Abstract: The optimal process for the hydrolysis of cotton stalks with dilute acid was investigated by orthogonal array design on the basis of the highest cellulose content and the lowest lignin content. The optimal acid hydrolysis conditions for cotton stalks was dilute acid concentration of 1.0%, solid-to-liquid ratio of 1:15, hydrolysis temperature of 100 ℃ and hydrolysis time of 2.0 h. Plackett-Burman design was used to screen 4 major factors including material-loading amount in a 250 mL fermentation vessel, bran content, co-fermentation time and Penicillium inoculation amount from 9 factors such as yeast inoculation amount, yeast inoculation time, Penicillium inoculation amount, co-fermentation time, initial pH, water content, temperature, bran content and material-loading amount, and their optimum levels were determined by response surface methodology to be 1/3, 4%, 53 h and 10%, respectively. An average content of single cell protein of 25.38% was obtained in validation experiments developed under the optimal parameters, between which and the theoretical value of 22.79%, there was 2.59% difference. Therefore, this established model is feasible.

Key words: cotton stalk, acid hydrolysis, microbes, co-fermentation, single cell protein (SCP)