Aminopeptidase Modified Hydrolytic Enzymes to Improve the Efficiency of Sugar Production from Alkaline Pretreated Switchgrass

Debra A. Clare, Ziyu Wang, Jay J. Cheng, Dhana Savithri

Abstract


Cellulases and β-glucosidases (βGSD) are enzymes commonly used in the biofuel industry. In this study, smaller-sized variants were generated with aminopeptidase such that high catalytic capabilities were retained. Under the defined experimental conditions, the degree of hydrolysis was greater using cellulase substrates, compared to βGSD, based on ortho phthaldialdehyde (OPA) assay data (44% versus 15%). Proteolysis of cellulases was also evident based on sodium dodecyl sulfate polyacrylamide electrophoresis (SDS-PAGE) protein banding patterns seen after peptidase treatment. Residual cellulase activity was retained after peptidase hydrolysis (67% to 73%) based on standard filter paper assays. Peptidase treated cellulases and βGSD were then utilized for hydrolysis of alkaline-pretreated switchgrass (Panicum virgatum). Interestingly, the efficiency of the reaction, defined as milligrams of sugar produced per filter paper unit, was higher using truncated cellulases for bioprocessing reactions (~14%), especially in the absence of sodium azide. Conversely, incubation of βGSD with peptidase revealed minimal proteolysis with low impact on the efficiency of hydrolysis.

Keywords


Biofuel; Panicum virgatum (switchgrass); Cellulase; Beta-glucosidase; Immobilized enzymes; Truncated enzymes; Proteases; Sodium azide

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