Identification and characterization of recombinant glycoside hydrolases recovered from metagenomes for the application in biorefineries

The aim of this study was to identify and characterize novel thermoactive and thermostable glycoside hydrolases for the degradation of lignocellulosic biomass. For bioethanol production, lignocellulose is decomposed mostly hydrothermally resulting in hemicellulosic, cellulosic and lignin-containing fractions. The goal of this work was to identify novel genes coding for enzymes for the degradation of the cellulosic fraction. Since biorefineries nowadays run at temperatures of approximatley 50 °C, a further increase of the temperature could have a positive effect on time and processing rate. Thus, cellulase-encoding genes should be mainly identified from metagenomes derived from habitats harboring thermophilic and hyperthermophilic microorganisms. Function-driven screenings as well as sequencedriven approaches were employed to investigate the entirety of genetic information present in an environmental sample, such as hot cores of compost heaps (Germany) and hot springs (Azores, Portugal). Requirements for application of enzymes in biorefinery processes are high activity and stability under harsh conditions and high tolerance towards reaction products as well as ethanol. Novel enzymes are suitable candidates when they meet these demands and can accordingly contribute to an optimization of bioethanol production.