Biofuels are originated from at least 80 percent of fuels from renewable materials. These renewable materials, named biomass, are fermented or degraded to obtain biofuels. This source of energy was originally used to run engines before it was replaced by petroleum as the most logical fuel source. However, the rarefaction of petroleum and the recent technological improvements in production of biofuels give new economical opportunities for these energy sources. The investment in biofuels increased by 670% between 2005 and 2006 with about one third of the total investment going to biodiesel producers (http://www.businessweek.com/).
Initially, energy crops such as jatropha, swichgrass, hybrid poplar and willow were the main source of biomass for biofuel production. Currently, the second generation of bioethanol, biodiesel, biohydrogen and methane is obtained from wastes of lignocellulose biomass (Rubin, 2008). This type of biomass can be divided into four groups: agricultural residues, dedicated energy crops, wood residues (sawmill and paper mill discards) and municipal paper waste. Each group presents advantages and drawbacks for biofuels synthesis with remaining poor yields and high production costs. Further improvements in bioconversion of lignocellulosic biomass into biofuels are possible and MetGen Oy proposes a technology platform to increase these yields with reduced costs.
Lignocellulose biomass is the largest renewable reservoir of fermentable carbohydrates (Mtui and Nakamura, 2005). It is composed of cellulose and hemicellulose embedded in lignin. Cellulose molecule is an unbranched polymer of 1000 to 1 million D-glucose units, linked together with beta-1,4 glycosidic bonds (Xiang et al., 2003). In contrast, hemicellulose is a branched polymer containing shorter chains (500 to 3000 sugar units) of different sugars such as xylose, mannose, galactose, rhamnose, and arabinose (Gupta and Lee, 2010). Lignin is a heterogene biopolymer without defined primary structure. It represents 25% of the dry mass of wood and is tightly enclosing cellulose and hemicellulose in the core of the wood (Harkin, 1967).
The conversion of cellulose into glucose is a well-established enzymatic reaction consisting of two steps. First, beta-1,4 glucanase breaks the glucosidic linkage to cellobiose. Second, this glucose dimer is broken into single glucose molecules by beta-glucosidase (Tsai et al., 2009). Hemicellulose originated ethanol requires additional enzymatic reactions to convert 5-carbon sugars into fermentable material (Réczey et al. 1998). All these steps from cellulose and hemicellulose to glucose and from glucose to ethanol are limited by the efficiency of the enzymes performing the reactions but also by the accessibility of the enzymes to their substrates. This interaction is physically limited by lignin which creates tight meshwork enclosing cellulose and hemicelluloses. Thus, lignin strongly prevents the conversion yield of polysaccharides to bioethanol (Pan 2008). At MetGen Oy, we generate delignifying enzymes which disrupt the lignin network and thereby facilitate the interaction between enzymes and polysaccharides. Furthermore, lignin can be used as a renewable energy source (Ragauskas et al. 2006). The technology platform used at MetGen Oy evolves enzymes to improve their performances to fit industrial needs and consequently increase the overall yield of bioethanol production from lignocellulosic biomass.
In summary, MetGen Oy is willing to develop projects together with its costumers to improve the industrial properties of enzymes involved in the whole process of biofuels production for lignocellulosic biomass.
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