Strain Screening for Bioconversion of Glycerol to Lactic Acid and Optimization of Culture Medium

Abstract:

A strain, Escherichia coli AC-521, which could efficiently covert glycerol to lactic acid, was isolated from soil samples. A series of morphological and biochemical characteristics and sequence analysis of 16S rDNA reveal that it belongs to Escherichia coli. Through orthogonal experiment of L16(45), the optimum medium compositions were determined as initial glycerol 70 g/L, yeast extract 4 g/L, peptone 7 g/L, (NH4)2SO4 10 g/L, and K2HPO4 2.5 g/L. The 5L fermenter fed-batch fermentation was performed under optimal conditions, giving 74.5 g/L lactic acid with a yield of 0.87 mol/mol glycerol after 80 hours.

Key words:Lactic acid, Glycerol, Isolation, Identification, Optimization