PRODUCTION OF EXOPOLYSACCHARIDE ETHAPOLAN UNDER Acinetobacter sp. IMV B-7005 CULTIVATION ON THE MIXTURE OF ACETATE AND SUNFLOWER OIL

The aim of the work was to establish the cultivation conditions of Acinetobacter sp. IMV B-7005 for providing the maximum indicators of the exopolysaccharide ethapolan synthesis on the mixture of acetate and sunflower oil, as well as to study the possibility of replacing the refined oil in the mixture with acetate on a waste one. The optimal molar ratio of concentrations for refined sunflower oil and acetate in the mixture was calculated theoretically according to Babel's concept of “auxiliary substrate”. The EPS concentration was determined gravimetrically after precipitation with isopropanol. The EPS-synthesizing ability was calculated as the ratio of the EPS concentration to the concentration of biomass and expressed in g EPS/g biomass. Based on theoretical calculations of energy requirements for EPS synthesis and biomass of Acinetobacter sp. B-7005 on energy-deficient substrate (acetate) it was found that molar ratio for the concentrations of sodium acetate and oil in the mixture, at which the maximum EPS synthesis was achieved, should be 1:0.13. It was experimentally confirmed that at this ratio of monosubstrate concentrations and the use of the inoculum grown on refined oil, the synthesis rates of ethapolan were higher than at the other ratios of acetate and oil concentrations in the mixture. However, the assimilation of sodium acetate through the symport with proton led to an increase in pH of the culture liquid to 9.0–9.3, which is not optimal for EPS synthesis. Decrease of the medium alkaline component and fractional introduction of substrates enabled not only to stabilize pH at the level of 7.8–7.9, but to increase the amount of synthesized ethapolan to 16–17 g/l, which was achieved regardless of the type of used oil (refined or mixed waste) in the mixture with acetate.