functional erythropoietin by yeast

It's the first time (?) in vivo biologically active form of erythropoietin was produced by engineered yeast, Pichia pastoris. The results were published in the last Science magazine [2006 Sep 8; 313(5792): 1441-3], titled "Humanization of yeast to produce complex terminally sialylated glycoproteins".

But, it's still a long distance producing pharmaceutical human erythropoietin by this engineered yeast strain since,

1. the exemplified erythropoietin belongs to rat, not human;
2. the titer is still low (~20mg/l);
3. the derived glycans are biantennary, not tetra antennary for carrying enough sialic acids.