Ph.D. student Ying Zhao

Status

I started my Ph.D. studies in 1991 and will finish my doctoral degree in 1996. My adviser is Prof. Sigurd Skogestad and co-adviser Prof. David W. Levine (Inst. Biotechnology).

Research area.

The proposed title for my Ph.D. thesis is «Modeling, Identification and Control of Biochemical Process». For the control system design of bioreactors, the following specific difficulties must be taken into account:

• The lack of reliable on-line sensors to detect the state variables such as the concentrati on of the cell mass and the metabolites.
• The lack of accurate mathematical models which describe the cell growth and the metabolite production.
• The time-varying and nonlinear nature of the system during the growth process.

Therefore my research work in 1995 was continuously concentrated on trying to cope with these problems through an industrial application of a continuous fermentation with cross-flow filtration, and further trying to make a final summary on what I have been doing in coping with these problems during my Dr.ing. study period, i.e., writing up my Dr.ing. thesis.

Activities

• Attended the 6th International Conference on Computer Applications in Biotechnology in Germany, May, 1995, and presented the work on modeling and control of a continuous bioreactor with cross-flow filtration.
• Attended the 6th NPC-Workshop (Nordic Workshop on Process Control) Aaland, Finland, August, 1995.
• Industrial contacts: The studied biochemical process is the {\em Propionibacteria} fermentation in a continuous loop bioreactor with cross-flow filtration, the produced Propionibacteria will be used for Norwegian-cheese production. This industrial project is proposed by Norske Meierier. I have participated in this project through the Biotechnology group in SINTEF Applied Chemistry. In last June, I have been in Voll (where the company Norske Meierier located) a few days and participated the first real Propionibacteria fermentation in the loop reactor and get some experiences, although the fermentation didn't run long time as planed due to some problems with the equip ment.

Publications

• Zhao, Y., and S. Skogestad. «Modeling and control of a continuous bioreactor with cross-flow filtration». Proc. 6th International Conference on Computer Applications in Biotechnology}, Garmisch-Partenkirchen, Germany, May, 1995.

Plans for 1996

I am now in the process of finishing my Dr.ing. work. I'm writing my thesis for my doctoral degree and planning to finish it by the end of this semester. In addition, I'm also expecting to get some experimental data on Propionibacteria fermentation in order to compare with my simulation work results, which would be a very positive addition to my thesis.