Production of extracellular 5-aminolevulinic acid by rhodopseudomonas palustris in solid-state fermentation

Abstract

Nowadays, 5-aminolevulinic acid (ALA) is widely used as non-toxic herbicide, as insecticide, and also as plant growth enhancer in agricultural application. However, their use is limited by high production cost via the route of chemical synthesis. Agricultural waste, which serves as inexpensive solid support medium, can be used to produce ALA through solid-state fermentation (SSF). In this study, production of ALA using empty fruit bunch (EFB) as solid support medium inoculated with Rhodopseudomonas palustris (R. palustris) NRRL-B4276 was conducted through SSF. Several environmental factors for the SSF process including the initial pH (2, 3, 4, 5, and 6), initial moisture content (40, 50, 60, 70, and 80%) of the solid support medium, and incubation period (1-5days) were investigated to study their effects for the production of ALA in SSF. The maximal yield of ALA was achieved at 38.22±0.15mg/kg substrate at the total viable cell count of 35±3-106CFU/g in SSF using EFB as the solid support medium inoculated with R. palustris. The optimized operating parameters including the initial pH, initial moisture content of the solid support medium, and incubation period were found to be pH 3, 60%, and 3days (72h), respectively, in the presence of 40%(v/w) inoculum at 37°C aerobically with light under static condition.