The aim was to allow the maximum number of fermenters in the minimum space, whilst maintaining individual operating volumes of 5 litres. We designed a two-tier rack, using one side for the fermenter vessels and the rear for pumps, bottles etc., with the control system mounted to the end. This allowed 24 x 5 litre fermenters to operate in less than 4m2 (42 sq.ft.) of floor space whilst still providing excellent access - in total 68 x 5 litre vessels occupy a laboratory of just 25m2.