Utilization of oil mill effluents as alternative substrate for biosurfactant production by Bacillus sp. GY19 and its application in crude oil contaminated soil washing

Abstract

In order to reduce the cost of biosurfactant production, wastes from vegetable oil processes were used as alternative substrate for chitosan immobilized Bacillus sp. GY19. Palm oil mill effluent and soy molasses were interesting as alternative substrate since the production of palm oil in Thailand is rated as 3rd rank of world market and soybean oil production also plays an important role in vegetable oil production in the country. Utilization of palm oil mill effluent resulted in small amount of crude biosurfactant produced with no activity of surface active agent shown. It was probably the palm oil mill effluent contained toxic phenolic compounds that affected production activity of bacteria. Meanwhile, utilization of soy molasses gave 4.37 g/l of crude biosurfactant with good activity of surface active agent. The determination of optimal condition and concentration of soy molasses as substrate revealed that 20% (w/v) of soy molasses gave the highest crude biosurfactant produced with productivity rate about 0.0365 g/l/h. Moreover, the produced biosurfactant could reduce the surface tension of medium from 64 to less than 40 mN/m and caused emulsification against diesel oil over 65%. Foam fractionation and freeze-dried biosurfactant were set to increase the concentration of biosurfactant above ACMC. The result of crude oil contaminated soil washing found that the biosurfactant from freeze-dried lyophilized with 8.43 g/l could wash crude oil out from the silt loam soil about 36.33 mg crude oil/g soil, comparable to 0.5 g/l of SDS and Tween 80. So, Bacillus sp. GY19 could utilize soy molasses as alternative substrate with good surface active agent produced.