RESEARCH SUMMARY FOR Dr. CURTIS

My laboratory is developing commercial applications of plant cell and tissue culture.

Expression of therapeutic Proteins in Plants:
Foreign proteins such as human therapeutic antibodies can be expressed in plant tissues and transgenic plants. In 1996 we undertook the development of a rapid transient gene expression technology that would deliver genes of interest to plant tissues grown in bioreactors (patented 2004). This was facilitated by creating Agrobacterium auxotrophs by mutating genes with transposons so this bacteria cannot grow without the addition of supplemental amino acids. Agrobacterium is a plant pathogen that can deliver genes to plants through a very specialized mechanism of T-DNA transfer.
We are currently trying to enhanced this gene expression technique by utilizing viral elements to amplify the DNA and prevent gene silencing.

During spring of 2006 I will be initiating work with GreenFuel Technology that will be exploring capture of CO₂ from power plants and adaptation of plant gene expression technologies to algae culture. This project also involves the production of biodiesel fuel from the oils that that algae produce to float on the surface for light capture.

Bioreactor Design and Operation:
Plant cells and roots can be grown in liquid culture similar to microbial fermentation. We initiated studies of use of bioreactors for plant propagation around 1992, but that work was premature for commercial application and was not revitalized till recently when the tissue culture technology for clonal propagation of trees has been established as a feasible means to enhance the speed of producing superior trees form (slow) breeding programs. We have just completed a project funded by Weyerhaeuser 2002-2005 on scale-up of clonal superior trees in bioreactors including the WAVE bioreactor and a rotating carboy reactor. In this work we identified oxygen mass transfer at the embryo-liquid interface as rate limiting for culture growth (not typical gas-liquid k_La). Bioreactor operation included computer controlled fed-batch operation. We are still assisting Weyerhauser as they are undertaking commercial implementation. We will be pursing further funding of bioreactor development for tree embryo culture to focus specifically on identifying the mechanistic basis for enhanced performance in a WAVE bioreactor and reduced growth performance in a rolling carboy configuration. The hypothesis is that local transient energy dissipation is insufficient in a gentile rolling carboy to overcome interface mass transfer resistance at the embryo surface where flux requirements are rather large due to cumulative respiration within the tissue.

Over the past decade, we have established ourselves as a world leader in the design of bioreactor systems for plant cell suspension and plant root culture. We fully characterized reactors in terms of mixing, oxygen mass transfer, monitoring, control and scale-up. In addition to characterizing reactor performance, we have developed strategies of improving performance such as use of growth hormones to eliminate root hairs in culture and increasing osmotic pressure to reduce tissue water content. We have patents on both low cost bioreactor designs and bioreactor operational strategies for plant tissue culture. We also have bioproduction pilot plant with bioreactors from 5 to 250 L.

Other:
We have recently initiated some collaboration with Dr. Jong-In Hahm on use of anaerobic bacteria to produce nanoparticles that act as catalysts for nanowires.