a b s t r a c tWe describe a new aerogel obtained from laccase-oxidized galactomannans of the leguminous plant fenugreek (Trigonella foenum-graecum) and suggest its potential practical use.Laccase/TEMPO oxidation of fenugreek in aqueous solution caused a viscosity increase of over 15-fold. A structured, elastic, stable hydrogel was generated, due to formation of carbonyl groups from primary OH of galactose side units and subsequent establishment of hemiacetalic bonds with available free hydroxyl groups.Upon lyophilization of this hydrogel, a water-insoluble aerogel was obtained (EOLFG), capable of uptaking aqueous or organic solvents over 20 times its own weight. The material was characterized by scanning electron microscopy, FT-IR, elemental analysis and 13 C CP-MAS NMR spectroscopy and its mechanical properties were investigated.To test the EOLFG as a delivery system, the anti-microbial enzyme lysozyme was used as model active principle. Lysozyme was added before or after formation of the aerogel, entrapped or absorbed in the gel, retained and released in active form, as proven by its hydrolytic glycosidase activity on lyophilized Micrococcus lysodeikticus cells wall peptidoglycans.This new biomaterial, composed of a chemo-enzymatically modified plant polysaccharide, might represent a versatile, biocompatible "delivery system" of active principles in food and non-food products.

We describe aerogels obtained by laccase/TEMPO-oxidation and lyophilization of galactomannans (GM) from fenugreek, sesbania and guar. Enzymatic oxidation of GM in aqueous solution caused viscosity increase up to fifteen-fold, generating structured, elastic, stable hydrogels, presumably due to establishment of hemiacetalic bonds between newly formed carbonyl groups and free hydroxyl groups. Upon lyophilization, water-insoluble aerogels were obtained, whose mechanical properties and porosity were investigated. Active principles were absorbed into the aerogels from aqueous solutions and, following rinsing, blotting, re-lyophilization, were released in an appropriate medium. The release of the antibiotic polymyxin B was tested against six different Gram-negative bacterial strains, of the antimicrobial peptide nisin against two Gram-positive and of the muraminidase lysozyme against one anaerobic strain. Protease and lipase release in solution from "enzyme loaded" aerogels was monitored by the increase in enzymatic activity. These biomaterials could represent new versatile, biocompatible "delivery systems" of actives for biomedical and industrial applications.

New biomaterials from renewable sources and the development of "functionalized biopolymers" are fields of growing industrial interest. Plant polysaccharides represent a valid alternative to traditional synthetic polymers, which are obtained from monomers of fossil, non-renewable origin. Several polysaccharides, either in their natural or chemically/biochemically modified forms, are currently employed in the biomedical, food and feed, and industrial fields, including packaging. Sustainable biochemical reactions, such as enzyme modifications of polysaccharides, open further possibilities for new product and process innovation. In the present review, we summarize the recent progress on enzyme oxidation of galactomannans (GM) from few leguminous plants (performed either with galactose oxidase or laccase) and we focus on the versatile and easily accessible laccase/TEMPO oxidative reaction. The latter causes a steep viscosity increase of GM water solutions and a transition of the gels from a viscous to an elastic form, due to formation of emiacetalic bonds and thus of internal cross-linking of the polymers. Following lyophilization of these hydrogels, stable aerogels can be obtained, which were shown to have good potential as delivery systems (DS) of actives. The active molecules tested and herewith described are polymyxin B, an antibiotic; nisin, an antimicrobial peptide; the enzymes lysozyme, protease and lipase; the mixture of the industrial microbiocides 5-chloro-2-methyl-4-isothiazolin-3-one (CIT) and 2-methyl-4-isothiazolin-3-one (MIT). The advantages of such aerogel systems and the possibilities they open for future developments, including as DS, are described.