Bioprocess development to add value to canola cake used as substrate for proteolytic enzyme production

Abstract

Microbial proteases are one of the largest groups of industrial enzymes. This important market has led to a need for technically and economically efficient bioprocesses for protease production that could be exploited commercially. The aim here was to develop a complete bioprocess for protease production, from microbial fermentation up to dried product formulation. Evaluation was made of the effects of operational conditions on the production of protease by a selected strain of Aspergillus oryzae, cultivated under solid-state fermentation (SSF) with canola cake as a sole carbon source in an instrumented lab-scale bioreactor. Statistical experimental design revealed that the air flow rate, inlet air relative humidity, and initial substrate moisture content had significant effects on the efficiency of protease production. The highest protease production by A. oryzae was achieved at a fixed air flow rate of 12mL/min, with inlet air relative humidity within the range 66–94% and initial substrate moisture content between 30% and 40%. The enzymatic extract produced under the selected conditions was spray dried using different concentrations of additives (glucose, maltodextrin, and CMC). The stability of the dried enzymatic powder during shelf storage was evaluated over a period of 90 days. There was a positive effect of CMC and a negative effect of glucose on protease activity and stability, while the influence of maltodextrin was negative in enzyme recovery at time zero, but it was positive on protease stability over a longer period. The spray dried proteolytic enzymatic formulation obtained from SSF of canola cake using A. oryzae has potential for applications in the industrial sector.