Poly-γ-glutamic production by solid-state fermentation of Bacillus natto in ammonia nitrogen movement and soil water retention processes

Abstract

A high polyglutamic acid (γ-PGA) producing strain of Bacillus natto UV-40-50 was screened by ultraviolet mutagenesis treatment and identified as still belonging to the Bacillus specie. The optimal fermentation medium composition for solid state fermentation (SSF) of B. natto strain UV-40-50 strain was determined by one-way analysis of variance, under which the yield of γ-PGA was 55.19g/kg, and the presence and molecular weight of γ-PGA in the γ-PGA-purified samples were determined by a series of characterizations. The purification ability of the unseparated solid fermentation product (SFP) on ammonia nitrogen and nitrite in the water column, as well as its effect on soil water retention, germination rate and seedling length of lettuce and cabbage were further investigated. The results showed that the addition of 1g/m3 SFP could effectively remove more than 60% of ammonia nitrogen and more than 40% of nitrite in the water body; the addition of 0.01% SFP could increase the water retention capacity of cabbage soil by 2.13 times, and increase the water retention capacity of lettuce soil by 12%; at the same time, the SFP could also significantly increase the germination rate and seedling length of both cabbage and lettuce.