Sunday, July 29, 2007
P69

The effect of media composition on the cell envelope of Rhodococcus DAP 96253 and on the stability of nitrile hydratase

Trudy M. Tucker, Sidney A. Crow, and George E. Pierce. Biology, Georgia State University, 24 Peachtree Center Avenue, 402 Kell Hall, Atlanta, GA 30341

 Growth media composition affects certain components of the Rhodococcal cell envelope such as the glycolipids and mycolic acids. Solid growth media consisting of yeast extract, malt extract and inducers (cobalt and urea) for Nitrile Hydratase were used for growing  cells of Rhodococcus strain DAP 96253. Different sugars were used in the media to examine the effect on the extractable glycolipids and on the trehalose content of the cells. The use of different sugars in growth media led to changes in the extractable glycolipids, it also affected the concentration of the cellular trehalose pools. Cellular trehalose concentrations were measured and nitrile hydratase (NHase) activity and stability of the cells were assessed. Fructose grown cells had the least stable NHase at 55oC and had the lowest trehalose pool. The addition of trehalose to media containing fructose resulted in significant increase in the stability of NHase. This showed that cellular trehalose pools had an impact on the stabilization of NHase which is influenced by sugars utilized in the media.  There is considerable interest in the use of Rhodococcal cells as catalysts.  In this proposed application, there is a need for the most stable native rhodococcal cell as this will produce a more stable and efficient catalyst.   The results suggest that the selection of carbohydrate for growth, influences cellular trehalose pools and cell envelope composition and this can have a significant impact on stability of NHase.

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