Enzymatic Hydrolysis of Cellulose Using Mixes of Mutant Forms of Cellulases from <Emphasis Type="Italic">Penicillium verruculosum</Emphasis>

Cellulases are the major components of multienzyme systems applied in processes of bioconversion of renewable lignocellulosic feedstocks to various useful products. The hydrolytic efficiency of enzyme mixes based on recombinant wild-type endoglucanase II, cellobiohydrolases I and II from the Penicillium verruculosum fungus (in the presence of Aspergillus niger β-glucosidase) with mixes of mutant forms of these enzymes in the hydrolysis of cellulosic materials is compared, and the influence of temperature and substrate concentration on the glucose yield is studied. The mutant cellulases represented proteins, in which N-linked glycans were partially removed using site-directed mutagenesis. In the hydrolysis of microcrystalline cellulose and milled aspen wood by mixes of mutant cellulases, the yields of glucose after 24–72 h of an enzymatic reaction were higher by 31–38% and 11–27%, respectively, than those for the compositions based on the wild-type enzymes. The highest product concentrations, using mutant enzyme compositions, are achieved at 50°С when the hydrolysis temperature is varied in the range of 40 to 60°С. Increasing the substrate concentration in the reaction system from 5 to 50 g/L (while maintaining the enzyme dosage at the same level) led to a 2.6–2.8-fold increase in the glucose yield, accompanied by a decrease in the cellulose conversion degree.     

Transfer of glycols through an MA-41 ion-exchange membrane from aqueous and salt-aqueous solutions

Experiments on the molecular diffusion of glycols through an MA-41 ionite membrane in the SO ₄ ^2? form demonstrated that the flux of the glycols decreases with increasing sodium sulfate concentration in the feed solution and with increasing molecular mass of the glycol. For ethylene glycol, as an example, it was demonstrated that its flux through the membrane nonlinearly depends on its concentration in the feed solution. Based on the observation that the fluxes of the nonelectrolyte and electrolyte differ significantly, we proposed a method for separating these components by means of dialysis through an ionite membrane. Computer simulations of the structure and IR spectra of the ethylene glycol-nine water molecules and ethylene glycol-nine water molecules-M⁺ (M⁺ = Na⁺, K⁺) systems were performed. It was revealed that, for the latter system, the activation energy of self-diffusion of ethylene glycol is lower than that for the former.     

Quasi-elastic neutron scattering by an aqueous dispersion of nanodiamonds

The relative fraction of water molecules involved in the hydration sphere of carbon nanoparticles is determined using the direct subtraction method from our previous data on neutron scattering by an aqueous dispersion of nanodiamonds.