硫酸盐木质素对预处理杨木酶水解糖化的影响

Effect of kraft lignin on enzymatic saccharification of pretreated poplar

为研究水溶性硫酸盐木质素对不同预处理杨木酶水解的影响,将硫酸盐木质素(KL)进行分级处理形成水溶性硫酸盐木质素(KL5)后,分别添加到纤维素酶(CTec2)水解体系中,考察KL与KL5对绿液(GL)、酸性亚硫酸氢钠(AS)及亚硫酸钠-甲醛(SF)预处理杨木底物浆料酶水解糖化效率的影响。结果表明:在GL预处理条件下,随着KL5用量的增加,各聚糖转化率和酶水解反应速率均显著提高,当KL5用量为0.1 g/g时,底物总糖转化率达到最大值83.1%,但添加KL会抑制酶水解糖化效率;在AS和SF预处理条件下,底物中添加KL5后各聚糖转化率与GL预处理酶水解各聚糖转化率相似;在较低浓度条件下,KL5对GL预处理酶水解效率的促进作用明显优于Reax 85A和PEG 4000添加剂。改性工业废渣硫酸盐木质素作为酶水解助剂能够明显提高酶水解糖化效率,为高效利用过程废液废渣组分、减少水解酶的用量成本提供理论依据。

Lignin,as the second largest resource of the lignocellulose biomass,is cheap and abundant.Kraft lignin is the main composition in the waste liquor from kraft pulping industry.In this study,kraft lignin was used to improve the process efficiency of cellulose saccharification.Water-souble lignin(KL5)was first fractionated from Kraft lignin(KL)and added to enhance the digestibility of lignocellulose with cellulase(CTec2).The effects of KL or KL5 on the saccharification of enzymatic hydrolysis were investigated by using green liquor(GL),sodium sulfite-formaldehyde(SF)and acid sodium bisulfite(AS)pretreated poplar as substrates.Wet chemical analysis indicated that,by GL pretreated,the increasing amount of soluble KL5 in the lignocellulose hydrolysis system could improve the efficiency of enzymatic hydrolysis as well as decreased the enzymatic incubation time.The addition of KL inhibited the saccharification of enzymatic hydrolysis.The effects of KL5 on the enzymatic hydrolysis of AS and SF pretreated poplar were the same as GL pretreated poplar,while it had no significant effect on the pure cellulose substrate.Furthermore,the efficiency of enzymatic hydrolysis with KL5 was significantly better than that with Reax 85A and PEG 4000 additives for GL pretreated substrates.The total sugar conversion rates were up to 83.1%,81.5%and 83.6%for GL-,AS-and SF-pretreated poplar,respectively,with the optimal addition of 0.1 g/g KL5.The results from this study showed that fraction of KL(KL5)can be used as an excellent additive for enhancing enzymatic efficiency of lignocellulosic materials by increasing enzymatic digestibility,reducing enzymatic incubation time,and reducing enzyme loading for certain pretreatment method.It is beneficial to utilize the whole lignocellulosic materials for producing bioenergy and bio-based materials.