Enzymatic hydrolysis of cellulose in aqueous two-phase systems. I. Partition of cellulases from Trichoderma reesei

The partitioning of endo-beta-glucanase, exo-beta-glucanase, and beta-glucosidase from Trichoderma reesei QM 9414 in aqueous two-phase systems has been studied with the object of designing a phase system for continuous bioconversion of cellulose. The partitioning of the enzymes in two-phase systems composed of various water soluble polymeric compounds were studied. Systems based on dextran and polyethylene glycol (PEG) were optimal for one-sidedly partitioning the enzymes to the bottom phase. The influence of polymer molecular weights, polymer concentration, ionic composition of the medium, pH, temperature, and adsorption of the enzymes to cellulose on the enzyme partition coefficients (K) were studied. By combining the effects of polymer molecular weight and adsorption to cellulose, K values could be reduced for endo-beta-glucanase to 0.02 and for beta-glucosidase to 0.005 at 20 degrees C in a phase system of Dextran 40-PEG 40000 in the presence of excess cellulose, At 50 degrees C, K values were increased by a factor of two. In a phase system based on inexpensive crude dextran and PEG, the partition coefficient for endo-beta-glucanase was 0.16 and for beta-glucosidase was 0.14 at 20 degrees C with excess cellulose present.