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Olive oil cake is a by-product from the olive oil processing industry and can be used for the lipase and protease production by Candida utilis in solid state fermentation. Different carbon and nitrogen sources were evaluated, and the results showed that the supplementation of the substrate with maltose and starch as carbon sources and yeast extract as a nitrogen source significantly increased the lipase production. The best results were obtained with maltose, whereas rather low lipase and protease activities were found with glucose and oleic acid. Response surface methodology and a five-level-three-factor central composite rotatable design were used to evaluate the effects of the initial moisture content, inoculum size and fermentation time on both lipase and protease activity levels. A lipase activity value of ≈25 U g(-1) and a protease activity value of 110 U g(-1) were obtained under the optimized fermentation conditions. An alkaline treatment of the substrate appeared to be efficient, leading to increases of 39% and 133% in the lipase and protease production, respectively. The results showed that the olive cake could be a good source for enzyme production by solid state fermentation.

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Ethyl cinnamate, an ester known as flavor and fragrance compound, has been synthesized using two immobilized bioreactor systems, batch and fluidized bed bioreactors. The enzyme used for this synthesis is a commercial lipase B preparation, Novozyme 435. Initial kinetic studies were conducted in both employed bioreactor configurations, and kinetic constants were obtained. Several models were tried for fitting of experimental data, but the best fit, for both bioreactors, was obtained when the ping-pong bi-bi mechanism was used. Interestingly enough, ethanol inhibition occurred in batch bioreactor, but it did not exist in the fluidized bed bioreactor. Solid−liquid mass transfer coefficients were calculated for both bioreactors to determine whether mass transfer limitations existed in either of these systems. The calculation of Damkoḧler numbers and Thiele modulus confirmed that mass transfer limitations had no effect on the overall reaction in both bioreactors.