The use of microorganisms in increasing the protein yield of cassava (Manihot esculenta Crantz) peel wastes

Abstract

Growth and microbial protein production on hydrolyzed cassava peel waste by Trichoderma viride and Lactobacillus delbrueckii NRRL B-763 were investigated. Trichoderma viride was selected based on its high cellulase activity on filter paper (2.91 mg glucose/mL), cotton wool (3.08 mg glucose/mL) and carboxymethylcellulose (3.46 mg glucose/ mL) while Lactobacillus delbrueckii NRRL B-763 produced 5.84 mg protein/g in cassava peel after 72 h. Samples of cassava peel were hydrolyzed with the solutions of HCl, H2SO4 and NaOH at 0.5% concentration. The hydrolysate was neutralized to pH 6.5 and supplemented with KH2PO4 (5% w/v), urea (2.7% w/v) and (NH4)2SO4 (9% w/v). The hydrolysates produced by the solutions of HCl contained higher reducing sugar and soluble sugar content than H2SO4 and NaOH hydrolysates. The culture of Trichoderma viride was used in single culture fermentation of hydrolyzed cassava peels or in mixed culture fermentation with Lactobacillus delbrueckii NRRL B-763. Protein yield produced in 0.5% HCl hydrolysates was significantly (p ≤ 0.01) higher than that in H2SO4. The unhydrolyzed control samples produced the lowest protein. This study demonstrated the potential of cassava peel waste as a substrate for a recycling process and by- product recovery.