The rationale for developing the proposed photobioreactor system is based on light physics, algae physiology and, most importantly, economic constraints that have resulted in the proliferation of poorly conceived bioreactor systems that have little hope of achieving economic feasibility based on simple mass and energy balance principles. The proposed bioreactor is discussed below in the context of the energy required to carry out critical basic bioreactor operation; specifically, fluid pumping, gas compression, algae dewatering, and energy removal.
NSF Grant Site (0828648)
Schematic of algae to fuel process based on alternative technologies for field-scale
implementable nutrient delivery, photobioreactor growth oil and biomass recovery and processing.
Algae is grown as a suspension that trickles-down a screen to induce turbulent mixing in a simple geometry that promotes efficient photon use by avoiding a surface that can foul between the algae and the light, to support densities of 30+g/L biomass correlating to some of the highest productivities found in literature irrespective of the intrinsic growth rate among various stains of algae. We have demonstrated that CO2 fertilization can be accomplished in the evaporative water make-up saturated with nearly pure CO2. This avoids prohibitive costs of heat removal and gas compression on agricultural scales. This approach also avoids the capital expense and safety/permitting issues of a light blocking ‘green-house’ enclosures and use of existing scrubbing technologies to provide concentrated CO2. Turbulent ultra-thin film culture will permit the highest possible cell concentrations, which will facilitate low-cost down stream dewatering and reduce ‘hydraulic load’ costs throughout the process.
The over-arching research objective of the current proposal is to fully characterize the pathway for tetramethyl-triterpene biosynthesis, and to assess novel strategies for the genetic and process engineering of these natural products into algae. This project leverages the Principal Investigators (PIs) recent success in isolating the genes coding for the biosynthesis of rather unique branched-chain, unsaturated hydrocarbons (methylated triterpenes), and the development of novel tools to engineer metabolic shunts for high-level terpene production in terrestrial plants. The proposed collaborative research brings together genetic engineering proof-of-principle with novel process engineering advances in algae culture required to evaluate these alternative platforms of agri-culture and alga-culture for commodity-scale displacement of fossil fuels with renewable, green-house-gas neutral biofuels.
We are proposing to produce methylated triterpenes in transgenic algae as a proof-of-principle that demonstrates high-value natural products can indeed be produced in a robust, renewable and sustainable platform.
Although production and extraction processes exist for terrestrial plants, comparable agricultural-scale systems have not been developed for algae. The proposed work therefore includes simultaneous development of photobioreactor design and operational optimization work that are needed to assess the feasibility of these alternative production platforms. A future collaboration will evaluate these algal-derived hydrocarbons as alternative fuel feedstocks with Dr. Mark Crocker at the UK Center for Applied Energy Research, an expert in the hydrocarbon catalytic cracking process and fuel characterization [Shumaker et al., 2007]. The potential of our proposal thus hinges on the biosynthesis of methylated triterpenes by genetic engineered algae, combined with development of algal cultural practices as they interface with downstream processing for extraction and conversion to aliphatic and aromatic precursors, and whether these aims can ultimately be brought together on a scale sufficient to meet the demands for a high volume commodity like liquid transportation fuels.
NSF Grant Site (0945592)
Curtis Lab Research Team: Graduate Students: Jun Wang
Penn State Undergraduate Students: Justin Yoo, Chris Colona, Ben Geveke, David Martino, Steve Tran
Technitions, Interns, Volunteers & Experts: Ryan Johnson
Technician: Scott Kinison