Hygiene requirements in the fermentation process

Although modern control systems have made sterilisation of fermenters and fermentation media in a small scale very easy, understanding the system design may well help in finding the cause when problems arise. In larger fermentation systems understanding engineering solutions and the reasons behind them will be very valuable, if contamination problems occur. Valve systems configurations with steam traps play an important role in sterilisation of fermentation systems. Avoiding dead legs, remembering "six tubediameter" rule and the nature of hydrophobic membranes will help in successful fermentations. In this presentation system design is considered more than calculating times and temperatures to achieve a certain Z-value or calculating heat transfer across a fouling tubular heat exchanger used in continuous sterilisation. Calculations of this kind can be found for example in Raju and Cooney (1993). Some comments are also presented in comparing batch and continuous sterilisation of fermentation media.