Advances in the vanillin synthesis and biotransformation: A review

Vanillin is one of the world's most extensively used flavoring compounds. Plant-based vanillin can no longer meet the annual global demand for bio-vanillin, thus chemical synthesis is commonly used to manufacture vanillin. Considering the environmental impact of chemical synthesis, the possibility of utilizing microbial genetic and metabolic engineering to transform renewable biomass-based substrates into vanillin offers a promising alternative to produce commercially viable bio-vanillin. However, research on this topic is still in its early stages, and there is still a need for an effective and dynamic method to achieve high vanillin productivity. This review aims to comprehensively discuss recent advances in microbial vanillin production through genetic and metabolic engineering strategies. Molecular mechanisms of vanillin toxicity in microbes and strategies for improving vanillin tolerance are also discussed. Finally, a comprehensive literature analysis explored the feasibility of new potential and sustainable methods for vanillin production from lignin on an industrial scale. However, the high cost of raw materials pretreatment, low yields, and complex downstream processes continue to be the primary factors hindering its industrialization. This review identifies potential areas for future research and optimization, emphasizing the importance of exploring eco-friendly and renewable approaches. Overall, the review provides valuable information for future research directions, industry professionals, and policymakers interested in vanillin synthesis, offering an overview of the latest advancements and potential for sustainable vanillin production.