Advances in the utilization of mannan-rich agricultural wastes and gums for the circular bioeconomy

Huge amounts of mannan-rich wastes are generated because of agro-industrial processing of legumes, oil palms, coffee seeds, yeasts etc. Looking into the enormity of this produce, it becomes important to utilize this agro-waste for human necessities and exploit it advantageously to create substances that are beneficial to both humans and animals, while avoiding its indiscriminate burning or dumping into water bodies. Plant cell wall mannans make the second most abundant hemicellulosic component after xylan. The use of mannans and mannan-rich agro-wastes in various industries has gained importance due to potential economic and environmental benefits. Mannan-rich biomass is dispersed over leguminous crops (guar gum, locust bean gum) and agro-industrial by products (spent coffee grounds, copra meal, palm kernel cake) and can be suitably exploited to produce biochar, prebiotic oligosaccharides, biofuel, bioethanol, and services such as dye remediation and drug delivery etc. This review summarizes recent developments of mannan rich agro-wastes and the prospects of their industrial and biomedical applications.