Optimization of extracellular lipase production from the biocontrol fungus Nomuraea rileyi

Abstract

Lipases are important cuticle-degrading enzymes that hydrolyze the ester bonds of waxes, fats and lipoproteins during the infection of insects by the fungus Nomuraea rileyi. Lipase production by the N. rileyi strain MJ was optimized by varying environmental and nutritional conditions in culture medium containing different vegetable oils at various concentrations with shaking at 150 rpm for 8 days at 25°C. The maximum lipase production was obtained using castor oil (30.5±0.6 U mL−1), followed in order by coconut oil (20.8±0.4 U mL−1), olive oil (20.8±0.4 U mL−1) and cottonseed oil (20.6±0.4 U mL−1). The highest lipase activity (37.7±0.4 U mL−1) was obtained when castor oil was used at a concentration of 4% (v/v) of basal medium. When the surfactant Tween 80 was added at the fourth day rather than at the beginning of incubation, a maximum lipase activity of 44.9±3.5 U mL−1 was obtained. The optimal temperature and pH for lipase production were 25°C and pH 8.0, respectively. This is the first report on lipase production by the biocontrol fungus N. rileyi.