Triterpene hydrocarbon production engineered into a metabolically versatile host--Rhodobacter capsulatus.
Triterpene hydrocarbon biosynthesis of the ancient algae Botryococcus braunii was installed into Rhodobacter capsulatus to explore the production of C30 hydrocarbon in a host capable of diverse growth habits-utilizing carbohydrate, sunlight or hydrogen (with CO2 fixation) as alternative energy feedstocks. Engineering an enhanced MEP pathway was also used to augment triterpene accumulation. Despite dramatically different sources of carbon and reducing power, nearly the same level of botryococcene or squalene (∼5 mg oil/g-dry-weight [gDW]) was achieved in small-scale aerobic heterotrophic, anaerobic photoheterotrophic, and aerobic chemoautotrophic growth conditions. A glucose fed-batch bioreactor reached 40 mg botryococcene/L (∼12 mg/gDW), while autotrophic bioreactor performance with CO2 , H2 , and O2 reached 110 mg/L (16.7 mg/gDW) during batch and 60 mg/L (23 mg/gDW) during continuous operation at a dilution rate corresponding to about 10% of μ(max). Batch and continuous autotrophic specific productivity was found to reach 0.5 and 0.32 mg triterpene/g DW/h, comparable to prior reports for terpene production driven by heterotrophic growth conditions. This demonstrates the feasibility of alternative feedstocks and trophic modes to provide comparable routes to biochemicals that do not rely on sugar.
Department of Chemical Engineering, The Pennsylvania State University, University Park, Pennsylvania, 16802.
Nymul E
NE
Khan
Department of Pharmaceutical Sciences, University of Kentucky, Lexington, Kentucky, 40536.
S Eric
SE
Nybo
Department of Pharmaceutical Sciences, University of Kentucky, Lexington, Kentucky, 40536.
Joe
J
Chappell
Department of Chemical Engineering, The Pennsylvania State University, University Park, Pennsylvania, 16802. wrc2@psu.edu.
Wayne R
WR
Curtis
D000332:Aerobiosis; D000693:Anaerobiosis; D019149:Bioreactors / Q000382:microbiology; D050260:Carbohydrate Metabolism; D000460:Chlorophyta / Q000235:genetics; D004734:Energy Metabolism; D005818:Genetic Engineering / Q000379:methods*; D006859:Hydrogen / Q000378:metabolism; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D010788:Photosynthesis; D016354:Rhodobacter capsulatus / Q000235:genetics* / Q000378:metabolism*; D014315:Triterpenes / Q000378:metabolism*
D014315:Triterpenes; D006859:Hydrogen
CO2 fixation; MEP pathway; botryococcene; continuous bioreactor; productivity; squalene