Isolation and characterization of biosurfactants-producing bacteria isolated from palm oil industry and evaluation for biosurfactants production using low-cost substrates

摘要

Biosurfactants-producing bacteria were isolated from various palm oil refinery industrial sites in the south of Thai- land. Isolates were screened for biosurfactant production by using low-cost, agro-industrial by-products or wastes as a substrate. Based on drop collapsing test and emulsification activity, 25 isolates were selected. All the selected isolates reduced the growth medium surface tension to 40 m N/m and produced emulsions with xylene. Twenty isolates exhibited high emulsion-stabilizing capacity, maintaining more than 50% of the original emulsion volume for 24 h. The phylogenetic position of these 25 isolates was evaluated by 16S r RNA gene sequence analysis.The production of biosurfactants was determined for strains representative of 15 different bacterial genera, six of them (Azorhizobium, Buttiauxella, Comamonas, Halopenitus, Haloplanus and Sinorhizobium ) have been for the first time reported in this study as biosurfactant-producing strains. Additionally, Sinorhizobium meliloti AS91 and Marinobacter hydrocarbonoclasticus AS51 produced extracellular biosurfactant which exhibited the lowest surface tension (32 m N/m) and emulsification activity (69%) when cashew apple juice and used vegetable oil were used as the carbon source, respectively. Overall, this is the first study of a phylogenetic analysis of biosurfactant-producing bacteria from palm oil refinery industry site and their ability to produce biosurfactant on renewable substrates.