Isolation, identification and characterization of effective bacteria on bioremediation from the waste parts of Stevia rebaudiana Berutoni

Four thermophilic strains were isolated by thermophilic treatment (2 days at 55 °C) of the stevia-powder, and were identified by the sequence analysis of the 16S rRNA gene; Ureibacillus thermosphaericus (FERM P-20039), Bacillus thermoamylovorans-1, B. thermoamylovorans-2 and Thermoactinomyces candidus. Since all of them have nitrate-reducing and ammonium-forming ability, it is highly possible that they can first produce nitrous acid from nitrate followed by the generation of ammonium. Only U. thermosphaericus had significantly large growing ability in the medium contained 1000 ppm of “Lannate®-45 water lenitive” (carbamate insecticide) and 400 ppm of “Ortran®” (organophosphorus insecticide) compared with the same concentration-level in the contrast medium without adding the pesticide.