Harnessing yeasts for sustainable methanol valorization: Metabolic and fermentation engineering strategies.

Methanol has emerged as a sustainable C1 feedstock owing to its compatibility with existing infrastructure and the potential for renewable production from CO₂ and green hydrogen. Methylotrophic yeasts, including Komagataella phaffii (also known as Pichia pastoris) and Ogataea polymorpha, can natively assimilate methanol and therefore represent attractive hosts for biomanufacturing. However, industrial application of methanol-based processes remains constrained by cytotoxicity, redox imbalance, and limited productivity compared to sugar-based fermentations. To address these challenges, extensive metabolic engineering strategies have been implemented to enhance methanol assimilation and redirect carbon flux toward value-added products. Over the past decade, remarkable progress has been achieved through the development of synthetic methylotrophy in non-methylotrophic yeasts, the expansion of product portfolios to glycans, fatty acid derivatives, polyketides, terpenoids, organic acids, and polyols, and the integration of multi-omics tools for systems-level design. This review summarizes recent advances in methanol assimilation enhancement, synthetic pathway construction, and fermentation engineering, highlighting strategies such as metabolic engineering and dynamic bioprocess control. In addition, current challenges and future perspectives are discussed with an emphasis on overcoming toxicity, improving efficiency, and establishing advanced methylotrophic yeasts as robust cell factories for sustainable C1-based biomanufacturing.