**4. Conclusion**

The production of biopharmaceuticals in microalgae currently requires a better understanding of the *N*-glycosylation pathway mechanism and regulation. Such information can be gained by the use of mutant libraries like the one recently developed for *C. reinhardtii*. Indeed, characterization of each individual mutants will allow an understanding of a specific step of the *N*-glycan processing, and mutant cells could represent interesting cell lines for the production of biopharmaceuticals bearing a chosen *N*-glycan profiling.

Once these pathways would be completely deciphered in the microalgae model intended to be used for the production of biopharmaceuticals, the humanization of the *N*-glycosylation pathway could be initiated using designed engineered nucleases strategies recently developed in microalgae. We can now consider that transformed microalgae by these innovative new genomic tools will constitute in a near future one of the most suitable green cell factories for the production of humanized biopharmaceuticals.
