Purification and biochemical characterization of an ionic liquid tolerant cellulase from Aspergillus assiutensis VS34 for potential biomass conversion applications

Ionic liquids (ILs) have gained immense attention as eco-friendly solvents for pretreatment of lignocellulosics for their potential bioconversion to biofuels, bio-chemicals, and other products. However, for saccharification of ionic liquid (IL)-pretreated biomass, IL-stable cellulases are desired. IL-stable cellulase and xylanase enzyme preparation developed from a previously isolated Aspergillus assiutensis VS34 was used for saccharification of IL-pretreated biomass. Current study reports the purification of IL-stable cellulase (CMCase) from A. assiutensis VS34 based on salt precipitation and ion exchange chromatography. Functionality of the purified cellulase (2.10-fold) was observed by native-PAGE and zymography, and the molecular weight (27 kDa) was assayed by SDS-PAGE. Though optimum temperature and pH of CMCase was 50 degree celsius and 6.0, respectively, but the enzyme showed considerable activity and stability over a wide range of temperature (40-80 degree celsius, 72-99%) and pH (3-11, 60-95%). The activity of enzymes was enhanced by certain metal ions (Ca2+, Cu2+, Mn2+, Mg2+, and Co-2(+)), but decreased considerably by Hg2+. K-m and V-max of CMCase were 6.996 mg/ml and 16.103 mu mol/min/mg, respectively. Process-apt properties of A. assiutensis VS34 CMCase reflect its application potential for a variety of processes including biomass conversion.