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Continous biopretreatment of cellulosic fibers

Deliverables

In this process a laccase enzyme is used in a pre-treatment. The direct bleaching effect in this pre-treatment is insufficient. It appeared that due to this substrate modification in the pre-treatment, the obtained whiteness level after a subsequent peroxide bleaching process is improved by 4 to 6 degrees. This is a benefit for certain fabric applications, especially when dealing with light shades. The pre-treatment method can also be used for reduction of the required peroxide concentration to reach the same level of whiteness. It appeared that in this way the amount of peroxide could be reduced by approximately 50%.
After screening certain libraries (of mo harvested around textile mills), 2 pectinase systems have been identified. The first system is a pectate lyase from B. pumilus. This alkaline enzyme showed a good bioscouring performance under alkaline conditions, a benefit when integrating the process with the desizing process as performed at those pH levels. This enzyme shows also a good temperature stability, better than all commercial available ones. This is of importance in the developed integrated continuous process where a high operating temperature is used in the first stage. The second system are two different polygalacturonases frm S. rolfsii. These enzymes are active under more acidic conditions (around pH 5) and show also reasonable performance. They can be used when acidic operating enzymes are required when processes are integrated. This may be of importance since it is not yet established with which enzyme the biobleaching process will run. The present identified enzymes are all operating in a more acidic environment. The PG�s are less temperature stable than the lyase. Therefore the lyase is the preferred enzyme system.
The new developed scouring process has been integrated with the existing enzyme-based desizing process. For this integration, the continuous bioscouring process had to be adapted in that way that enzyme incubation has to be build in two phases. One phase should be done at high temperature whereas the other is operated at moderate temperature. A second essential element in this process is the incorporation of a method to enhance mass transport. With these adaptations, a total process duration of 3-5 minutes including the subsequent rinsing process is sufficient to obtain a fabric which can be dyed and finished with conventional methods without consequences. This means a substantial time reduction of these processes, which brings substantial benefits in terms of time efficiency and logistics, energy and water reduction, and also an environment improvement in the mills since the irritating hydroxide smell is eliminated.
A new bioscouring process has been developed for cotton fabrics based on the use of pectinase technology. For batch mode of operation, the process can be done at moderate temperatures for somewhat longer time periods followed by a rinsing process at higher temperature. This high temperature is required for efficient removal of the destabilised pectin, together with the hydrophobic substances. For continuous operating when dealing with fabric speed of 60 - 100m/min, a high temperature pre-treatment is required to obtain a fast process wherein the amount of fabric hold-up in the process is kept at minimum. A total duration of 3-5 minutes including the subsequent rinsing process is sufficient to obtain a fabric, which can be dyed and finished with conventional methods without consequences.
After screening certain libraries (of mo harvested around textile mills), a laccase system from T. hirsuta has been identified. This enzyme can be used for biobleaching. However, the present developed processes for direct biobleaching results in insufficient bleaching result. Modification of the process is required. However, the enzyme can be used in 2 alternative bleaching processes in which: - The amount of required peroxide can be reduced or - On-top-of whiteness can be obtained after enzymatic treatment followed by peroxide bleaching.

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