Lipase‐catalyzed acylation of konjac glucomannan in ionic liquids

Abstract

A comparative study was made of lipase-catalyzed acylation of konjac glucomannan (KGM) with vinyl acetate as the acyl donor in five ionic liquids (ILs) and also in the presence of the organic solvent tert-butanol (t-BuOH). An obvious enhancement in enzyme activity and stability was observed using ILs as the reaction media when compared with t-BuOH. The maximum degree of substitution (DS) of the modified KGM in ILs and t-BuOH under the conditions employed is 0.71 and 0.54, respectively. The water activity (a w ) of the reaction system affected the acylation of KGM to some extent. 1-Butyl-3-methylimidazolium tetrafluoroborate (C 4 MIm.BF 4 ) was the best IL medium for the reaction, and an a w of 0.75 was optimum. It was also found that the nature of both the cation and the anion of ILs had an effect on the reaction. Candida antarctica lipase B immobilized on an acrylic resin (Novozym 435) displayed no acylation activity to KGM in 1-butyl-3-methylimidazolium chloride (C 4 MIm.Cl). The optimum reaction temperature for enzymatic acylation in ILs was shown to be 45-55• C. Enzymatic acylation of KGM in IL-t-BuOH co-solvent systems was also investigated. When an appropriate amount of t-BuOH was added to ILs, the DS of the modified KGM was enhanced. Additionally, the enzymatic acylation of KGM in all the media examined was shown to be regioselective, with acylation occurring predominantly at the C-6-OH.

Lipase‐catalyzed esterification of konjac glucomannan in isooctane

“…As a check on the accuracy of the method, triplicate samples were carried out. DS was calculated from the amount of sodium hydroxide consumed during the saponification, after the excess has been titrated back to pH value measured prior to sodium hydroxide . The calculating formula was as following: where is the volume of HCl consumed for the blank in liter, is the volume of HCl consumed for the sample in liter, stands for the normality of the hydrochloric acid, = 265.47 g/mol and is the mass of the sample in gram.…”

“…As a check on the accuracy of the method, triplicate samples were carried out. DS was calculated from the amount of sodium hydroxide consumed during the saponification, after the excess has been titrated back to pH value measured prior to sodium hydroxide [19]. The calculating formula was as following:…”

Effect of ultrasound on enzymatic acylation of konjac glucomannan

“…However, its application to enzymatic reactions is still little explored [12][13][14][15], and no research on the use of ultrasound to accelerate the enzymatic synthesis of polysaccharide esters has been reported. We have reported recently enzymatic acetylation of KGM with vinyl acetate in non-aqueous media under shaking [1][2][3]. In organic media, tert-butanol (t-BuOH) was the most suitable reaction medium among the organic solvents studied by the degree of substitution (DS) of the modified KGM into account [1].…”

“…It consists of b-1,4-linked D-glucose and D-mannose units, and the molar ratio of glucose and mannose has been reported to be around 1-1.60 [1][2][3][4][5]. Chemically modified forms of KGM have been studied and showed to be promising as a novel medicine [4,6], an environmentally benign emulsifier [7] and drug carriers [8].…”

Lipases efficiently stearate and cutinases acetylate the surface of arabinoxylan films

“…Klibanov and co-workers were pioneers in the field of using enzymes in non-aqueous media (Ikeda and Klibanov, 1993;Klibanov, 1989;Patel et al, 1996;Zaks and Klibanov, 1988). While the presence of water is essential in the hydrolysis reaction, esterification on various substrates has been demonstrated using esterases and lipases in non-aqueous media (Chen et al, 2006;Gremos et al, 2011;Kirk et al, 1995;Ljunger et al, 1994;Micaelo et al, 2005;Patel et al, 1996). Enzymatic acylation of polysaccharide derivatives in organic media was also an important landmark in the field, showing activity on not only monomer or oligomer units (Sereti et al, 1998(Sereti et al, , 2001.…”