Isolation and screening of microorganisms for high yield of succinic acid production

This study involves the isolation of succinic acid (SA)-producing microorganisms from different samples, including the rumen, sludge, soil, and wastewater. For primary screening, 29 isolates exhibited a zone of clearance around the colony, indicating acid production. For secondary screening using thin-layer chromatography, only two isolates symbolized SA production according to their R-f values. These two isolates were further identified as Bacillus velezensis and Enterococcus gallinarum by phylogenetic analysis using the neighbor-joining method. The high SA concentrations of 50.2 and 66.9 g/L were produced by B. velezensis and E. gallinarum with an SA yield of 0.836 and 1.12 g/g glucose, respectively. The high SA concentration from these newly isolated strains was achieved with a low formation of unwanted acids compared with those from Actinobacillus succinogenes ATCC 55618. Moreover, E. gallinarum was cultured in palm oil mill wastewater (POMW) and molasses, which were cheap substrates. The high SA production of 73.9 g/L with low other acids (the ratio of SA to total acids = 0.917) was achieved using POMW and molasses (80:20) as substrates.

Automated summary

This study isolated microorganisms capable of producing succinic acid (SA) from various samples, including rumen, sludge, soil, and wastewater. Two isolates, identified as Bacillus velezensis and Enterococcus gallinarum, exhibited high SA concentrations of 50.2 g/L and 66.9 g/L, respectively, with SA yields of 0.836 g/g glucose and 1.12 g/g glucose. These newly isolated strains showed higher SA concentrations and lower unwanted acid formation compared to Actinobacillus succinogenes ATCC 55618. Furthermore, E. gallinarum was cultured using cheap substrates, such as palm oil mill wastewater (POMW) and molasses, achieving a high SA production of 73.9 g/L with a low ratio of other acids to SA (0.917).