Abstract:
Sequencing batch reactors (SBRs) were used for producing biosurfactants by Pseudomonas aeruginosa SP4, which was isolated from a petroleum-contaminated soil in Thailand. The studied SBRs were operated at a constant temperature of 37°C under aseptic conditions with a 1,500 ml working volume, 500 ml feeding volume, and 500 ml decanting volume. Palm oil and a mineral medium were used as the carbon source and the nutrient source, respectively. Glucose (another type of carbon source) was added to the mineral medium for the enhancement of microbial growth which, in turn, increases the biosurfactant production. The oil-to-glucose ratio was varied in this work in order to determine the optimum ratio of oil-to-glucose for a maximum yield of biosurfactant. The results showed that the optimum ratio for biosurfactant production was 40/1. It provided a surface tension reduction of 58.5% and a surface tension of 29.9 mN/m, corresponding to a highest COD and oil removal of 85.1% and 77.7%, respectively. The finding exhibited that the biosurfactant was produced after 6 h of the aeration step caused the sharply decrease of surface tension before constant at around 28 to 31 mN/m. From the critical micelle dilution (CMD) method results, that the biosurfactant concentration was found to be 1.11 times CMC.
