Identification of a cold-adapted and metal-stimulated beta-1,4-glucanase with potential use in the extraction of bioactive compounds from plants

Cold-adapted endo-beta-1,4-glucanases hold great potential for industrial processes requiring high activity at mild temperatures such as in food processing and extraction of bioactive compounds from plants. Here, we identified and explored the specificity, mode of action, kinetic behavior, molecular structure and biotechnological application of a novel endo-beta-1,4-glucanase (XacCel8) from the phytopathogen Xanthomonas citri subsp. citri. This enzyme belongs to an uncharacterized phylogenetic branch of the glycoside hydrolase family 8 (GH8) and specifically deaves internal beta-1.4-linkages of cellulose and mixed-linkage beta-glucans releasing short cellooligosaccharides ranging from cellobiose to cellohexaose. XacCel8 acts in near-neutral pHs and in a broad temperature range (10-50 degrees C), which are distinguishing features from conventional thermophilic beta-1,4-glucanases. Interestingly, XacCel8 was greatly stimulated by cobalt ions, which conferred higher conformational stability and boosted the enzyme turnover number. The potential application of XacCel8 was demonstrated in the caffeine extraction from guarana seeds, which improved the yield by 25 g/kg compared to the traditional hydroethanolic method (HEM), indicating to be an effective additive in this industrial process. Therefore, XacCel8 is a metalstimulated and cold-adapted endo-beta-1,4-glucanase that could be applied in a diverse range of biotechnological processes under mild conditions such as caffeine extraction from guarana seeds. (C) 2020 Elsevier B.V. All rights reserved. (AU)