Selection of Suitable Starter Cultures for Nutrient Composition Enhancement of Spent Sorghum Grains and Sweet Potato Leaves

Abstract

In an effort to find suitable starter cultures for enhancing the nutrient compositions of spent sorghum grains (SSG) and sweet potato leaves (SPL), three microorganisms, Aspergillus niger, Chaetomium globosum and Saccharomyces cerevisiae were used in singles and in combinations to ferment SSG and SPL for 21 days at a temperature of 25 ± 2oC. All the microbial treatments brought about increases in crude protein, crude fat and energy contents of both substrates, with accompanying reductions in crude fibre contents. SPL fermented with the combination of C. globosum and S. cerevisiae had the highest protein, fat and energy increases observed (96%, 368% and 10.2% respectively). The combination of C. globosum and S. cerevisiae also caused the highest crude fibre reduction in SSG (33.86%) while the combination of all three test organisms caused the highest crude fibre reduction in SPL (37.44%). Ash content increased in most cases while nitrogen free extract (NFE) values generally declined. The consortium of the three test organisms was concluded to be the best starter culture for enhancing the nutrient composition of SSG while the combination of C. globosum and S. cerevisiae was best for SPL.