Rice: Unconventional Wisdom
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Metabolic Engineering and Synthetic & Systems Biology Laboratory

Microbial & Cell Culture


  There are two general steps involved in the development of a microbial fermentation process: (1) the development of a biocatalyst that efficiently catalyzes the desired biochemical reaction(s) (accomplished through Metabolic Engineering), and (2) the identification of the optimum culture conditions and the appropriate fermentation system. This research area addresses the latter. Once efficient strains are obtained, they are tested for their capacity to produce the desired product using industrial-grade media. Optimum composition of the media and culture conditions are determined. Using the engineered biocatalyst and optimized medium and culture conditions, we then identify the appropriate fermentation system, which include the cultivation technique (e.g., suspended vs immobilized cells), the type of fermentor (e.g., reactors with internal mechanical agitation vs reactors with agitation provided either by sparged/injected gas or a mechanical pump), and the mode of operation (batch, fed-batch, continuous, etc.). Two valuable statistical tools are being used in this research area: (1) statistically-based experimental design (SBED) for the designing and planning of the experiments and (2) response surface methodology (RSM) to analyze the results and identified optimum conditions. The use of SBED allows researchers to obtain the information needed to achieve the objectives of a given experimental study, and to do so by obtaining as much of the desired information as possible with the minimum number of experiments. On the other hand, RSM is a method that includes not only the design but also the analysis of the experiments, e.g. obtaining models that will relate factors (independent variables) to response variables, evaluating the effects of the factors, and identifying optimum conditions. We have successfully used SBED and RSM for the optimization of solids suspension in bioreactors and the identification of optimum conditions for the simultaneous quantification of sugars, organic acids, and alcohols in a fermentation broth. We are currently using this approach to identify optimum culture conditions and appropriate fermentation systems for the production of biofuels and biochemicals from renewables.