This system can be affected by factors such as humidity and temperature. The fermentor temperature has a marked effect on the mass transport of organic volatiles across
the probe membrane. This has not been a problem since most fermentor systems maintain a steady temperature very close to the setpoint,. However, because of the influence of temperature on the output of the sensor, the calibration must be done at the operating temperature. Other combustible organic vapours such as other alcohols acetone, etc. will interfere since the sensor is not methanol specific. This is not a problem in aerobic cultures since interfering species are normally absent. It can be an advantage, if, for example, ethanol is produced eg under oxygen limitation. This could be repressive. Since Pichia pastoris will utilize ethanol as a carbon source, allowing consumption of the ethanol prior to induction with methanol can be monitored. Another infrequent source of interference can be produced by overheating of a complex media additive such as yeast extract, which in turn may produce organic volatiles as degradation products.