The aim is to use purified components of the cellulase and the hemicellulase systems of bacteria and fungi, produced commercially and in the laboratory, in order to identify those enzymes which effect desirable changes in the properties of the waste paper pulp. These changes include improved drainage, better de-inking properties and improved bleaching behaviour.
The project is to investigate possibilities of increasing the use of recycled waste paper for sanitary products and for printing paper, if further special treatments of waster pulps besides those of deinking and deashing can be used.
The recycling of pulps is limited to a few times because pulp fibres loose their flexibility after repeated use, resulting in a decreased efficiency of fibre fibre bonding during papermaking and an increase in Schopper-Riegler fineness. These undesirable effects lead to decreased efficiency of paper machines, such as reduced dewatering properties and high steam consumption. With repeated use the amounts of impurities such as ink colours, adhesives, filling agents and paper auxiliary agents increase.
With minimal weight loss of waster pulps certain cellulolytic and/or hemicellulolytic enzymes can specially hydrolyse the bonds and create new surfaces on pulp fibre for effective fibre fibre bonding. The whole enzyme spectra of cellulolytic microorganisms is not needed, because these are adapted for total hydrolysis. Only certain enzymes are selected in order to prevent damage of pulp fibres but to ensure the desired effects.
Enzyme addition for improvement of pulp quality is possible during the disintegration procedure (before de-inking) and after de-inking. Because enzymes may be affected by the de-inking chemicals (detergents, complexing agents, water glass, sodium hydroxide, peroxide) alternative enzyme addition is possible after de-inking. Both possibilities of enzyme involvement for upgrading of recycled pulp will be investigated.
The approach to the project work is divided into the following steps:
Collection of high and low quality pulps from 4 EC countries.
Physical and chemical characterization of different pulps.
Drainage performance test of recycled classified pulps after treatment with existing crude enzyme preparations.
Strength properties and chemical characterization from pulps with positive drainage performance.
Drainage performance test of recycled classified pulps with pure enzymes.
Strength properties of pulps treated with pure enzymes and characterisation of the solubles.
Fractionation of recycled classified pulps according to fibre length.
Chemical characterization of the fractions.
Provision of new substrates for screening of commercial enzyme products and new organisms: fine fraction from recycled pulp, differently substituted xylan fragments, native xylan and mannan, galectan.
Screening of commercial enzyme preparations for cellulases, mannanases and xylanases.
Screening of new organisms, particularly for accessory enzymes.
Production of enzymes.
Purification and characterization of enzymes.
Application of pure enzymes for upgrading of recycled pulps.
Large scale trials.
Funding SchemeCSC - Cost-sharing contracts
6703 HD Wageningen
AB2 9SB Aberdeen