Algae Biofuels

Recent Publications

  1. Wang, Jun, Curtis, Wayne R. (2015Proton stochiometric imbalance during algae photosynthetic growth on various nitrogen sources: Toward metabolic pH control. Journal of Applied Phycology. DOI: 10.1007/s10811-015-0551-3
  2. Khatri W, Hendrix R, Niehaus T, Chappell J, Curtis WR (2013Hydrocarbon Production in High Density Botryococcus braunii Race B Continuous Culture, Biotechnology & Bioengineering, 111 (3), 493-503 doi:10.1002/bit.25126
  3. Myers JA, Curtis BS, Curtis WR (2013Improving accuracy of cell and chromophore concentration measurements using optical density. BMC Biophysics 2013, 6:4, 1-16.    
  4. Scherholz ML, Curtis WR. (2013) Achieving pH control in microalgal cultures through fed-batch addition of stoichiometrically-balanced growth media. BMC Biotechnol. 13(1):39, 1-16.
  5. Curtis WR, Curtis MS (2014Biomass-2-Energy, Chapter 3, In: Systems Engineering for Clean and Renewable Energy Manufacturing in Europe and Asia, NSF sponsored Report, WTEC.  (Full Report on Web; 
  6. Johnson, Ryan, Khatri, W., Curtis, W. (Calyx Bioprocess Technology, LLC., Port Royal, PA) SBIR Phase I: Hydro-ThermAlgae, Photobioreactor for Minimal Water Loss. Final Proposal [not accepted] Arlington, VA: National Science Foundation; 2012 Sep. IIP-Small Business Phase I. 

Recent Presentations

Metabolism based feed forward pH control of high-density microalgae cultures
Jun Wang, WR Curtis. Poster at DOE-BIOMASS 2014, July 29-30, Washington, DC

Feed-Forward Control of Dynamic High-Density Microalgae Cultures Using Model Based Predictive pH Control and a Novel Biomass Sensor
Jun Wang, Benjamin Geveke, Ryan Johnson and Wayne R. Curtis. AIChE Annual meeting, November 3-8, 2013. San Francisco, CA.

Overall Energy Considerations for Algae Species Comparison and Selection in Algae-to-Fuels Processes
Dirk Link, Amalie Tuerk. Alternative Energy NOW Conference, Lake Buena Vista, FL, February 23, 2011.

Algae-Based Hydrocarbon Production
Amalie Tuerk*, Wayne R. Curtis. USDA Research Center, Philadelphia, PA, April 2010.

Algae-Based Hydrocarbon Production
Waqas Khatri, Steve Gabauer, Joseph Chappell, Wayne Curtis. AIChE Annual Meeting, Philadelphia, PA, Nov. 18 2008

Genetic Engineering Hydrocarbon Production in Algae
Stephen Gabauer, Thomas D. Niehaus, Waqas Khatri, Joseph Chappell, Wayne Curtis. AIChE Annual Meeting, Philadelphia, PA, Nov 19 2008

Research Overview

CurtisLab Algae Projects

The algae biotechnology efforts of the Curtis Lab started in earnest in roughly 2005 to assist the first major algal biofuels company, Greenfuels Technology, including having several of their earliest employees undertake training at Penn State as they setup laboratories in Boston. This work also included producing 100 liters of innoculum for the MIT powerplant demonstration.

The first federal-funded research in algae biofuels from the NSF focused on thin-film bioreactors to achieve ultra-high density algae growth ( > 20 gDW/L), while a collaboration with Joe Chappell focused on the hydrocarbon biosynthetic pathway of Botryococcus braunii. This high density algae culture work revealed fundamental issues of pH control and nitrogen metabolism. Continued efforts follow these same areas of feed-forward process control of algae photobioreactors and factors that control lipid accumulation.

Reactor Design and Operational strategies

There has recently been a flourish of startup companies claiming various superior processes and photobioreactors for algae production. Many of these designs have obvious or hidden limitations that have significant impact – not only on productivity, but also on the cost of operation. The following rationale includes considerations of the entire algae biomass production process that needs to be critically analyzed to minimize processing costs. Photobioreactor designs are often divided into open pond and enclosed photobioreactors. Reactors should be more appropriately divided into high-density/intensity and low-density/intensity photobioreactors. In order to achieve low cost biomass production, energy use must be minimized. Using this perspective, the bioreactor shown in figure 1 is proposed as the most promising high-intensity photobioreactor system to implement for the production of low cost biomass. Application of a minimum thickness turbulent mixed film in conjunction with light-limited high-density algae growth achieves maximum productivity.

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.
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.

Molecular Biology

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.
  We will perform the initial work with transgenic Chlamydomonas reinhardtii because of the available tools and speed with which this species can be genetic engineered. This will set the stage for evaluating alternative species such as terrestrial plants or marine algae which are more difficult to manipulate. 

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: Petroleum-Based Algal Oils

NSF Grant Site (0828648)

NSF SBIR Phase 1

NSF Grant Site (0945592)


Curtis Lab Research Team 
Graduate StudentsJun Wang
Penn State Undergraduate Students:  Layne Steen, Haonan Xu, Katie Leginski, Justin YooChris ColonaBen GevekeDavid MartinoSteve Tran, Amalie Tuerk
Technitions, Interns, Volunteers & Experts:   Ryan Johnson

Chappell Lab Research Team
Graduate StudentsTom Niehaus, Steve 
Technician:  Scott Kinison  .

Collaborators: Joe! (the legend =),  

More Papers / Presentations / Patents

Honors Theses:
Yoo, Justin. Establishment and Maintenance of Axenic Botryococcus braunii race B Algae Culture. Dissertation. Penn State University: University Park, PA (2014).

Taylor, Christine. A Continuous Bioreactor to Study the Persistence of Extracellular Biofuel Candidate Molecules in a Non-axenic Algae Culture. Dissertation. Penn State University: University Park, PA (2013).

Tuerk, Amalie. Transient expression of therapeutic proteins and oxygen transport limitations in plant tissue culture. Dissertation. Penn State University: University Park, PA (2005).