PRODUCTION OF CITRIC ACID BY Yarrowia lipolytica IN STIRRED TANK REACTOR
Luana Vieira da Silva, Raquel Grando de Oliveira, Priscilla Filomena Fonseca Amaral, Maria
Alice Zarur Coelho. Escola de Química, Universidade Federal do Rio de Janeiro, Cidade
Universitária, Ilha do Fundão, 21941-909, Rio de Janeiro, RJ, Brasil
A promising application of raw glycerol stemming from biodiesel industries is the citric acid
microbiological conversion. The purpose of this work was to evaluate the production of citric
acid by Yarrowia lipolytica IMUFRJ 50682 in a 2 liter New Brunswick bioreactor with Rushton
turbine, containing this renewable substrate in the production medium. Citric acid production
was carried out at different agitation speed, since the yeast is strictly aerobic, at 28 °C for 5
days. The production medium contained 30 gl-1 of glycerol and 0.1 gl-1 of yeast extract. Agitation
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was varied from 350 to 650 rpm. Citric acid production ranged from 5.64 to 7.03 gl . The
rightest citric acid concentration was obtained when the agitation speed was 550 rpm, while the
volumetric productivity in this condition was the same as when 450 rpm was used. The kinetic
parameters obtained at 550 rpm were 0.47 g of citric acid per g of glycerol, 0.17 g of biomass
per g of glycerol and 2.74 g of citric acid per g of biomass. The isocitric acid concentration
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produced was 9.65 gl , with citric and isocitric acids ratio 0.73. The lower YX/S was obtained at
650 rpm. Probably, the highest agitation generated shear stress to the cells, reducing cell
concentration and thus lowering citric acid. In this condition, the citric acid concentration
obtained was 5.64 gl-1 (the same as at 350 rpm), the lower result obtained in this study. Thus,
this study identifies that there is an optimal agitation to maximize citric acid production of citric
acid without shearing cells.