Plant-available inorganic nutrient levels are increased in rice-derived distillery effluents inoculated with microbes.

Abstract

The purpose of this study was to assess the effects of microbes on plant-available inorganic nutrients and a phytohormone in rice-derived distillery effluents. The effects of 37 microbial strains on the components of distillery effluents were investigated. Inoculation of several Aspergillus and Bacillus strains resulted in accumulation of a large quantity of ammonium nitrogen (NH4-N; 774 ± 490 and 1059 ± 463 mg l(-1), respectively) in the effluent. However, a decrease in the liquid phase during Aspergillus incubation suggested the requirement for additional treatment of the solid residue, whereas the growth of Bacillus subtilis was inhibited by the acidic conditions in the raw distillery effluent. Interestingly, Aspergillus caelatus, Aspergillus oryzae and Aspergillus tamarii yielded greater increases in nitrate concentrations (30-39 mg l(-1)). Colorimetric and gas chromatography-mass spectrometry analyses revealed that Wickerhamomyces strains generated 7-26 mg l(-1) of indole-3-acetic acid (IAA) when the effluent pH was adjusted to 7·0. Inoculation of several Aspergillus and Bacillus strains into distillery effluents resulted in the production of a large quantity of NH4-N. This study provides information that will facilitate the bioconversion of distillery effluent into fast-acting liquid fertilizers.