Reducing the stringency of chemical and thermal treatments of plant biomass for bio-fuel production by developing more efficient enzyme mixtures.

Plant biomass is a major substrate for many industries, such as food and feed, paper and pulp, and bio-fuel. Fungal enzymes have a long history of use in plant biomass degradation. However, currently available commercial fungal enzyme preparations that are suitable for many applications, are not sufficiently efficient for bio-fuel pre-treatments. For cost-effective bio-fuel production complete hydrolysis is required, while in many other applications only part of the biomass needs to be hydrolysed. In bio-fuel production steam-explosion or strong acid treatments are used alone or followed by enzymatic hydrolysis (hybrid process). These treatments have either high energy requirements or generate large amounts of waste. Development of better enzyme mixtures would enable a reduction of the stringency of these treatments. Through other collaborations we already have access to a range of chemically and thermally pre-treated substrates with different stringencies. In this project we want to use those substrates to test the novel enzyme mixtures we develop. This will generate knowledge to design a more efficient hybrid process with reduced stringency of the chemical/thermal pre-treatment by employing better enzyme mixtures. We will develop novel enzyme mixtures using the two major industrial fungi: Aspergillus niger and Trichoderma reesei. Analysis of their genomes revealed that both contain a broad, but different, set of polysaccharide degrading enzymes. However, many of these enzymes are not or only lowly produced by wild-type strains under standard production conditions. We will modify the production of these enzymes by genetic engineering to generate mixtures that contain a broader range and higher level of enzyme activities. We will then test the novel mixtures of these two fungi in combination on the pre-treated substrates to analyse to which level the stringency of the thermal/chemical pre-treatment can be reduced. This will result in a more environmentally friendly hybrid process for biomass pre-treatment.