Tan Luoxi, Scott Haden L, Smith Micholas Dean, Pingali Sai Venkatesh, Cheng Xiaolin, O'Neill Hugh M, Katsaras John, Smith Jeremy C, Elkins James G, Davison Brian H, Nickels Jonathan D
Department of Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, Ohio 45220, United States.
Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States.
Langmuir. 2025 Jan 21;41(2):1281-1296. doi: 10.1021/acs.langmuir.4c03677. Epub 2025 Jan 8.
Solvent toxicity limits -butanol fermentation titer, increasing the cost and energy consumption for subsequent separation processes and making biobased production more expensive and energy-intensive than petrochemical approaches. Amphiphilic solvents such as -butanol partition into the cell membrane of fermenting microorganisms, thinning the transverse structure, and eventually causing a loss of membrane potential and cell death. In this work, we demonstrate the deleterious effects of -butanol partitioning upon the lateral dimension of the membrane structure, called membrane domains or lipid rafts. Lipid rafts are regions of the cell membrane enriched with certain lipids, providing a reservoir of high melting temperature lipids and a platform for membrane protein partitioning and oligomerization. Neutron scattering experiments and molecular dynamics simulations revealed that -butanol increased the size of the lipid domains in a model membrane system. The data showed that -butanol partitions more into the disordered lipid regions than into the raft-like phase, leading to a differential thinning of these coexisting phases in the plane of the membrane and increasing the hydrophobic mismatch. The resulting increase in line tension at the interface favors domain coalescence to minimize the ratio of the interfacial length to domain area. A detailed computational investigation of the lipid domain interface identifies the boundary as a site of membrane disorder and thinning due to an accumulation of -butanol. Solvent-induced changes to domain morphology and membrane instability at the domain interface are unrecognized modes of solvent-induced stress to fermenting microbes, representing targets for new solvent tolerance strategies to increase the -butanol titer.
溶剂毒性限制了丁醇发酵的滴度，增加了后续分离过程的成本和能源消耗，使得生物基生产比石化方法更昂贵且能源密集。像丁醇这样的两亲性溶剂会进入发酵微生物的细胞膜，使横向结构变薄，最终导致膜电位丧失和细胞死亡。在这项工作中，我们证明了丁醇分配对膜结构横向尺寸（称为膜结构域或脂筏）的有害影响。脂筏是细胞膜中富含某些脂质的区域，提供了高熔点脂质的储存库以及膜蛋白分配和寡聚化的平台。中子散射实验和分子动力学模拟表明，丁醇增加了模型膜系统中脂质结构域的大小。数据显示，丁醇更多地分配到无序脂质区域而不是筏状相中，导致这些共存相在膜平面内的差异变薄并增加了疏水不匹配。界面处线张力的增加有利于结构域合并，以最小化界面长度与结构域面积的比率。对脂质结构域界面的详细计算研究确定该边界是由于丁醇积累导致膜无序和变薄的部位。溶剂诱导的结构域形态变化和结构域界面处的膜不稳定性是溶剂诱导发酵微生物应激的未被认识的模式，代表了提高丁醇滴度的新溶剂耐受性策略的目标。
