abstract
Industrially produced bleached recycled pulp (R) comprising essentially hardwood fibres was subjected to enzymatic treatment with endo-xylanase from Thermomyces lanuginosus with or without ultra-high hydrostatic pressure (UHP) pre-treatment at 300-600 MPa for 10 min. The kinetics and the extent of enzymatic hydrolysis after UHP pre-treatment under different conditions have been evaluated by released reducing sugars and the analysis of neutral sugars in pulps, respectively. The changes in surface chemical composition of pulps were assessed by UV-vis diffuse reflectance spectroscopy. UHP-pre-treated R under optimal conditions (400 MPa), with or without posterior enzymatic treatment, was used for the production of handsheets and evaluation of its mechanical properties. It was suggested that enzymatic modification improves significantly the papermaking properties of recycled pulp. These improvements were related with selective removal of xylan bound to impurities and to aggregated cellulose fibrils on the fibre surface, thus favouring the ensuing swelling and inter-fibre bonding in paper. UHP pre-treatment and posterior enzymatic treatment revealed a synergetic effect on the mechanical properties of recycled pulp. This fact was assigned to enhanced accessibility of fibres towards xylanase and by forced hydration and favourable rearrangement of cellulosic fibrils in fibres after UHP pre-treatment. The increase of basic strength properties after UHP-promoted xylanase treatment was up to 30 % being the most pronounced for the tensile strength and the burst resistance.
keywords
WASTE PAPER; ENZYMATIC DEINKING; CELLULOSIC FIBERS; ENZYMES
subject category
Biotechnology & Applied Microbiology
authors
Salgueiro, AM; Evtuguin, DV; Saraiva, JA; Almeida, F
our authors
Ana Margarida Martins Salgueiro Carta
PhD Student
Dmitry Evtyugin
Associate Professor with Aggregationacknowledgements
The authors acknowledge the Fundacao para a Ciencia e Tecnologia (FCT) and Renova FPA S.A. for PhD grant SFRH/BDE/51855/2012. This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT Ref. UID/CTM/50011/2013), and financed by ERDF Funds through the Operational Competitiveness Programme COMPETE, in the frame of project FCOMP-01-0124-FEDER-30203. The authors would also like to acknowledge FCT/MEC for the financial support to QOPNA Research Unit (FCT UID/QUI/00062/2013), through national funds and where applicable co-financed by the FEDER, within the PT2020 Partnership Agreement. Finally, the authors thank Renova FPA S.A. for supplying the materials and technical facilities.