Provided herein is a gaseous isoprene composition comprising isoprene, carbon dioxide and water, wherein the isoprene is in an amount between about 0.1% and about 15% by volume; wherein the carbon dioxide is in an amount between about 0.04% and about 35% by volume; wherein the water is in an amount greater than about 70% of its saturation amount. Also provided herein is a liquid isoprene composition comprising isoprene in an amount of at least 65% by weight and carbon dioxide in an amount between about 0.01% and about 1% by weight.