Isolation and characterization of lipid-degrading Bacillus thermoleovorans IHI-91 from an icelandic hot spring

Abstract

An efficient lipid-degrading thermophilic aerobic bacterium was isolated from an icelandic hot spring and classified as Bacillus thermoleovorans IHI-91. The aerobic bacterium grows optimally at 65°C and pH 6.0 and secretes a high level of lipase (300 U l⁻¹). The newly isolated strain utilizes several lipids such as palmitic acid, stearic acid, lanolin, olive oil, sunflower seed oil, soya oil, and fish oil as sole carbon and energy source without an additional supply of growth factors. The degradation of about 93% of triolein, which is present in olive oil, was observed after only 7 h of fermentation at a maximal growth rate of 1.0 h⁻¹. During growth at optimal conditions on yeast extract, the doubling time was only 15 min. Based on 16S rDNA studies, DNA–DNA hybridization and morphological and physiological properties, the isolate IHI-91 was identified as Bacillus thermoleovorans IHI-91 sp. nov. Because of its production of high concentrations of thermoactive lipases and esterases and the capability of degrading a wide range of lipids at high temperatures, the isolated strain is an ideal candidate for application in various biotechnological processes such as wastewater treatment.