Separation of clavulanic acid from fermented broth of amino acids by an aqueous two-phase system and ion-exchange adsorption.

The clavulanic acid is a substance which inhibits the ß-lactamases used with penicillins for therapeutic treatment. After the fermentation, by-products of low molecular weight such as amino acids lysine, histidine, proline and tyrosine are present in the fermented broth. To remove these impurities the techniques of extraction by an aqueous two-phase system of 17% polyethylene glycol molecular weight 600 and 15% potassium phosphate were used for a partial purification. A subsequent ion-exchange adsorption was used for the recuperation of the clavulanic acid of the top phase and purification getting a concentration factor of 2 and purification of 100% in relation to the amino acids lysine, histidine, proline and tyrosine.

Determination of the average shear rate in a stirred and aerated tank bioreactor.

A method for evaluating the average shear rate ((.)gamma(av)) in a stirred and aerated tank bioreactor has been proposed for non-Newtonian fluids. The volumetric oxygen transfer coefficient (k(L)a) was chosen as the appropriate characteristic parameter to evaluate the average shear rate ((.)gamma(av)). The correlations for the average shear rate as a function of N and rheological properties of the fluid (K and n) were obtained for two airflow rate conditions (phi(air)). The shear rate values estimated by the proposed methodology lay within the range of the values calculated by classical correlations. The proposed correlations were utilized to predict the (.)gamma(av) during the Streptomyces clavuligerus cultivations carried out at 0.5 vvm and four different rotational impeller speeds. The results show that the values of the average shear rate ((.)gamma(av)) varied from 437 to 2,693 s(-1) by increasing with N and flow index (n) and decreasing with the fluid consistency index (K).

Influence of feeding conditions on clavulanic acid production in fed-batch cultivation with medium containing glycerol.

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.

Cephalosporin C production by immobilized Cephalosporium acremonium cells in a repeated batch tower bioreactor.

The industrial production of antibiotics with filamentous fungi is usually carried out in conventional aerated and agitated tank fermentors. Highly viscous non-Newtonian broths are produced and a compromise must be found between convenient shear stress and adequate oxygen transfer. In this work, cephalosporin C production by bioparticles of immobilized cells of Cephalosporium acremonium ATCC 48272 was studied in a repeated batch tower bioreactor as an alternative to the conventional process. Also, gas-liquid oxygen transfer volumetric coefficients, k(L)a, were determined at various air flow-rates and alumina contents in the bioparticle. The bioparticles were composed of calcium alginate (2.0% w/w), alumina ( < 44 micra), cells, and water. A model describing the cell growth, cephalosporin C production, oxygen, glucose, and sucrose consumption was proposed. To describe the radial variation of oxygen concentration within the pellet, the reaction-diffusion model forecasting a dead core bioparticle was adopted. The k(L)a measurements with gel beads prepared with 0.0, 1.0, 1.5, and 2.0% alumina showed that a higher k(L)a value is attained with 1.5 and 2.0%. An expression relating this coefficient to particle density, liquid density, and air velocity was obtained and further utilized in the simulation of the proposed model. Batch, followed by repeated batch experiments, were accomplished by draining the spent medium, washing with saline solution, and pouring fresh medium into the bioreactor. Results showed that glucose is consumed very quickly, within 24 h, followed by sucrose consumption and cephalosporin C production. Higher productivities were attained during the second batch, as cell concentration was already high, resulting in rapid glucose consumption and an early derepression of cephalosporin C synthesizing enzymes. The model incorporated this improvement predicting higher cephalosporin C productivity.

Continuous clavulanic acid adsorption process.

Adsorption kinetics and equilibrium data of clavulanic acid, a beta-lactam antibiotic, on ion-exchange resin Amberlite IRA 400 were utilized to carry out the modeling and simulation of a continuous adsorption process. These simulations allowed the estimation of yield, concentration, and purification factors of the process utilizing the product final concentration. Experimental runs of this process were carried out using the conditions pointed out by simulation studies. Comparison of the experimental results and those calculated by the proposed model showed that the model could describe very well the main features of the continuous process.