76 hot springs in Thailand were investigated for their biosurfactant, biocatalytic, and antimicrobial properties. DNA samples purified from 148 pure isolates were PCR amplified using primers specific for the 16S rDNA hypervariable region of the genus Bacillus. The DNAPAR phylogenetic tree clearly demonstrated that these isolates were related to Bacillus niacini, B. korensis, B. firmus, B. flexus, B. megaterium, B. pumilus, B. licheniformis, B. subtilis, B. fusiformis, Oceanobacillus picturae, Anoxybacillus gonensis, Aneurinibacillus thermoaerophilus, and Anoxybacillus flavithermus. Determination of their biosurfactant properties using the oil spreading technique indicated that B. megaterium (SR8.5), B. licheniformis (CM8.2), and B. pumilus (SR4.4) possessed the highest biosurfactant activity. In addition, lipase, cellulase, and xylanase activities were detected from B. megaterium (CP1, SR8.5), B. pumilus (PR3.2), and B. licheniformis (CM1.1, LP3, MH11.3, LP3, NN2.3, PR2.3, PR2.2, PT1.2). While B. subtilis (CM3.3, CM14.1) had the highest cellulase activity, most isolates showed either undetectable or relatively low lipase and xylanase activities.