Abstract:

The present study was conducted to optimize fermentation conditions for the production of 3-phenoxybenzoic
acid-degrading enzyme by Sphingomonas sp. SC-1. The significant factors for the enzyme activity were screened from
medium components and culture conditions by Plackett-Burman design and optimized by Box-Bohnken design. The
optimal medium was composed of 0.5 g/L peptone, 0.5 g/L yeast extract, 0.8 g/L glucose, and 0.01 g/L MgSO4, 0.1 mg/mL
3-phenoxybenzoic acid. The optimal culture conditions were found to be as follows: initial pH, 8.33; inoculum age, 40.0 h;
inoculum size, 4 mL/100 mL (at a cell density of 108 CFU/mL); rotation rate, 180 r/min, culture temperature, 30 ℃; medium
volume in 250-mL conical flask, 30 mL; and culture time, 37.75 h. Under the optimal conditions, the enzyme activity was
1.870 5 mU/g, a 9.24-fold increase over that observed before optimization (0.226 9 mU/g).

Key words: 3-phenoxybenzoic acid-degrading enzyme, fermentation, Sphingomonas sp.