Production of biomass and extracellular 5-aminolevulinic acid by Rhodopseudomonas palustris KG31 under light and dark conditions using volatile fatty acid

ABSTRACTKinetic 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 7.29–12.49 h and 0.038–0.094 h− 1, respectively, whereas under aerobic-dark cultivations, they were 2.03–14.25 h and 0.016–0.022 h− 1, respectively. The lag phase for extracellular ALA production and the maximum specific extracellular ALA production rate under microaerobic-light cultivations (15.72–24.74 h and 0.222–0.299 h− 1, respectively) were better than those obtained under aerobic-dark cultivations (24.57–44.84 h and 0.103–0.215 h− 1, respectively). The biomass and the extracellular ALA yields of 39.66–56.25 gDCW/l/molC, and 148.47–245.75 μM/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 (48.36 μM) by the addition of 10 mM succinate, 4.5 mM glycine, and 15 mM levulinic acid (LA). By controlling dissolved oxygen (DO) and pH values, a maximum extracellular ALA yield of 66.38 μM was found. The degradation rate of ALA in the culture broth was closely related to the pH value.