Use of carbohydrases to promote protein extraction from rice bran and soybean meal: A comparative study

An in-depth study of commercial carbohydrases was performed to select those that are most performing to increase the protein content of two valuable agri-food waste, rice bran (RB) and soybean meal (SM). In particular, defatted RB (DRB) and SM were subjected to hydrolysis mediated by both one and the combination of two commercially available enzyme formulations, i.e. Ceremix® Plus MG, Celluclast® 1.5L, Ultraflo® L and Viscozyme® L. Sugar extraction yields, a useful parameter to evaluate the carbohydrase efficiency, were calculated as weight of the dried supernatants obtained after each enzymatic treatment, with respect to the starting weight. Instead, the percentage of proteins of the solid residues (DRBP and SMP) was evaluated according to the AOAC Dumas method, using elemental analysis. In case of RB, starting from a 19% protein content, a protein enrichment of 105 ± 4% was achieved using Ceremix® Plus MG and Celluclast® 1.5L. Regarding SM, an enrichment of 33 ± 4% was reached with Viscozyme® L. In both cases, the highest sugar extraction yields, specifically 64 ± 1% and 49 ± 2%, were obtained for DRB and SM, respectively. Results showed that the selection of specific carbohydrases tuned according to the polysaccharides composition is essential to increase the availability of proteins present in agri-food waste.