Economical production of poly(γ-glutamic acid) using untreated cane molasses and monosodium glutamate waste liquor by Bacillus subtilis NX-2
The production of poly(Î³-glutamic acid) by Bacillus subtilis NX-2 from cane molasses and monosodium glutamate waste liquor (MGWL) was studied for the first time in this work. When batch fermentation was carried out with untreated molasses, 33.6 ± 0.37 g L−1 PGA was obtained with a productivity of 0.46 ± 0.006 g L−1 h−1. In order to minimize the substrate inhibition, fed-batch fermentation was performed with untreated or hydrolyzed molasses in 7.5 L bioreactor, giving 50.2 ± 0.53 and 51.1 ± 0.51 g L−1 of PGA at 96 h, respectively. Further studies were carried out by using MGWL as another carbon source, resulting in a PGA concentration of 52.1 ± 0.52 g L−1 with a productivity of 0.54 ± 0.003 g L−1 h−1. These results suggest that the low-cost cane molasses and MGWL can be used for the environmental-friendly and economical production of PGA by B. subtilis NX-2. âº Economical and high yield production of PGA used waste materials was realized. âº Untreated cane molasses was used as carbon source. âº MGWL was used by supplying glutamate and (NH4)2SO4. âº Half of the material cost could be saved by using these low-cost materials.