Optimization of culture condition for a strain D-31 producing 4-ethylguaiacol

The important factors influencing the growth of Bacillus subtilis D-31,which were selected by PlackettBurman design were temperature,starch soluble,and KCl.Then steepest ascent path was applied to approach the optimal region and the optimum levels of these three main factors were further optimized by Box-Behnken design and response surface analysis.The results showed that the OD600nmof the broth increased from 1.24 to 10.32 and the concentration of Bacillus subtilis D-31 was significantly increased by 8.25 times from 6.27 × 108CFU /mL to 5.17 ×109CFU /mL under the optimal culture conditions( starch soluble 27.70g /L,yeast extract 50g /L,KCl 6.66g /L,pH 8,temperature 36.9℃ and inoculum concentration 3%).The culture obtained was used to convert ferulic acid( FA) into4-ethyl guaiacol( 4-EG) and the yield of 4-EG was increased by 3.9 times from 9.48mg /L to 36.94mg /L.