A Study On Yeasts Fermented Feed From Cottonseed Meal

Objective:The experimental design of two factors with repeated samples and uniform design method were used to optimize the inocula level and strains ratio of Candida tropicalis and Saccharomyces cerevisiae, fermentation condition parameters, the supplementary material composition and microelement additive amount in substrate. After that, yeasts fermented feed could be produced with optimized fermentation parameters, and then through determining free gossypol (FG), yeast amount, protease and amylase activity, and nutrients to evaluate the biological characteristicsand and nutritional value of the fermented feed. The main objective of this research was to develop a new protein feed with biological active, i.e. yeasts fermented feed from cotton meal, so as to exploit the rich cotton meal resource of Xinjiang and apply the biological characteristics of yeast culture.Methods:The dissertation consists of four optimization experiment and a comprehensive optimization experiment. The statistial experimental design of two factors with repeated samples was applied, from inocula level (1 mL,2mL,4mL,8mL and 16mL), and strains ratio (1/9,3/7,5/5,7/3,9/1) two factors and five levels, according to the design table of the two factor repetitived experimental values, altogether designing 25 experiment deals, by measuring the free gossypol (FG) content of fermented product, to optimize the inocula level and strains ratio of Candida tropicalis ZD-3 (CT) and Saccharomyces cerevisiae ZD-5 (SC) during solid substrate fermentation, then we can draw the optimization inocula level and strains ratio of biological protein feed from cottonseed meal during binary cultures solid substrate fermentation. The method of experiment 2 was that based on the optimization result of experiment 1, the uniform design method was used, from incubation temperature (20℃,25℃,30℃,35℃,40℃), period (12h,24h,36h,48h,60h), initial substrate moisture (35%,40%,45%,50%,55%), and pH value (5.5,6.0, 6.5,7.0,7.5), i.e., four factors five levels, to design experiment and to measure FG content and yeast amount of fermented samples from different treatments. Then, through analysing the regression equation, obtained optimal fermentation condition parameters such as the incubation temperature, period, initial substrate moisture and pH value. The purpose of this trial was to optimize the process parameters for biological protein feed from cottonseed meal during binary cultures solid substrate fermentation. The method of experiment 3 was that on the basis of the optimization of the inocula level and strains ratio, and fermentation condition parameters, to optimize the supplementary material composition in substrate for biological protein feed from cottonseed meal, which provided microorganisms nutritional sources. The uniform design of 9 factors and 12 levels was applied by measuring the free gossypol and yeast content of fermented product, to optimize the supplementary material composition in medium during solid state fermentation with Candida tropicalis ZD-3 and Saccharomyces cerevisiae ZD-5. The experimental data was analyzed to obtain the regression model, and to achieved the optimal supplementary material composition by optimization with DPS v7.05 software. The main purpose was to ensure that toxin-free, more yeast content fermented protein feed was produced. The method of experiment 4 was that on the basis of optimization results of the experiment one and experiment two, to optimize the microelement additive amount in substrate for biological protein feed from cottonseed meal during solid state fermentation, which participated in microbial life metabolism and constructed the activity center of many enzymes. The uniform design of 5 factors and 6 levels was applied, by measuring the free gossypol and yeast content of fermented product, to optimize the microelement additive amount in medium during solid state fermentation with Candida tropicalis ZD-3 and Saccharomyces cerevisiae ZD-5. The experimental data was analyzed to obtain the regression model and the optimal supplementary material composition was achieved by optimization with DPS7.05 software. The method of experiment 5 was that, based on the 4 experiments results above, the optimal fermentation process parameters was composed, and then the high-quality yeasts culture could be produced. After fermentation, the fermented product recovery, product yeast number, protease activity, amylase activity, free gossypol content and nutrients content (DM, CP, AA, EE, NDF, Ash, Ca, P) were determined. So as to assess the biological characteristics and nutritional value of fermented product, and also to prepare for animals feeding experiment.Results:(1). The optimal inocula level and strains ratio of CT and SC were 8 ml/100g and 3:7, respectively, during mixed culture fermentation for biological protein feed from cottonseed meal. (2). The optimum fermentation conditions for biological protein feed were incubation temperature at 32℃, incubation period of 48 h, initial moisture content of soild substrate 40% and pH in nature. (3).To produce the biological protein feed from cottonseed meal during binary cultures solid substrate fermentation with Candida tropicalis ZD-3 and Saccharomyces cerevisiae ZD-5, the optimal supplementary material consisted of 5.99 g/lOOg fish meal,1.05 g/lOOg urea,2.09 g/lOOg molasses,0.73 g/lOOg mannose,0.39 g/100g MgSO4,0.64 g/lOOg NaCl,0.4 g/lOOg K2HPO4/KH2PO4,1.6 g/lOOg CaHPO4 and 0.56 mg/kg thiamine. (4). To produce the biologic protein feed from cottonseed meal with Candida tropicalis ZD-3 and Saccharomyces cerevisiae ZD-5, the optimal microelement additive amount consisted of 540 mg/kg FeSO4,4 mg/kg CuSO4,180 mg/kg MnSO4,15 mg/kg ZnSO4,0 mg/kg Na2Se03. (5). Yeasts fermented feed from cottonseed meal contained FG 8.9 mg/kg, yeasts amount 4.98x 108 cfu/g. The nutrients such as DM CP, EE, Ca, and P content were all significantly increased. The fermented feed contained amylase. The free amino acids (AA) and hydrolytic AA of the fermented substrate were significantly improved.This showed that yeasts fermented feed from cottonseed meal was a biological fermented feed, which contained high free AA and amylase activity.