Rattanaporn Thakaew^{1, 2}, Suraphon Jaiwongsa³, Chayakorn Pumas⁴, Suparin Chaiklangmuang^{2, 5,}

This study aimed to enhance protein content in low-grade maize to higher than 24%w/w, though fermentation with yeast (Saccharomyces cerevisiae, Candida utilis, Candida tropicalis) and bacteria (Bacillus subtilis, Lactobacillus plantarum, and Streptococcus thermophilus). Starch in low-grade maize was digested through enzyme hydrolysis into monosaccharide or glucose, which used as the main substrate in fermentation. Yeast consumed more glucose (95%) and at a faster rate than bacteria, which consumed glucose less than 20% glucose from low-grade maize hydrolysate. After the fermentation, protein contents from the cultures of yeast and bacteria significantly increased from low-grade maize substrate (8.68%w/w) to 29.05%, 31.30%, 29.85%, 28.95%, 29.85%, and 18.85%w/w when cultivated with S. cerevisiae, C. utilis, C. tropicalis, B. subtilis, and L. plantarum, respectively, which were significantly increased about 4 times from initial protein content in low-grade maize that higher than 24%w/w protein. But S. thermophilus obtained the lowest protein content as 18.85%w/w with 2 times increase. The results indicated that, the cultivation of yeast and bacteria effectively enhanced the protein cell in low-grade maize through fermentation. The reduction in carbohydrate content was inversely proportional to the increase of cell number of biomass and the amount of protein production that can be used as alternative protein sources for feeds.

bacteria, fermentation, maize, single cell protein, yeast