Production of biomass and extracellular 5-aminolevulinic acid by Rhodopseudomonas palustris KG31 under light and dark conditions using volatile fatty acid(MICROBIAL PHYSIOLOGY AND BIOTECHNOLOGY)

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Kinetic parameters for growth and extracellular 5-aminolevulinic acid (ALA) production of Rhodopseudomonas palustris KG31 under light and dark conditions in a medium containing volatile fatty acids (VFA) as the carbon sources were estimated using a Gompertz model. The lag phase for growth and the maximum specific growth rate under microaerobic-light cultivations were 7.29-12.49h and 0.038-0.094h^<-1>, respectively, whereas under aerobic-dark cultivations, they were 2.03-14.25h and 0.016-0.022h^<-1>, respectively. The lag phase for extracellular ALA production and the maximum specific extracellular ALA production rate under microaerobic-light cultivations (15.72-24.74h and 0.222-0.299h^<-1>, respectively) were better than those obtained under aerobic-dark cultivations (24.57-44.84h and 0.103-0.215h^<-1>, respectively). The biomass and the extracellular ALA yields of 39.66-56.25gDCW/l/molC, and 148.47-245.75μM/molC, respectively, under microaerobic-light cultivations were higher than of those obtained under aerobic-dark conditions. An enhancement of extracellular ALA production under aerobic-dark conditions revealed that the ALA yield was markedly increased 8-fold (48.36μM) by the addition of 10mM succinate, 4.5mM glycine, and 15mM levulinic acid (LA). By controlling dissolved oxygen (DO) and pH values, a maximum extracellular ALA yield of 66.38μM was found. The degradation rate of ALA in the culture broth was closely related to the pH value.