On the false positive urease activity of Yarrowia lipolytica.

The ability of Yarrowia lipolytica to produce ammonia from urea was found variable on some media. The colour change of the indicator in Christensen's urea agar was not due to the urease activity of this species but was a non-specific alkalization reaction. Rapid urea broth was reliable giving no false positive results. It was found that Y. lipolytica is a urease negative yeast species.