Professor Friedrich Srienc

email: srienc@umn.edu
B.S., Chemistry, Technical University in Graz, 1974,
M.S., Chemistry, Technical University in Graz, 1976,
Ph.D., Biotechnology, Technical University in Graz, 1980

I work in the general area of biochemical engineering. A diverse set of approaches to biotechnology and bioengineering ranging from molecular biology, metabolic engineering and mathematical modeling are employed to study fundamental processes of gene expression, protein synthesis and metabolic networks and how these relate to the growth physiology of cells.

A fundamental problem in biochemical engineering is the dynamics of cell populations and how it is related to the formation of useful products. This problem is complicated by the fact that cell populations are heterogeneous, i.e they consist of cells that differ from each other in age, chemical composition and functional properties. The operation of the cell cycle and its regulation contributes much to this heterogeneity. Experimental as well as theoretical tools are little developed to investigate the variability of cell cultures at the single cell level. However, automation of flow cytometry analysis operations and new methods for solving so called population balance equations that have recently been developed by my group, provide unique methods to approach this problem in a rigorous way in bacterial, yeast and mammalian cell populations.

A further component in my work is the study of the biosynthesis of polyhydroxyalkanoic acids (PHA). These biopolymers represent biodegradable thermoplastics that could replace certain petrochemically derived plastics that are not biodegradable and contribute considerably to the pollution of our environment. In this work, new reaction pathways are engineered into host cells using genetic engineering tools with the purpose of economically synthesizing new types of PHA polymers with useful properties. The PHA pathway in the context of overall cellular metabolism represents a unique model to study the limits of metabolic networks. This work extends into aspects of materials science and nanotechnology. Using specific bioprocessing strategies cells can be made to synthesize microstructured architectures of this polymer that confer to the final product desirable physical properties. Moreover, control of cellular biosynthesis can be extended to the molecular level resulting in the formation of block-copolymers that self assemble into defined structures.