Protein Enhancement of Yam (Dioscorea rotundata) Peels with Single-or Co-Inoculation of Aspergillus niger Van Tieghem and Trichoderma viride Pers Ex Fr. Under Solid-State Fermentation

This study assessed the protein enrichment of sterilized and non-sterilised yam peels substrates fermented for 21 days at 25°C with mono- and co-cultures of Aspergillus niger and Trichoderma viride. Yam substrates were harvested at 0, 7, 14, and 21 days intervals for protein content and other chemical composition analyses. Results showed an overall percentage increase in protein contents of sterilised yam peels by 71.80% for A. niger, 58.03% for T. viride, and 80.60% for co-culture of A. niger and T. viride. Protein contents in non-sterilised yam peels increased by 113.30%, 95.00%, and 96.45% for A. niger, T. viride and co-culture of the test fungi, respectively. The significantly (p ≤ 0.05) higher protein contents of the fermented, non-sterilised yam peels suggest possible successional microbial colonization of the substrate, and their combined, cumulative contributions to protein enhancement, unlike the sterilised yam peels. Ash content significantly (p ≤ 0.05) increased in both sterilised and non-sterilised yam peels. These findings underscore the fact that, through fungal bioprocessing, protein contents of yam peels can be significantly enriched for value-addition. The practical implications of the findings are discussed