Assimilation of labelled carbon substrates by Streptomyces thermovulgaris strain 127 variants obtained following gamma radiation

As a result of a mutagenic gamma-irradiation treatment (dose rate 23,25 Gy/min and intensity 1x103 - 1.2x104) of a parent strain of S. thermovulgaris 127, high (+) and low glucose isomerase activity (-) variants have been obtained by screening in liquid media. A comparative study is conducted of the two variants relative to the control strain on cultivation for 12 to 66 hours in a liquid nutritional medium. The biomass level and the changes in the level of specific glucose isomerase activity (SGIA) has been determined. Results indicate that the maximum SGIA in the (+) var. is higher by 14.3% than the SGIA in the initial strain, and in the (-) var. - considerably lower (by 77%). A simmilar pattern has been observed with biomass accumulation. The kinetics of respiratory activity and the assimilation and dissimilation of radioactive sustrates 14C-glucose, 14C-xylose and 14C-xylitol and thier combimation have been studied as well. The results obtained witness the differences in the oxidation rates of the individual substrates. Radioactive carbon incorporation in cell biomass and the level of 14CO2 released are determined radiorespirometrically. An almost twofold enhancement of assimilation and dissimilation with respect to 14C-xylose in the (+) var. and their sharp reduction in the (-) var. is observed. It is concluded that demonstrained differences in the extends of assimilation and dissimination is important for undustrial cultivation of the discussed mutant forms. 4 fig., 6 refs