Quarterly report for Potato Commission
TITLE:Production of Omega-3 Polyunsaturated Fatty Acids from Cull Potato
PERSONNEL:
Principal Investigators:
Dr. Shulin Chen, Professor, Department of Biological Systems Engineering, Washington State University 99164-6120 Phone: (509)335-3743; Fax: (509) 335-2272
Co PI Ron Kincaid, Department of Animal Sciences, WashingtonStateUniversity, PullmanWA 99164-6351, Phone (509) 335 2457 Fax (509) 335-1082,
Co PI Zhanyou Chi, Department of Biological Systems Engineering, WashingtonStateUniversity, Pullman, WA99164-6120 Phone: (509) 335-6239 Fax: (509) 335-2272,
REPORTING PERIOD: 1/1/2006~4/1/2006
ACCOMPALISHMENTS
In previous work, 21.7 g/L dry cell algae biomass and 5.35 g/L DHAwas obtainedin the batch culture with 50% hydrolyzed potato broth supplemented with extra 20 g/L glucose, as described in the annual report. However, higher cell density culture was not reachable in the fed batch culture. The repeat culture indicates that there was some metabolites inhibited the algae’s growth. So, our work in this quarter was focused on determining what the inhibitor is.
We learned that the growth of this algae strain is divided into two phases. In the phase I, the algae cells propagated by releasing zoospores. In the phase II, the zoospores mature to the vegetative cells and the cell size increased. We hypothesized that the inhibition occurred in the phase I. To verify this, after the propagationphase, two or three flasks’ cells were combined into one flask. As a result, the culture obtained more than 40 g/L dry cell biomass, which is probably the maximum with that concentration of carbon source (100 g/L) used in that culture. Thus, this experiment verified that inhibition was occurred in the first phase, i.e. propagation phase. Further investigation of the limiting factor will be focus on the effect of dissolved oxygen in phase I, since it was found that the zoospores prefer high oxygen concentration.
Based on the discovery of caritenoids also produced in our previous cultures, a proposal, CO-PRODUCTION OF DHAAND CAROTENOIDS BY HIGH-DENSITY CULTURE OF MARINE ALGAE SCHIZOCHYTRIUM, has been submitted to Washington Sea Grant (see the attachment). Before this, the preproposal of this project has been authorized by them.
A paper, Production of Omega-3 Polyunsaturated Fatty Acids from Cull Potato Using a High Density Algae Culture Process, has been submitted to the journal, Applied Biochemistry and Biotechnology. And the main content was presented to the 28th Symposium on Biotechnology for Fuels and Chemicalswith a poster. Many scientists and Engineer expressed their interest on this workduring this symposium.
RESULTS
The cultures were conducted with the same condition in our previous culture. At the time shown in the table I, cells in 2 or 3 flasks were centrifuged and combined into 1 flask, cultured with the medium in only 1 flask of previous 2 or 3. The maximum of the production is 42.7 g/L, which is far more than the control. This indicates the nutrients in our previous culture are enough to support 42.7 g/L biomass’ growth, if there was no inhibition. This production is probably the maximum, with the 100 g/L of carbon source used in this culture.
TableI. the dry cell weight of algae biomass in the fermentation broth.
Dry cell weight after combining(g/L) / Dry cell weight 5 days
(g/L) / Dry cell weight
10 days
(g/L)
control / 5.6 / 14.5 / 29.8
2 in 1 / Combine at 40 hrs. / 11.2 / 21.3 / 33.2
3 in 1 / 16.8 / 25.7 / 42.7
2 in 1 / Combine at 66 hrs. / 16.4 / 23.0 / 38.7
Based on this new high, further investigation will be conducted to determine what the inhibition is, and how to eliminate it. We are sure that higher cell density, as obtained in the commercialized process, will be reachable based on these work. Then, the pilot study will be conducted to assess the feasibility of commercialization of our process.