Chemical and enzymatic modifications of polygalactomannans (PGM) as co-formulants & eccipients in industrial, cosmetic, pharmaceutical and food products

Polymers from natural, renewable sources, particularly plant polysaccharides (e.g., celluloses, hemicelluloses, starches, etc.), are employed in a growing number of applications, in their native or in chemically and/or biochemically modified forms. These b iodegradable compounds are used mostly as: emulsion stabilizers; thickeners; rheology modifiers; agents for coating, binding, suspending, conditioning, levelling ; in drilling fluids; for water - retention, etc., in a wide variety of food, feed, cosmetics, ph armaceuticals and industrial fields (e.g., oil operations, detergency, textile printing, building materials, paints and coatings, adhesives, inks, paper making, packaging material, as excipients , etc.). They often represent a valid and sustainable alternat ive to traditional synthetic polymers produced from monomers of fossil, non - renewable origin. Several chemical and biochemical modifications can be applied to polysaccharides to generate new polymeric compounds with versatile and innovative properties, sti ll largely to be explored and fuelled into the global bio - economy. One important class of polysaccharides, not yet fully exploited by industry, are polygalactomanns (PGM) present as reserve polysaccharides contained in the seed endosperms of many leguminou s plants grown in different areas of the world (e.g., cassia, locust bean, tara, guar, sesbania, fenugreek). Their structure is composed of a backbone of mannose units linked by ? - 1,4 glycosidic bonds with side units of galactose linked to mannose by ? - 1,6 glycosidic bonds. The average ratio of galactose to mannose is species - specific and determines the solubility and rheological features of the polysaccharide. It can span from 1:4.5 (Cassia) to 1:3.5 (Locust bean), to 1:2.5 (Tara), to 1:1.3 - 1.6 (Sesbania, Guar), to 1:1 (Fenugreek). Because of their solubility, versatility and reactivity, several chemical modifications are applied to guar gum: cationization, hydrophobization, conjugation, hydroxyalkylation, etc., to modify solubility and viscoelastic propert ies for any given specific application. In addition, at least three types of enzymatic reactions can be applied to PGM and their chemical derivates: depolymerization with mannanase, debranching with ? - galattosidase, oxidation with galactose oxidase or lacc ase, to generate new compounds. Laccase oxidation of PGM will be illustrated in more details