ISOLATION, SCREENING, AND CHARACTERIZATION OF BIOSURFACTANT-PRODUCING Bacillus spp. FROM SOIL AND THEIR POTENTIAL BIOFILM INHIBITORY ACTIVITIES AGAINST Pseudomonas aeruginosa

Biosurfactants are surface-active compounds usually produced by microbial cells, thus, their biodegradable nature and low toxicity. The capability to lessen surface and interfacial tensions characteristic of these compounds paved the way for their potential to inhibit biofilm formation. Biofilms are complex matrices of microbial cells formed on surfaces which provide microorganisms protection against substances found in the environment, including antimicrobials. In this study, Bacillus spp. isolated from soil samples were screened for their production of biosurfactants through Oil Drop Collapse and Parafilm M assays. Out of 12 isolates, our, GAT-01, GAT-04, GAT-05, and GAT-07, tested positive, and were identified based on their phenotypic and genotypic characteristics as B. pseudomycoides, B. cereus, B. pseudomycoides, and B. mycoides, respectively. GAT-01 was able to yield the highest biofilm inhibition activity against Pseudomonas aeruginosa ATCC 27853 with 43.12%, GAT-04 with 32.42%, GAT-05 with 35.78%, while GAT-07 showed the lowest activity with 26.91%. No antibacterial activities against P. aeruginosa ATCC 27853 were observed. Quorum sensing inhibition assay using Chromobacterium violaceum ATCC 12472 also showed negative results for all the biosurfactants. These present the potential of biosurfactants from Bacillus spp. as bioactive substances against biofilm formation through physical interactions.