Lignin polyphenol: From biomass to innovative food applications, and influence on gut microflora

There is an increasing need for green materials to replace or reduce the already commercialized synthetic materials use in the food and beverage industry. One such green and under-utilized raw material available in nature is lignin. Lignin is a high molecular weight phenolic macromolecule contained in biomass (about 10–50%) aside from other major components like cellulose and hemicellulose. This review presented a state-of-the-art on the lignin polyphenols in biomass and a pathway on how it can be practically integrated in food-related applications such as: natural antioxidants, antibacterial film, hydrogels, improving intestinal flora, etc. Furthermore, details on the mechanism of action, production process, characterization methods, limiting factors, advantages, and prospects are provided. Depolymerization of large unit's lignin polyphenols such as p-hydroxyphenyl, guaiacyl, and syringyl, produces ferulic acid, vanillin, syringaldehyde, etc., which has high antioxidant and antibacterial potential and can improve the gut microbiota. Lignin polyphenols can be preferable to other natural antioxidants because they act as a physical barrier that prevents oxidation of nearby molecules. The antimicrobial activity of lignin is due to its binding to the adhesin, thereby reducing the bacteria's adherence to the host cell and the interaction of the lignin functional groups with the peptidoglycan layers of the bacterial cell wall.