Production of acetate by mutant strains of Clostridium thermoaceticum

Mutant strains were derived from Clostridium thermoaceticum ATCC 39,289 by treatment with chemical mutagenic agents and selective enrichment procedures. Some mutant strains exhibited growth when cultured in media containing 20 mM (1.75 g/l) pyruvate of high-magnesium lime (dolime) above pH 6.0. ONe strain (G-20) grew and produced acetate when 80 mM (7 g/l) pyruvate or 50 mM (2.3 g/l) formate at pH 5.6 was the sole energy source. In a fed-batch process controlled at pH 6.2, this mutant produced 52.5 g/l acetate (equivalent to 72.5 g/l Na acetate)and 67 g/l calcium-magnesium acetate (CMA) in 140 h when dolime was the neutralizing agent, with 93% substrate utilization.