The Influence Of Cyclodextrin Structure On The Characteristics Of Arthrobactr Simplex

Cyclodextrin(CD)have multiple effects on the hydrophobic compounds biotransformation,besides increase the substrates solubility the interaction with microorganisms may have positive effects on the bioconversion.The influence and the mechanism of CD structure on steroid-transforming microbe characteristics is not clear.In this paper,the biotransformation of cortisone acetate(CA)by Arthrobacter simplex(A.simplex)was selected as a model system for evaluating cyclodextrin and its derivatives on cell growth characteristics,enzyme activity,cell permeability and other implications.The study would provide basic data and theoretical basis for the application of cyclodextrin in the steroid biotransformation.The effects of different CDs on A.simplex cell growth were investigated.The results showed that the structure and CD concentration had different effects on A..simplex growth.At low concentrations,three natural CD can promoted the growth of A.simplex.When concentration of natural CDs were higher,the A.simplex growth significantly inhibited.The ?-CD with a smaller cavity in natural CDs,the greater impact on the A.simplex growth due to its strong inclusion with phospholipids..The A.simplex growth inhibition of ?-CD derivatives was in the order RM-?-CD>HP-?-CD>HE-?-CD>CM-?-CD>S-?-CD>SBE-?-CD.RM-?-CD is a lipophilic cyclodextrin derivatives,which has a strong inclusion characteristics due to its stronger hydrophobic cavity.Different substitution degrees of HP-?-CD on cell growth were not significantly different.The micrographs performed by SEM illustrated that after being treated by ?-CD derivative treated,the length and width of the cell were increased.?-CD derivative impacted on A.simplex resting bacterial cell morphology as:RM-?-CD>HP-?-CD>HE-?-CD,which in accordance with the effect of CD on A.simplex growth.The effects of CD structure on the A.simplex activity were investigated.The A.simplex dehydrogenase activity were reduced by 32%,61%and 95%,respectively,after treated by 15 mmol/L ?-CD,?-CD and y-CD.?-CD derivative(30 mmol/L)and different degrees of substitution HP-?-CD decreased the dehydrogenase activity of A.simplex.The A.simplex dehydrogenase activity was only 5%of the control after RM-?-CD treatment.The A.simplex dehydrogenase activity inhibition of different substituents of ?-CD derivatives were in the order RM-?-CD>CM-?-CD>HE-?-CD>SBE-?-CD>S-?-CD>HP-?-CD.The effects of CD structure on A.simplex cell permeability were investigated.The results showed that the structure and CD concentration had different effects on A.simplex cell permeability.The CA conversion rate and A.simplex cell permeability were increased after pretreatment with different natural CDs.The increase of A.simplex cell permeability was in the order ?-CD>?-CD>y-CD.The CA conversion rate was 6.40-folds when RM-?-CD in the concentrations of 30mmol/L compared with control.The A.simplex cell permeability of different substituents of ?-CD derivatives was in the order RM-?-CD>CM-?-CD>HE-?-CD>SBE-?-CD>S-?-CD>HP-?-CD.Different substitution degrees of HP-?-CD on cell permeability were not significantly different.