Cloning and characterization of a new ribitol dehydrogenase from Providencia alcalifaciens RIMD 1656011.

BACKGROUND A new ribitol dehydrogenase gene was cloned from Providencia alcalifaciens RIMD 1656011 and expressed in Escherichia coli BL21. This study aimed to purify and characterize the ribitol dehydrogenase from P. alcalifaciens RIMD 1656011 and investigate its substrate specificity for potential use as an industrial enzyme. RESULTS The protein was purified by nickel affinity chromatography. The molecular mass of the purified enzyme was determined as ∼25 000 and 26 650 Da through sodium dodecyl sulfate polyacrylamide gel electrophoresis and liquid chromatography/mass spectrometry respectively. The result for native molecular mass (104 kDa) suggested that the enzyme functions as a tetramer. Optimum activity of the enzyme was determined at pH 10.0 and a temperature of 35 °C. Regarding its thermal stability, the enzyme retained 72, 72, 48 and 0% of its initial activity after 4 h at 25, 30, 40 and 50 °C respectively. The Km , kcat and kcat /Km values of the enzyme for the substrate ribitol were determined as 13.9 mmol L(-1) , 10.0 s(-1) and 0.71 L mmol(-1) s(-1) respectively. The Km of NAD(+) was 0.042 mmol L(-1) . CONCLUSION The substrate specificity indicated that the ribitol dehydrogenase from P. alcalifaciens RIMD 1656011 can be used for direct production of allitol from d-fructose without any by-product formation. © 2015 Society of Chemical Industry.