Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS

FP5

TIME Streszczenie raportu

Project ID: ENK6-CT-2002-00604
Źródło dofinansowania: FP5-EESD
Kraj: Finland

A novel process concept based on enzymes acting at high-temperature and high consistency

The process concepts studied in the project aimed at increasing the ethanol concentration (by high consistency hydrolysis and fermentation technology) and yield (by using tolerant yeast strains. The specific objective was to develop integrated high temperature (HT) conversion technology based on improved thermophilic enzymes and enhanced accessibility of the substrates. The proposed concept for high temperature and consistency hydrolysis technology involved a first stage prehydrolysis at high temperature, followed by a complete hydrolysis at lower temperature. The high number of cloned thermophilic enzymes during the project allowed, however, a more flexible approach for different process concepts.

Enzymes needed for both a prehydrolysis (liquefaction) stage and a complete hydrolysis of various pretreated raw materials were identified. The new optimised thermophilic enzyme mixtures were evaluated in high temperature hydrolysis experiments. Hydrolysis temperature could be increased with technical steam pre-treated raw materials by about 10 XC. Operation at high consistency was also demonstrated. The concept has been preliminarily proven in experiments leading to high concentration of ethanol (4V5 %). The project also aimed at reduced water use in fermentation (high consistency, higher concentration ethanol process) and focused at high hydrolysis and fermentation yield.

The results showed that a separate high temperature stage for liquefaction of the material at the start of the procedure can be feasible. A decrease of viscosity can be achieved using only endoglucanases. A more beneficial result may, however, be obtained, if a complete set of thermophilic hydrolytic enzymes is used already at the prehydrolysis stage. It was thus possible to replace a present commercial cellulase mixture in the first 24h stage of a two-step process with an artificial three component mixture of selected cellulase proteins with a high hydrolysis yield and without increasing the overall protein dosage. Thus, a high temperature prehydrolysis stage on spruce substrate using only selected cloned components of cellulase system could be carried out with at least comparable efficiency of total hydrolysis than with the present commercial mixtures.

For an efficient total hydrolysis, the requirements for the composition of enzyme mixtures depend strongly on the substrates and the process configuration selected. Thus for example, the amount of beta-glucosidase can be reduced in case SSF is used. The new optimised thermophilic enzyme mixtures were evaluated in high temperature hydrolysis experiments. Hydrolysis temperature could be increased with technical steam pre-treated raw materials by about 10 C when compared to the present state-of-art industrial enzyme products. Operation in high dry matter conditions was also demonstrated, although the reactor design and mixing should be further optimised for high viscose fibre suspensions. Clearly more efficient hydrolysis per assayed FPU unit or CBHI protein amount used was obtained. The results provide a promising basis to produce and formulate improved enzyme products. These products can have high temperature stability in process conditions in the range of 55-60 C (with present industrial products at 45-50 C) and clearly improved specific activity, essentially decreasing the protein dosage required for efficient hydrolysis of lignocellulosics.

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Liisa VIIKARI, (Research Professor)
Tel.: +358-207225140
Faks: +358-207227071
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