Project leader: Jonas Brändström

 Microbial degradation of pulp wood

Ultrastructural studies of post harvest changes in wood

Aim: This project strives to elucidate post harvest pre process mechanisms that negatively affect the quality properties of the wood raw material intended for pulp and paper production. The project focuses mainly on mechanisms causing discoloration of wood.

Background: The properties of raw wood raw material (i.e. the native trees) are known to significantly affect the final properties of the pulp and paper produced, however product quality is also affected by the treatment of the raw material after felling. It is often necessary to store wood intended for industrial use in sawmills and pulp mills for shorter- or longer periods. During this storage period, the logs are often water sprinkled during the warm season in order to prevent quality losses due to insect infestations and by staining fungi etc. Sprinkling is an efficient method to prevent losses related to the drying-out of logs. One drawback with water sprinkling and wet storage of wood in general, is the discolouration of the outer part of the xylem caused by the inward movement of substances from the bark. Water sprinkling and wet storage is also known to facilitate bacterial degradation of pit membranes in the wood. Several substances (e.g. tannins) in the bark are thought to be involved in the discolouration of stored wood.

Project description: Wood stored under different conditions is studied using light- and scanning electron microscopy (LM and SEM) in order to study how microorganisms deteriorate the wood and facilitate the penetration of substances from the bark into the wood. Fluorescence microscopy is used to study how these discolouring substances from the bark are located within the wood structure and how different storage systems affect their localisation. The ultrastructural cause for differences in bark substance allocation is studied using fluorescence microscopy in combination with the use of specific enzymes and pre-treatment systems. Scanning electron microscopy is used to reveal how these enzymes have affected the wood structure. Possible enzymatic and abiotic systems for removing discoloured substances are also being tested.  

Brändström, J. & E. Persson. 2003. Spatial distribution of fluorescent substances in stored Norway spruce pulpwood. Submitted to Paperi ja Puu.

Project group:
Jonas Brändström, SLU
Erik Persson, Holmen Paper,
Lars Hildén, Uppsala Univ.
Jing Zhang, Uppsala Univ.
Gunnar Johansson, Uppsala Univ.

For more information contact:
Jonas Brändström,
or Erik Persson,