Biofuel enzymes are hot stuff

Catalysis plays an important role in many industrial processes, speeding up the rate of a chemical reaction by lowering the energy required for the reaction to take place. Enzymes are a promising green alternative to synthetic catalysts, yet very few are produced industrially. Finding or generating enzymes that are stable at the very high temperatures required would have wide-ranging benefits.

The search for heat-resistant enzymes provided the impetus for the EU-funded project HOTZYME (Systematic screening for novel hydrolases from hot environments). Scientists used state-of-the-art metagenomics screening methods to predict the protein function of the collective genomes of microbes in their natural environments. The gene pool of interest came from microbes living in hot terrestrial environments that were explored for hydrolases. These enzymes catalyse hydrolysis, the splitting of a molecule through the addition of a hydrogen and hydroxyl groups.

Project partners found promising enzymatic degradation activity in some isolates recovered from hot environments. These included the isolation of a Thermus strain capable of degrading xylan at high temperatures and a thermoanaerobacter that showed resistance to epoxide. Two additional metagenomes were obtained from environmental sampling.

Other achievements include the development of protein classifiers and a tracking system for samples, strains and libraries. Scientists developed different screening methods for rapid screening of lactonase and hydrolase enzymes. These enzymes were cloned and characterised for their substrate specificity and functional activity. In addition, eight expression libraries were constructed and subjected to functional screening for novel hydrolases.

The consortium identified a novel cellulose that can be applied to biomass-based bioethanol production and the paper pulp industry. It offers significant environmental benefits by substituting fossil fuels, thereby reducing the increase in atmospheric greenhouse gases (particularly carbon dioxide) and improving air quality. The hyperthermostable protease identified from the novel Thermococcus genome shows significant potential in washing powder development and food processing for animals.

HOTZYME provided information about the existence of more efficient enzymes at high temperature than those produced by fungi to carry out cellulose hydrolysis. Furthermore, the huge biodiversity obtained by the consortium constitutes a rich reservoir for further exploitation.