Cellulose hydrolysis with thermo- and alkali-tolerant cellulases in cellulose-dissolving superbase ionic liquids
Cellulose hydrolysis with thermo- and alkali-tolerant cellulases in cellulose-dissolving superbase ionic liquids
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DOI：
10.1039/c3ra42987c
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发表时间：
2013-10
期刊：
影响因子：
3.9
通讯作者：
Ronny Wahlström;Alistair W. T. King;A. Parviainen;K. Kruus;A. Suurnäkki
中科院分区：
文献类型：
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作者：
Ronny Wahlström;Alistair W. T. King;A. Parviainen;K. Kruus;A. Suurnäkki
已知用离子液体（IL）预处理大大增加随后的生物质用酶水解。然而，即使少量IL的存在也对纤维素酶作用具有负面影响。大多数关于离子液体灭活纤维素酶的研究都集中在咪唑类离子液体上，直到最近，咪唑类离子液体还是已知的少数几种溶解纤维素的离子液体之一。在这篇文章中，我们描述了纤维素酶的行动在矩阵中含有IL属于两个IL类最近报道的纤维素溶剂的结果。这些离子液体基于有机超强碱1，1，3，3-四甲基胍（TMG）或1，5-二氮杂双环[4.3.0]壬-5-烯（DBN）。在该研究中，使用商业热稳定性和碱稳定性纤维素酶产品，因为预期这些产品在IL中也具有更高的稳定性。为了比较，还用来自里氏木霉的充分表征的内切葡聚糖酶（Cel 5A）和在含有1-乙基-3-甲基咪唑乙酸盐[EMIM]AcO的基质中进行水解实验。使用两种不同的基质，微晶纤维素（MCC）和桉树预水解硫酸盐溶解级纸浆。这两种底物的水解产率在相同的水平上，但仅在溶解级纸浆中观察到纤维素分子量的降低。通过使用具有良好的热稳定性和碱稳定性的商业纤维素酶，在IL相容性方面获得了一些益处。酶的热稳定性与含IL基质中较高的水解产率相关，而高pH值下的活性并没有在IL耐受性方面提供益处。新型的溶解纤维素的超强碱离子液体在纤维素酶相容性方面与充分研究的咪唑鎓基离子液体没有不同。在所测试的新型超强碱离子液体中，发现[TMGH]AcO抑制酶水解最少。
Pretreatment with ionic liquids (ILs) is known to greatly increase the subsequent biomass hydrolysis with enzymes. However, the presence of even low amounts of ILs has negative effects on cellulase action. Most studies on cellulase inactivation by ILs have focused on imidazolium-based ILs, which until recently were one of the few IL classes known to dissolve cellulose. In this article we describe results of cellulase action in matrices containing ILs belonging to two IL classes recently reported as cellulose solvents. These ILs are based on the organic superbases 1,1,3,3-tetramethylguanidine (TMG) or 1,5-diazabicyclo[4.3.0]non-5-ene (DBN). In this study commercial thermo- and alkaline stabile cellulase products were employed, as these were anticipated to also have a higher stability in ILs. For comparison, hydrolysis experiments were also carried out with a well-characterised endoglucanase (Cel5A) from Trichoderma reesei and in matrices containing 1-ethyl-3-methylimidazolium acetate, [EMIM]AcO. Two different substrates were used, microcrystalline cellulose (MCC) and eucalyptus pre-hydrolysis kraft dissolving grade pulp. The hydrolysis yields were on the same level for both of these substrates, but decreases in molecular weight of the cellulose was observed only for the dissolving grade pulp. By using commercial cellulases with good thermo- and alkali-stability some benefits were obtained in terms of IL compatibility. Enzyme thermostability correlated with higher hydrolysis yields in IL-containing matrices, whereas activity at high pH values did not offer benefits in terms of IL tolerance. The new classes of cellulose-dissolving superbase ILs did not differ in terms of cellulase compatibility from the well-studied imidazolium-based ILs. Of the novel superbase ILs tested, [TMGH]AcO was found to inhibit the enzymatic hydrolysis the least.