First, the effect of different levels of nitrogen source on clavulanic acid (CA) production was evaluated in batch cultivations utilizing complex culture medium containing glycerol and three different levels of soy protein isolate (SPI). Cellular growth, evaluated in terms of the rheological parameter K, was highest with a SPI concentration of 30 g.L(-1) (4.42 g.L(-1) N total). However, the highest production of CA (380 mg.L(-1)) was obtained when an intermediate concentration of 20 g.L(-1) of SPI (2.95 g.L(-1) total N) was used. To address this, the influences of volumetric flow rate (F) and glycerol concentration in the complex feed medium (Cs(F)) in fed-batch cultivations were investigated. The best experimental condition for CA production was F=0.01 L.h(-1) and Cs(F)=120 g.L(-1), and under these conditions maximum CA production was practically twice that obtained in the batch cultivation. A single empirical equation was proposed to relate maximum CA production with F and Cs(F) in fed-batch experiments.

-The influence of glycerol and ornithine feeding on clavulanic acid (CA) production by Streptomyces clavuligerus was investigated. In batch experiments, CA maximum concentration (Cp max ) ranged randomly from 430 to 560 mg.L -1 , with a maximum increase of 10% in relation to the control run, without ornithine. However, the maximum volumetric productivity of CA (Pp max ) of 13.7 mg.L -1 .h -1 was obtained with 0.66 g.L -1 of ornithine, 44.2% higher than the Pp max in the control run. In fed-batch experiments, Cp max varied within the narrow range from 1.254 to 1.405 g.L -1 , 2.5 times higher than that obtained in the control run. The presence of ornithine increased the Pp max , although it influenced only slightly the Cp max . Concerning glycerol, the highest CA production of 1.6 g.L -1 was obtained in the fed-batch with glycerol and ornithine (180 and 3.7 g.L −1 ) in a 10-L bioreactor, showing a positive effect of ornithine and glycerol, in the proper proportion (48.6:1), on CA biosynthesis.

Citric acid (CA) production has been conducted through a careful strain selection, physical-chemical optimization and mutation. The aim of this work was to optimize the physical-chemical conditions of CA production by solid-state fermentation (SSF) using the Aspergillus niger LPB BC strain, which was isolated in our laboratory. The parental and mutant strain showed a good production of CA using citric pulp (CP) as a substrate. The physical-chemical parameters were optimized and the best production was reached at 65% moisture, 30 degrees C and pH 5.5. The influence of the addition of commercial and alternative sugars, nitrogen sources, salts, and alcohols was also studied. The best results (445.4 g of CA/kg of CP) were obtained with sugarcane molasses and 4% methanol (v/w). The mutagenesis induction of LPB BC was performed with UV irradiation. Eleven mutant strains were tested in SSF where two mutants showed a higher CA production when compared to the parental strain. A. niger LPB B3 produced 537.6 g of CA/kg of CP on the sixth day of fermentation, while A. niger LPB B6 produced 616.5 g of CA/kg of CP on the fourth day of fermentation, representing a 19.5% and 37% gain, respectively.

Gibberellic acid (GA 3

No abstract