Cloning, expression and characterization of novel thermostable plant cell wall degrading enzymes

Numerous thermostable enzymes from extremophiles are described in literature and their benefits for industry are indisputable (Niehaus et al. 1999; Bertoldo et al. 2004; Haki and Rakshit 2003). The aim of the present study was to identify and characterize novel thermostable enzymes for the degradation of plant matter. Samples from two different environments where collected for the construction of metagenomic libraries. Compost was chosen since it is expected to contain a great diversity of microorganisms able to degrade plant derived matter (Gautam et al. 2012) and a volcanic hot spring for its potential of harboring highly thermophilic bacteria (Antranikian et al. 2005). As traditional cultivation-based strategies often fail to represent the diversity found in nature (Rondon et al. 2000; Entcheva et al. 2001) the environmental samples were enriched on complex substrates followed by the construction of metagenomic libraries. The novel enzymes were identified by activity based screening of the recombinant clone library. With the aim of increasing the thermal stability of the novel enzymes the effect of pressure was tested. It has been observed that pressure can have a stabilizing effect on enzymes both from mesophilic and thermophilic organisms (Hei and Clark 1994; Athès et al. 1997). However, to date, there are not many enzymes which have been investigated with regard to their response to pressure and this might be an interesting characteristic for industrial application.