Partial Purification and Characterization of Limonoate Dehydrogenase from Rhodococcus fascians for the Degradation of Limonin

Abstract

\n\t\t\t\t\tAn extracellular limonoate dehydrogenase was purified 10-fold from a cell-free extract of <i>Rhodococcus</i> <i>fascians </i>by ammonium sulfate precipitation, dialysis, and ultrafiltration. This purified dehydrogenase catalyzed the<br />conversion of limonoate to 17-dehydrolimonoate. The enzyme showed optimum activity at pH 8.0 and 40oC, with K<sub>m</sub> value of 0.9 µM, and requires Zn ions and sulfhydryl groups for catalytic action. The enzyme activity was inhibited by Hg<sup>2+</sup> and NaN<sub>3</sub> ions. The degradation of limonin (66%) in Kinnow mandarin juice was successfully demonstrated with partially<br />purified limonoate dehydrogenase. With scale-up preparation of limonoate dehydrogenase, a successful debittering operation of fruit juices appears feasible.<br />\n\t\t\t\t