Biosurfactant Production from Acetic Acid as a Strategy for Waste Sludge Utilization

We propose here the bioproduction of a surface active agent (biosurfactant) from acetic acid as an innovative strategy for using waste sludge as a source of acetic acid by anaerobic digestion, and basic studies on biosurfactant production, characterization and application were performed. Pseudomonas putida BH was screened out of 23 laboratory stock culture strains as a bacterial strain capable of producing (a) kerosene-emulsifying surfactant (s) form acetic acid. It produced a biosurfactant during the logarithmic growth phase from acetic and propionic acids. The crude biosurfactant, recovered by extraction with benzene, contained sugar, protein and lipid at 16, 22, and 3% (w/w), respectively. Molecular weight of the surfactant was estimated as approximately 2 million by gel filtration. The crude biosurfactant showed emulsifying and solubilizing activities against a variety of hydrocarbons, and was especially effective against aromatics. Addition of 50 mg/l of the crude biosurfactant markedly enhanced biodegradation of kerosene by an enrichment culture, while the biosurfactant itself was readily mineralized by a non-acclimated activated sludge, suggesting its successful application to oilbioremediation. Experimental results indicate that it may be possible to apply the proposed strategy in future.