LIPASE BIOCATALYSIS IN THE PRODUCTION OF ESTERS

Lipase biocatalysis was investigated as a tool for the production of b utyl oleate and rapeseed oil 2-ethyl-1-hexyl ester by esterification a nd transesterification, respectively. We screened 25 commercially avai lable lipases and found that butyl oleate was produced at high yields from oleic acid and 1-butanol by lipases from Candida rugosa, Chromoba cterium viscosum, Rhizomucor miehei, and Pseudomonas fluorescens. The initial water content of the system, lipase quantity, and the molar ra tio of l-butanol to oleic acid were important factors in influencing t he ester yield In general, no ester was formed without the addition of water. The exception was Ch. viscosum lipase, which yielded 98% of es ter in 12 h with 1-butanol excess without additional water. The additi on of 3.2% water increased the initial rate of reaction. With an oleic acid excess and only 0.3% lipase, C. rugosa and R. miehei lipases yie lded 94 and 100% esters with initial water contents of 3.2 and 14%, re spectively. Lipase-catalyzed alcoholysis of low-erucic aci rapeseed oi l and 2-ethyl-1-hexanol without additional organic solvent also was st udied in stirred batch reactors. ln this case, C. rugosa lipase was th e best biocatalyst with an optimal 2-ethyl-1-hexanol to rapeseed oil m olar ratio of 2.8, a minimum of 1.0% added water, and 37 degrees C. An increase in temperature up to 55 degrees C increased the rate of reac tion but did not affect the final ester yield. The enzyme was inactiva ted at 60 degrees C. Under optimal conditions the ester yield increase d from 88% in 7 h to nearly complete conversion in 1 h when the lipase content was increased from 0.3 to 14.6%. ln a 2-kg small pilot scale, up to 90% conversion (97% of theoretical) was obtained in 8 h at 37 d egrees C with 3.4% lipase in the presence of Amberlite XAD-7 resin wit h 3% added water.