Abstract Biological pretreatment using microorganisms or enzymes offers an eco-friendly process for biomass processing. Herein, the efficiency of pretreatment of rice straw with the cellulase-free xylanolytic enzyme-producing Bacillus firmus K-1 and its enzymes was assessed. After pretreatment with strain K-1 (BRS), the xylan content in rice straw reduced significantly (21% removal), thus increasing exposure of the cellulose crystal structure (Crystallinity index (CrI) = 40.2%) and creating biomass porosity. Subsequent treatment of BRS with the in-house xylanase preparation (BRS-E) slightly increased xylan removal (30% removal). The reduction of xylan thus led to larger pore size and increased crystallinity (CrI = 42.8%). Compared to untreated rice straw (24% glucan conversion), hydrolysis of BRS and BRS-E with the commercial cellulase preparation Accellerase 1500 at 100 g/L substrate load showed comparable glucose yield, giving about 74% glucan conversion. The results indicate that the removal of xylan can enhance accessibility of cellulose to cellulases, although the lignin content was not reduced (24% for BRS and 25% for BRS-E). This work demonstrates a new insight into the improvement of pretreatment efficiency using a xylan-degrading microorganism, which is an alternative to conventional lignin removal by fungal pretreatment.

中文翻译：

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用无纤维素酶产木聚糖酶的 Bacillus Firmus K-1 生物预处理稻草：结构改性和生物质消化率

摘要 使用微生物或酶的生物预处理为生物质加工提供了一种生态友好的过程。在此，评估了用不含纤维素酶的产木聚糖酶的 Bacillus Firmus K-1 及其酶预处理稻草的效率。用菌株 K-1 (BRS) 预处理后，稻草中的木聚糖含量显着降低（去除 21%），从而增加了纤维素晶体结构的暴露（结晶度指数 (CrI) = 40.2%）并产生了生物质孔隙率。随后用内部木聚糖酶制剂 (BRS-E) 处理 BRS 略微增加了木聚糖去除率（去除率 30%）。因此，木聚糖的减少导致更大的孔径和增加的结晶度（CrI = 42.8%）。与未经处理的稻草相比（葡聚糖转化率为 24%），BRS 和 BRS-E 与商业纤维素酶制剂 Accellerase 1500 在 100 g/L 底物负载下的水解显示出相当的葡萄糖产量，葡聚糖转化率约为 74%。结果表明，木聚糖的去除可以提高纤维素对纤维素酶的可及性，尽管木质素含量没有降低（BRS 为 24%，BRS-E 为 25%）。这项工作展示了对使用木聚糖降解微生物提高预处理效率的新见解，这是通过真菌预处理去除传统木质素的替代方法。