ISOLATION AND GROWTH PHYSIOLOGY OF NOVEL THERMOACTINOMYCETES

A total of 34 thermophilic isolates identified as members of the genus Thermoactinomyces by a range of chemotaxonomic, microscopic and deter minative biochemical tests, were isolated from two acid soils. Growth studies in shake flask and fermenter identified the isolates to be mod erately acidophilic with growth occurring between pH 4.5 and 6.0 with optima at pH 5.0. The isolates differed considerably from known Thermo actinomyces cultures in their pH profile, colony morphology and in sev eral biochemical tests. Extracellular enzyme activities are identified and partially characterized in terms of their thermostability, pH and temperature profiles from crude supernatant fluid samples. Optimal pr otease, amylase and pullulanase activity was observed at pH 5.0-5.5 an d 75-80 degrees C with each showing T-(50) values of 10, 30 and 30 min , respectively. A highly thermotolerant extracellular esterase was als o identified which retained 50% activity after 8 h at 90 degrees C. Th is is the first report of an acidophilic member of the genus Thermoact inomyces.