Towards circular economy: Agro-industrial by-products enabling in situ enzyme production for food and pharmaceutical applications

By-product materials impact the environment, cause global changes, and affect final product prices. Wheat bran, one of the most popular by-products of the milling industry, owing to its ample supply and cost-effectiveness, finds its primary application in animal feed and human consumption. Leveraging this material in various ways, not only reduces the amount of waste, but also promotes a circular economic model, allowing the preparation of value-added products, including enzymes. The present study demonstrates the potential of wheat bran's as a substrate for producing a "green-enzyme" mix through solid-state fermentation (SsF). On the second day of the SsF, cellulase activity (FPase) exhibited a notable value, exceeding 25 FPU/g ds , accompanied by endoglucanase (CMCase) values that greatly exceeded 140 U/g ds and glucoamylases over 60 U/g ds on day 6. A hydrolysis test on wheat bran showcases an increase in TRS by over 280% after 48 h. Further, the effect of different enzyme extraction procedures and storage conditions on the enzyme activity was studied. FPase and CMCase exhibited high stability when extracted with sodium citrate buffer and freeze-dried. In contrast, glucoamylase extracted with water retained activity under the same conditions. In addition, enzyme immobilization in a silanic matrix resulted in highly stable preparates: a weight loss of only 13.18% at 407.69 °C and a mere 19.38% loss at 734.56 °C was observed. SsF used for in situ enzyme production is an accessible and cost-effective process. The process possesses ecological and sustainable characteristics and can be easily integrated into various biotechnological processes. • A. awamori has successfully produced enzymes (FPase, glucoamylase, CMCase). • The enzymes obtained showed stability over 5 weeks. • The enzymatic blend increased total sugars by 280% in 48 h of hydrolysis. • Enzymes were efficiently immobilized by entrapment in sol-gel, a silanic matrix.