Succinic Acid Production by Actinobacillus succinogenes Using Spent Brewer's Yeast Hydrolysate as a Nitrogen Source

To develop a cost-effective fermentation medium, spent brewer's yeast hydrolysate was evaluated as a nitrogen source for succinic acid production by Actinobacillus succinogenes NJ113 in glucose-containing media. Autolysis and enzymatic hydrolysis were used to hydrolyze the spent brewer's yeast cells to release the nutrients. The results showed that enzymatic hydrolysis was a more effective method due to the higher succinic acid yield and cell growth. However, the incomplete glucose consumption indicated existence of nutrient limitation. Vitamins were subsequently identified as the main limiting factors for succinic acid production using enzymatically hydrolyzed spent brewer's yeast as a nitrogen source. After the addition of vitamins, cell growth and succinic acid concentration both improved. As a result, 15 g/L yeast extract could be successfully replaced with the enzymatic hydrolysate of spent brewer's yeast with vitamins supplementation, resulting in a production of 46.8 g/L succinic acid from 68 g/L glucose.