应用LH与PB设计筛选影响Candida shehatae乙醇产量的无机盐因子

应用空间填充——拉丁超立方(LH)设计与Plackett-Burman设计,研究了无机盐对休哈塔假丝酵母利用木糖产乙醇的影响。以逐步回归与标准最小二乘法对试验结果进行统计分析,从9种无机盐中选出了3个对乙醇产量有显著性影响的因子,即硫酸镁、氯化铁、磷酸二氢钾。

Research on the Nature of Thermophilic Anaerobic Ethanol Producer Thermo anaerobacter sp DF3 in Petroleum Reservoirs

[Objective] The aim was to study the physiological and biochemical char- acteristics of Thermoanaerobacter sp DF3 in petroleum reservoirs and optimize the culture plan of producing ethanol from xylose. [Method] DF3, an anaerobic bacillus producing ethanol, was isolated from produced liquid from oil layer of Dagang oil field with anaerobic isolation technique. The phylogenetic position was analyzed by physiological and biochemical identification and phylogeny of 16S rDNA sequence. The metabolites were analyzed by gas chromatograph. [Result] The strain DF3 was a strict anaerobic thermophilic bacterium, which was straight in rod shape,and gram negative. Besides, it was 0.42 μmx（1.60-5.20） iJm in length. The strains can be soli- tary,in pairs or string and apical spore usually produced. Its growth temperature was 45-78 and 65 ℃ was the optimum. Many substances could be used as carbon sources, including glucose, xylose, fructose, ribose, mannose, arabinose, sucrose, galactose, lactose, cellobiose, melizitose, raffinose-, and starch. The similarity between strain DF3 and T. pseudoethanolicus achieved 99.7%. The main product of glucose and xylose fermentation was ethanol. After the culture plan was optimized,the final concentration of ethanol was 2.0 g/L. [Conclusion] It was proved through experiments that the strain DF3 was one of the strains with higher activity to produce ethanol at present and it could produce 2.0 g/L ethanol from xylose metabolization at 65 ℃. It has been demonstrated that DF3 is one of the known strains with high-production to produce ethanol,for example, 2.0 g/L ethano at 65℃. Presently, all the high-yield ethanol can be produced from metabolic xylose strains of metabolic xylose were isolat- ed by foreign countries, therefore, isolation of strain DF3 has provided an excellent original strain for studying ethanol production from lignocellulose in China.

Effects of Mutagenesis by UV Irradiation and ^(60)Co-γ Irradiation on Fermentation of Xylose to Ethanol by Pichia stipitis

ln this study, effects of UV irradiation and 60Co-γ irradiation on fermenta-tion of xylose to ethanol by Pichia stipitis were analyzed to investigate the optimal mutagenic conditions. According to the growth curve and fermentation curve of P. stipi-tis, the optimal incubation duration and fermentation duration of P. stipitis mutant strain were 18 and 48 h, respectively. The cel concentration of original yeast liquid was 107 cel s/ml. After mutagenesis by UV irradiation and 60Co-γ irradiation, yeast liquid was incubated in 20 g/L xylose media for 48 h. According to the results, after UV irradiation for 45-75 s, transformation efficiency reached 0.3794 g/g, which was 74.39% of the theoretical value; after irradiation with 800-1 000 Gy 60Co-γ, transforma-tion efficiency reached 0.3165 g/g, which was 62.06% of the theoretical value. Therefore, both UV irradiation and 60Co-γ irradiation could improve the efficiency of xylose fermentation to ethanol by P. stipitis under appropriate conditions.

The Effect of pH Control on Acetone-Butanol—Ethanol Fermentation by Clostridium acetobutylicum ATCC 824 with Xylose and D-Glucose and D-Xylose Mixture

D-Glucose, L-arabinose, D-mannose, D-xylose, and cellobiose are saccharification products of lignocellulose and important carbon sources for industrial fermentation. The fermentation efficiency with each of the five sugars and the mixture of the two most dominant sugars, D-glucose and D-xylose, was evaluated for acetone- butanol-ethanol （ABE） fermentation by Clostridium acetobutylicum ATCC 824. The utilization efficacy of the five reducing sugars was in the order of D-glucose, L-arabinose, D-mannose, o-xylose and cellobiose, o-Xylose, the second most abundant component in lignocellulosic hydrolysate, was used in the fermentation either as sole carbon source or mixed with glucose. The results indicated that maintaining pH at 4.8, the optimal pH value for solventogenesis, could increase D-xylose consumption when it was the sole carbon source. Different media con- taining D-glucose and D-xylose at different ratios （1：2, 1：5, 1.5：1, 2：1 ） were then attempted for the ABE fermenta- tion. When pH was at 4.8 and xylose concentration was five times that of glucose, a 256.9% increase in xylose utilization and 263.7% increase in solvent production were obtained compared to those without pH control. These results demonstrate a possible approach combining optimized pH control and D-glucose and D-xylose ratio to increase the fermentation efficiency of lignocellulosic hydrolysate.

A Mathematical Model for Simultaneous Saccharification and Co-fermentation （SSCF） of C6 and C5 Sugars

Reliable production of biofuels and specifically bioethanol has attracted a significant amount of re-search recently.Within this context,this study deals with dynamic simulation of bioethanol production processes and in particular aims at developing a mathematical model for describing simultaneous saccharification and co-fermentation （SSCF） of C6 and C5 sugars.The model is constructed by combining existing mathematical mod-els for enzymatic hydrolysis and co-fermentation.An inhibition of ethanol on cellulose conversion is introduced in order to increase the reliability.The mathematical model for the SSCF is verified by comparing the model predic-tions with experimental data obtained from the ethanol production based on kraft paper mill sludge.When fitting the model to the data,only the yield coefficients for glucose and xylose metabolism were fine-tuned,which were found to be 0.43 g·g-1 （ethanol/glucose） and 0.35 g·g-1 （ethanol/xylose） respectively.These promising validation results encourage further model application to evaluate different process configurations for lignocellulosic bioetha-nol technology.