Abstract
BackgroundSynechocystis sp. PCC 6803 is an attractive organism for the production of alcohols, such as isobutanol and ethanol. However, because stress against the produced alcohol is a major barrier for industrial applications, it is highly desirable to engineer organisms with strong alcohol tolerance.ResultsIsobutanol-tolerant strains of Synechocystis sp. PCC 6803 were obtained by long-term passage culture experiments using medium containing 2 g/L isobutanol. These evolved strains grew on medium containing 5 g/L isobutanol on which the parental strain could not grow. Mutation analysis of the evolved strains revealed that they acquired resistance ability due to combinatorial malfunctions of slr1044 (mcpA) and slr0369 (envD), or slr0322 (hik43) and envD. The tolerant strains demonstrated stress resistance against isobutanol as well as a wide variety of alcohols such as ethanol, n-butanol, and isopentanol. As a result of introducing an ethanol-producing pathway into the evolved strain, its productivity successfully increased to 142% of the control strain.ConclusionsNovel mutations were identified that improved the stress tolerance ability of various alcohols in Synechocystis sp. PCC 6803.
Highlights
IntroductionPCC 6803 is an attractive organism for the production of alcohols, such as isobutanol and ethanol
PCC 6803 under isobutanol stress conditions Isobutanol-tolerant strains were obtained via long-term passage culture experiments
The OD730 at 72 h decreased by one-half in medium containing 2 g/L isobutanol compared to samples under no isobutanol condition (Additional file 1: Fig. S1)
Summary
PCC 6803 is an attractive organism for the production of alcohols, such as isobutanol and ethanol. The cyanobacterial production of alcohols, such as ethanol, n-butanol, and isobutanol, as an alternative to petroleum has attracted attention [1]. Isobutanol is an attractive fuel because of its higher energy density and lower hygroscopicity than ethanol. PCC 6803 to 1-butanol identified candidate genes for enhancing 1-butanol tolerance, and the expression of small heat-shock protein HspA (sll1514) and hypothetical protein CccS (slr1617) successfully improved 1-butanol tolerance [6]. Screening from the response regulator library revealed that sll0039 and slr1037 are involved in 1-butanol tolerance in Matsusako et al Biotechnol Biofuels (2017) 10:307
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