The effect of olive cake types on lipase production by isolated Rhizopus sp. and process statistical optimization

The aim of this work was to study the production of extracellular lipase by solid-state fermentation with different olive cakes varieties including Mary, Shenghe and Yellow from isolated fungi using agro-industries waste such as rice straw, rice barn and wheat straw. The highest yields of enzyme were obtained in solid-state fermentation using rice straw as solid substrate in combination with 40% Mary olive cakes as inducer. The initial screening by using Plackett-Burman's design demonstrated that among the tested factors, lactose and ammonium sulfate of the medium significantly (p < 0.05) enhanced the lipase production. Further optimization of lipase production by isolated fungi in solid-state fermentation by applying response surface methodology was achieved, which revealed these as follows: 0.42 (% w/v) for lactose and 0.09 (% w/v) for ammonium sulfate. Also the enzyme kinetics parameters, biochemical properties, thermodynamic of thermal deactivation and deactivation rate constant of enzyme were determined.