| Due to increasing energy consumption and environmental concerns, the use of fuel ethanol as a cheap, clean, alternative energy is expected to become a new source of energy. Grains such as corn and wheat are the primary materials for ethanol production in the world. However, it is not sustainable to produce ethanol from grains in china. Lignocellulosic materials are attractive feedstock for ethanol production since they are cheap, renewable resources, available in large quantities. In this paper, there was selection of some strains that could ferment perennial ryegrass's hydrolysis products. Separate hydrolysis and fermentation (SHF for short) was used to ethanol fermentation. The pretreatment and fermentation process were optimized in SHF, providing a basis for further study. The main contents were as follows:(1) Experiments xylose was screening factor, and was used selected the strain NS2 which could make use of the hydrolysates of perennial ryegrass. The strain NS2 was identified as Saccharomyces cerevisiae.(2) Component analysis of the perennial ryegrass material was used to the feasibility analysis of a fermentation material:moisture 11.37%, volatile matter 73.38%, ash 4.78%, reducing sugar 16.67%, total sugar 34.27%, lignin 6.33%, and crude fiber 6.68%.(3)Factors analysis about treating perennial ryegrass powder with dilute hydrochloric acid showed that: the best HC1 concentration was 1.0%(v/v), and when hydrolysis temperature was 120℃, hydrolysis time was 120min, solid-to-liquid ratio was 10%, the hydrolysis rate came to a head. In the orthogonal experiment that was hydrochloric acid pretreatment way at low temperature, when concentration of hydrochloric acid was 15%(v/v), hydrolysis temperature was 60℃, hydrolysis time was 100min, the solid-liquid ratio was 5%, the pretreatment had the best effect. (4)In this chapter, the hydrolysis effects of different pretreating agents for perennial ryegrass were compared. When the concentration of hydrochloric acid was 1.0%(v/v), hydrolysis of perennial ryegrass can achieve the highest rate,48.36%; when the volume concentration of sulfuric acid was 50%(v/v), the hydrolysis rate of the perennial ryegrass was 31.64%; but perennial ryegrass was hydrolyzed with NaOH which mass concentration was 8% and ammonia which volume concentration was 10%(v/v), reducing sugar concentration in two kinds of fermentations were 16.11% and 14.58%.(5) Fermented perennial ryegrass to ethanol by separate hydrolysis and fermentation step, the best initial conditions was the temperature of 38℃, pH 4.5, inoculation 10%, rotation speed was 150r/min.(6) Using response surface methodology (RSM) to analysised of the bacteria inoculum size, fermentation time, the ratio of the yield of ethanol, and the fitting the second model:Y1=49.18+ 3.82 X1-1.47X2+8.64X3+5.57X,X2+5.31X1X3-0.32X2X3-10.14X12-5.77X22-10.07X32 (R2=93.05%). The optimum process parameters for the fermentation of bacteria were inoculum of 10%, solid-liquid ratio of 10%, and fermentation time of 60h.(7) Studied on the effect of different pre-processing: In acid hydrolysis process, the hydrochloric acid treatment of ethanol was higher than that of sulfuric acid treatment. The yield of ethanol was 9.76%; In alkali treatment, the sodium hydroxide pretreatment way was better than ammonia pretreatment, ethanol yield was 10.01%; Organic solvents and acid combined with the ethanol yield was much better than the separate use of organic solvents ethanol production.(8) Studied on the separate hydrolysis and fermentation, fitted the fermentation process of cell growth, ethanol production and sugar consumption dynamic model. The reused of the perennial ryegrass residues was discussed in this part.The study of this paper was simulated in the laboratory, which limited by time and experimental condition. It's need further improvement of strain and optimization of the fermentation process. The used of perennial ryegrass product ethanol used in industrial also requires further study. |
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