Enhanced enzymatic cellulose degradation by cellobiohydrolases via product removal.
Product inhibition by cellobiose decreases the rate of enzymatic cellulose degradation. The optimal reaction conditions for two Emericella (Aspergillus) nidulans-derived cellobiohydrolases I and II produced in Pichia pastoris were identified as CBHI: 52 °C, pH 4.5-6.5, and CBHII: 46 °C, pH 4.8. The optimum in a mixture of the two was 50 °C, pH 4.9. An almost fourfold increase in enzymatic hydrolysis yield was achieved with intermittent product removal of cellobiose with membrane filtration (2 kDa cut-off): The conversion of cotton cellulose after 72 h was ~19 % by weight, whereas the conversion in the parallel batch reaction was only ~5 % by weight. Also, a synergistic effect, achieving ~27 % substrate conversion, was obtained by addition of endo-1,4-β-D-glucanase. The synergistic effect was only obtained with product removal. By using pure, monoactive enzymes, the work illustrates the profound gains achievable by intermittent product removal during cellulose hydrolysis.
Department of Chemical and Biochemical Engineering, Center for Bioprocess Engineering, Technical University of Denmark, Kongens Lyngby, Denmark.
Hassan Ahmadi
HA
Gavlighi
Anne S
AS
Meyer
J Dalgaard
JD
Mikkelsen
D001233:Aspergillus nidulans / Q000201:enzymology* / Q000235:genetics; D002475:Cellobiose / Q000302:isolation & purification / Q000378:metabolism; D002480:Cellulase / Q000378:metabolism; D002482:Cellulose / Q000378:metabolism*; D043366:Cellulose 1,4-beta-Cellobiosidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000302:isolation & purification / Q000378:metabolism; D004795:Enzyme Stability; D003368:Gossypium / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D010843:Pichia / Q000235:genetics*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013696:Temperature
D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D002475:Cellobiose; D002482:Cellulose; D002480:Cellulase; D043366:Cellulose 1,4-beta-Cellobiosidase