[Influence of the intensity of oxygen mass transfer on the biosynthesis of amphotericin B]. / Vliianie intensivnosti massoperedachi kisloroda na biosintez amfoteritsina B.

Influence of oxygen mass transfer intensity characterized by the rate of oxygen dissolution (S) and the agitation rate (n), as well as influence of dissolved oxygen concentration on the process of amphotericin B biosynthesis was studied. It was shown that S = 40 and 110 mg/l. min and n = 450 and 800 min-1 were respectively the lower and the upper levels of the optimal conditions by oxygen mass transfer during amphotericin B biosynthesis. When biosynthesis of amphotericin B was conducted under conditions of the optimal oxygen mass transfer, the dissolved oxygen concentration of about 12 to 15 per cent of the saturation level was critical for the culture respiration. Inhibition of the culture respiration and antibiotic synthesis was induced under conditions of increased oxygen mass transfer intensity (S greater than 110 mg/l. min and n greater than 800 min-1) by high intensity mechanical agitation of the fermentation broth. Under conditions of decreased oxygen mass transfer (S less than 40 mg/l. min and n = less than 450 min-1) it was induced by insufficient supply of oxygen to the culture. On the basis of the results it was shown possible to control the aeration and agitation conditions by the rate of oxygen uptake and dissolved oxygen concentration. The data should be considered in optimization of aeration and agitation conditions in biosynthesis of amphotericin B in large fermenters.

[Oxidation-reduction status of the culture medium during the biosynthesis of amphotericin B]. / Izuchenie okislitel'no-vosstanovitel'nogo sostoianiia kul'tural'noi zhidkosti v protsesse biosinteza amfoteritsina B.

The possibility of potentiometric estimation of the oxidation-reduction state of the fermentation broth during production of amphotericin B was studied. It was shown that the reduction capacity of the fermentation broth was high and did not change significantly during the antibiotic biosynthesis. It contained electrochemically active compounds in amounts providing stable potentials on the indicator electrodes. Both the platinum and the glass redoxmetric electrodes not sensitive to changes in the level of oxygen dissolved in the fermentation broth might be used for measuring the oxidation potential of the fermentation broth. Investigation of the dynamics of the oxidation potential changing revealed that during the process of amphotericin B biosynthesis the potential changed within wide ranges and every stage of the culture development was characterized by particular direction of the potential changing. This allowed, in combination with other parameters of the process, estimation of physiological activity of the culture at any moment of its growth.

[Spectrophotometric analysis of amphotericin B in technological objects]. / Spektrofotometricheskii analiz amforteritsina B v tekhnologicheskikh ob"ektakh.

The same samples of the fermentation broth and mycelium of the amphotericin B-producing organism, (S. nodosus, strain 258) were assayed with the agar diffusion method and spectrophotometrically. The comparison of the results showed that the spectrophotometric findings did not depent on the wave lengths and the equation type. However, the values of the spectrophotometric assay were higher than those of the biological assay. This was partially due to the presence of a biologically inactive admixture of the heptaenic nature in the semiproducts of amphotericin B. At the same time when the strain, nutrient medium and biosynthetic conditions were stable, the results of the biological and spectrophotometric assays had a linear dependence. This allowed one to suggest equations for spectrophotometric determinations providing results correlating with those of the biological assay.

[Characteristics of the electrophysical parameters of the growing mycelium of Act. nodosus, a producer of amphotericin B]. / Osobennosti élektrofizicheskikh parametrov rastushchego mitseliia Act. nodosus--produtsent amfoteritsina B.

The dielectric constants E1 and impedance Z of the growing mycelium of Act. nodosus producing amphotericin B were determined with the method of dielectric estimations at 10(3)-10(8), the concentrations of the biomass and antibiotic being determined simultaneously. It was found that the values of the dielectric permeability and impedance may be indicative of the biomass volume and antibiotic accumulation respectively. It is suggested that standard curves be plotted and the electrophysic parameters be used for automatic and continuous control of the Act. nodosus growth. Calculation of the viability coefficient according to B. N. Tarusov showed that it directly correlated with the economic coefficient. It is concluded that additional information on the medium such as the dipole moment, Z-potential and others, may be obtained using the electrophysic parameters.