Abstract:

In order to develop low-cost nitrogen source for replacing commercial yeast extract in fermentation production of succinic acid, alkaline protease hydrolysates of baker s, molasses and spent brewer's yeasts were exploited as nitrogen sources for high productivity of succinic acid. Content analyses of -amino nitrogen, total nitrogen and free amino acids in the three yeast hydrolysates were carried out, and effects of the three yeast hydrolysates as nitrogen sources on succinic acid production by Actinobacillus succinogenes NJ113 fermentation were investigated. Results showed that the contents of -amino nitrogen, total free amino acids and glutamate were 0.428, 56.51 and 8.125 mg/ml respectively in hydrolysate of baker's yeast, which were all higher than those in hydrolysates of other two yeasts. The yield of succinic acid using hydrolysate of baker's yeast was 68% at an initial glucose concentration of 100 g/L; in contrast, hydrolysates of molasses and spent brewer's yeasts did not exhibit effects on growth and fermentation of Actinobacillus succinogenes NJ113 at identical glucose concentration. Therefore, hydrolysate of baker s yeast could be an alternative nitrogen source to yeast extract for the production of succinic acid.

Key words: yeast , enzymatic hydrolysis , succinic acid, nitrogen source