Synthesis Of Alkyl Glucosides Research Articles

Enzymatic Synthesis of Alkyl Glucosides byβ‐Glucosidases in a 2‐in‐1 Deep Eutectic Solvent System

AbstractAlkyl glycosides are biodegradable surfactants with excellent physico‐chemical properties. Although their wide‐range application is considered ecofriendly, their synthesis is not due to the need for toxic organic solvents and corrosive acids as catalysts. Moreover, chemical synthesis results in complex mixtures rather than defined compounds. To overcome both disadvantages as well as the limited solubility of sugars in organic solvents, a highly selective enzymatic synthesis was set up with aβ‐glucosidase condensing D‐glucose and different fatty alcohols in a deep eutectic solvent.

β-glucosidase from Streptomyces griseus: Ester hydrolysis and alkyl glucoside synthesis in the presence of Deep Eutectic Solvents

Deep Eutectic Solvents (DES) are ionic liquid analogs that have attracted considerable attention as green solvents for biocatalytic transformations. The use of DES as part of a ‘solvent engineering’ approach to enhance enzyme stability holds great promise since they are biodegradable, relatively inexpensive and environmentally safe media for enzyme reactions. However, the behaviour of specific enzymes in such solvents is complex; some enzymes are inhibited in DES, while others appear to be activated.Glucosidases are among the most widely used enzymes for commercial chemoenzymatic synthesis. In particular, their application in the synthesis of biodegradable alkyl glucosides by reverse hydrolysis is of great interest. Previous work in this laboratory identified Streptomyces griseus glucosidase (Sgβgl) as an interesting enzyme for biotechnological applications. In this study, we examined its behaviour in the presence of DES as a co-solvent using choline chloride as hydrogen bond donor and using glycerol, glucose and urea as hydrogen bond acceptors. We show that Sgβgl activity depends on both the nature of DES components, and their ratio in the eutectic mixture, as well as the water content of the reaction medium. A choline chloride/glycerol DES mixture at a level of 40% (v/v) caused activation of Sgβgl and increased its optimum temperature from 70 to 80 ​°C: it also led to a striking increase in its thermostability, doubling its half-life at 60 ​°C and almost tripling its half-life at 80 ​°C.The synthesis of alkyl glucosides was explored using DES as a co-solvent. In the presence of DES, Sgβgl catalysed the formation of a range of alkyl glucosides. The presence of DES resulted in enhanced product yield, which was observed to increase with increasing temperature, up to 60 ​°C.These studies show that the application of DES at relatively low % (v/v) levels can dramatically effect enzyme activity and stability. Specifically, enhanced thermostability can significantly increase the operating range for glucosidases for biocatalytic applications. Solvent engineering offers a simple and effective way to enhance glucosidase stability and will be useful as an alternative and/or adjunct to more complex methods such as immobilisation or protein engineering.

Multiple mutations in the aglycone binding pocket to convert the substrate specificity of dalcochinase to linamarase

Dalcochinase from Dalbergia cochinchinensis Pierre and linamarase from Manihot esculenta Crantz are β-glucosidases which share 47% sequence identity, but show distinct substrate specificities in hydrolysis and transglucosylation. Previously, three amino acid residues of dalcochinase, namely I185, N189 and V255, were identified as being important for determining substrate specificity. In this study, kinetic analysis of the ensuing double and triple mutants of dalcochinase showed that only those containing the 185A mutation could appreciably hydrolyze linamarin as well as transfer glucose to 2-methyl-2-propanol. So, the space provided by the I185A mutation appeared to be a prerequisite for accommodation of the aglycone moiety containing three substituents at the carbinol carbon. However, quantitative analysis of the energy parameters revealed mostly antagonistic interactions between these mutations. In addition, the N189F mutant showed a potential for use in enzymatic synthesis of alkyl glucosides via transglucosylation and reverse hydrolysis reactions. Thus, substitution of only 2–3 key residues in the aglycone binding pocket of dalcochinase could convert its specificities to that of linamarase, as well as to be suitable for any chosen hydrolytic or synthetic applications.

Micellar effect on the direct Fischer synthesis of alkyl glucosides

This manuscript presents results from the investigation on the synthesis of alkyl glucosides by the novel, very efficient and environmentally friendly protocol of the Fischer-type synthesis from unprotected glucose and aliphatic alcohols. The use of the dual functionality catalysts (surfactant+acid catalyst) and micellar reaction system are the main novelty of described method. It has been found, that in developed method of synthesis the reaction of unprotected glucose with aliphatic alcohols carried out with significantly different route, than the normal (classical) route and leads to alkyl glucopyranoside derivatives with high yields. In progress analyses by DLS, HPLC and GC/MS confirm the general postulated pathway of developed method.

β-Glucosidase from Streptomyces griseus: Nanoparticle immobilisation and application to alkyl glucoside synthesis

A novel β-glucosidase from Streptomyces griseus was cloned and overexpressed in E. coli. The purified β-glucosidase (44 kDa) had a Km of 8.6 ± 0.5 mM and a Vmax of 217 ± 5.0 μmoles−1min−1mg at 37 °C, pH 7.2 with p-nitrophenyl-β-D glucopyranoside as substrate. The enzyme was characterised in terms of pH optimum (pH 6.9), temperature optimum (69 °C) and the influence of solvents and effectors. Purified S. griseus β-glucosidase was successfully immobilised, by simple absorption, onto zinc oxide (ZnO) nanoparticles without covalent modification. It remained tightly bound even after extensive washing and could be reused up to ten times without significant loss of activity. The immobilised enzyme had a higher optimum temperature and greater thermostability than the free enzyme. In immobilised form the enzyme readily catalysed the synthesis of alkyl glucosides.

Isobornyl acrylate: an impurity in alkyl glucosides

Context: Alkyl glucosides and alkyl poly-glucosides are widely used as wetting agents, surfactants and emulsifiers in several industrial and cosmetic products. They are known as well-tolerated and are usually added to the primary surfactants in order to reduce the irritating potential of the main foaming agents.Objective: Recently, some authors suggested that allergic contact dermatitis to alkyl glucosides might be more frequent than suspected. On the other hand, the chemical structures of glucosides do not show potentially allergenic chemical groups or strongly polarized structures. The aim of our study is to investigate alkyl glucosides carrying out a detailed chemical analysis on samples of raw materials to identify potentially allergenic impurities or by-products contained in commercial samples of alkyl glucosides.Materials and methods: We chemically analyzed samples of cocoyl glucoside, decyl glucoside and lauryl glucoside by three different analytical methods, in order to identify any undesired or polluting substances.Result: In each of the three samples, we detected the presence of isobornyl acrylate. Its approximate content in the tested samples is 500 ng/g of the product.Discussion: Isobornyl acrylate is not used in the synthesis of alkyl glucosides, but as a plasticizer in many plastic materials. It can be easily released to materials flowing over these surfaces when they have high extraction power, as glucosides.Conclusion: Isobornyl acrylate may play a role as hidden allergen, in the form of an impurity collected during the industrial process, explaining some cases of allergic reaction to alkyl glucosides.

A New Method of Synthesis of Alkyl β-Glycosides Using Sucrose as Sugar Donor

Cellobiose phosphorylase from Clostridium thermocellum catalyzed the beta-anomer-selective synthesis of alkyl glucosides from cellobiose. Synthesis of alkyl beta-glucoside from inexpensive sucrose using cellobiose phosphorylase and sucrose phosphorylase from Pseudomonas saccharophilia was investigated. By combined use of these two phosphorylases, alkyl beta-glucoside was anomer-selectively synthesized from sucrose and alkyl alcohol.

A novel variant of Thermotoga neapolitana β-glucosidase B is an efficient catalyst for the synthesis of alkyl glucosides by transglycosylation

Alkyl glycosides are surfactants with good biodegradability and low toxicity, attractive to produce by an enzymatic method to get a well-defined product. In this paper, we report a novel thermostable variant of a family 3 beta-glucosidase to be an efficient catalyst in alkyl-glucoside forming reactions using transglycosylation with hexanol or octanol as the acceptor molecule. The enzyme has an apparent optimum for hydrolysis at 90 degrees C, which coincides with its unfolding temperature. The total activity is lower at lower temperature (60 degrees C), but the ratio of alcoholysis/hydrolysis is slightly more favourable. This ratio is however more heavily influenced by the water content and the pH. Optimal reaction conditions for hexyl glucoside synthesis from p-nitrophenyl-beta-glucopyranoside were a water/hexanol two-phase system containing 16% (v/v) water, pH 5.8, and a temperature of 60 degrees C. Under these conditions, the total initial reaction rate was 153 micromol min(-1)mg(-1) and the alcoholysis/hydrolysis ratio was 5.1. Comparing with alcoholysis/hydrolysis ratios of other beta-glycosidases, TnBgl3B can be considered to be a very promising catalyst for alkyl glucoside production.

Competition between transglycosylation and hydrolysis in almond β-glucosidase-catalyzed conversion of p-nitrophenyl-β-d-glucoside in monophasic water/alcohol mixtures

Almond β-glucosidase was used to catalyze the transglycosylation of p-nitrophenyl-β-d-glucoside to alkyl glucosides, with hydrolysis to glucose as a side reaction. The conversions were carried out in alcohols with varying water contents below water saturation. Both the total reaction rate and the ratio between the transglycosylation and hydrolysis increased with increasing water activity, and at a fixed water activity in the different alcohols, rate and transglycosylation/hydrolysis ratio increased in the following order: 1-octanol<1-hexanol<1-butanol. Synthesis of alkyl glucosides by transglycosylation in monophasic alcohol media is thus most favorable for short chain alcohols, and should be carried out at high water content.

ChemInform Abstract: Synthesis of Alkyl Glucosides and Alkyl Polyglucosides

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Enzymatic synthesis of alkylglucosides by amphiphilic phase enzyme reaction

Alkyl-β-glucosides were synthesized with β-glucosidase, from almond, in an amphiphilic phase reaction system using different water-miscible cosolvents. By means of stepwise addition of glucose, we obtained about 1.5 times higher concentration of hexylglucoside than that of normal reaction. Using the same way, octyl-, decyl- and dodecylglucoside were synthesized and their concentrations were 6.64, 5.3 and 4.48 g l−1, respectively.

Mesoporous Materials as Catalysts for the Production of Chemicals: Synthesis of Alkyl Glucosides on MCM-41

The synthesis of alkylglucosides from glucose andn-butanol has been carried out successfully on Al–MCM-41 mesoporous materials. The influence of the chemical composition (Si/Al) and pore dimensions on activity and selectivity has been studied. It has been found that a higher concentration of acid sites does not guarantee a better catalytic performance, and the adsorption–desorption properties of the material play a determinant role in this reaction where the two reactants and the product have very different polarities. On the other hand, in the range of pore sizes studied here, the larger the diameter of the pore at the same level of Al contents, the more active is the final catalyst. The catalyst loses activity during the process due to the presence of strongly adsorbed molecules. Soxhlet extraction by methanol followed by water does not recover all the initial activity but produces a loss of crystallinity. However, the catalyst could be fully regenerated by calcination in air at 773 K.

Enzyme-catalysed synthesis of alkyl β-D-Glucosides in organic media.

The synthetic potential of Almond β-D-Glucosidase for the synthesis of alkyl glucosides was studied. The regio and stereoselectivity of the synthesis were analysed for the reverse hydrolysis and the transglucosylation methods in tert-butanol and acetonitrile media.