Filamentous fungi are capable of producing and secreting a variety of enzymes. Aspergillus sp. and Trichoderma sp. are the major fungal cell factories for industrial enzymes production. Aspergillus oryzae is recognized as GRAS (generally regarded as a safe organism) and has the ability to secrete a large amount of proteins. Therefore, A. oryzae has been used as a low-cost microbial cell factory for the production of recombinant proteins and has the potential to be engineered to produce therapeutic proteins. However, a bottleneck in the production of humanized proteins in A. oryzae is the N-glycan pattern of glycoproteins, which is significantly different from humans. N-glycosylation plays a key role in protein stability, secretion, folding and activity and therefore can be a barrier to protein production. A viable alternative is the remodeling of the N-glycosylation pathway in filamentous fungi so that recombinant proteins produced in this host receive N-glycan chains similar to those found in humans. The objective here is to design A. oryzae strains in which the majority of glycoforms appear to be GlcNAcMan5GlcNAc2 species, which is the core structure for hybrid glycan synthesis. For that, we will delete and overexpress genes involved in N-glycan assembly and processing. To monitor the predominant N-glycan species in A. oryzae, the GH3 beta-xylosidase (AN8401; BxlB) from A. nidulans has been used as a model recombinant protein.
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