The cis-epoxysuccinate hydrolase(CESH) from Rhizobium strain BK-20 is the key enzyme for L(+)-tartaric acid production. To establish a highly efficient and stable production process, we first optimized the enzyme production from Rhizobium strain BK-20, and then developed an immobilized cell-culture process for sustained production of L(+)-tartaric acid. The enzyme activity of free cells reached(3 498.0±142.6) U/g, and increased by 643% after optimization. The enzyme activity of immobilized cells reached(2 8...