scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Biopulping : an overview of developments in an environmentally safe paper-making technology

01 Mar 1994-Fems Microbiology Reviews (Blackwell Publishing Ltd)-Vol. 13, pp 351-364
TL;DR: Information obtained by immunoelectron microscopy and differential staining led to the conclusion that the biopulping effect obtained after 2 weeks of incubation cannot be explained by the direct action of enzymes on lignin or polysaccharides, and a low molecular mass agent is considered to be responsible for the biopsies.
Abstract: Treatment of wood chips with lignin-degrading fungi prior to pulping has been shown to have great potential for mechanical as well as chemical pulping on a laboratory scale. Ceriporiopsis subvermispora, when grown on aspen or loblolly pine for 4 weeks, was found to be superior to other fungi. On aspen there was an energy savings of 47%, and an increase in burst and tear indices of 22% and 119%, respectively. With loblolly pine, energy savings amounted to 37%, while burst and tear indices increased by 41% and 54%, respectively. The weight loss was only 6%, but a decrease in optical properties had to be accepted. After sulfite cooking of wood chips pretreated for 2 weeks, the Kappa number decreased by 30% with hard- and softwood. Tensile and tear indices decreased by only 10%, while the brightness of unbleached pulp increased by 4% with birch. Information obtained by immunoelectron microscopy and differential staining led to the conclusion that the biopulping effect obtained after 2 weeks of incubation cannot be explained by the direct action of enzymes on lignin or polysaccharides. Instead, a low molecular mass agent is considered to be responsible for the biopulping effect. These results have changed the aims of biopulping from an emphasis on removing the bulk of lignin to an emphasis on a short-term process, lasting 2 weeks and yielding a low mass loss. Data on these kinetics of fungal development and the degree of asepsis will help to scale-up the process. An advanced chip pile is assumed to be the most feasible process design, rather than a controlled enclosed reactor.
Citations
More filters
Journal ArticleDOI
TL;DR: Many lines of evidence suggest that xylanases operate via a double displacement mechanism in which the anomeric configuration is retained, although some of the enzymes catalyze single displacement reactions with inversion of configuration.
Abstract: Hemicellulolytic microorganisms play a significant role in nature by recycling hemicellulose, one of the main components of plant polysaccharides. Xylanases (EC 3.2.1.8) catalyze the hydrolysis of xylan, the major constituent of hemicellulose. The use of these enzymes could greatly improve the overall economics of processing lignocellulosic materials for the generation of liquid fuels and chemicals. Recently cellulase-free xylanases have received great attention in the development of environmentally friendly technologies in the paper and pulp industry. In microorganisms that produce xylanases low molecular mass fragments of xylan and their positional isomers play a key role in regulating its biosynthesis. Xylanase and cellulase production appear to be regulated separately, although the pleiotropy of mutations, which causes the elimination of both genes, suggests some linkage in the synthesis of the two enzymes. Xylanases are found in a cornucopia of organisms and the genes encoding them have been cloned in homologous and heterologous hosts with the objectives of overproducing the enzyme and altering its properties to suit commercial applications. Sequence analyses of xylanases have revealed distinct catalytic and cellulose binding domains, with a separate non-catalytic domain that has been reported to confer enhanced thermostability in some xylanases. Analyses of three-dimensional structures and the properties of mutants have revealed the involvement of specific tyrosine and tryptophan residues in the substrate binding site and of glutamate and aspartate residues in the catalytic mechanism. Many lines of evidence suggest that xylanases operate via a double displacement mechanism in which the anomeric configuration is retained, although some of the enzymes catalyze single displacement reactions with inversion of configuration. Based on a dendrogram obtained from amino acid sequence similarities the evolutionary relationship between xylanases is assessed. In addition the properties of xylanases from extremophilic organisms have been evaluated in terms of biotechnological applications.

922 citations

Journal ArticleDOI
TL;DR: The general applicability of the laccase-mediator-system (Lignozym®-process) will be given by a comparison of results obtained with pulps from different sources of wood and from several pulping processes, especially regarding effects on pulps, kinetic data and specificity of the reaction.

679 citations

Journal ArticleDOI
TL;DR: Effluent decolorization may not be limited by the small molecule metabolites which are not produced in large amount by fungus in most industrial effluents, and implies that the laccase-substrate dyes in an industrial effluent can promote the decolorized of those nonsubstrate dye.

500 citations

Journal ArticleDOI
TL;DR: In this paper, the authors summarize the current status of the 2nd generation biofuel technologies including bioethanol from lignocellulosic materials and biodiesel from microalgae.

388 citations

OtherDOI
TL;DR: This paper focuses on the characterization of the phytochemical properties of lignin and its application in the context of 14C-Labeled Lignins.
Abstract: Introduction Historical Outline Bacteria and Microfungi Actinomycetes Other Bacteria Soft-Rot Fungi and Other Microfungi Brown-Rot Basidiomycetes White-Rot Basidiomycetes Mineralization of 14C-Labeled Lignins Ligninolytic Enzymes Catabolism of Primary Degradation Products Outlook and Perspectives Patents Keywords: lignin; wood; lignocellulose; white-rot fungi; brown-rot fungi; soft-rot fungi; actinomycetes; lignin peroxidase; manganese peroxidase; laccase; molecular biology; radicals; mediators; manganese; veratryl alcohol; oxalate; vanillic acid

376 citations

References
More filters
Journal ArticleDOI
TL;DR: This paper presents a meta-analyses of IGNIN as a stimulus and its applications in medicine and physiology, and discusses the role that IGNIN plays in the development of disease and its role in medicine.
Abstract: INTRODUCTION ....................................................................................................................................... 465 LIGNIN AS A SUBSTRATE ............................................................................................................................... 466 MICROBIOLOGY OF LIGNIN BIODEGRADATI ON ........................................................................... 468 Anaerobic Conditions ............................................................................................................................... 469 Aerobic Conditions ................................................................................................................................... 469 LIGNIN DEGRADATION BY WHITEROT FUNGI ............................................................................. 471 Physiology .......................................................................................................................................................... 472 Biochemistry ............................................................................................................................................ 475 Genetics ..............................................................................................................................................................486 Molecular Biology .................................................................................................................................... 489 CONCLUSIONS AND RECOMMENDATIONS ..................................................................................... 491 ENZYMATIC “COMBUSTION” ........................................................................................................................ 493

2,556 citations

Journal ArticleDOI
TL;DR: Laccase is capable of oxidizing both phenolic and non‐phenolic moieties of lignin but that the latter is dependent on the co‐presence of primary laccase substrates.

1,296 citations

Journal ArticleDOI
TL;DR: Results indicate that the enzyme oxidizes Mn(II) to Mn( III) and that the Mn(III) complexed to lactate or other alpha-hydroxy acids acts as an obligatory oxidation intermediate in the oxidation of various dyes and lignin model compounds.

460 citations

Journal ArticleDOI
TL;DR: In this paper, a decomposition pathway for decay by some fungi in the Basidiomycotina, such as those that cause brown rots, involves the degradation of all wood carbohydrates, including crystalline cellulose.
Abstract: Wood decay fungi are unique because of their capacity to decompose lignified cell walls. A few species are of special interest because they can selectively remove lignin from wood without extensive cellulose degradation. Lignin is a complex, heterogeneous phenylpropanoid structural polymer that occurs throughout the cell wall (71, 112). Spatially, lignin is intimately interspersed with hemicelluloses forming a matrix that surrounds cellulose microfibrils (67, 75), and provides a formidable physical and chemical barrier to biodeg­ radative systems. Although most saprophytic fungi produce some degradative enzymes, such as cellulases, xylanases, mannanases and others, these en­ zymes do not permeate and degrade effectively woody substrates unless lignin is unbound, modified, or removed. Investigations of decomposition processes in forest ecosystems have usual­ ly considered lignin to be the most recalcitrant component and the last degraded (l0, 88). The decomposition pathway for decay by some fungi in the Basidiomycotina, such as those that cause brown rots, involves the degradation of all wood carbohydrates, including crystalline cellulose. A residual lignin matrix, consisting of chemically modified lignin, is left to be gradually converted to humic substances by long-term processes involving other microbes (38, 41, 106). However, this is not always the sequence of events. Fungi in the Basidiomycotina that cause white rots of wood may simultaneously degrade lignin along with all cell wall carbohydrates, or lignin

412 citations

Journal ArticleDOI
TL;DR: Results suggest that manganese peroxidase plays a significant role in the depolymerization of lignin by Phanerochaete chrysosporium.

315 citations