Breeding Of Gaba-high Yielding Monascus Strain And Optimizating Of Fermentation Process

Mutation screening for monascus strains was studied by UV mutagenesis,LiCl mutation and microwave mutation in this paper,74 strains were obtained after prescreening, and 28 strains were obtained after re-screeing through the determination ofγ-aminobutyric(GABA) content with Berthelot method. The results showed that the production of L10 strain increased significantly, reached 6.67 mg/g,373% higher than the original strain.The content of GABA of fermentation products were determined with Berthelot method,which is fast and high sensitivity.1.0 mL sample was taken after 60 min ultrasonic extraction,plus 0.6 mL 0.2 mol/L borate buffer,adding 2 mL 6% phenol solution and 0.8 mL 10% sodium hypochlorite solution,placed it in the boiling water for 8 min and in the ice for 10 min, measured the wavelength absorbance at 640 nm,and then calculated the concentration of GABA by the method of standard curve.The process conditions of solid-state fermentation experimental of Monascus purpureus L11 which is stable genetically , and found that the best culture temperature is 30℃,the best incubation time is 10 days.It showed the best carbon source is glucose,the best nitrogen source is soy protein powder,and the best inorganic ions is 0.5% KH2PO4 by examining the effect of carbon,nitrogen and inorganic ions on the fermentation.And then through orthogonal experiments with the L11 strain,determined the best process parameters of solid-state fermentation are:5% glucose,4% soy protein powder,0.15%KH2PO4,0.3%ZnSO4,0.5%NaNO3 and 0.1%MgSO4.The content of GABA under this condition is up to 5.08 mg/g.The effect of temperature,heating time,pH,preservatives,metal ions and anti-oxidant on the stability of GABA were examined,the results showed that the stability of GABA is stable relatively,the effect of preservatives,metal ions and anti-oxidant on GABA is not obvious relatively,but temperature is significant relatively,the content of GABA decreased 39% after boiling water bath 80 min; GABA is not stable under the condition of pH4～5 and alkaline conditions.