Formulation of apple pomace, orange peel, and hazelnut shell mix for co-production of bacterial pectinase and cellulase enzymes by mixture design method

The cost of enzyme is high due to mostly pure carbon and nitrogen sources. Thus, there is a still need for exploring alternative feedstock to enhance enzyme production and reduce the cost. In this study, proportions of apple pomace, orange peels, and hazelnut shells were formulated by the extreme vertices mixture design (EVMD) method in an attempt to enhance co-production of bacterial pectinase and cellulase enzymes in comparison to production medium with single feedstock. Bacillus subtilis was grown in fermentation media containing acid-pretreated feedstock and minerals at initial pH of 7.0 and 30 degrees C for 72 h. Analysis of results from EVMD resulted in a mix of 20% apple pomace, 30% orange peels, and 50% hazelnut shells as optimal, which provided 8.27 U/mL of pectinase and 0.5 U/mL of cellulase under experimentation. These results implied 40% increase in pectinase but no change in cellulase production compared to the pectinase (5.93 U/mL) and cellulase (0.49 U/mL) obtained with hazelnut shell hydrolysate medium. It was also found that hazelnut shells gave slightly higher pectinase than apple pomace and orange peel media. This study proves the use of food processing wastes in mixed form rather than separate feedstock for enhancing pectinase production.