A deep gold mine metagenome as a source of novel Esterases

New sources of enzymes for biotechnological applications are continually being sought for. While diverse microbial ecosysyems have been demonstrated in the deep sub surfaces, deep mines provide easy access to these specialist communities. Therefore, the aim of this study was to assess a deep mine bio film as a source of novel esterase enzymes. Bio film was collected from the Beatrix Mine in South Africa, at a depth of 808 m. Assessment of the diversity revealed a group of previously uncultured bacteria and archaea. A metagenome library was screened for esterolytic activity, producing two esterolytic clones: a phospholipase patatin protein and an isochorismatase family protein. The isochorismatase family protein contained the catalytic Asp and Cys but not the Arg, which is considered as important for catalysis. The patatin showed 55% similarity to its closest relative; the patatin family protein from Plesiocystis pacifica. The expressed patatin displayed a preference for the C6 ester and was maximally active at pH 8 and 30°C. This study reported that screening of a relatively small metagenome library from the deep mine bio film provided two esterolytic clones, which differed from their known counterparts. This indicates that the deep mine ecosystems contain an untapped resource of novel and potentially useful enzymes which may have applications in chemical syntheses.