Wu Xiao-Xi, Li Jian-Wei, Xing Su-Fang, Chen Hui-Ting, Song Chao, Wang Shu-Guang, Yan Zhen
Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao, 266237, Shandong, China.
Suzhou Research Institute, Shandong University, Suzhou, 215123, Jiangsu, China.
Biotechnol Biofuels. 2021 Aug 30;14(1):174. doi: 10.1186/s13068-021-02023-8.
Isobutanol is an attractive biofuel with many advantages. Third-generation biorefineries that convert CO into bio-based fuels have drawn considerable attention due to their lower feedstock cost and more ecofriendly refining process. Although autotrophic cyanobacteria have been genetically modified for isobutanol biosynthesis, there is a lack of stable and convenient strategies to improve their production.
In this study, we first engineered Synechococcus elongatus for isobutanol biosynthesis by introducing five exogenous enzymes, reaching a production titer of 0.126 g/L at day 20. It was then discovered that high salinity stress could result in a whopping fivefold increase in isobutanol production, with a maximal in-flask titer of 0.637 g/L at day 20. Metabolomics analysis revealed that high salinity stress substantially altered the metabolic profiles of the engineered S. elongatus. A major reason for the enhanced isobutanol production is the acceleration of lipid degradation under high salinity stress, which increases NADH. The NADH then participates in the engineered isobutanol-producing pathway. In addition, increased membrane permeability also contributed to the isobutanol production titer. A cultivation system was subsequently developed by mixing synthetic wastewater with seawater to grow the engineered cyanobacteria, reaching a similar isobutanol production titer as cultivation in the medium.
High salinity stress on engineered cyanobacteria is a practical and feasible biotechnology to optimize isobutanol production. This biotechnology provides a cost-effective approach to biofuel production, and simultaneously recycles chemical nutrients from wastewater and seawater.
异丁醇是一种具有诸多优点的有吸引力的生物燃料。将二氧化碳转化为生物基燃料的第三代生物精炼厂因其较低的原料成本和更环保的精炼工艺而备受关注。尽管自养蓝藻已被基因改造用于异丁醇生物合成，但仍缺乏稳定且便捷的策略来提高其产量。
在本研究中，我们首先通过引入五种外源酶对聚球藻进行工程改造以用于异丁醇生物合成，在第20天时产量达到0.126克/升。随后发现高盐胁迫可导致异丁醇产量大幅增加五倍，在第20天时摇瓶中的最高产量为0.637克/升。代谢组学分析表明，高盐胁迫显著改变了工程化聚球藻的代谢谱。异丁醇产量提高的一个主要原因是高盐胁迫下脂质降解加速，这增加了NADH。然后NADH参与工程化的异丁醇生产途径。此外，膜通透性的增加也有助于提高异丁醇产量。随后开发了一种通过将合成废水与海水混合来培养工程化蓝藻的培养系统，其异丁醇产量与在培养基中培养时相似。
对工程化蓝藻施加高盐胁迫是一种优化异丁醇生产的切实可行的生物技术。这种生物技术为生物燃料生产提供了一种经济高效的方法，同时还能从废水和海水中回收化学养分。
