Production of gamma-aminobutyric acid (GABA) by Bacillus subtilis BBEL02 fermentation using nitrogen-rich industrial wastes as crude feedstocks

Industrial-scale fermentation of gamma-aminobutyric acid (GABA) is often limited by high cost of the starting raw materials. Increasing commercial applications of GABA in various industries have urged the research on finding the alternative substrates for the GABA production. The effects of concentration of different types of carbon and nitrogen sources; concentration of monosodium glutamate (MSG) in the defined medium for GABA production using the newly isolated Bacillus subtilis BBEL02 were studied. The feasibility of corn steep liquor (CSL) and soybean hydrolysate (SBH) as the replacement of nitrogen sources in the fermentation media for GABA pro-duction was also investigated. Highest GABA content (10.9 gL-1) and productivity (3.7 gL-1d-1) were achieved with defined medium containing 1 % (w/v) glucose, 2 % (v/v) SBH and 5 % (w/v) MSG. Dissolved oxygen (DO) of 80 % in 2-L fermenter presented the highest productivity (4.2 gL- 1d- 1) and GABA concentration (12.5 gL-1), however DO of 50 % was preferred because of the lower rotation speed to prevent cells deterioration.