Biomass represents an abundant carbon-neutral renewable resource for the production of bioenergy and biomaterials.  Bio-ethanol is one of the predominant bio-fuels, which is produced mainly by yeast (saccharomyces cerevisiae) fermentation.  During ethanol fermentation, more than forty percent of the carbons are released into the atmosphere as carbon dioxide.  The ability to capture part of the CO2 released during fermentation will provide an alternative way to improve ethanol productivity per unit of biomass used.  To achieve this objective, we explored the feasibility of expressing cyanobacterial photosynthetic enzymes in fermentative yeast to capture CO2.  The genes for ribulose bisphophate carboxylase and phosphoribulokinase were isolated from cyanobacterium Synechococcus sp. and were heterologously expressed in the yeast under the control of the yeast actin, pgk1 or adh1 promoters.  RNA and protein blotting analyses confirmed that both genes were properly expressed in S. cerevisiae.  Codon optimization of both genes significantly improved protein accumulation in the yeast.  The 14C labeling analysis demonstrated that ribulose bisphosphate carboxylase was active in the yeast cells though the activity was low.  The effects of both enzymes on yeast ethanol production were also examined in culture media supplemented with a xylose-xylulose mixture.  Some improvement was observed.  Further improvement of this CO2 capturing process is on-going.