Abstract: To improve the commercial application of fermented wheat bran, the processes of polyphenol production from fermented wheat bran with complex probiotics strains were optimized using response surface method. PlackettBurman design was used to examine the importance of eight factors influencing polyphenol production. The main effect factors with significant influence were found, and the test center point was determined by the steepest climbing experiment. The optimal levels of the significant impact factors were determined with response surface analysis. The optimal fermentation techniques were 1% of soybean meal, 1% of molasses, 7.5% of inoculationamount of NHS05, 1% of inoculation amount of NHS03, 1% of inoculation amount of NHS01, 35.5% of water content, incubation temperature of 25 ℃, fermentation period of 105.8 hours. After the optimization by response surface method, the amount of polyphenol produced by composite probitics fermenting bran increased by 188% from 2.43 mg·g^-1 to 4.54 mg·g^-1.

Key words: Plackett-Burman test, the steepest ascent experiment, fermented feed, polyphenol.