Tri-valorization of methanol in a single bioreactor: co-production of enzyme, chemical, and single-cell protein using engineered Pichia pastoris (Komagataella phaffii).

The economic viability of methanol-based biomanufacturing, particularly with green methanol as feedstock, is often limited by the low value of single-product processes. Here, we developed an integrated co-production strategy in the methylotrophic yeast Pichia pastoris (Komagataella phaffii) for the simultaneous conversion of methanol into three products: the sweetener erythritol, the industrial biocatalyst β-mannanase, and single-cell protein (SCP) biomass. This new strategy explores the inherent spatial and functional separation between the ER-Golgi secretory pathway for enzyme production and the cytosolic pathway for chemical synthesis, thereby reducing interference between the two pathways. The engineered co-production strain achieved β-mannanase and erythritol titers comparable to those of the corresponding β-mannanase- and erythritol-producing reference strains in both shake-flask and fed-batch fermentor cultures. Furthermore, transcriptomic analysis revealed distinct regulatory responses related to enzyme production and erythritol synthesis, supporting the limited cross-pathway interference between the two pathways. In addition, we showed that ultrafiltration enabled efficient downstream separation of the small-molecule erythritol from the secreted β-mannanase, with recovery efficiencies exceeding 89%. These results demonstrate a feasible strategy for methanol valorization into multiple value-added products and expand the potential of methylotrophic yeasts for integrated biomanufacturing.