Biotechnological Application of Saccharomyces cerevisiae and Lactobacillus delbrueckii sp. bulgaricus for Protein Enrichment of Fermented Unmalted and Malted Sorghum (Sorghum bicolor (L.) Moench)

Abstract

This study evaluated changes in protein contents of malted and unmalted sorghum, and their formulated blends, after fermentation for 10 days at 25°C with mono and cocultures of Saccharomyces cerevisiae and Lactobacillus delbrueckii sp. bulgaricus. Fermentation of unmalted and malted sorghum and their formulated blends of 1 : 1 ( $w/w$ ), 3 : 1 ( $w/w$ ), and 1 : 3 ( $w/w$ ) by S. cerevisiae and L. bulgaricus could increase their protein contents. Thus, there was an increase in protein content of fermented, malted sorghum by 68.40% for S. cerevisiae, 34.98% for L. bulgaricus, and 76.59% for cocultures of S. cerevisiae and L. bulgaricus; protein contents of fermented, unmalted sorghum also increased by 58.20, 39.36, and 55.00% for monoculture of S. cerevisiae, monoculture of L. bulgaricus, and coculture of S. cerevisiae and L. bulgaricus, respectively. S. cerevisiae was more effective in enriching protein content of the 1 : 3 ( $w/w$ ) formulated blend of unmalted-malted sorghum by 77.59%; L. bulgaricus was more effective in enriching protein content of the 3 : 1 ( $w/w$ ) unmalted-malted sorghum blend by 60.00%; coculture of S. cerevisiae and L. bulgaricus enriched the protein content of 3 : 1 ( $w/w$ ) unmalted-malted sorghum substrate by 44.54%. Significant ( $p\le 0.05$ ) increases in fat with corresponding decreases in carbohydrate and fibre contents were consistently recorded in malted and unmalted sorghum. In the formulated blends of sorghum, fat, carbohydrate, and fibre contents either increased or decreased erratically after fermentation. There were significantly ( $p\le 0.05$ ) higher protein contents in malted sorghum, compared to unmalted sorghum. These findings show that solid-state microbial fermentation technology, using S. cerevisiae and L. bulgaricus, either as mono- or coculture, could effectively enrich the protein contents of unmalted and malted sorghum and their formulated blends. The implications of the findings for infant and adult nutrition are discussed, and future work to augment findings is suggested.