Purification, biochemical characterization, and industrial potential of a thermostable lipase from <i>Aeribacillus pallidus</i> IO3 isolated from a geothermal source

Lipases obtained from thermophilic microorganisms are attracting great interest in the industrial field due to their stability under high-temperature conditions and their wide range of industrial applications. In this study, thermophilic bacterial strains were isolated from water and mud samples collected from Erzurum Ilica Hot Springs (Turkey). An isolate producing a potent extracellular lipase was selected, named IO3, and identified by 16S rRNA sequencing. Sequencing analysis revealed that this isolate showed 99% similarity to Aeribacillus pallidus. The lipase enzyme purified from the isolate was obtained using two comparative strategies. The conventional multi-stage chromatographic approach, which includes ammonium sulfate precipitation, ion exchange chromatography, and gel filtration chromatography, provided 9.3-fold purification with a 3.18% recovery. However, the alternative Three-Phase Partitioning (TPP) system provided rapid, single-step recovery with a significantly higher yield of 38.79%, although the purification fold remained 0.65 under the tested conditions. The molecular weight of the purified A. pallidus IO3 lipase was determined to be approximately 33.88 kDa by SDS-PAGE. The enzyme showed optimum activity at pH 8.0 and 50 °C and maintained considerable thermal stability; the enzyme retained significant activity levels (45-69%) even at high temperatures such as 70 °C and 80 °C after an incubation period of 120 minutes. Among the tested metal ions, Fe2+, Fe³+, Cu2+, and Zn2+ enhanced enzyme activity, while the enzyme showed stability in the presence of Li+ and Cu2+ ions. Lipase activity also increased in the presence of surfactants, while chloroform enhanced enzyme activity by 22–338% depending on solvent concentration. The enzyme showed the highest activity toward p-nitrophenyl palmitate. The enzyme was completely inhibited by DTNB, IAA, and EDTA. In addition, the enzyme retained low activity in the presence of β-mercaptoethanol. The Km and Vmax values were calculated as 0.46 mM and 51.44 µmol·min−1·mg−1, respectively, using nonlinear regression analysis. Overall, these findings indicate that A. pallidus IO3 lipase is a thermostable and chemically tolerant enzyme with potential applicability in industrial biocatalysis and detergent-related processes.