Microbial xylanolytic systems

One of natures most important biological processes is the degradation of lignocellulosic materials to carbon dioxide, water and humic substances. This implies possibilities to use biotechnology in the pulp and paper industry and consequently, the use of microorganisms and their enzymes to replace or supplement chemical methods is gaining interest. This chapter describes the structure of wood and the main wood components, cellulose, hemicelluloses and lignins. The enzyme and enzyme mechanisms used by fungi and bacteria to modify and degrade these components are described in detail. Techniques for how to assay for these enzyme activities are also described. The possibilities for biotechnology in the pulp and paper industry and other fiber utilizing industries based on these enzymes are discussed.

Microorganisms and enzymes involved in the degradation of plant fiber cell walls

Production of fungal xylanases

Status and barriers of advanced biofuel technologies: A review

The lignin degradation abilities of wildtype, a phenol oxidase-less mutant and a phenol oxidase-positive revertant of Sporotrichum pulverulentum were compared to determine if phenol oxidase activity is necessary for lignin degradation by white-rot fungi. The phenol oxidase-less mutant was unable to degrade kraft lignin or wood. The phenol oxidase-positive revertant, however, regained the ability of the wildtype to degrade kraft lignin and all of the major components of wood. It was found that kraft lignin and lignin-related phenols decreased cellulase and xylanase production by the phenol oxidase-less mutant. Addition of highly purified laccase increased the production of endo-1,4-β-glucanase in the phenol oxidase-less mutant in the presence of vanillic acid and kraft lignin. After addition of laccase to kraft lignin agar plates, the phenol oxidase-less mutant could degrade kraft lignin.

The importance of phenol oxidase activity in lignin degradation by the white-rot fungus Sporotrichum pulverulentum

By screening for mutants which could not degrade cellulose, several cellulase-less mutants were isolated from the wood-rotting fungus Polyporus adustus. Most of the mutants lacked mannanase and xylanase as well. In wild type, the level of cellulase, mannanase, and xylanase was higher when the fungus was grown in a medium containing cellulose than in a medium lacking cellulose. It is proposed that in P. adustus, the induction of this group of enzymes is under the control of a single common regulator gene.

Pleiotropic mutants of the wood-rotting fungus Polyporus adustus lacking cellulase, mannanase, and xylanase

A method of producing cellulose pulp from a starting material containing lignin and cellulose, particularly from wood, wherein the starting material is treated with an organism capable of forming lignin-decomposing enzymes under conditions such that the lignin is substantially decomposed without appreciably affecting the cellulose

Method for producing cellulose pulp

Vanillic and syringic acid metabolism in the white-rot fungus Sporotrichum pulverulentum Nov. at varied concentrations of glucose and nitrogen was investigated. Vanillic acid metabolism was stimulated by 20.6 mM nitrogen and repressed by 1% glucose when measured as formation of 14CO2 from 14C-labelled vanillic acids. Metabolism of 14C-methoxy labelled syringic acid was initially most rapid in the presence of 0.25% glucose and 20.6 mM nitrogen but total 14CO2 evolution was higher in cultures containing 1% glucose.

Karl-Erik Eriksson

Papers

Pleiotropic mutants of the wood-rotting fungus Polyporus adustus lacking cellulase, mannanase, and xylanase

Method for producing cellulose pulp

Physiological requirements for degradation of lignin and lignin related substances by Sporotrichum pulverulentum