Uronic acid dehydrogenase mutant and application thereof in preparation of saccharic acid

The invention discloses uronic acid dehydrogenase mutants and application of the uronic acid dehydrogenase mutants in preparation of saccharic acid, the uronic acid dehydrogenase mutants are derived from wild type uronic acid dehydrogenase of thermophilic double-spore bacteria, 15 uronic acid dehydrogenase mutants are obtained through site-directed mutagenesis construction, and the specific enzyme activity of the three mutants A97H/L104F/E231K and the specific enzyme activity of the three mutants A110V/T170V/E242N are 3.14 times and 2.47 times of the specific enzyme activity of the wild type respectively; the kcat/Km of the optimal mutant A97H/L104F/E231K for producing glucaric acid by converting glucuronic acid is 3.08 times of that of wild type dehydrogenase, and the kcat/Km of the optimal mutant A110V/T170V/E242N for producing galactose diacid by converting galacturonic acid is 1.85 times of that of wild type uronic acid dehydrogenase. The saccharic acid prepared by using the mutant disclosed by the invent