Screening, purification and characterization of the thermoalkalophilic lipase produced by Bacillus thermoleovorans CCR11

Abstract

Among eleven aerobic thermophilic Bacillus strains, isolated from “El Carrizal” hot springs in Veracruz, Mexico, Bacillus thermoleovorans CCR11 (EMBL # AJ536599) was selected for lipase characterization because of its high lipase specific activity. Lipase was purified by diafiltration (polyethersulfone ultrafiltration membrane co500,000), and preparative isoelectrofocusing. The lipase had a relative molecular mass of 11 kDa (the lowest M r reported), although it formed higher molecular weight aggregates in native form. The optimum catalytic conditions for Bacillus thermoleovorans CCR11 lipase were 60 °C and pH 9–10. Hg 2+, PMSF, SDS, Tween 80 and Tween 20 had an inhibitory effect on lipase activity, whereas Ca 2+ salts and Triton X-100 increased it. Lipase activity was compatible with the presence of organic solvents, except for butanol. Lipase showed a notable preference for C6–C10 p-nitrophenyl esters, with the highest activity toward p-nitrophenyl caproate (C10). Lipase stability in the presence of organic solvents, as well as in acidic and alkaline pHs and at high temperatures makes it a good candidate for its application in non-aqueous biocatalysis.