Development ofoptimal steam explosion pretreatment andhighly effective cell factory forbioconversion ofgrain vinegar residue to butanol

Development ofoptimal steam explosion pretreatment andhighly effective cell factory forbioconversion ofgrain vinegar residue to butanol

Abstract .Background: The industrial vinegar residue (VR) from solid-state fermentation, mainly cereals and their bran, will be a potential feedstock for future biofuels because of their low cost and easy availability. However, utilization of VR for butanol production has not been as much optimized as other sources of lignocellulose, which mainly stem from two key elements: (i) high biomass recalcitrance to enzymatic sugar release; (ii) lacking of suitable industrial biobutanol production strain. Though steam explosion has been proved effective for bio-refinery, few studies report SE for VR pretreatment. Much of the relevant knowledge remains unknown. Meanwhile, recent efforts on rational metabolic engineering approaches to increase butanol production in Clostridium strain are quite limited. In this study, we assessed the impact of SE pretreatment, enzymatic hydrolysis kinetics, overall sugar recovery and applied atmospheric and room temperature plasma (ARTP) mutant method for the Clostridium strain development to solve the long-standing problem..Results: SE pretreatment was first performed. At the optimal condition, 29.47% of glucan, 71.62% of xylan and 22.21% of arabinan were depolymerized and obtained in the water extraction. In the sequential enzymatic hydrolysis process, enzymatic hydrolysis rate was increased by 13-fold compared to the VR without pretreatment and 19.60 g glucose, 15.21 g xylose and 5.63 g arabinose can be obtained after the two-step treatment from 100 g VR. Porous properties analysis indicated that steam explosion can effectively generate holes with diameter within 10–20 nm. Statistical analysis proved that enzymatic hydrolysis rate of VR followed the Pseudop-second-order kinetics equation and the relationship between SE severity and enzymatic hydrolysis rate can be well revealed by Boltzmann model. Finally, a superior inhibitor-tolerant strain, Clostridium acetobutylicum Tust-001, was generated with ARTP treatment. The water extraction and enzymolysis liquid gathered were successfully fermented, resulting in butanol titer of 7.98 g/L and 12.59 g/L of ABE..Conclusions: SE proved to be quite effective for VR due to high fermentable sugar recovery and enzymatic hydro-lysate fermentability. Inverse strategy employing ARTP and repetitive domestication for strain breeding is quite feasible, providing us with a new tool for solving the problem in the biofuel fields...

摘要。背景：固态发酵产生的工业醋糟（VR）主要来自谷物及其麸皮，由于其成本低且易于获取，将成为未来生物燃料的潜在原料。然而，VR用于丁醇生产的利用尚未像其他木质纤维素来源那样得到充分优化，这主要源于两个关键因素：（i）生物质对酶促糖释放的高度抗性；（ii）缺乏合适的工业生物丁醇生产菌株。尽管蒸汽爆破已被证明对生物炼制有效，但很少有研究报道蒸汽爆破用于VR预处理。许多相关知识仍然未知。同时，近期通过合理的代谢工程方法提高梭菌菌株丁醇产量的努力相当有限。在本研究中，我们评估了蒸汽爆破预处理、酶水解动力学、总糖回收率的影响，并应用常压室温等离子体（ARTP）突变方法开发梭菌菌株，以解决长期存在的问题。结果：首先进行了蒸汽爆破预处理。在最佳条件下，29.47%的葡聚糖、71.62%的木聚糖和22.21%的阿拉伯聚糖被解聚，并在水提取中获得。在连续的酶水解过程中，与未预处理的VR相比，酶水解速率提高了13倍，从100g VR经过两步处理后可获得19.60g葡萄糖、15.21g木糖和5.63g阿拉伯糖。孔隙特性分析表明，蒸汽爆破可有效产生直径在10 - 20nm范围内的孔洞。统计分析证明，VR的酶水解速率遵循伪二级动力学方程，蒸汽爆破强度与酶水解速率之间的关系可以通过玻尔兹曼模型很好地揭示。最后，通过ARTP处理产生了一种优良的耐抑制剂菌株，丙酮丁醇梭菌Tust - 001。收集的水提取物和酶解液成功发酵，丁醇滴度达到7.98g/L，ABE达到12.59g/L。结论：由于高可发酵糖回收率和酶水解产物的可发酵性，蒸汽爆破对VR非常有效。采用ARTP和重复驯化进行菌株选育的反向策略是相当可行的，为我们提供了解决生物燃料领域问题的新工具。