碱性亚硫酸盐预处理对杂交狼尾草酶水解特性的影响

杂交狼尾草(Pennisetum americanum × P. purpureum)生长速度快、产量大、抗逆性和适应性强,是制备生物能源和化学品的极具潜力的原料。为实现杂交狼尾草高效酶水解,分别采用氢氧化钠、亚硫酸钠和碱性亚硫酸钠对其进行预处理,分析其对原料化学组成和结晶度的影响,探讨纤维素酶剂量、纤维素酶与木聚糖酶的协同、酶系组成对酶水解的影响。结果表明,1% NaOH或4% Na2SO3预处理可将杂交狼尾草木质素质量分数从19.5%降为10%～15%。在1% NaOH预处理时加入Na2SO3可将底物中木质素质量分数降为5%以下,细胞壁多糖质量分数达95%以上。由于其良好的可降解性能,纤维素酶水解预处理杂交狼尾草时剂量可低于10 U/g,且添加木聚糖酶的效果较增加纤维素酶剂量效果更好。在底物质量分数为10%时,每克底物添加10 U纤维素酶、1 000 nkat β-葡萄糖苷酶和 2 mg木聚糖酶进行水解,经4% Na2SO3+1% NaOH预处理后杂交狼尾草的葡萄糖和木糖得率分别高达94.2%和84.0%。碱性亚硫酸盐预处理在高底物质量分数、高效酶水解杂交狼尾草中具有较大应用潜力。
With the increase in global energy demand and global warming concerns caused by the consumption of fossil fuels, the use of diverse biomass to produce biofuels is of particular interest. Biomass, such as agricultural residue, grasses, and forestry wastes, is considered to be a viable and sustainable source for biofuels production. Hybrid China wolftailgrass(Pennisetum americanum × P. purpureum)is an attractive alternative biomass for the production of biofuels and biochemicals due to its advantages of fast growth, high biomass contents, and wide environmental adaptability. In this study, P. americanum × P. purpureum was pretreated with Na2SO3, NaOH and Na2SO3-NaOH to investigate the effects of various pretreatments on its chemical compositions and crystallinity index. In addition, the effects of enzyme dosages, the synergistic effects between cellulases and xylanase and the combination of enzyme cocktails on enzymatic digestibility during the hydrolysis process were also investigated for the purpose of decreasing enzyme dosage and enhancing hydrolysis yield. The results showed that after pretreatments with 1% NaOH or 4% Na2SO3, the contents of lignin in P. americanum × P. purpureum decreased from 19.5% to 10%-15%. The Na2SO3-NaOH pretreatment achieved low lignin content(<5%)and high carbohydrates content( ？？Symbol～@@ 95%). Less than 10 U/g loading could be used in enzymatic hydrolysis of Na2SO3-, NaOH- and Na2SO3+NaOH- pretreated P. americanum × P. purpureum. Supplementation of xylanase was more effective to increase the hydrolysis yield than increasing cellulases loading. High glucose(94.2%)and xylose(84.0%)yields were obtained after supplementation of low enzyme dosages(cellulases of 10 U/g, β-glucosidase of 1 000 nkat/g, and xylanase of 2 mg/g in dry matter)in the hydrolysis of 10% P. americanum × P. purpureum. The results suggested that alkaline sulfite pretreatment exhibited great potential and efficient enzymatic hydrolysis of P. americanum × P. purpureum with low enzyme dosages