木质素与半纤维素对稻草秸秆酶解的影响

Effect of Lignin and Hemicellulose on Enzymatic Hydrolysis of Cellulose from Rice Straw

分别采用稀酸和酸碱顺序两种方法处理稻草秸秆,20 FPU/g(底物干重)的纤维素酶、底物质量浓度为80 g/L,45℃酶解72 h。结果表明,木质素与半纤维素对纤维素转化为葡萄糖都有较大影响,稀酸处理的秸秆酶解纤维素转化率(43.4%,葡萄糖质量浓度24.1 g/L)是未处理秸秆(16.8%,葡萄糖质量浓度6.2 g/L)的2.6倍,而酸碱顺序处理的秸秆(60.6%,葡萄糖质量浓度47.7 g/L)则是未处理秸秆的3.6倍。采用上述两种方法处理秸秆后,秸秆木质素和半纤维素被移去,秸秆结构发生改变,从而秸秆纤维更易受纤维素酶的攻击,并且秸秆木质素和半纤维素质量分数越低,纤维素的酶解得率就越高。

In this manuscript,the enzymatic hydrolysis of rice straw in three different forms： original（untreated）,pretreated by dilute acid,and pretreated by a sequence of dilute acid and dilute alkali,were studied.The hydrolysis was carried out in an enzyme/substrate ratio of 20 FPU/g,8%（w/v） substrate concentration,45 ℃ for 72 h.The digestibility results suggested that the cellulose hydrolysis was greatly affected by the presence of hemicellulose and/or lignin in the rice straw.The cellulose conversion ratio 43.4% from dilute acid-treated rice straw was 2.6 times higher than that 16.8% from untreated rice straw,whereas from dilute acid and alkali rice straw such value was higher 3.6 times（60.6%）.This result was probably due to the fact that the strong modification in the material structure caused by the hemicellulose and lignin removal from the rice straw.As a consequence,the cellulose fibers were separated being more susceptible to the enzymatic attack.It was concluded that the lower the hemicellulose and lignin in the rice straw,the higher efficiency of cellulose hydrolysis could be achieved at.