| Cottonseed meal (CSM) with high concentration of Protein is a good resource to plant protein feed stuff and the content of crude protein is up to 40%. However, the potential of cottonseed meal for animal feed is limited by the presence of gossypol, a toxic polyphenolic pigment. It has an important significance that finding a appropriate dctoxifieation method to reduce freegossypol and to make cottonseed meal become good protein feed stuff.In this paper,it was analyzed that the factors of affecting fermentation dctoxifieation, and employed that microorganism fermentation method to reduce freegossypol. Microbial fermentation may offer the promise as a detoxication method and was paid more attention, because not only fermented CSM can lower toxicity freegossypol, but also the nutritional value of raw materials is also greatly improved.Microbial fermentation detoxication can detoxicate gossypol by transformating and degradating gossypol with microbial fermentation .The point is selecting appropriate strain.12 bacterial strains were isolated from many soil samples used for the cultivation of cotton, and the best degradation strain was determined according to the freegossypol degradation rate of the strains determined by HPLC. It was found that the number 2 strain is the best strain to degradation, degradation rate is 49.80%; the degradation rate of number 1, 7 and 12 is more than 40.0%; number 5,6 and 10 is down with effect from ideal, that is less than 40.0%. The rest bacterial strains had bad degradation effect. It was examined and determined that the number 2 strain is Candida tropicalis.In this experiment, solid-state fermentation of Candida tropicalis was used and the fermentation kinetics of that was studied. Solid-state fermentation has simple process, low energy consumption, small equipment investment, high yield and other characteristics. For promoting the technology development about exploiting biomass resources with low-cost, low cost and wide range sources cottonseed meal and wheat bran were used as the medium to achieve free gossypol degradation and total carbohydrate consumption.It was found that the parameters changes of the solid fermentation process had shown S-type with time passing. 0 h~24 h, dry matter loss was slow; 24 h~56 h, dry matter loss increaseed exponentially, indicating that Candida tropicalis grow rapidly; 56 h~72 h, the increasing of dry matter loss changeed slowly, and the maximum amount of dry matter loss was 19.73%. 0 h~24 h, total carbohydrate consumption was less; 24 h~56 h, total carbohydrate consumption decreased obviously;56 h~72 h, total carbohydrate consumption has stabilized. Free gossypol degradation depends on microbial growth, the loss of dry matter. 0 h~24 h, free gossypol degradation rate is very low; 24 h~56 h, free gossypol was quickly degraded; 56 h~72 h, free gossypol degradation rates were stable, 76.30%. It was indicated that the loss of dry matter, total carbohydrate concentration and content of gossypol were interrelated.The fermentation kinetics of Candida tropicalis was studied in this paper. Throught the Logistic equation, based on the use of measured dry matter weight loss for showing the biomass estimation, the model of kinetics by the process of solid-state fermentation included microorganism growth, total carbohydrate concentration and free gossypol content was developed. The data was analyzed with the Origin8.0 software to generate the kinetics parameters of solid-state fermentation to Candida tropicalis. Based on the kinetics results, it was showed that the model could fit the experiment data well and provide a reasonable description for the Candida tropicalis fermentation process.
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