Effects of different neutralizing agents on succinate production by Actinobacillus succinogenes NJ113

Different neutralizing agents were used as pH controller to investigate their effects on the growth and succinic acid production of Actinobacillus succinogenes NJ113. The fermentation results showed that Ca(OH) ₂, CaCO ₃ and NH ₄OH were not suitable for succinic acid production by A. succinogenes NJ113 because of their negative effects on cell growth. When Na-base was used, cells would flocculate and lump, and due to the sodium ion concentration reaching to a high level, OD ₆₆₀ dropped sharply after 12 h of fermentation. Mg-base was better because there was no significant inhibition by magnesium ion. Two combined neutralizing agents were used to maintain pH level, one with NaOH and Mg(OH) ₂ while the other with Na ₂CO ₃ and Mg(OH) ₂. The optimum ratios of the combined neutralizing agents were both 1:1(g:g) when using 100 g/L glucose. When NaOH and Mg(OH) ₂ were chosen with the ratio of 1:1(g:g), 69.8 g/L of the succinic acid and 74.5% of the yield was obtained.