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Penicillium chrysogenum exo-arabinanase (Abnx), which releases arabinobiose from the nonreducing terminus of α-1,5-l-arabinan, was found to possess trans-arabinobiosylation activity on various acceptors, such as aliphatic alcohols, sugars, and sugar alcohols. Abnx was found to prefer primary hydroxyl groups in polyhydric alcohols as acceptors over primary hydroxyl groups in monohydric alcohols. Among the 21 different compounds tested, glycerol was the best acceptor for the enzyme. The transfer product of glycerol was identified as O-α-l-arabinosyl-(1→5)-O-α-l-arabinosyl-(1→1)-glycerol on the basis of the spectral data, fast atom bombardment-mass and 1H- and 13C-NMR. Unlike endo-arabinanases, Abnx catalyzed the hydrolysis of linear arabinan without inverting the anomeric configuration. [Copyright &y& Elsevier]

Abstract: Commercially available enzyme preparations were screened for enzymes that have a high ability to catalyze direct ester-synthesis of ferulic acid with glycerol. Only a preparation, Pectinase PL “Amano” produced by Aspergillus niger, feruloylated glycerol under the experimental conditions. The enzyme responsible for the esterification was purified and characterized. This enzyme, called FAE-PL, was found to be quite similar to an A. niger ferulic acid esterase (FAE-III) in terms of molecular mass, pH and temperature optima, substrate specificity on synthetic substrates, and the N-terminal amino acid sequence. FAE-PL highly catalyzed direct esterification of ferulic acid and sinapinic acid with glycerol. FAE-PL could feruloylate monomeric sugars including arabinose, fructose, galactose, glucose, and xylose. We determined the suitable conditions for direct esterification of ferulic acid with glycerol to be as follows: 1% ferulic acid in the presence of 85% glycerol and 5% dimethyl sulfoxide at pH 4.0 and 50 °C. Under these conditions, 81% of ferulic acid could be converted to 1-glyceryl ferulate, which was identified by 1H-NMR. The ability of 1-glyceryl ferulate to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals was higher than that of the anti-oxidant butyl hydroxytoluene. [Copyright &y& Elsevier]