Discovery, Expression, Modification, and Application of Raw Starch-Degrading Enzymes: Current Status and Future Perspectives

Starch is an abundant, low-cost, renewable carbohydrate, yet conventional enzymatic biorefining requires energy-intensive liquefaction and saccharification that reduce economic viability. Raw starch-degrading enzymes (RSDEs) promise low-temperature, direct granular hydrolysis, but native forms show low catalytic efficiency, poor stability, and limited yields. This review summarizes recent advances in the discovery, expression, modification, and application of RSDEs. It discusses strategies to enhance RSDE expression through genetic manipulation of regulatory factors, particularly transcription factors governing amylolytic gene networks. Subsequently, it details molecular modification approaches, including protein engineering and genetic modification, to improve RSDE performance and production. Furthermore, we highlight the development of engineered microbial strains with high-yield of RSDE for scalable RSDE production and application. Finally, the future development and prospects of next-generation RSDEs are proposed. This review provides a comprehensive foundation for industrial implementation of RSDEs and offers strategic insights into the development of high-performance enzymes and robust production platforms.