I recently did a batch study with S.pasteurii and yeast extract plus some urea solution containing 20g/L urea.
At 0hr sampling the urea conc was 13g/L, at 4 hrs sampling was 17g/L then it was 0g/L at 24 hrs sampling.
Is there a reason for the increase in urea concentration? After the initial measurement already showed some level of decrease in the urea concentration.
Dear Olayinka Durojaye
To assayed the batch dispense 20 µl of it in tube and add 130 µl of urease stabilized (dissolve 4444 UI urease type IV in a mixture containing 63.0 ml phosphate buffer 0.08 N at pH 6.5, and 37 ml of ethylene glycol, and then dissolve 0.08 g of sodium nitroprusside. The solution will keep for months and will keep indefinitely in a freezer), and the mixture is incubated at 37 °C for 20 min. At the end of the incubation add 1.2 ml of sodium phenate solution (mix 3.1 g of liquefied phenol at the 88% to 87.5 ml of water and adding then 12.5 ml of 10% sodium hydroxide. The solution is stable), add 100 µl of sodium hypochlorite (dilute 60 ml of 5% sodium hypochlorite to 100 ml with dH2O. The solution is stable), mix and incubate for 15 min. at 37 °C. The resulting incubated solution has an intense blue colour. It is diluted with 6.55 ml of dH2O to bring optical density within a suitable range, which intensity is read, against the blank at 550 nm, (530 – 570 nm). As urea standard to 60 mg/dl, dissolve 0.129 g urea in 100 ml of saturated solution of benzoic acid, resulting stable a 4 °C.
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