Lipolytic production from solid-state fermentation of the filamentous fungus Penicillium polonicum and its applicability as biocatalyst in the synthesis of ethyl oleate.

Abstract

Lipases represent versatile biocatalysts extensively employed in transesterification reactions for ester production. Ethyl oleate holds significance in biodiesel production, serving as a sustainable alternative to petroleum-derived diesel. In this study, our goal was to prospect lipase and assess its efficacy as a biocatalyst for ethyl oleate synthesis. For quantitative analysis, a base medium supplemented with Rhodamine B, olive oil, and Tween 80 was used. Solid-state fermentation utilized crambe seeds of varying particle sizes and humidity levels as substrates. In the synthesis of ethyl oleate, molar ratios of 1:3, 1:6, and 1:9, along with a total enzymatic activity of 60 U in n-heptane, were utilized at temperatures of 30°C, 37°C, and 44°C. Reactions were conducted in a shaker at 200rpm for 60min. As a result, we first identified Penicillium polonicum and employed the method of solid-state fermentation using crambe seeds as a substrate to produce lipase. Our findings revealed heightened lipolytic activity (22.5 Ug-1) after 96h of fermentation using crambe cake as the substrate. Optimal results were achieved with crambe seeds at a granulometry of 0.6mm and a fermentation medium humidity of 60%. Additionally, electron microscopy suggested the immobilization of lipase in the substrate, enabling enzyme reuse for up to 4 cycles with 100% enzymatic activity. Subsequently, we conducted applicability tests of biocatalysts for ethyl oleate synthesis, optimizing parameters such as the acid/alcohol molar ratio, temperature, and reaction time. We attained 100% conversion within 30min at 37°C, and our results indicated that the molar ratio proportion did not significantly influence the outcome. These findings provide a methodological alternative for the utilization of biocatalysts in ethyl oleate synthesis.