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以木糖为唯一碳源,从高、中温酒曲中分离到16株能利用木糖的丝状真菌;通过发酵试验复筛,获得一株能产乙醇的丝状真菌Z7;综合形态学和ITS序列分析,初步鉴定为Aspergillus flavus。通过单因素试验确定最佳氮源和发酵温度;通过正交试验和SPSS软件分析得到了不同N、P、K成分对乙醇、残糖和菌体干重的影响,获得最佳的发酵条件为:尿素1g/L,NH_4NO_3 1g/L,K_2 HPO_4 2g/L,KCl 0.5g/L,MgSO_4·7H_2O 0.5g/L,NaNO_3 1g/L,pH自然,培养温度33℃。以玉米芯半纤维素水解液为底物进行乙醇发酵,根据稀酸水解的单糖释放量和乙醇产量,确定115℃,1h为最佳玉米芯预处理条件;添加1 g/L的吐温20能获得最大的乙醇浓度8.31 g/L。因此,Aspergillus flavusZ7能利用半纤维素水解产物产乙醇,其中木糖的利用率在80%以上。
Xylose as the sole carbon source, 16 filamentous fungi that could utilize xylose were isolated from high and medium temperature wine yeast. One filamentous fungus Z7 producing ethanol was screened by fermentation test. The morphological and ITS Sequence analysis, preliminary identification as Aspergillus flavus. The optimum nitrogen source and fermentation temperature were determined by single factor test. The effects of different N, P and K components on the dry weight of ethanol, residual sugar and cell were obtained by orthogonal test and SPSS software. The optimum fermentation conditions were : Urea 1 g / L, NH 4 NO 3 1 g / L, K 2 HPO 4 2 g / L, KCl 0.5 g / L, MgSO 4 4.7H 2 O 0.5 g / L and NaNO 3 1 g / L. The corn cob hemicellulose hydrolyzate was used as the substrate for ethanol fermentation. According to the amount of monosaccharides released by dilute acid hydrolysis and the yield of ethanol, 115 ℃ and 1h were the best pretreatment conditions for corn cob. Adding 1 g / L Tween 20 can get the maximum ethanol concentration of 8.31 g / L. Therefore, Aspergillus flavusZ7 can utilize hemicellulose hydrolyzate to produce ethanol, of which xylose utilization is over 80%.