Research Of The Key Technologies Of Ethanol Production From Soybean Molasses

The soybean molasses is a byproduct from the process of product soybean protein concentrate by ethanol.The soybean molasses is mainly sold as cheap raw product at present, used in feed processing. Its added valueis very low. Using the soybean molasses as raw material to ferment ethanol will enhance its use value andincrease economically viable of factory. This research is aimed to expand the use range of soybean molasses,to isolate, select and identify high-alcohol-yield yeast from the soybean molasses. In addition, this researchwill also optimize the fermentation medium and fermentation conditions so that provide theoretical basis forindustrial producing of ethanol with soybean molasses.1380yeast strains had been isolated from soybean molasses after enrichment and cultivating from the wildyeast in the soybean molasses. After three-grade screening including the TTC plate method screening, theethanol tolerance determinating and the ethanol production performance measuring, the yeast strain P14,which had the ethanol tolerance of20%（v/v） and the initial fermentation ethanal yields up to9.07%, wasfinally obtained. By the morphological characteristics, physiological and biochemical tests and the molecularmethod of the sequence analysis in the26S rDNA D1/D2area, the strain P14was identified as Saccharomycescerevisiae.Taking cell concentration as index, the effects of sugar concentration, inoculum concentration, growthtemperature, pH value and the rotate-speed in the fermentation on the growth of Saccharomyces cerevisiae P14were investigated by single factor experiment. The experimental results show that the optimum growthconditions are sugar concentration of12%, inoculum concentration of4%, growth temperature of26℃, pHvalue of6.0, rotate-speed of140r/min. The best seed culture was obtained by shaking flask culture for16h onthe optimum growth conditions.On the basis of the results of the single factor experiments, the fermentation medium of soy malesses foralcohol fermentation by Saccharomyces cerevisiae P14with the high-alcohol-yield was optimized by theresponse surface method using the design of four element Second power general rotation combinationexperiment with SAS system9.2. The optimum fermentation medium composition of the high-alchol-yieldyeast Saccharomyces cerevisiae P14in the soybean molasses were sugar concentration of40%, the peptoneadding amount of1.2g/L, MgSO₄adding amount of0.34g/L, Na2HPO₄adding amount of1.87g/L, FeSO₄adding amount of0.025g/L and the growth factor adding amount of2.78g/L. The ethanol production rate canachieve to12.43%under the optimum fermentation medium compositions.The fermentation conditions for alcohol fermentation by Saccharomyces cerevisiae P14in the soybeanmolasses were optimized by the single factor and orthogonal experiments. Tthe optimum fermentationconditions were determined as the inoculum concentration of10%, initial pH of6.5, fermentation temperatureof26°C and the fermentation time of84h. The ethanol production rate can achieve to13.56%under theoptimum fermentation conditions.