Yeast-based expression systems have been extensively engineered to enable the production of therapeutic glycoproteins with human-type glycosylation. Platform development has focused on systematic disruption of endogenous glycosylation pathways and large-scale introduction of mammalian glycosyltransferases, nucleotide sugar biosynthesis enzymes, and Golgi transporters. These efforts have enabled the synthesis of sialylated and mucin-type glycans, despite the absence of native CMP-sialic acid and GDP-fucose pathways in yeast. Engineering strategies, including combinatorial marker-based gene integration and partial suppression of O-mannosylation, have improved controllability and scalability. As a result, yeast glycoengineering has evolved into a versatile manufacturing platform for antibodies, glycopeptide vaccines, diagnostics, and synthetic biology applications, while further optimization of O-glycosylation control remains a key engineering challenge