BACKGROUND: Thermophilic microorganisms are receiving significant attention as a source of useful thermostable enzymes. However, the number of known strains is still limited, and very often their most interesting biocatalysts are intracellular or membrane-bound and produced at low levels. Thus, the isolation and study of novel extracellular enzyme-producing thermophilic microorganisms is very interesting. Moreover, the assessment of bioreactor performance is crucial, given the scarce information on the large-scale culture of these strains. RESULTS: The production of a thermostable extracellular lipase in submerged cultures of a thermophilic microorganism, recently isolated in north-west Spain, was investigated. The strain was identified by 16S rDNA sequencing as belonging to genus Bacillus. The influence of operating variables (i.e. pH, temperature, aeration) on lipase biosynthesis was analysed. Enzyme production at bioreactor scale was investigated, special attention being paid to the effect of aeration and agitation rates. CONCLUSION: The best conditions for the studied process were determined in shake flasks as pH 7.0, 55 degrees C and high aeration levels. Also, the non-association between lipase production and cell growth was ascertained. The culture of this novel strain was successfully carried out in laboratory-scale bioreactors, thus proving its potential for further applications. (C) 2009 Society of Chemical Industry