"That was the proof of concept," said Mayfield. "It showed us that the system worksthat we could produce complex mammalian proteins in algae. What we did in this next study was to say, 'Let's take seven diverse human therapeutic proteins and see if we can express them in algae and report the good and the bad.'"
The scientists found that in algae they were able to produce VEGF, HMGB1 and domain 14 of human fibronectin at levels above one percent of total soluble protein, levels sufficient for easy purification. Domain 10 of human fibronectin could also be produced from algae at these levels when fused to the protein M-SAA, which they had previously used to increase the accumulation of other proteins. Human proinsulin could be produced by algae, but only at lower levels, the study showed, while human interferon β1 and EPO were not produced by algae.
"What our results show is that algae are a robust platform for the production of human therapeutic proteins," said Mayfield. "While not every protein can be produced in algae, a good fraction can, just like in any other system. You can get expression of about 25 percent in bacteria and about 40 to 50 percent in mammalian cells, so we're in the same ball park as these other systems."
What makes algae particularly attractive compared to bacterial and mammalian systems, the scientists say, is its ability to produce proteins cheaply and at very large scale. With algae currently being produced at about $3 per kilogram at commercial scale, the researchers estimate that making recombinant protein would cost about 60 cents per gram prior to purification.
"This is about the same cost estimates for the least expensive protein expression systems presently available, and considerably cheaper than mammalian cell
|Contact: Kim McDonald|
University of California - San Diego