利用木糖产乙醇的真菌筛选及发酵条件优化

ISOLATION OF A FILAMENTOUS FUNGUS WITH ABILITIES OF ETHANOL PRODUCTION AND XYLOSE UTILIZATION AND OPTIMIZATION OF ITS FERMENTATION CONDITION

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。

According to the morphologic observation and ITS sequences analysis, Z7 was identified as Aspergillus flavus at the first step. Additionally, the optional nitrogen resource and temperature of the fermentation were fixed by the single factor experiment; meanwhile, through the orthogonal array tests and the analysis of statistic software SPSS, the optional component of the culture medium and the fermentation condition were organized as follows： urea 0. 1g/L, NH4NO3 1g/L,K2HPO4 2g/L,KCI 0.5g/L,MgSO4·7H2O 0.5g/L,NaNO3 1g/L, pH nature, temperature 33℃. Based on these optimal parameters, the fermentation of dilute-acid hydrolyzate of the corn core was carried on by Z7. According to the quantities of released sugar monomers and content of the ethanol, 115℃ in lh is the best pretreatment condition; the maximal ethanol content can be obtained when lg/L Tween 20 was added to. Therefore, the filamentous fungus Aspergillusflavus can use the hydrolysate of hemicellulose to produce ethanol, and the rate of xylose utilization is over 80%.