Abstract
The global transition to renewable energy sources requires efficient microbial platforms capable of fermenting carbon sources present in lignocellulosic biomass. Conventional yeasts like Saccharomyces cerevisiae face critical limitations, particularly in pentose sugar utilization and inhibitor resistance. This review focuses on two emerging nonconventional yeasts, Candida famata and Ogataea polymorpha, which exhibit native or engineered capacities to overcome these bottlenecks. We present a comparative analysis of their stress tolerance, metabolic versatility, and recent advances in genetic engineering, adaptive laboratory evolution, and heterologous expression systems. Their ability to grow on a wide range of sugars, tolerate fermentation inhibitors, and operate under industrial conditions underscores their potential as microbial platforms for sustainable bioprocessing. Key challenges and future directions are discussed to guide further development.