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AIR2-CT93-1272
Cellulases and Hemicellulases from the Thermophilic Fungus Thermoascus aurantiacus |
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Contract No | AIR2-CT93-1272 |
| Total Cost | 1 411 430 | |
| EC Contribution | 850 000 | |
| Start Date | 01/10/1993 | |
| Duration | 36 months |
SUMMARY
This item is based on the final report of project 0321, which was subtitled Investigation of the Structure and Mechanism of Individual Enzymes and Study of the Organization of the Cellulase Complex and the second annual report from project 1271. The objective of the proposed work was to improve the feasibility of enzymatic conversion of cellulosic materials into sugars by gaining a better understanding of the factors that effect the efficiency of conversion by the enzymes responsible. The released sugars can be used as a carbon source for fermentations generating chemicals, pharmaceuticals and fuels, as well as in modification of animal feed. Such plant cell wall degrading enzymes also find applications in fibre processing, vegetable oil extraction, flavour release, textiles, detergent and chemicals. The main problems with current commercial enzymes relate to heat-stability, activity and pH profile. In both projects reported here thermophilic (heat loving) organisms are used since these provide a source of more stable enzymes. However, the approaches differ, reflecting differences between the bacterial system (in which the enzymes are organised into a complex known as the cellulosome) and the fungal system in which a wide range of enzymes are released into the growth medium.
The primary objective is to obtain high yields of stable and efficient enzymes from a thermophilic fungus, Thermoascus aurantiacus, which produces a complete cellulase and hemicellulase enzyme system, for use in valorization of agricultural wastes of agronomic importance from colder (wheat straw) and warmer (sorghum bagasse) regions of the Community. Changes in policy concerning wheat straw burning combined with an increasing interest in sweet sorghum as a non-food crop will result in millions of tonnes of such residues becoming available. Biological treatment will yield sugars, chemicals, environmentally friendly paper pulp, peat substitutes and organic fertilizers. In a wider context the cellulolytic enzymes have applications in depolymerization of wastes from the agro-food industries and in the food industry for example in preparation of instant coffee, natural flavours and colours, and cleaning of industrial filters. Previous work on bacterial and fungal systems has established mechanisms, and exposed the limitations of the commercially available enzymes. This is the first integrated project aimed at overcoming deficiencies in enzyme yield, stability and specific activity using a thermophilic fungus, in this case T. aurantiacus.
This work will produce enzymes to be used at or above 70ºC in industrial processes. Although these enzymes are potentially suited for commercial use, their yield and efficiency require improvement.
This will be done by protein engineering and cloning into T. reesei, whilst strain improvement of T. aurantiacus will also be attempted using UV and chemical mutagenesis. Mutants resistant to catabolite repression will be selected. Individual enzymes will be purified and characterized using novel substrates and physical techniques including crystallography. Based on their structure-function relationships, research will focus on cloning and modifying these enzymes in order to increase their yield and catalytic efficiency in collaboration with an industrial partner. Cellulase and hemicellulase production by wild and mutant strains will be optimized at pilot scale and used in trials for pulping and saccharification.
Contacts
Coordinator
EC Scientific Officer
Participant
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