• Food engineering transport phenomena
• Industrial microbiology
• food microbiology
• yeast cell biology
• genetics

EDUCATION:

1968   B.S., Life Science Massachusetts Institute of Technology, Cambridge
1975   Ph.D., Food Science Massachusetts Institute of Technology, Cambridge

POSITIONS HELD:

Process Engineer, Shell Oil Company, 1980-82
Postgraduate Research Microbiologist, University of California, 1975-77
Visiting Scientist, Department of Genetics, Institut National Agronomique, Paris, France, 1985-86
Asst/Assoc/Professor and Marine Microbiologist, Department of Food Science and Technology, UC Davis, Davis, California, 1977 - present

RESEARCH OBJECTIVES - LAY TERMS

My research objectives are most closely related to fermentation and food processing, primarily, use of microorganisms for production of proteins such as enzymes or milk proteins useful in food processing. Specifically, my objectives are to understand early events in the process by which proteins are secreted from the cell and how the proteins are modified as they are transported through the cell. The yeast Yarrowia lipolytica, which has been used industrially to produce citric acid, and the protease it secretes in large amounts are used in these studies. The results of our studies will be useful in optimization of production of proteins useful in foods and food processing, in modification of enzyme secreting microorganisms used in food fermentations, and in development of Yarrowia lipolytica as a host for production of valuable proteins coded for by genes from other organisms.

RESEARCH OBJECTIVES - FOR PEERS

My research objectives are to understand protein processing and secretion from the yeast Yarrowia lipolytica and to develop Y. lipolytica as a host for secretion of heterologous proteins. Specifically, we are examining the in vivo role of components of the Y. lipolytica signal recognition particle (SRP) and alternative pathways for protein translocation across the endoplasmic reticulum. Better understanding of SRP structure/function could make possible optimization of production of proteins useful in foods and food processing and improvements of enzyme secreting microorganisms used in food fermentations.

RECENT SIGNIFICANT FINDINGS/ACCOMPLISHMENTS

• a) The genes coding for two of the six polypeptides of SRP are important but not essential for growth of Y. lipolytica. This suggests there is an alternative pathway for secretion which does not involve SRP and which works at low efficiency.
• b) A mutation in a gene coding for the RNA component of SRP preferentially affects synthesis of the alkaline extracellular protease secreted by Yarrowia lipolytica. This was one of the first demonstrations of in vivo involvement of SRP with a secreted protein.
• c) A mutated form of the alkaline extracellular protease (AEP) can be secreted posttranslationally without SRP involvement, whereas normally wild type AEP's translocation is cotranslational and SRP-mediated. This raises the possibility that even higher eukaryotes may translocate proteins posttranslationally.
• d) The gene (XPR2) coding for the alkaline extracellular protease was cloned and sequenced and intracellular processing events determined. These results made possible use of this gene and Y. lipolytica for expression and secretion of correctly processed foreign proteins.

SELECTED PUBLICATIONS:

• Processing and secretion of the Yarrowia lipolytica Rnase. S-C. Cheng and D.M. Ogrydziak. 1987. Journal of Bacteriology 169(4):1433-1440.
• Intracellular precursors and secretion of alkaline extracellular protease of Yarrowia lipolytica. S. Matoba, J. Fukayama, R.A. Wing and D.M. Ogrydziak. 1988. Molecular and Cellular Biology 8(11):4904-4916.
• A novel location for dipeptidyl aminopeptidase processing sites in the alkaline extracellular protease of Yarrowia lipolytica. S. Matoba and D.M. Ogrydziak. 1989. The Journal of Biological Chemistry 264(11):6037-6043.
• A mutation in the signal recognition particle 7S RNA of the yeast Yarrowia lipolytica preferentially affects synthesis of the alkaline extracellular protease: In vivo evidence for translation arrest. D.S. Yaver, S. Matoba and D.M. Ogrydziak. 1992. Journal of Cell Biology 116(3):605-616.
• Yeast extracellular proteases. D.M. Ogrydziak. 1993. Critical Reviews in Biotechnology 13(1):1-55.
• Cloning, nucleotide sequence and functions of XPR6, which codes for a dibasic processing endoprotease from the yeast Yarrowia lipolytica. C.S. Enderlin and D.M. Ogrydziak. 1994. Yeast 10:67-79.