Multipurpose fixed-bed bioreactor to simplify lipase production by solid-state fermentation and application in biocatalysis

Abstract

A multipurpose fixed-bed bioreactor was evaluated, to simplify the process of producing lipase and its application in biocatalysis. Rhizomucor miehei lipase was produced by solid-state fermentation (SSF) in the fixed-bed bioreactor and generated a fermented solid with 30 U/g lipase activity and a synthesis capacity of 80% (conversion at 6 h of reaction in a standard stirred reactor). The fermented solid was then dried by forced aeration in the same column (1.0 L air/min, 35 °C) and the dried fermented solid (5 wt.% water) showed the same synthesis capacity as the freeze-dried standard, with high storage stability at 4 °C and 25 °C (14 months with no decrease in synthesis capacity). The reaction performed in the multipurpose bioreactor (one-pot system) showed relatively low conversion (30% of the conversion obtained in the stirred reactor at 6 h) when only babassu cake was employed as the fermentation substrate, due to the preferred pathways formed as a consequence of bed retraction during drying. Therefore, SSF was carried out with a mixture of 60:40 wt.% babassu cake and palm fiber (used to give structure to the fermented solid and prevent retraction during drying), and the reaction in the one-pot system reached a maximum conversion of 71%.