Abstract
Lactobacillus acetotolerans is a major microbe contributing to the Chinese liquor fermentation with unknown function. It can be grown well in a high concentration of ethanol. RNA sequencing (RNA-seq) was performed on L. acetotolerans F28 growing in 12% ethanol to determine important genetic mechanisms for both a short and long term adaption to this environment. A genome-wide transcriptional analysis revealed that the most important genetic elements for L. acetotolerans F28 grown in ethanol are related to high levels of stress response and fatty acid biosynthesis, and a reduction of amino acid transport and metabolism after both a short and long time stress. The fatty acid methyl ester analyses showed that most fatty acids were increased in L. acetotolerans F28 after exposure to ethanol while the unsaturated fatty acid octadecenoic acid (C18:1) was significantly increased. The increasing unsaturated fatty acid biosynthesis in L. acetotolerans F28 might enhance cell membrane fluidity and protect the cells against high concentration of ethanol. Overall, the transcriptome and functional analysis indicated that the elevated stress response and fatty acid biosynthesis, and the decrease of amino acid transport and metabolism might play important roles for L. acetotolerans F28 to adapt to environmental ethanol.
Highlights
Lactobacillus is the largest genus of lactic acid bacteria and is widely used in various foods and beverages fermentation including yoghurt, sausage, wine and liquor[1,2,3,4]
These results demonstrated that L. acetotolerans F28 was able to resist a comparable high concentration of ethanol ( > 12%)
L. acetotolerans was reported to be a kind of beer-spoilage bacteria, it seems to play an important role in liquor production
Summary
Lactobacillus is the largest genus of lactic acid bacteria and is widely used in various foods and beverages fermentation including yoghurt, sausage, wine and liquor[1,2,3,4]. Lactobacillus is exposed to several stresses, such as high content of acids or alcohol, low or high temperature, growth-inhibitory compounds and so on. They are required to survive and grow under specific stress environmental conditions[5]. The changes suggested that Lactobacillus buchneri respond to ethanol by proteins and fatty acids degradation and increased production of specific enzymes and molecular chaperones[13]. It is unclear if the above genetic pathways are important for the growth of L. acetotolerans under ethanol stress. Gene variations associated with the adaption of L. acetotolerans to ethanol in both a short and a long time stage were revealed
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