Sustainable vanillin production: Biotechnological advances, catalytic innovations, and integrated assessment

Vanillin (4-hydroxy-3-methoxy-benzaldehyde) is one of the world's most commercially important flavour molecules, used across food, fragrance, pharmaceutical, and emerging materials sectors. Global demand far exceeds the supply that can be met by vanilla bean extraction, driving interest in alternative synthetic and biotechnological routes to production. This review traces the evolution of vanillin production from traditional extraction through petro-based synthesis to the latest biotechnological and hybrid chemo-enzymatic processes. Each route utilizes an integrated assessment framework that combines sustainability metrics, economic viability, and technological readiness level (TRL), highlighting recent breakthroughs in metabolic pathway engineering, microbial chassis development, and green catalysis. Plant-derived vanillin accounts for only ∼1.5 % of supply, whereas petro-based synthesis still dominates (∼88 %). Emerging biotechnological processes-now ∼10 % of the market-offer the greatest potential for sustainable scale-up. Our analysis identifies two high-promise avenues: (i) hybrid chemical-enzymatic systems and (ii) consolidated bioprocessing with engineered microbes, both capable of lowering carbon footprint and cost simultaneously. The remaining bottlenecks include enzyme stability, feedstock variability, and downstream purification. The review closes with a strategic research roadmap for academics, industry, and policymakers to accelerate the transition toward economically viable, low-impact vanillin production.