Solid-state fermentation for 'whole-cell synthetic lipase' production from Rhizopus chinensis and identification of the functional enzyme

Major process parameters affecting the production of whole-cell synthetic lipase (WCSL) by Rhizopus chinensis in solid-state fermentation were optimized based on synthetic activity. A combined substrate of wheat flour with wheat bran (3/2, w/w) supported both good biomass growth and enzyme production. The maximum synthetic activity of 24,447 U/kg substrate was reached by selecting a moisture content of 70%, initial pH of 6.5, supplementation of peptone (2%, w/w) as additional nitrogen source and olive oil (2%, v/w) as inducer, after 72 h of incubation. This production represented a 15.27-fold increase of lipase synthetic activity compared to the initial medium. The synthetic lipase was purified by ammonium sulfate precipitation, hydrophobic interaction and gel filtration to homogeneity, with yield and purification fold of 2.6% and 55.2, respectively, and the molecular weight was estimated to be 60 kDa by SDS-PAGE. Validation of functional enzyme was carried out by catalyzing the synthesis of ethyl flavor esters, and the result showed that conversion of ethyl octanoate and ethyl caprate reached 95%. (c) 2007 Elsevier Ltd. All rights reserved.