Enzymatic synthesis of highly flexible lignin cross-linked succinyl-chitosan hydrogels reinforced with reed cellulose fibres

• Published in: European polymer journal 2019-11, Vol.120, p.109201, Article 109201
• Main Authors: Haske-Cornelius, O., Bischof, S., Beer, B., Jimenez Bartolome, M., Olatunde Olakanmi, E., Mokoba, M., Guebitz, G.M., Nyanhongo, G.S.
• Format: Article
• Language: English
• Subjects: Cellulose; Cellulose fibers; Cellulosic resins; Chemical synthesis; Chitosan; Coupling (molecular); Crosslinking; Elongation; Glycerol; Hydrogels; Laccase; Laccases; Lignin; Lignosulfonates; Mechanical properties; Oxidation; Oxygen scavenger; Plasticizers; Reed cellulose fibres; Stiffness; Studies; Succinyl-chitosan hydrogels; Synthesis
• ISSN: 0014-3057; 1873-1945
• DOI: 10.1016/j.eurpolymj.2019.08.028

[Display omitted] •Converting chitosan into succinyl chitosan makes is miscible with lignosulfonates withour forming flocs.•Incorporation of laccase promotes cross-links lignosulfonates with succinyl chitosan.•Laccase copolymerization of lignosulfonates and sucnninyl chitosan produces hydrogels.•Incoporation of glycerol as plasticizer and reed cellulose fibers results in highly flexible hydrogels. This study reports on a novel strategy for laccase mediated synthesis of highly flexible succinyl chitosan (SucCTS) hydrogels cross-linked with lignosulfonates whose mechanical properties were further enhanced by incorporating glycerol as a plasticizer and reed cellulose fibres as reinforcement agent. Laccase enzyme was used to oxidize lignosulfonates resulting in the formation of phenoxyl radicals that reacted with NH2 groups SucCTS either through radical coupling or Michaeĺs addition. The oxidation of lignosulfonates resulted in 51 decrease in lignosulfonate OH groups and 74% SucCTS-NH2 groups, and concomitant gradual increase in molecular weight of the copolymer from an average 15 kDa to above 600 kDa. Incorporation of glycerol as plasticizer prevented stiffness, shrinking and random breaking of the hydrogels, as evidenced by the remarkable increase in elongation at break (up to160%) of the hydrogels. The laccase remained active and completely reduced oxygen to water in a closed system, making it suitable for application as oxygen barrier system. This study therefore demonstrate an environmentally friendly process for synthesizing 100% biobased (chitosan based hydrogels) using naturally occurring lignin as cross-linking agent and laccase as biocatalyst.