期刊
MICROORGANISMS
卷 8, 期 12, 页码 -出版社
MDPI
DOI: 10.3390/microorganisms8121970
关键词
novel clostridial species; carboxylate platform; medium-chain carboxylates; branched-chain carboxylates; anaerobic fermentation; reverse β -oxidation
类别
资金
- China Scholarship Council [201606350010]
- BMBF-German Federal Ministry of Education and Research [031B0389B, 01DQ17016, 031A317]
- Helmholtz Association
- University of Konstanz
- Deutsche Forschungsgemeinschaft (DFG)
The platform chemicals n-caproate and iso-butyrate can be produced by anaerobic fermentation from agro-industrial residues in a process known as microbial chain elongation. Few lactate-consuming chain-elongating species have been isolated and knowledge on their shared genetic features is still limited. Recently we isolated three novel clostridial strains (BL-3, BL-4, and BL-6) that convert lactate to n-caproate and iso-butyrate. Here, we analyzed the genetic background of lactate-based chain elongation in these isolates and other chain-elongating species by comparative genomics. The three strains produced n-caproate, n-butyrate, iso-butyrate, and acetate from lactate, with the highest proportions of n-caproate (18%) for BL-6 and of iso-butyrate (23%) for BL-4 in batch cultivation at pH 5.5. They show high genomic heterogeneity and a relatively small core-genome size. The genomes contain highly conserved genes involved in lactate oxidation, reverse beta-oxidation, hydrogen formation and either of two types of energy conservation systems (Rnf and Ech). Including genomes of another eleven experimentally validated chain-elongating strains, we found that the chain elongation-specific core-genome encodes the pathways for reverse beta-oxidation, hydrogen formation and energy conservation, while displaying substantial genome heterogeneity. Metabolic features of these isolates are important for biotechnological applications in n-caproate and iso-butyrate production.
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