A simple assay procedure for β-D-mannanase.
McCleary, B. V. (1978). Carbohydrate Research, 67(1), 213-221.
A simple assay procedure for β-D-mannanase enzyme has been developed which employs carob D-galacto-D-mannan dyed with Remazolbrilliant Blue. Additionally, the procedure is quantitative, relatively sensitive, and highly specific for β-D-mannanase enzyme. It can be readily used for the determination of β-D-mannanase activity in crude enzyme preparations and column-chromatography eluates.
Enzyme resistance and biostability of hydroxyalkylated cellulose and galactomannan as thickeners in waterborne paints.
Cheroni, S., Gatti, B., Margheritis, G., Formantici, C., Perrone, L. & Galante, Y. M. (2012). International Biodeterioration & Biodegradation, 69, 106-112.
Chemically modified polysaccharides are widely used as rheology modifiers in several applications, such as food and feed, personal care, detergents, textile printing, building materials, paints and coating, paper manufacturing, and oil operations. Hydroxyalkylation, performed with ethylene or propylene oxide, is one of the most common chemical reactions applied to modulate the rheological profile and other properties of polysaccharides. Hydroxyethyl cellulose (HEC) and hydroxypropyl guar (HPG) are widely used as thickening and stability agents in waterborne paints. Hydroxyalkylation also increases the resistance of polysaccharides to enzyme degradation due to steric hindrance by the substituents on the susceptible bonds along the polysaccharide backbone. This feature of “enzyme resistance” is often referred to as “biostability,” yet it does not mimic a real-life situation of microbial contamination that can occur in a production plant or storehouse. We have compared viscosity decreases of HECs and HPGs in the presence of their specific hydrolyzing enzyme (cellulase and mannanase, respectively) to actual microbial contamination by consortia of fungi or bacteria. We found that the behaviour of HEC and HPG solutions inoculated with microorganisms differs and cannot be predicted from enzyme challenge data alone. Thus, “enzyme resistance” and “biostability” are not equivalent properties. For practical purposes, it is important to bear this in mind when selecting the most appropriate polysaccharide thickener, the manufacturing conditions of waterborne paints and the optimal stage of biocide addition.
Oxidation of galactomannan by laccase plus TEMPO yields an elastic gel.
Lavazza, M., Formantici, C., Langella, V., Monti, D., Pfeiffer, U. & Galante, Y. M. (2011). Journal of Biotechnology, 156(2), 108-116.
Chemical modifications of galactomannans are applied to improve and/or modify their solubility, rheological and functional properties, but have limited specificity and are often difficult to control. Enzymatic reactions, catalyzed under mild process conditions, such as depolymerization, debranching and oxidation, represent a viable and eco-friendly alternative. In this study, we describe oxidation of guar galactomannan primary hydroxyl groups by a fungal laccase using the stable radical TEMPO as mediator. Four fungal laccases were investigated from: Trametes versicolor, Myceliophthora thermophila, Thielavia arenaria, Cerrena unicolor. The laccase from T. versicolor was found to efficiently oxidize TEMPO and to be free of mannanase side activity. Oxidation of galactomannan with this enzyme plus TEMPO brought about a ten-fold increase in viscosity of a guar galactomannan solution and altered its rheological profile, by converting a viscous polysaccharide solution into an elastic gel. This structural modification is presumably due to formation of inter-chain hemiacetalic bonds between newly generated carbonyl groups and free OH groups, yielding a cross-linked gel. These findings could be of practical importance, considering that polysaccharides with high viscosity, gelling and elastic properties can find interesting and novel applications as thickeners, viscosifiers and emulsion stabilizers in several industrial applications such as: personal care, oil operations, paper coating, paints, construction and mining.
Enzymatic improvement of guar‐based thickener for better‐quality silk screen printing.
Baldaro, E., Gallucci, M., Formantici, C., Issi, L., Cheroni, S. & Galante, Y. M. (2012). Coloration Technology, 128(4), 315-322.
Guar galactomannan (referred to as guar gum) is a versatile polysaccharide, obtained from the seeds of the shrub Cyamopsis tetragonolobus, which finds several applications in either its native or chemically modified form. For textile printing, guar gum can also be partially depolymerised in order to promote dye penetration, improve swelling in water and achieve the desired rheological properties. Guar gum is obtained from guar seeds by a thermo-mechanical process that leaves ca. 3% of largely insoluble proteins in the gum, originating from the endosperms aleurone layer. When printing silk fabrics with acid or premetallised dyes, guar endogenous insoluble proteins bind tightly to anionic dyes, causing deposition of coloured aggregates on the fabric. This causes imperfections on the printed fabric in the form of tiny, but visible, ‘dots’, which lowers the quality of the final articles. In order to eliminate ‘dotting’, a novel printing thickener composed of depolymerised guar gum mixed with a bioengineered subtilisin protease has been developed. Upon solubilisation of the gum, and during preparation of the printing paste mixture, the protease hydrolyses guar gum insoluble proteins, generating soluble peptides that are washed off by the post-printing treatments of the fabric. This enzymatic application prevents ‘dotting’ and significantly improves the quality of the silk print, without any measurable tensile strength loss of the fabric.