Factors Affecting The Fermentation Optimization Of Monascus Strains With High Gamma-Aminobutyric Acid Yield

The gamma-aminobutyric acid (GABA) is one of the main functional components of red yeast rice (RYR), which has blood pressure lowering, anti-depressant, nerve cell nourishing and brain health supporting properties. This study aimed to improve GABA production from RYR, using germinated brown rice as the fermentation substrate to isolate and screen strains and optimize fermentation conditions. Six Monascus strains with a GABA yield of at least 20.0 mg/100 g were obtained: CICC 5008, GD-05, G9, HB-05, Z3 and FG-04. Strain CICC 5008 showed the greatest GABA yield (22.43 mg/100 g), which was 70.6% greater than the control strain CICC 5009. Using single factor optimization, Plackett-Burman design and Box-Behnken response surface analysis, the optimal fermentation process for producing GABA from strain CICC 5008 was determined as follows: brown rice soaking time 9 h, rice steaming time 15 min, fermentation bottle rice mass 80 g, fermentation temperature 25 degrees C, brown rice soaking solution pH 5.0, 5 fermentation flask air holes and fermentation time 11 d. The GABA yield under this fermentation condition was 26.54 mg/100 g. Among the seven factors, fermentation time was the most important factor affecting GABA production from RYR, followed by fermentation temperature and flask permeability, while the other four factors had less influence. (C) 2019 Friends Science Publishers