Enhancement of the Nutritive Value Of Cocoa (Theobroma Cacao) Bean Shells For Use as Feed For Animals Through a Two- Stage Solid State Fermentation With Pleurotus Ostreatus and Aspergillus Niger

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The animal industry is being faced with several challenges one of them is the high cost of feeding as a result of the exorbitant prices of feed ingredients. This challenge facing particularly the poultry industry is being addressed by the use of agro-industrial by-products (AIBPs) as alternative energy sources for animal feeding. However, these by-products are faced with certain limitations such as their low inclusions in animal diet especially poultry and pigs due to their high fibre content and high levels of anti-nutritional factors. One of such agro-wastes is the cocoa bean shells (CBS) produced from the cocoa processing factories and underutilized due to its high fibre content (mainly lignocellulose) and high theobromine content. The application of biotechnology by the use of fungi with GRAS status to improve its feed value for animals was therefore investigated. The dried CBS obtained from the factory was taken through a two-stage solid state fermentation. The CBS was milled into 2mm particle size, composted and pasteurized. The pasteurized substrate was then fermented with the spawn of Pleurotus ostreatus for 6 weeks followed by Aspergillus niger fermentation for seven days. The fermentation of the CBS with P. ostreatus significantly increased (p<0.05) the protein content by 25.22% and decreased (p<0.05) the cellulose, hemicellulose and lignin by 49.93%, 39.99% and 34.65% respectively at the sixth week, the optimum fermentation period. The mineral content (calcium, phosphorus and potassium) of the P. ostreatus fermented CBS was also significantly enhanced (p<0.05) at the sixth week of fermentation. The P.ostreatus fermented CBS used as substrate for the second stage A. niger fermentation had its theobromine content significantly reduced (p<0.05) by 72.89% at the end of the seven days of fermentation. The degradation of the complex carbohydrates of the CBS by the fungi increased the level of soluble carbohydrates (from 35.05% to 45.30%) which resulted in a 33.64% increase in Metabolizable Energy (M.E) in the fermented product. These results make the CBS fermented with P. ostreatus and A. niger more suitable for use as feed material for animals.
A Thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the Degree of Master of Science in Biotechnology