Sun Lingling, Wu Bo, Zhang Zengqin, Yan Jing, Liu Panting, Song Chao, Shabbir Samina, Zhu Qili, Yang Shihui, Peng Nan, He Mingxiong, Tan Furong
Key Laboratory of Development and Application of Rural Renewable Energy, Ministry of Agriculture and Rural Affairs, Biogas Institute of Ministry of Agriculture and Rural Affairs, Chengdu, 610041, China.
Graduate School of Chinese Academy of Agricultural Sciences, Beijing, 100081, China.
Biotechnol Biofuels. 2021 Nov 25;14(1):221. doi: 10.1186/s13068-021-02069-8.
As one of the clean and sustainable energies, lignocellulosic ethanol has achieved much attention around the world. The production of lignocellulosic ethanol does not compete with people for food, while the consumption of ethanol could contribute to the carbon dioxide emission reduction. However, the simultaneous transformation of glucose and xylose to ethanol is one of the key technologies for attaining cost-efficient lignocellulosic ethanol production at an industrial scale. Genetic modification of strains and constructing consortia were two approaches to resolve this issue. Compared with strain improvement, the synergistic interaction of consortia in metabolic pathways should be more useful than using each one separately.
In this study, the consortia consisting of suspended Scheffersomyces stipitis CICC1960 and Zymomonas mobilis 8b were cultivated to successfully depress carbon catabolite repression (CCR) in artificially simulated 80G40XRM. With this strategy, a 5.52% more xylose consumption and a 6.52% higher ethanol titer were achieved by the consortium, in which the inoculation ratio between S. stipitis and Z. mobilis was 1:3, compared with the Z. mobilis 8b mono-fermentation. Subsequently, one copy of the xylose metabolic genes was inserted into the Z. mobilis 8b genome to construct Z. mobilis FR2, leading to the xylose final-consumption amount and ethanol titer improvement by 15.36% and 6.81%, respectively. Finally, various corn stover hydrolysates with different sugar concentrations (glucose and xylose 60, 90, 120 g/L), were used to evaluate the fermentation performance of the consortium consisting of S. stipitis CICC1960 and Z. mobilis FR2. Fermentation results showed that a 1.56-4.59% higher ethanol titer was achieved by the consortium compared with the Z. mobilis FR2 mono-fermentation, and a 46.12-102.14% higher ethanol titer was observed in the consortium fermentation when compared with the S. stipitis CICC1960 mono-fermentation. Furthermore, qRT-PCR analysis of xylose/glucose transporter and other genes responsible for CCR explained the reason why the initial ratio inoculation of 1:3 in artificially simulated 80G40XRM had the best fermentation performance in the consortium.
The fermentation strategy used in this study, i.e., using a genetically modified consortium, had a superior performance in ethanol production, as compared with the S. stipitis CICC1960 mono-fermentation and the Z. mobilis FR2 mono-fermentation alone. This result showed that this strategy has potential for future lignocellulosic ethanol production.
作为清洁且可持续的能源之一，木质纤维素乙醇已在全球范围内备受关注。木质纤维素乙醇的生产不与人争夺粮食，而乙醇的消耗有助于减少二氧化碳排放。然而，将葡萄糖和木糖同时转化为乙醇是实现工业规模经济高效生产木质纤维素乙醇的关键技术之一。菌株的基因改造和构建菌群是解决这一问题的两种方法。与菌株改良相比，菌群在代谢途径中的协同相互作用应比单独使用每个菌株更有用。
在本研究中，培养了由悬浮的树干毕赤酵母CICC1960和运动发酵单胞菌8b组成的菌群，以成功抑制人工模拟的80G40XRM中的碳分解代谢物阻遏（CCR）。采用该策略，与运动发酵单胞菌8b单发酵相比，菌群实现了木糖消耗量增加5.52%，乙醇产量提高6.52%，其中树干毕赤酵母与运动发酵单胞菌的接种比例为1:3。随后，将一个木糖代谢基因拷贝插入运动发酵单胞菌8b基因组中构建运动发酵单胞菌FR2，导致木糖最终消耗量和乙醇产量分别提高了15.36%和6.81%。最后，使用不同糖浓度（葡萄糖和木糖60、90、120 g/L）的各种玉米秸秆水解物来评估由树干毕赤酵母CICC1960和运动发酵单胞菌FR2组成的菌群的发酵性能。发酵结果表明，与运动发酵单胞菌FR2单发酵相比，菌群的乙醇产量提高了1.56 - 4.59%，与树干毕赤酵母CICC1960单发酵相比，菌群发酵时乙醇产量提高了46.12 - 102.14%。此外，对木糖/葡萄糖转运蛋白和其他负责CCR的基因进行qRT-PCR分析，解释了在人工模拟的80G40XRM中初始接种比例为1:3时菌群具有最佳发酵性能的原因。
本研究中使用的发酵策略，即使用基因改造的菌群，与单独的树干毕赤酵母CICC1960单发酵和运动发酵单胞菌FR2单发酵相比，在乙醇生产方面具有卓越的性能。这一结果表明该策略在未来木质纤维素乙醇生产中具有潜力。
