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Abstract

A process for the bacterial production of the hydrocarbon isoprene (2-methyl-1,3-butadiene) is described and claimed. Various bacterial species, both Gram-negative and Gram-positive, were found to produce isoprene, and a method to isolate isoprene-producing bacteria from natural sources is described. Production of isoprene is confirmed by gas chromatography and gas chromatography-mass spectrometry. Of the tested species, Bacillus produces the most isoprene. Growth in a variety of media, including a chemically defined salts medium, in the presence of amino acid sources (casein, gelatin, or lactalbumin hydrolysates) supports isoprene production in logarithmic phase of growth, and with Bacillus cultured in a stirred fermentor, isoprene production occurs both in growing and non-growing cells. High isoprene production rates can also be restored to nutrient-limited cells by adding fresh media, suggesting isoprene production is dependent on nutrient availability. Isoprene can be produced under aerobic or anaerobic growth conditions. Temperature profiles for bacterial isoprene production show optima of 40°-60° C. that are suggestive of an enzymatic mechanism for isoprene formation; use of the thermophile Bacillus stearothermophilus allows more rapid bacterial growth and isoprene production at high temperature (e.g., 60° C.). Isoprene produced by bacteria, in contrast to petroleum-based isoprene, is essentially a pure hydrocarbon and can be harvested as a valuable feedstock for the manufacture of synthetic isoprene-based rubber and elastomers.

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