Stimulatory effects of some amino acids on glycerol production by Candida glycerinogenes / 生物工程学报

ABSTRACT

By using some intermediate metabolites in EMP pathway and TCA cycle as the control, the effects of amino acid supplements on glycerol production by Candida glycerinogenes in shake-flask fermentations with urea as nitrogen resource were investigated. The results showed that ten kinds of amino acids, including L-glutamic acid, L-glutamine, L-aspartic acid, L-asparagine, L-glycin, L-lysine, L-tyrosine, L-proline, L-histidine, and L-serine, had strong promotional effects on glycerol production; The optimal concentrations of these amino acids were 0.40, 0.45, 0.36, 0.35, 0.39, 0.36, 0.35, 0.45, 0.26, and 0.45 g/L, respectively. Accordingly the optimum contents of pyruvic acid, a-oxoglutarate, oxaloacetic acid, citrate, and succinate were 0.24, 0.42, 0.40, 0.37, and 0.38 g/L, respectively. The advantageous opportunities of supplement were as follows L-lysine at the beginning of fermentation; pyruvic acid and oxaloacetic acid at the fourteenth hour; L-glutamic acid, L-glutamine, L-histidine, L-proline, L-aspartic acid, L-tyrosine, L-glycin, alpha-oxoglutarate, and succinate at the thirtieth hour; and L-asparagine, L-serine, and citrate at the forty-eighth hour. The addition of each stimulant at the optimal conditions could significantly promote glycerol production, with the glycerol yield on initial glucose and its increased speed exceeding 60% and 16%, respectively. The possible stimulatory mechanism due to the amino acid supplements is that the increased intermediate metabolites levels from amino acids degradation may have enhanced the flux through TCA cycle, which improve cell energetics. Meanwhile, the shift of carbon metabolism flux at the glyceraldhyde-3-phosphate node can result in the incremental flux through glycerol biosynthesis pathway.