Non-thermal atmospheric plasma (NTAP) is a physical technology that has been previously employed for surface treatment (cleaning, coating, erosion, etc.) and water or air depollution. We show here that, beyond surface effects, NTAP is capable of enabling the complete and fast polymerization of various mono- and disaccharides in the solid state within only a few minutes and at low temperature (40-80 [degree]C). NTAP-induced polymerization involves a radical mechanism and yields water soluble polysaccharides with a mean molar mass of up to 100 000 g mol-1 and a mean hydrodynamic radius of 3 nm. Although polymerization reactions promoted by NTAP occurs in a random manner, the [small alpha]-1,6 and [small beta]-1,6 linkages are however dominant. Furthermore, we discovered that NTAP is highly selective, strongly favoring glycosylation over other chemical transformations in the bulk. Under our working conditions, glycosyl units are preserved that constitute the repeating units of the polysaccharide product. No chemical degradation (e.g. intramolecular dehydration reactions) was observed, allowing a white powder to be recovered with a yield higher than 93 wt%. From a practical point of view, NTAP has great potential for breakthrough in the production of polysaccharides, notably because it does not require the use of a solvent or catalyst, thus by-passing the traditional post-treatment of aqueous effluents and catalyst recycling characteristic of biotechnological polysaccharide production. Its efficiency at low temperature also prevents carbohydrates from degradation. Finally, NTAP proceeds on an on/off switch basis, allowing the polymerization reaction to be started and stopped quasi instantaneously

Abstract:We have investigatedt he effect of non-thermala tmospheric plasma (NTAP) on the structure of microcrystalline cellulose. In particular,b ym eans of different characterization methods, we demonstrate that NTAP promotes the partial cleavage of the b-1,4 glycosidicb ond of cellulose leadingt ot he releaseo fs hort-chain cellodextrins that are reassembledi nsitu, preferentially at the C6 position, to form branched glucans with either ag lucosyl or anhydroglucosyl terminal residue. The ramificationo fc ellulosic chain induced by NTAP yields branched glucans that are soluble in DMSO or in water,t hus opening as traightforward access to processableg lucans from cellulose. Importantly,t he absence of solventa nd catalystc onsiderably facilitates downstream processing as compared to (bio)catalyticp rocessesw hich typicallyo ccur in diluted conditions.