초록
In this study, a genetically engineered Escherichia coli strain, HBUT-D (ΔpflB Δpta ΔfrdABCD ΔadhE Δald ΔcscR), was initially evaluated on a laboratory scale (7L) in a glucose (130gL<SUP>-1</SUP>) mineral salts medium for d-lactic acid fermentation using 6N KOH, Ca(OH)<SUB>2</SUB> or NH<SUB>4</SUB>OH as the neutralizing agent. Fermentations neutralized by Ca(OH) <SUB>2</SUB> achieved a volumetric productivity of 6.35gL<SUP>-1</SUP>h<SUP>-1</SUP>, tripling that achieved by KOH (1.71gL<SUP>-1</SUP>h<SUP>-1</SUP>) and NH<SUB>4</SUB>OH (1.5gL<SUP>-1</SUP>h<SUP>-1</SUP>). The facilitative effect of Ca(OH)<SUB>2</SUB> neutralization was then demonstrated on a pilot scale (6ton vessel, 130kgglucoseton<SUP>-1</SUP>), resulting in a volumetric productivity of 6kgton<SUP>-1</SUP>h<SUP>-1</SUP>, a titer of 126kgton<SUP>-1</SUP>, a yield of 97%, and an optical purity of 99.5%. These results demonstrated that E. coli HBUT-D is a promising strain for large scale d-lactic acid fermentation using mineral salts medium and Ca(OH)<SUB>2</SUB> for neutralization.