Production of Fermented Solid Containing Lipases from Penicillium polonicum and Its Direct Use as Biocatalyst in the Synthesis of Ethyl Oleate

Abstract

Enzymatic catalysts, such as lipases, have been extensively studied due to their promise as an alternative to chemical catalysts. They offer advantages like biodegradability (green biotechnology) and the potential for enzyme recycling (turnover), leading to reduced operational costs. The primary objective of this study was to produce lipase from the fungus Penicillium polonicum through solid-state fermentation, utilizing agro-industrial waste as substrate. The aim was to apply the obtained lipase as a biological catalyst in the synthesis of ethyl oleate ester. In the lipase production process, the filamentous fungus P. polonicum, along with sunflower seed cake (SSC) and rice husk (RH), served as substrate and support, respectively, for solid-state fermentation (SSF). Experiments involved varying proportions of both substrate and support (0%, 25%, 50%, 75%, and 100% (RH) and 100% (SSC)). Subsequently, the impact of glycerol as an inducer (1%, 3%, and 5%, with a 25/75% SSC/RH ratio) at SSF was investigated. The obtained results revealed a catalytic activity of 29.3 U g⁻¹ under optimal conditions: 55% moisture, 25/75% SSC/RH, and at 27 °C during 96 h of fermentation. The lipase produced was employed as an enzymatic catalyst in studies involving the synthesis of ethyl oleate ester in n-heptane, utilizing experimental design 2³. Variables such as temperature, enzymatic activity, and molar ratio (alcohol/acid) were modified. The best experimental conditions for the enzymatic synthesis of ethyl oleate ester were determined to be an alcohol/acid molar ratio of 6:1, a temperature of 37 °C, and an enzymatic activity of 60 U. This resulted in 100% conversion into ester within 5 h of reaction time. The outcomes demonstrated that lipase effectively catalyzed the synthesis of ethyl oleate, a biodiesel ester, with a high yield.