Fig. 5

Application of alginate lyases and associated metabolic pathways. The schematic diagram shows the application of single (A) and combined (B) enzymes. C Schematic pathways for the production of bioethanol and other value-added biochemicals. A workflow for ethanol production in industrial microbes (E. coli and S. cerevisiae) is shown as red solid arrows. In S. cerevisiae, the eukaryotic DEH transporter DHT1 is introduced for DEH entry. The workflow for bioethanol production in native alginate-utilising bacteria Sphingomonas sp. A1 and Vibrio sp. dhg is shown as green dashed arrows. Besides ethanol production, Vibrio sp. dhg was also engineered to synthesise 2,3-butanediol and lycopene. Alginate-utilising strain D. phaphyphila harbours a distinct pathway and stepwise converts pyruvate into acetyl-CoA and ethanol, which is shown as orange solid arrows. In E. coli and Vibrio sp. dhg, endogenous genes including frd encoding fumarate reductase, ldh encoding lactate dehydrogenase, and pfl encoding pyruvate-formate lyase, were deleted to block by-product synthesis, shown as green crosses. In Sphingomonas sp. A1, only lactate formation is inhibited by deletion of ldh gene