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Enhanced Microbial Utilization of Recalcitrant Cellulose by an Ex Vivo Cellulosome-Microbe Complex

机译:体外纤维素-微生物复合物增强了难降解纤维素的微生物利用

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A cellulosome-microbe complex was assembled ex vivo on the surface of Bacillus subtilis displaying a miniscaffoldin that can bind with three dockerin-containing cellulase components: the endoglucanase Cel5, the processive endoglucanase Cel9, and the cellobiohydrolase Cel48. The hydrolysis performances of the synthetic cellulosome bound to living cells, the synthetic cellulosome, a noncomplexed cellulase mixture with the same catalytic components, and a commercial fungal enzyme mixture were investigated on low-accessibility recalcitrant Avicel and high-accessibility regenerated amorphous cellulose (RAC). The cell-bound cellulosome exhibited 4.5- and 2.3-fold-higher hydrolysis ability than cell-free cellulosome on Avicel and RAC, respectively. The cellulosome-microbe synergy was not completely explained by the removal of hydrolysis products from the bulk fermentation broth by free-living cells and appeared to be due to substrate channeling of long-chain hydrolysis products assimilated by the adjacent cells located in the boundary layer. Our results implied that long-chain hydrolysis products in the boundary layer may inhibit cellulosome activity to a greater extent than the short-chain products in bulk phase. The findings that cell-bound cellulosome expedited the microbial cellulose utilization rate by 2.3- to 4.5-fold would help in the development of better consolidated bioprocessing microorganisms (e.g., B. subtilis ) that can hydrolyze recalcitrant cellulose rapidly at low secretory cellulase levels.
机译:纤维素酶-微生物复合物在枯草芽孢杆菌表面离体组装,显示出一种微支架蛋白,该微支架蛋白可以与三种含dockerin的纤维素酶成分结合:内切葡聚糖酶Cel5,进行性内切葡聚糖酶Cel9和纤维二糖水解酶Cel48。在低可及性顽固性Avicel和高可及性再生无定形纤维素(RAC)上研究了与活细胞结合的合成纤维素,合成纤维素体,具有相同催化成分的非复合纤维素酶混合物和商业真菌酶混合物的水解性能。 。细胞结合的纤维素体在Avicel和RAC上的水解能力分别比无细胞的纤维素体高4.5和2.3倍。纤维素-微生物的协同作用不能完全通过自由活动的细胞从大量发酵液中除去水解产物来解释,似乎是由于长链水解产物的底物通道被位于边界层的相邻细胞所吸收。我们的结果表明,与本体相中的短链产物相比,边界层中的长链水解产物可能会更大程度地抑制纤维素酶的活性。细胞结合的纤维素体将微生物纤维素利用率提高了2.3到4.5倍的发现将有助于开发更好的固结生物加工微生物(例如枯草芽孢杆菌),这些微生物可以在低分泌纤维素酶水平下迅速水解难降解的纤维素。

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