Characterization of Partially Purified Cellulase From Muscadine Grapes (Vitis rotundifolia Michx.)

¹ Center for Viticultural Science and Small Farm Development, Florida A&M University, Tallahassee, FL 32307.

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Center for Viticultural Science and Small Farm Development, Florida A&M University, Tallahassee, Florida 32307. The unique flavor of muscadine grapes has been exploited in the production of value-added grape products and for blending in juices and wines. Juice yield may be increased through the synergistic reaction of naturally occurring cellulase with native enzymes. The objective of this study was to characterize partially purified cellulase from muscadine grapes and to determine optimal conditions for natural cellulase action. The 40% to 60% ammonium sulfate fraction was isolated, and the effects of pH (3.0 to 8.0), temperature (40°C to 70°C), metal ions, inhibitors, and other substances were investigated. Reaction of cellulase with different substrates was investigated to determine whether the enzyme had endo- or exoglucanase activity. Cellulase from muscadine grapes had an optimum pH of 4.0 and maximum temperature of 45°C. The enzyme remained stable at temperatures up to 50°C for one hour but lost activity rapidly at 60°C and over. Zn²⁺ and Mg²⁺ inhibited cellulase activity 32% and 30%, respectively, at a concentration of 10 mM, while Cu²⁺ and Fe²⁺ stimulated enzyme activity. The enzyme degraded CM-cellulose, cellotetraose, and cellopentaose as an endoglucanase and cleaved aglycosidic bonds in p-nitrophenyl-ß-D-cellobioside as an exoglucanase. Cellulase activity was confirmed by the ability to degrade CM-cellulose to form a zone of clearing in cellulose-polyacrylamide gel.

Key words: cellulase, muscadine

Submitted on September 29, 1997
Revised on May 11, 1998