Proteomic Analysis Identifies Dysregulated Proteins in Butanol-Tolerant Gram-Positive BR0713-33.

Butanol can be produced biologically through fermentation of lignocellulosic biomass-derived sugars by Gram-positive species. For cost-effective production, increased butanol fermentation titers are desired. However, the currently available butanol-fermenting microbes do not tolerate sufficiently high butanol concentrations; thus, new butanol-tolerant strains are desired. One promising strategy is to genetically modify species by introducing stress tolerance-associated genes. This study was aimed to seek butanol tolerance genes from other Gram-positive species, which might be better suited than those from Gram-negative or eukaryotic . Several butanol-tolerant lactobacilli were reported previously, and BR0713-33, which showed the most robust anaerobic growth in 4% butanol, was used here for proteomics analyses. Cellular proteins that responded to 2, 3, and 4% butanol were characterized. Twenty-nine proteins that were identified were dysregulated in response to increased concentrations of butanol in Seventeen genes involved in coding for stress-tolerant proteins GroES, GroEL, and DnaK and genes involved in substrate utilization, fatty acid metabolism, and nucleotide synthesis were induced by increased butanol, and 12 genes involving energy production (FFATP synthases) and redox balance preservation were repressed by increased butanol. These results can help guide targeted engineering strategies to improve tolerance and production of biobutanol.