TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preparation (claimed): The butanol tolerant bacterial cell is produced by (i) providing bacterial cell comprising engineered butanol biosynthetic pathway and feeding the bacterial cell with at least one trans fatty acid under conditions where the concentration of trans unsaturated fatty acids in the membrane of the cell are increased, or (b) providing bacterial cell comprising engineered butanol biosynthetic pathway and at least one gene encoding fatty acid cis-trans isomerase, and expressing the gene encoding fatty acid cis-trans isomerase, such that the concentration of unsaturated trans fatty acids in the membrane of the cell are increased. Preferred Microorganism: The cell is chosen from Zymomonas, Escherichia, Salmonella, Rhodococcus, Pseudomonas, Bacillus, Lactobacillus, Enterococcus, Pediococcus, Alcaligenes, Klebsiella, Paenibacillus, Arthrobacter, Corynebacterium, Leuconostoc and Brevibacterium, preferably Lactobacillus. Preferred Method: The butanol biosynthetic pathway is chosen from 1-butanol biosynthetic pathway, 2-butanol biosynthetic pathway and isobutanol biosynthetic pathway. Preferred Nucleic acid: The butanol tolerant bacterial cell comprises at least one gene encoding fatty acid cis-trans isomerase. The isobutanol biosynthetic pathway comprises at least one gene encoding acetolactate synthase, acetohydroxy acid isomeroreductase, acetohydroxy acid dehydratase, branched-chain keto acid decarboxylase and branched-chain alcohol dehydrogenase. EXAMPLE - Esterified fatty acid cis-trans isomerase (cti) coding region of Pseudomonas putida KT2440 comprising 2301 base pair sequence (SEQ ID NO: 135) fully defined in the specification was amplified by PCR using sense and antisense primers, respectively comprising 37 base pair sequence (SEQ ID NO: 153) fully defined in the specification, and 5'-tcagaggttctcgtagcggt-3' (SEQ ID NO: 154). The amplified fragment was cloned into pTrcHis2-TOPO vector, and pTrcCti plasmid with cti coding region was obtained. The Escherichia coli cells were transformed with the pTrcCti plasmid. The transformed E.coli MG1655 cells were grown in Luria-Bertani (LB) medium at 30 degrees C or 37 degrees C. The cultured cells having increased tolerance to isobutanol, 1-butanol, and 2-butanol were harvested.