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Open Access Publications from the University of California

Optimizing Biodiesel Production of a Cell-Free System by Feedback System Control Scheme

  • Author(s): Zhao, Yitong
  • Advisor(s): Pilon, Laurent G
  • Ho, Chih-Ming
  • et al.

Due to environmental benefits, rising crude oil prices, and limited resources of fossil oil, there has been renewed focus on vegetable oils as a source of biodiesel fuels. Microalgae, which are characterized by rapid growth and high oil content, have excellent potential to provide algae-derived biodiesel to help alleviate the world's dependency on petroleum-based fuels. However, the cost of mass algal production remains high, and the potential to substitute algal biodiesel for traditional fuel is still unrealized.

The initial goal of this thesis research was to optimize culture parameters for the alga, Botryococcus braunii, for increased production of fatty acids and generation of biodiesel. The results demonstrated that, with a supplied carbon source, lysed B. braunii could produce high levels of fatty acids at a rapid rate. Thus, a cell-free system was developed that can effectively produce biodiesel, saving significant effort by eliminating the need to maintain live cells. The new approach is not light-dependent, greatly reducing the requirement for land area. The newly designed system can maintain a rate of fatty acid production that is an order of magnitude greater than the production rate in traditional algal culture for at least four months. Furthermore, the new system uses an unorthodox top-down approach, called Feedback System Control (FSC), which employs experiment design for large dimensions and response surfaces method in searching optimum with only a small number of iterations. It enabled a replacement of commercial medium containing more than sixteen chemicals with a medium containing only four chemicals, reducing the cost of the medium tenfold. Overall, the new culture method significantly increases the cost efficiency of algal biodiesel production, and has the potential to provide a scalable and cost effective method for economically viable commercial use.

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