Nuclear magnetic resonance investigation of water accessibility in cellulose of pretreated sugarcane bagasse.
Nuclear magnetic resonance investigation of water accessibility in cellulose of pretreated sugarcane bagasse.
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DOI：
10.1186/s13068-014-0127-5
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发表时间：
2014
影响因子：
6.3
通讯作者：
Bonagamba TJ
中科院分区：
文献类型：
--
作者：
Tsuchida JE;Rezende CA;de Oliveira-Silva R;Lima MA;d'Eurydice MN;Polikarpov I;Bonagamba TJ
酶水解是生物质转化为生物燃料的关键步骤，不同的预处理方法已被提出来提高工艺效率。在影响生物质样品的水解产率的各种因素中，孔隙率和水可及性由于其与生物质的纤维素和半纤维素部分的酶可及性的密切关系而突出。本文对甘蔗渣进行了酸、碱预处理。通过扫描电镜（SEM）和核磁共振（NMR）研究了纤维素的总表面积、亲水性、孔隙率和水可及性的变化。在化学和物理性质的样品，所造成的半纤维素和木质素的部分去除的变化，导致增加的孔隙率的细胞壁和解旋的纤维素束，如通过SEM观察到的。1H NMR弛豫数据揭示了水分子占据宽和窄导管的核心以及细胞壁内部结构的存在。干燥后，与细胞壁结构相关的水分子没有发生显著的动态和部分水分变化，而位于宽容器和窄容器核心中的水分子保持持续蒸发，直到达到约20%的相对湿度。这表明水首先从管腔的核心中除去，并且在干燥样品中，唯一剩余的水分子是结合到细胞壁的那些。水与预处理的甘蔗渣的较强的相互作用与更好的酶对纤维素的可及性和更高的酶水解效率一致。我们能够确定，酸和碱预处理下的甘蔗渣改性改变了样品不同部位的水可及性，与甘蔗渣结构（管腔和细胞壁）和亲水性（木质素去除）相关。此外，我们表明，增加水的可及性的基板对应于那些具有较高的水解产率和实验NMR测量的横向弛豫时间和酶水解的效率之间存在相关性。这可能允许使用廉价和非破坏性的低场1H NMR弛豫方法的生物质样品的酶水解效率的半定量估计。
Enzymatic hydrolysis is a crucial step of biomass conversion into biofuels and different pretreatments have been proposed to improve the process efficiency. Amongst the various factors affecting hydrolysis yields of biomass samples, porosity and water accessibility stand out due to their intimate relation with enzymes accessibility to the cellulose and hemicellulose fractions of the biomass. In this work, sugarcane bagasse was subjected to acid and alkali pretreatments. The changes in the total surface area, hydrophilicity, porosity and water accessibility of cellulose were investigated by scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR). Changes in chemical and physical properties of the samples, caused by the partial removal of hemicellulose and lignin, led to the increase in porosity of the cell walls and unwinding of the cellulose bundles, as observed by SEM. 1H NMR relaxation data revealed the existence of water molecules occupying the cores of wide and narrow vessels as well as the cell wall internal structure. Upon drying, the water molecules associated with the structure of the cell wall did not undergo significant dynamical and partial moisture changes, while those located in the cores of wide and narrow vessels kept continuously evaporating until reaching approximately 20% of relative humidity. This indicates that water is first removed from the cores of lumens and, in the dry sample, the only remaining water molecules are those bound to the cell walls. The stronger interaction of water with pretreated bagasse is consistent with better enzymes accessibility to cellulose and higher efficiency of the enzymatic hydrolysis. We were able to identify that sugarcane bagasse modification under acid and basic pretreatments change the water accessibility to different sites of the sample, associated with both bagasse structure (lumens and cell walls) and hydrophilicity (lignin removal). Furthermore, we show that the substrates with increased water accessibility correspond to those with higher hydrolysis yields and that there is a correlation between experimentally NMR-measured transverse relaxation times and the efficiency of enzymatic hydrolysis. This might allow for semiquantitative estimates of the enzymatic hydrolysis efficiency of biomass samples using inexpensive and non-destructive low-field 1H NMR relaxometry methods.
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影响因子：
5.7
作者：
Felby, Claus;Thygesen, Lisbeth G.;Elder, Thomas
通讯作者：
Elder, Thomas
影响因子：
2.7
作者：
Betancur, Gabriel J. Vargas;Pereira, Nei, Jr.
通讯作者：
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影响因子：
3
作者：
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通讯作者：
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通讯作者：
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