PRELIMINARY SCREENING OF BIOSURFACTANT-PRODUCING MICROORGANISMS ISOLATED FROM HOT SPRING AND GARAGES IN NORTHERN THAILAND

Biosurfactants are surface-active compounds produced by microorganisms. These molecules reduce surface tension between aqueous solutions and hydrocarbon mixtures. In this study, we collected soil samples from different hot spring resources in Chiang Mai and Chiang Rai provinces, as well as contaminated soil from garages and screened for biosurfactant-producing microorganisms. Furthermore, we also used stock culturing strains (18 strains of actinomyces and 13 strains of bacteria) from Culture Collection of Excellent Center for Sustainable Development on Bioresources, Chiang Mai University. One hundred and ninety-seven bacterial strains (69 strains from the hot spring and 128 strains from the garage) were isolated  and cultured by enriching carbon and nitrogen sources. Each culture medium was sampling to confirm the ability in biosurfactant production. These were conducted using emulsification activity determination (EA), oil spreading technique and parafilm M method. The results reveal that twenty-five strains of bacteria from garage sites  presented  positive activity which are better than stock bacterial strains. Among these, the emulsifying capacity evaluated by the E24 emulsification index range from 7.8-63.3% EA. In addition, the oil displacement area (ODA) was displayed at 9.62-66.50 cm2 and the collapse of droplets on parafilm M method was showed with the average of 5-8 mm. Interestingly,   the bacterial isolate (SCMU106) selected from garage site gave the highest values in emulsification activity, oil spreading and parafilm M determination. This will be further investigated in biosurfactant production for health and cosmetics application.  

Keywords: biosurfactant, surface tension, oil spreading, emulsification index

Corresponding author: E-mail: scboi009@chiangmai.ac.th