Purification And Characterization Of Xanthan-degradation Enzyme From Enterobacter Cloacae Sp.LB37

Enterobacter cloacae LB37 is an excellent xanthan-degrading strain isolated in our previous work.LB37 strain could specially degrade petrol-grade xanthan other than food-grade xanthan.At present,the molecular mechanism of xanthan-degradation by LB 3 7 remains unclear.Furthermore,some white cellulose-like sediment formed during the xanthan degradation by LB3 7,which is possible due to the removal of the side chain of xanthan by a-Mannosidase and thus a novel way to produce pure cellulose could be possible.In this work,the a-Mannosidase of Enterobacter cloacae LB37 was purified using anion-exchange chromatography and hydrophobic chromatography.The SDS-PAGE indicated that the molecular weight of a-Mannosidase was approximate 110 kDa.The optimum pH for a-Mannosidase was 7.0.The optimum temperature for a-Mannosidase was 50 ?.The Vmax of a-Mannosidase is 2.432 mmol/min·ml,Km=0.0207 mmol/ml.The effects of xanthan with different chemical modification on the activity of a-Mannosidase were determined.The results showed that,a-Mannosidase could not act directly on the intact xanthan and pyruvate/acetate-free xanthan.Though our research proved that a-Mannosidase could not directly cut the side chain of the intact xanthan,our results should be valuable for clarifying the cleaving mechanism of xanthan by Enterobacter cloacae LB37..