Abstract

Six strains of phototrophic purple non-sulfur bacteria were isolated from paddy soil, lake water and pond sediment samples. They showed the ability to produce 5-aminolevulinic acid under anaerobic-light (3,000 lux) condition. A selected strain, designated as PS-5, produced the highest 5-aminolevulinic acid (ALA) concentration (45.10 mM) and productivity (0.94 mM h^-1) in glutamate-malate (GM) medium as well as possessed self-flocculating ability. Based on physiological and 16S rRNA sequence, the isolate PS-5 was identified to be Rubrivivax benzoatilyticus. The optimum concentration of C₄ pathway precursors was 7.5 mM glycine and 10 mM succinate with supplementation of 10 mM levulinic acid. This resulted in 4.2 fold increase of 5-aminolevulinic acid production to 190.74 mM and 2.7-fold increase of its productivity to 2.57 mM h^-1 compared to the control. In addition, the optimum concentration of C₅pathway precursor was 50 mM glutamate with the maximum 5-aminolevulinic acid production of 84.12 mM and productivity of 1.56 mM h^-1. Therefore, R. benzoatilyticusPS-5 could produce 5-aminolevulinic acid using both C₄ and C₅ pathway precursors and preferred C₄ pathway over C₅ pathway as it produced more than 2.3 folds higher 5-aminolevulinic acid concentration.

Key words: 5-Aminolevulinic acid, photosynthetic bacteria, self-flocculation, optimization, Rubrivivax benzoatilyticus.

Abbreviation

ALA, 5-Aminolevulinic acid; GM, glutamate-malate.