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UV mutagenesis , mutagenesis of lithium chloride , microwave mutagenesis three methods of Monascus strains Mutagenesis , screening 74 mutation strains Berthelot method Determination of gamma - aminobutyric acid ( GABA) content rescreening , 28 high-yielding strains of GABA . The L10 strains the highest yield , 6.67 mg / g , yielding 373 % from the original bacteria , production increased significantly . GABA content was measured using the Berthelot method , the sample ultrasonic extraction time was 60 min , then 1.0 mL of the sample , add of 0.6 mL0.2 mol / L boric acid buffer solution , add 2 mL of 6 % phenol solution and the mass fraction of 10% sodium hypochlorite solution 0.8 mL of a boiling water bath for heating 8 min , and then the ice bath for 10 min , the absorbance was measured at a wavelength of 640 nm , a standard curve method to determine the mass fraction of the gamma - aminobutyric acid , the method has high sensitivity , fast . Monascus strains L11 solid-state fermentation test, select the stability of the genetic traits of their process conditions were optimized solid-state fermentation optimal incubation temperature is 30 ° C , the optimal incubation time is 10 days . Examine carbon source, nitrogen source and inorganic ions on the fermentation , solid-state fermentation of GABA best carbon source is glucose ; best nitrogen source soy protein powder , medium supplemented with 0.15% KH2PO4 favorable on the production of GABA . After orthogonal experiment to determine the the L11 solid state fermentation GABA optimal conditions were as follows: 5% glucose , soy protein powder 4 % , KH2PO4 0.15 % , ZnSO4 0.3 % , NaNO3 0.5 % , MgSO4 0.1 % , under this condition GABA production can reach 5.08 mg / g . Found that GABA is relatively stable and relatively small , preservatives , metal ions , and antioxidants , while affected by high temperature influence of ScS temperature, heating time , pH , preservatives , metal ions , as well as antioxidants and other factors on the GABA , its content in water bath for 80 min , 100 ° C under reduced 39 % at pH 4 ~ 5 and under alkaline conditions , GABA is also less stable .
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