Citric acid production by Yarrowia lipolytica under increased air pressure

摘要

Oxygen mass transfer rate (OTR) fromair to liquid phase has been a serious handicapto the productivity of several biologicalprocesses, particularly for bioprocessesbased in aerobic cultures. OTR improvementcan be achieved by the increase oftotal air pressure in bioreactors with microbialcultures, due to the increase of oxygensolubility in the medium [1].Yarrowia lipolytica, strictly aerobic yeast,is known for the ability of producingseveral high value compounds such as enzymes,aroma and organic acids [2]. Citricacid is produced under limited nitrogenconditions but the production can be in-fluenced by other conditions, like pH andoxygen availability. High levels of dissolvedoxygen tension between 50 % and 80% have been reported as required for efficientcitric acid production [3].In this work air pressure increase (up to4 bar) was applied as a way of OTR enhancementin the production of citric acid byYarrowia lipolytica W29 from crude glycerol,a byproduct from the biodiesel production.Preliminary results indicated thatY. lipolytica batch growth was not inhibitedby pressure and the production of citricacid was slightly accelerated by the bioreactorpressurization