Overexpression of the MAPK Transcription Factor Gene MSS11 Enhances Ethanol Biosynthesis in Saccharomyces cerevisiae via Coordinated Metabolic and Stress-Response Reprogramming

Bioethanol is a pivotal sustainable alternative to fossil fuels. Saccharomyces cerevisiae is the primary microorganism for its industrial production. Enhancing the fermentative performance of S. cerevisiae is crucial for sustainable bioethanol production. To systematically enhance the fermentative capacity of yeast, this study employed targeted genetic engineering to overexpress MSS11-a principal transcription factor within the mitogen-activated protein kinase (MAPK) signaling cascade. The resultant recombinant strain, Eng-1, demonstrated a marked 23.9% enhancement in final ethanol titer (18.94 g/L versus 15.29 g/L) and a commensurate 23.8% improvement in yield coefficient (0.473 versus 0.382 g ethanol per g glucose) relative to the isogenic control strain Eng-0 under microaerobic batch fermentation. This phenotype was consistently validated in a distinct genetic background (JT139 derivative), underscoring the generalizable function of MSS11. Transcriptomic analysis revealed that MSS11 orchestrates a dual regulatory mechanism: it upregulates pyruvate-supplying pathway genes to enhance carbon flux toward ethanol, while concurrently activating a suite of genes involved in oxidative, osmotic, and ethanol stress tolerance to improve cellular robustness. These findings establish MSS11 as a novel and effective metabolic engineering target for yeast, and they elucidate its dual regulatory mechanism in coordinately enhancing carbon conversion and cellular robustness, thereby providing a strategic framework for constructing high-performance microbial cell factories for advanced biofuel production.