Effect of Pleurotus ostreatus fermentation on cocoa pod husk composition: Influence of fermentation period and Mn2+ supplementation on the fermentation process

Cocoa pod husk (CPH) is a major agro-industrial residue in Ghana with a potential value as a low-cost unconventional feedstuff for livestock. However, its effective use is limited by poor nutrient composition, mainly due to its high lignocellulose or fibre and also low protein levels. White-rot fungi such as Pleurotus species are bio-catalytic systems for bioconversion processes such as the bioconversion of lignocellulose materials into value-added products including nutritious animal feed. Presence of metals such as manganese (II) ions is reported to enhance fungal enzyme activity in the bioconversion of industrial lignocellulosic residues. The current study investigated the viability of using and optimising a fermentation process involving edible oyster mushroom (Pleurotus ostreatus) as biocatalyst to improve the nutritional status of CPH. Fermentation period and level of manganese (Mn2+) ion supplementation of CPH were the two major factors of the fermentation process evaluated and optimised in this study. Mn supplementation was critical in producing a positive bioconversion effect on CPH by P. ostreatus. Five (5) weeks of P. ostreatus solid-state fermentation of CPH amended with MnCl2 at 0.075% (w/w) concentration, was observed as an economic and optimum treatment to produce positive and significant (P < 0.05) changes in CPH composition, i.e. 36% increment in crude protein and total soluble carbohydrates; 17% reduction in crude fibre and lignin as well as 88% reduction in total tannins.