The novel catabolic pathway of 3,6-anhydro-L-galactose, the main component of red macroalgae, in a marine bacterium

Eun Ju Yun, Saeyoung Lee, Hee Taek Kim, Jeffrey G. Pelton, Sooah Kim, Hyeok Jin Ko, In Geol Choi, Kyoung Heon Kim

Research output: Contribution to journalArticlepeer-review

80 Citations (Scopus)


The catabolic fate of the major monomeric sugar of red macroalgae, 3,6-anhydro-L-galactose (AHG), is completely unknown in any organisms. AHG is not catabolized by ordinary fermentative microorganisms, and it hampers the utilization of red macroalgae as renewable biomass for biofuel and chemical production. In this study, metabolite and transcriptomic analyses of Vibrio sp., a marine bacterium capable of catabolizing AHG as a sole carbon source, revealed two key metabolic intermediates of AHG, 3,6-anhydrogalactonate (AHGA) and 2-keto-3-deoxy-galactonate; the corresponding genes were verified in vitro enzymatic reactions using their recombinant proteins. Oxidation by an NADP+-dependent AHG dehydrogenase and isomerization by an AHGA cycloisomerase are the two key AHG metabolic processes. This newly discovered metabolic route was verified in vivo by demonstrating the growth of Escherichia coli harbouring the genes of these two enzymes on AHG as a sole carbon source. Also, the introduction of only these two enzymes into an ethanologenic E.coli strain increased the ethanol production in E.coli by fermenting both AHG and galactose in an agarose hydrolysate. These findings provide not only insights for the evolutionary adaptation of a central metabolic pathway to utilize uncommon substrates in microbes, but also a metabolic design principle for bioconversion of red macroalgal biomass into biofuels or industrial chemicals.

Original languageEnglish
Pages (from-to)1677-1688
Number of pages12
JournalEnvironmental Microbiology
Issue number5
Publication statusPublished - 2015 May 1

Bibliographical note

Publisher Copyright:
© 2014 Society for Applied Microbiology and John Wiley & Sons Ltd.

ASJC Scopus subject areas

  • Microbiology
  • Ecology, Evolution, Behavior and Systematics


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