Engineering the Autotroph Methanococcus maripaludis for Geraniol Production

The rapid autotrophic growth of the methanogenic archaeon Methanococcus maripaludis on H-2 and CO2 makes it an attractive microbial chassis to inexpensively produce biochemicals. To explore this potential, a synthetic gene encoding geraniol synthase (GES) derived from Ocimum basilicum was cloned into a M. maripaludis expression vector under selection for puromycin resistance. Recombinant expression of GES in M. maripaludis during autotrophic growth on H-2/CO2 or formate yielded geraniol at 2.8 and 4.0 mg g(-1) of dry weight, respectively. The yield of geraniol decreased 23-fold when organic carbon sources were added to stimulate heterotrophic growth. In the absence of puromycin, geraniol production during autotrophic growth on formate increased to 4.6 mg g(-1) of dry weight. A conceptual model centered on the autotrophic acetyl coenzyme A biosynthetic pathway identified strategies to divert more autotrophic carbon flux to geraniol production.