Lipopeptide biosurfactant production by chitosan-immobilized Bacillus sp. GY19 and their recovery by foam fractionation

Abstract

Bacillus sp. GY19 was immobilized on chitosan to increase cell density and facilitate lipopeptide production. Palm oil was added to a waste glycerol based medium as precursor for the lipopeptides. The immobilized cells could be reused in stirred tank fermenter for at least 6 cycles with an optimal condition of 80g/L immobilized cells, 10% (v/v) waste glycerol and 1.25% (v/v) palm oil. The highest lipopeptide concentration observed during the steady state was 7.12g/L. The presence of chitosan in the fermenter reduced foaming problems due to its absorption property, which could interrupt the aggregation of air bubble and lipopeptides. The lipopeptides were separated and purified from the culture medium by a simple design foam fractionation unit. The amounts of lipopeptides in foamate produced from palm oil and crude palm oil added culture media were 10.9 and 9.8g/L, respectively. HPLC profile of lipopeptide extracted from the foamate had less impurity peaks than that from the culture medium. Both foamate samples showed 100% oil displacement efficiency with diesel oil, followed by Arabian light oil and heavy oil. It is thus possible to apply the sequential lipopeptide production and recovery process for producing a ready-to-use foamate for petroleum remediation.