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Featured researches published by Per Stenius.


Colloids and Surfaces B: Biointerfaces | 2011

Adsorption of bacteria and polycations on model surfaces of cellulose, hemicellulose and wood extractives studied by QCM-D

Taina Leino; Mari Raulio; Mirja Salkinoja-Salonen; Per Stenius; Janne Laine

Quartz crystal microbalance with dissipation monitoring (QCM-D), atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) were used as the tools to study the adsorption of bacteria onto surfaces of silica and polystyrene coated with materials related to papermaking. Cationic polyelectrolytes used as fixatives and retention aids in paper industry were found to promote irreversible adsorption of the ubiquitous white water bacterium, Pseudoxanthomonas taiwanensis, onto model surfaces of cellulose (pH 8). The high charged low molecular weight polyelectrolyte, poly(diallyldimethyl) ammonium chloride (pDADMAC) adsorbed to silica surface as a flat and rigid layer, whereas the low charged cationic polyacryl amide (C-PAM) of high molecular weight adsorbed as a thick and loose layer. AFM images showed that the polyelectrolytes accumulated as layers around each bacterial cell. In the presence of wood hemicellulose (O-acetyl-galactoglucomannan) the bacteria adsorbed massively, as large, tightly packed rafts (up to 0.05mm in size) onto the polystyrene crystal surface coated with wood extractives (pH 4.7). AFM and FESEM micrographs also showed large naked areas (with no bacteria) in between the bacterial rafts on the crystal surface. In this case, QCM-D only incompletely responded to the massiveness of the bacterial adsorption. The results indicate that cationic polymers can be used to increase the retention of bacteria from the process water onto the fibre web and that, depending on the balance between hemicelluloses and wood extractives and pH of the process waters, bacteria can be drawn from process waters onto surfaces.


Journal of Industrial Microbiology & Biotechnology | 2012

Pseudoxanthomonas bacteria that drive deposit formation of wood extractives can be flocculated by cationic polyelectrolytes

Taina Leino; Mari Raulio; Per Stenius; Janne Laine; Mirja Salkinoja-Salonen

Runnability problems caused by suspended bacteria in water using industries, have, in contrast to biofilms, received little attention. We describe here that Pseudoxanthomonas taiwanensis, a wide-spread and abundant bacterium in paper machine water circuits, aggregated dispersions of wood extractives (pitch) and resin acid, under conditions prevailing in machine water circuits (109xa0cfuxa0ml−1, pH 8, 45°C). The aggregates were large enough (up to 50xa0μm) so that they could be expected to clog wires and felts and to reduce dewatering of the fiber web. The Pseudoxanthomonas bacteria were negatively charged over a pH range of 3.2–10. Cationic polyelectrolytes of the types used as retention aids or fixatives to flocculate anionic trash in paper machines were effective in flocculating the Pseudoxanthomonas bacteria. The polyelectrolyte most effective for this purpose was of high molecular weight (7–8xa0×xa0106xa0gxa0mol−1) and low charge density (1xa0meqxa0g−1), whereas polyelectrolytes that effectively zeroed the electrophoretic mobility (i.e., neutralized the negative charge) of the bacterium were less effective in flocculating the bacteria. Based on the results, we concluded that the polyelectrolytes functioning by bridging mechanism, rather than by neutralization of the negative charge, may be useful as tools for reducing harmful deposits resulting from interaction of bacteria with wood extractives in warm water industry.


PAPERI JA PUU-PAPER AND TIMBER | 1997

The effect of charge on the fibre and paper properties of bleached industrial kraft pulps

Janne Laine; Per Stenius


Archive | 2003

The effect of polyelectrolyte adsorption on the strength properties of paper made from mixtures of mechanical and chemical pulps

Krista Koljonen; Anna Vainio; Eero Hiltunen; Janne Laine; Per Stenius


Archive | 2003

The effect of cationic polyelectrolytes on surface forces and structure of cellulose-polyelectrolyte interface

Jani Salmi; Terhi Saarinen; Janne Laine; Per Stenius


Archive | 2007

Internal sizing of paper

Janne Laine; Per Stenius


Archive | 2005

Method for topochemical modification of cotton fibres

Lidija Fras; Karin Stana-Kleinschek; Janne Laine; Per Stenius; Volker Ribitsch


Archive | 2002

Adsorption of lignin-cationic starch complexes on the cellulose fibres

Natalia Maximova; Janne Laine; Per Stenius


Contact Angle, Wettability and Adhesion | 2008

Adhesion of hydrophobizing agents: A comparison of values determined by contact angle and the JKR approaches.In

Juha Lindfors; Janne Laine; Per Stenius


Archive | 2006

Adhesion of hydrophobing agents to wet and dry surfaces

Juha Lindfors; Janne Laine; Per Stenius

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Janne Laine

Helsinki University of Technology

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Juha Lindfors

Helsinki University of Technology

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Natalia Maximova

Helsinki University of Technology

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Susanna Ylisuvanto

Helsinki University of Technology

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Timo Kallio

Helsinki University of Technology

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Mari Raulio

University of Helsinki

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