Liquid-surface immobilization system and liquid–liquid interface bioreactor: Application to fungal hydrolysis

Novel fungal cultivation and bioconversion systems are proposed. Spores and mycelia of a fungus suspended in a liquid medium were effectively floated on a liquid surface by the aid of a ballooned microsphere (MS). Many fungi such as Aspergillus and Penicillium formed a thick and physically strong fungus-MS mat on the liquid surface followed by stationary cultivation (LSI). The fungus-MS mat of Absidia coerulea IFO 4423 was overlaid by a solution of 2-ethylhexyl acetate (1) in n-decane (liquid–liquid interface bioreactor, L-L IBR). The strain could efficiently catalyze the hydrolysis of 1 to 2-ethyl-1-hexanol (2). The accumulation of 2 in the L-L IBR was significantly higher than those in emulsion and organic-aqueous two-liquid-phase systems and a formerly reported interface bioreactor (solid–liquid interface bioreactor, S-L IBR). Furthermore, lipase production in the LSI system was also higher than that in a submerged cultivation system.