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.
Aerogels of chemo-enzymatically oxidized, lyophilized fenugreek gum (EOLFG) were evaluated as "delivery system" (DS) of the microbiocide mix 5-chloro-2-methyl-4-isothiazolin-3-one (CIT) and 2-methyl-4-isothiazolin-3-one (MIT). These biocides have a broad activity spectrum and a low MIC (minimal inhibitory concentration) in the ppm range. They are approved under the EU Biocidal Product Directive for various applications, including cosmetics, are classified as skin sensitizers, and are under increasing scrutiny to limit or eliminate their use.We demonstrate that CIT/MIT can be uptaken into EOLFG aerogel corks by immersion into aqueous solutions of microbiocides, followed by blotting and re-lyophilization to generate "loaded" EOLFG aerogels. Incubation of "loaded" corks in water brings about a slow and almost complete release of the absorbed actives having the same MIC of free biocides against selected bacterial pathogens.This new biomaterial could represent an innovative DS of microbiocides and other actives for a variety of industrial, food, cosmetic, and biomedical applications.
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