Screening and Identification of Limonin Degrading Strains and Optimization of Fermentation Conditions

In order to solve the debittering problem of limonin,strains degrading limonin were selected and the enzyme production conditions of the strains were optimized. Eight strains degrading limonin were selected and isolated from the soil of perennial orange orchards and vinegar during fermentation.C-1-5,C-1-2-2,and JJ-3 strains with better limonin degradation rates were identified by morphology and molecular biology.On the basis of single-factor experiments,JJ-3 strain was selected for fermentation optimization by response surface optimization. Among them,C-1-5,C-1-2-2,and JJ-3 strains had relatively high degradation rates of limonin,which were 27%,36%,and 38%,respectively. The C-1-5 strain was identified as Cellulomonas sp. by morphology and molecular biology. The JJ-3 strain and C-1-2-2 strain were identified as Ochrobactrum sp.by morphology and molecular biology.Through the single factor optimization,the limonin degradation rates of C-1-5,JJ-3,and C-1-2-2 strains were increased to 65.90%,72.79%,and 74.66%,respectively.Through the response surface experiment,the optimal fermentation process conditions for JJ-3 were:pH3.5,temperature 30℃,nitrogen source was ammonium nitrate,and the inoculation amount was 3×10⁸ CFU/mL. Under this process condition,the degradation rate of limonin was 78.90%. The strains with optimized fermentation conditions had a higher degradation rate.This study can provide help for the research of enzymes degrading limonin.