Advances in vanillin synthesis: focusing on microbial synthesis pathways and prospects

Vanillin, often referred to as the 'Queen of Spices', is extensively utilized in the food industry, pharmaceutical manufacturing, cosmetic formulations, agricultural crop protection, and tobacco processing owing to its distinctive flavor properties. In recent years, the biosynthesis of vanillin from suitable substrates through microbial transformation technology has emerged as a prominent research topic, driven by the increasing global demand for "green and natural" products and the growing awareness of environmental protection. In this review, we examine the three primary synthesis methods of vanillin: natural extraction, chemical synthesis, and biosynthesis, and elucidate the principles, developmental history, and current technological advancements of each approach. Building on this foundation, the review emphasizes recent advancements in vanillin biosynthesis, analyzes the specific applications, technological innovations, and potential advantages of microbial conversion strategies in vanillin production, and addresses the challenges of low conversion efficiency and weak strain tolerance in microbial synthesis. Furthermore, this review offers insights into the future development trends of vanillin biosynthesis. It proposes research recommendations for optimizing microbial strains, enhancing bioconversion efficiency, and achieving industrial-scale production, aiming to serve as a valuable reference for the continued advancement of vanillin biosynthesis technology.