Engineering a Synthetic Dual-Organism System for Hydrogen Production

Molecular hydrogen produced biologically from renewable biomass is an attractive replacement for fossil fuels. One potential route for biological hydrogen production is the conversion of biomass into formate, which can subsequently be processed into hydrogen byEscherichia coli . Formate is also a widely used commodity chemical, making its bioproduction even more attractive. Here we demonstrate the implementation of a formate-overproducing pathway inSaccharomyces cerevisiae , a well-established industrial organism. By expressing the anaerobic enzyme pyruvate formate lyase fromE. coli , we engineered a strain of yeast that overproduced formate relative to undetectable levels in the wild type. The addition of a downstream enzyme, AdhE ofE. coli , resulted in an additional 4.5-fold formate production increase as well as an increase in growth rate and biomass yield. Overall, an 18-fold formate increase was achieved in a strain background whose formate degradation pathway had been deleted. Finally, as a proof of concept, we were able to produce hydrogen from this formate-containing medium by usingE. coli as a catalyst in a two-step process. With further optimizations, it may be feasible to useS. cerevisiae on a larger scale as the foundation for yeast-based biohydrogen.