Influência das condições de alimentação de glicerol e ornitina na produção de ácido clavulânico por Streptomyces clavuligerus
Abstract
The clavulanic acid (CA) is a powerful inhibitor of β-lactamases, enzymes that clives the β-
lactam ring of penicillins and cephalosporins, inactivating these compounds. CA is
traditionally produced by Streptomyces clavuligerus in batch and fed-batch cultivations.
Considering that the products of the catabolism of easily assimilable carbon source repress the
biosynthesis of secondary metabolites, including CA, its production in fed-batch mode is
preferable because the control of nutrient level can be performed. In the present work the
influence of glycerol and ornithine feeding on the clavulanic acid (CA) production by S.
clavuligerus in batch and fed-batch cultivations was studied. Batch and fed-batch cultivations
were performed at 800 rpm, 0.5 vvm and pH at 6.8. In batch experiments under different
concentrations of ornithine, the maximum concentration of CA was within of a closed range
between 0.46 and 0.56 g.L-1. Nevertheless, the maximum value of volumetric productivity in
CA (Ppmax=13.7 mg.L-1.h-1) was obtained in the experiment with ornithine at concentration of
0.66 g.L-1, a value that is 40% higher than the Ppmax obtained in run control without ornithine.
In fed-batch experiments in 5 L bioreactor, with different ornithine feeding conditions, the
maximum concentration of CA varied within the limited range of 1.254 and 1.405 g.L-1.
Therefore, under these experimental conditions, it can be concluded that the presence of
ornithine increases the Ppmax in CA but not its maximum concentration, contradicting
literature. The kinetic model considering non-associated production with CA degradation was
fitted to the experimental results of the batch and fed-batch cultivations. The experimental
results showed that the rate of production of CA and glycerol consumption, were directly
related, condition not predicted by model, besides, its negative effect on the AC production
after the feeding indicate a possible inhibition/repression effect of glycerol. With the model, it
was possible to simulate conditions that the cultivations should be performed with the
intention of obtaining larger production of AC. With respect to the influence of glycerol in
fed-batch experiments, in the presence of ornithine at the concentration of 3.7 g.L−1 in feeding
medium, the maximum CA concentration of 1.506 g.L-1 was obtained in the run BA7 showing
a positive effect of the combination ornithine/glycerol in the biosynthesis of CA. In fed-batch
experiments in 10-L bioreactor, with different ornithine feeding conditions, the maximum
concentrations of CA were near of 1.6 g.L-1, validating the results obtained in 5-L bioreactor.