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Ionic Liquids in Sustainable Carbohydrate Catalysis
Published in Pedro Lozano, Sustainable Catalysis in Ionic Liquids, 2018
Pilar Hoyos, Cecilia García-Oliva, María J. Hernáiz
Very recently, Yang and co-workers have reported the synthesis of different alkyl galactopyranosides in a sustainable process mediated by Thermotoga naphthophila RKU-10 β-galactosidase and milk processing waste lactose as galactosyl donor in ILs (Yang et al., 2017). Different alkyl alcohols were tested as nucleophiles (from n-butanol to n-tetradecanol) in systems containing different ILs. Most promising results were achieved with AMMOENG 102, a type of amphiphilic tetraammonium-ethylsulfate containing a C18 acyl chain and oligoethyleneglycol, which presented a better protective effect for the enzyme, allowing the reaction performance at 95ºC. Interestingly, another IL from this amphiphilic group, AMMOENG 101, resulted to be compatible with the cellobiose phosphorylase from Clostridium thermocellum, permitting the glycosylation of aliphatic and aromatic alcohols (De Winter et al., 2015). Cellobiose phosphorylase catalyzes the reversible phosphorolysis of cellobiose into α-D-glucose 1-phosphate and D-glucose with inversion of the anomeric configuration. It also possesses synthetic activity, using α-D-glucose 1-phosphate as sugar donor and glucose as sugar acceptor. The immobilization of the enzyme and the use of this IL contributed to the stabilization of the biocatalyst, and its acceptor promiscuity was widely explored, obtaining the corresponding α-glucosides in different yields, depending on the alcohol employed.
Cellulase Production
Published in Charles E. Wyman, Handbook on Bioethanol, 2018
There has been a proclivity to compare bacterial cellulase systems with the fungal one; hence, bacterial cellulolytic complexes are often characterized in the same fashion. All cellulolytic bacteria produce EG and β-D-glucosidase or cellobiose Phosphorylase, or a combination of the two. The existence of exoglucanases in bacteria has long been disputed; however, they have now been purified from several cellulolytic bacteria. The composition of the cellulase complex, along with its optimum pH/temperature, is important if it is to be successfully used in SSF along with the yeast of choice. The ease of enzyme recovery; hence, the extracellular/intracellular nature of the complex is of interest.
Fusion of cellobiose phosphorylase and potato alpha-glucan phosphorylase facilitates substrate channeling for enzymatic conversion of cellobiose to starch
Published in Preparative Biochemistry & Biotechnology, 2022
Xinyu Liu, Huawei Hou, Yapeng Li, Sen Yang, Hui Lin, Hongge Chen
Currently, lignocellulosic biomass, the most abundant renewable material in the world, is attracting increasing attention for the production of biofuels and chemicals, such as ethanol,[1] butanol,[2] methane,[3] citric acid,[4] and succinic acid.[5] In 2013, we reported the enzymatic conversion of nonfood lignocellulose to starch, opening up the possibility of using cellulose as a source of energy for humans.[6] This transformation pathway was observed to consist of the following two modules: a hydrolysis module and a synthesis module. In the hydrolysis module, cellulose was partially hydrolyzed to cellobiose by optimized ratio of cellobiohydrolase (CBH) and endoglucanase (EG); in the synthesis module, cellobiose was phosphorolyzed to glucose-1-phosphate (G-1-P) and glucose by cellobiose phosphorylase (CBP) from Clostridium thermocellum, and then, one glucose unit from G-1-P was added to the nonreducing end of maltodextrins or nascent amylose by potato alpha-glucan phosphorylase (PGP) from Solanum tuberosum. Using this in vitro system, up to 30% of the anhydroglucose units in cellulose were converted to starch. The synthesis module was the rate-limiting module for the whole transformation pathway because the rapid consumption of cellobiose in the course of amylose synthesis could relieve the inhibition of cellobiose on CBH and EG in the hydrolysis module and drive cellulose hydrolysis forward. Thus, the performance of CBP and PGP is presumed to be pivotal for high rate of conversion of cellulose into starch.