Pure vegetable oil, from rapeseed, was obtained from a
local supermarket. Waste frying oil was provided by a
food establishment, which deep-fries chips and chicken.
Heated oil was obtained by heating pure vegetable oil in
an open container at 180°C for 1 week. 180°C is a common
frying temperature (Costa et al. 2001). All oils were
sterilised separately in a steam autoclave and added
directly to fermentations. Since the oils were either
refined or subjected to prolonged heating, only few
spores were present in the oils. Speadplating of 1 ml of
oil on TSA showed no colonies after incubation at 30°C
for 24 hours.