Use of Rhodotorula minuta live cells hosted in water-in-oil macroemulsion for biotransformation reaction

A lecithin/water/isooctane water-in-oil macroemulsion was used as a host system for biotransformation reactions. In particular, the hydrolytic activity of the yeast Rhodotorula minuta towards (±)-succinic acid bis-2-isopropyl-5-methylcyclohexyl ester and p-nithrophenylbutirate is reported. Evidence that R. minuta entrapped in w/o macroemulsion is able to hydrolyze the p-nithrophenylbutirate ester is presented. By performing the yeast-catalyzed hydrolysis of (±)-succinic acid bis-2-isopropyl-5-methylcyclohexyl ester, the synthesis of (-)-menthol was obtained, indicating that R. minuta retains its high stereoselectivity in the macroemulsion system. In addition, no significant differences were observed among the hydrolysis rates and yields obtained using yeast cells hosted into w/o macroemulsions containing different amounts of water. Optical microscopy studies on the distribution of diameters of the dispersed phase indicate that the macroemulsion system is stable in terms of polidispersity. The diameter of the w/o macroemulsion droplets is indeed constant irrespective of the addition of water and/or chemicals (involved in the biotransformation reaction) to the system hosting yeast cells. The reactor devised here might be applied to other interesting bioconversion processes.