National Key Laboratory of Crop Genetic Improvement and National Centre of Plant Gene Research, Huazhong Agricultural University, Wuhan, 430070, China.
Biomass and Bioenergy Research Centre, Huazhong Agricultural University, Wuhan, 430070, China.
Biotechnol Biofuels. 2012 Aug 11;5(1):58. doi: 10.1186/1754-6834-5-58.
Lignocellulose is the most abundant biomass on earth. However, biomass recalcitrance has become a major factor affecting biofuel production. Although cellulose crystallinity significantly influences biomass saccharification, little is known about the impact of three major wall polymers on cellulose crystallization. In this study, we selected six typical pairs of Miscanthus samples that presented different cell wall compositions, and then compared their cellulose crystallinity and biomass digestibility after various chemical pretreatments.
A Miscanthus sample with a high hemicelluloses level was determined to have a relatively low cellulose crystallinity index (CrI) and enhanced biomass digestibility at similar rates after pretreatments of NaOH and H2SO4 with three concentrations. By contrast, a Miscanthus sample with a high cellulose or lignin level showed increased CrI and low biomass saccharification, particularly after H2SO4 pretreatment. Correlation analysis revealed that the cellulose CrI negatively affected biomass digestion. Increased hemicelluloses level by 25% or decreased cellulose and lignin contents by 31% and 37% were also found to result in increased hexose yields by 1.3-times to 2.2-times released from enzymatic hydrolysis after NaOH or H2SO4 pretreatments. The findings indicated that hemicelluloses were the dominant and positive factor, whereas cellulose and lignin had synergistic and negative effects on biomass digestibility.
Using six pairs of Miscanthus samples with different cell wall compositions, hemicelluloses were revealed to be the dominant factor that positively determined biomass digestibility after pretreatments with NaOH or H2SO4 by negatively affecting cellulose crystallinity. The results suggested potential approaches to the genetic modifications of bioenergy crops.
木质纤维素是地球上最丰富的生物质。然而，生物质的抗降解性已成为影响生物燃料生产的主要因素。尽管纤维素结晶度显著影响生物质的糖化，但对于三种主要细胞壁聚合物对纤维素结晶的影响知之甚少。在这项研究中，我们选择了 6 对具有不同细胞壁成分的芒草样品，然后比较了它们在各种化学预处理后的纤维素结晶度和生物质消化率。
发现具有高半纤维素水平的芒草样品具有相对较低的纤维素结晶度指数（CrI），并且在相同的预处理条件下，NaOH 和 H2SO4 的三个浓度处理后，其生物质消化率提高的速率相似。相比之下，具有高纤维素或木质素水平的芒草样品表现出增加的 CrI 和低生物质糖化，特别是在 H2SO4 预处理后。相关分析表明，纤维素 CrI 对生物质消化有负面影响。还发现，半纤维素水平增加 25%，或纤维素和木质素含量分别减少 31%和 37%，经 NaOH 或 H2SO4 预处理后，酶解释放的六碳糖产量也分别增加 1.3 倍至 2.2 倍。这些发现表明，半纤维素是主要的正向因素，而纤维素和木质素对生物质消化有协同的负向影响。
使用 6 对具有不同细胞壁成分的芒草样品，发现半纤维素是通过负向影响纤维素结晶度来决定 NaOH 或 H2SO4 预处理后生物质消化率的主要正向因素。研究结果为生物能源作物的遗传改良提供了潜在的方法。
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