Solid-state Fermentation of Cassava (Manihot esculenta) Peels Using Rhizopus Oligosporus: Application of the Fermented Peels in Yeast Production and Characterization of α-amylase Enzyme Produced in the Process

Abstract

Solid-State Fermentation (SSF) of cassava peels was studied using Rhizopus oligosporus. Several biochemical parameters of the fermented cassava peels extract (FCPE) were determined. The applicability of the FCPE as nutrient source for Saccharomyces cerevisiae (yeast) growth was also investigated. There was a significant (p < 0.05) decrease in glucose, reducing sugar concentrations, in vitro antioxidant capacity and an increase in soluble protein content across the pH range (5–9) in FCPE when compared with the unfermented control. The fermented cassava peels supported higher growth of yeast (O.D600nm, 0.465 ± 0.005) than the unfermented cassava peels (O.D600nm, 0.113 ± 0.001), probably due to its higher protein content. α-Amylase was produced extracellularly from R. oligosporus during the fermentation process with an optimum substrate concentration of 1%w/v starch and optimum contact time of 30 min. The optimal temperature and pH of the partially purified enzyme were 60 °C and pH 7, respectively, with Vmax and Km values of 17.36 Units/mL and 0.33%w/v. Ca2+ increased the activity of the enzyme, but Na+ and Al3+ inhibited its activity. Sodium dodecyl sulphate (SDS) and ethylene diamine tetra acetic acid (EDTA) also inhibited the enzyme. The findings of the present study could serve as a precursor data source for protein, α-amylase and yeast production by allied industries such as animal feeds and biotechnology industries.