Reactive sites and functionalization pathways in guar gum: A review on enzymatic, chemical and physical modification...

Guar gum (GG), a galactomannan derived from Cyamopsis tetragonoloba, is a biopolymer of increasing industrial significance due to its biodegradability, non-toxicity and unique rheological properties. However, the industrial utility of the native form of GG is often limited by its poor solubility in non-polar media, inconsistent molecular weight and low mechanical strength. This review provides a detailed analysis of GG's molecular architecture, focusing on the reactive hydroxyl groups at C-2, C-3, and C-6 positions as primary targets for chemical derivatization, specifically through etherification, esterification, oxidation and graft copolymerization. Furthermore, it explores sustainable, site-specific enzymatic modifications using Endo-β-mannanase and α-galactosidase. The physical methods for guar gum hydrolysis using ultrasound, microwave irradiation, gamma irradiation, and hydrodynamic cavitation are also discussed in detail. This paper explains how customized GG derivatives satisfy the demanding requirements of the petroleum, food, and pharmaceutical industries by emphasizing the synergy between chemical and enzymatic techniques. In the end, it suggests hybrid functionalization pathways to increase its application in emerging technologies.