Aspergilli and lignocellulosics: enzymology and biotechnological applications.

Aspergilli are versatile ascomycetes that are able to transform at a rapid rate a wide spectrum of lignin-related aromatic compounds. While it is clear that these fungi can degrade phenolic and polysaccharide components from lignocellulosic material, the status regarding degradation of high-molecular mass lignins is controversial. This review compiles data from the literature as well as that from the authors' laboratory with the aim of clarifying this point. The main body of evidence points towards the inability of aspergilli alone to degrade lignin free of low-molecular mass contaminants. Nevertheless, the ability of this genus to efficiently degrade hemicelluloses makes it an essential participant in the complex microbial system necessary for wood decay under natural conditions. Aspergilli are known to overproduce high levels of hemicellulolytic enzymes. Out of the large array of these enzymes that act in concert to degrade lignocellulosic material, only endoxylanases of aspergilli are described in so far as these are the main activities required for enzyme-aided bleaching. The biochemical features of the endoxylanases from Aspergillus niger are briefly described as these serve to illustrate how a complex family of isozymes is necessary to deal with the structural and chemical heterogeneity of xylans. Emphasis is placed on the biotechnological applications of lignocellulosic materials transformed by aspergilli. The key application areas are biopulping and biobleaching where a reduction in the use of environmentally harmful chemicals traditionally used in the pulp and paper industry is envisaged. Waste water treatment represents another vast application area where aspergilli have been shown to be effective not only in colour removal but also in the bioconversion of potentially noxious substances into useful bioproducts.

[1]  Liisa Viikari,et al.  Xylanases in bleaching: From an idea to the industry , 1994 .

[2]  J. Duarte,et al.  Xylanolytic enzyme production by anAspergillus niger isolate , 1994, Applied biochemistry and biotechnology.

[3]  Zhao Xin,et al.  Acceleration of ethanol production from paper mill waste fiber by supplementation with β-glucosidase , 1993 .

[4]  L. Viikari,et al.  Production of xylanases byAspergillus fumigatus andAspergillus oryzae on xylan-based media , 1993, World journal of microbiology & biotechnology.

[5]  L. M. Nieto,et al.  The biological purification of waste products from olive oil extraction , 1993 .

[6]  K. Poutanen,et al.  Interlaboratory testing of methods for assay of xylanase activity , 1992 .

[7]  T. Wood,et al.  Xylanase production by Aspergillus awamori. Development of a medium and optimization of the fermentation parameters for the production of extracellular xylanase and β‐xylosidase while maintaining low protease production , 1991, Biotechnology and bioengineering.

[8]  Robert A. Blanchette,et al.  Microbial and Enzymatic Degradation of Wood and Wood Components , 2012, Springer Series in Wood Science.

[9]  K. Kannan,et al.  Decolorization of pulp and paper mill effluent by growth ofAspergillus niger , 1990, World journal of microbiology & biotechnology.

[10]  D. Gavrilescu,et al.  Biodegradation of lignosulfonic products with microorganisms adapted through repeated cultures on lignin substrates , 1990 .

[11]  R. Blanchette,et al.  Biodegradation of Hemicelluloses , 1990 .

[12]  J. P. Nakas,et al.  Xylanase production by Trichoderma longibrachiatum , 1989 .

[13]  M. Paice,et al.  Viscosity-enhancing bleaching of hardwood kraft pulp with xylanase from a cloned gene. , 1988, Biotechnology and bioengineering.

[14]  W. B. Betts,et al.  Scanning Electron Microscope Observations of Fungal Associations with Lignin and Insoluble Dimeric Lignin Model Compounds , 2009 .

[15]  Alan J. McCarthy,et al.  Lignocellulose-degrading actinomycetes , 1987 .

[16]  W. B. Betts,et al.  Physical aspects of the degradation of insoluble tri- and tetrameric lignin model compounds by Aspergillus flavus , 1987 .

[17]  W. B. Betts,et al.  Dimerization of 2,6-dimethoxyphenol by Aspergillus flavus: evidence for the reaction occurring close to mycelia. , 1987, Microbios.

[18]  A. Bunch,et al.  The manipulation of micro-organisms for the production of secondary metabolites. , 1986, Biotechnology & genetic engineering reviews.

[19]  A. Leduy,et al.  Assay of xylanase and xylosidase activities in bacterial and fungal cultures , 1986 .

[20]  K. Kadam,et al.  Study of lignin biotransformation by Aspergillus fumigatus and white‐rot fungi using 14C‐labeled and unlabeled kraft lignins , 1986, Biotechnology and Bioengineering.

[21]  P. Reilly,et al.  Purification and characterization of endo‐xylanases from Aspergillus niger. II. An enzyme of pl 4.5 , 1985, Biotechnology and bioengineering.

[22]  P. Reilly,et al.  Purification and characterization of endo‐xylanases from Aspergillus niger. I. Two isozymes active on xylan backbones near branch points , 1985, Biotechnology and bioengineering.

[23]  T. Enari,et al.  Measurement of xylanase activity with insoluble xylan substrate. , 1985, The Biochemical journal.

[24]  R. Dekker.  CHAPTER 18 – Biodegradation of the Hemicelluloses , 1985 .

[25]  P. Biely,et al.  Soluble chromogenic substrates for the assay of endo-1,4-β-xylanases and endo-1,4-β-glucanases , 1985 .

[26]  R. Rowlands,et al.  Industrial strain improvement: Mutagenesis and random screening procedures , 1984 .

[27]  J. Gressel,et al.  Fungal Biodegradation and Biotransformation of Soluble Lignocarbohydrate Complexes from Straw , 1983, Applied and environmental microbiology.

[28]  R. Dart,et al.  The Degradation of p-Coumaryl Alcohol by Aspergillus flavus , 1982 .

[29]  H. E. Klei,et al.  Uses of by-product lignins from alcohol fuel processes , 1982 .

[30]  P. Reilly,et al.  Purification and characterization of a xylobiose- and xylose-producing endo-xylanase from Aspergillus niger , 1981 .

[31]  R. Crawford,et al.  Microbial degradation of lignin , 1979 .

[32]  Jürgen Schmidt,et al.  Purification and some properties of five endo-1,4-β-D-xylanases and β-D-xylosidase produced by a strain of Aspergillus niger , 1979 .

[33]  R. Blanchette,et al.  Associations among bacteria, yeasts, and basidiomycetes during wood decay. , 1978 .

[34]  N. Rodionova,et al.  Studies on xylan degrading enzymes. I. Purification and characterization of endo-1,4-beta-xylanase from Aspergillus niger str. 14. , 1977, Biochimica et biophysica acta.

[35]  N. Rodionova,et al.  Studies on xylan-degrading enzymes. II. Action pattern of endo-1,4-beta-xylanase from Aspergillus niger str. 14 on xylan and xylooligosaccharides. , 1977, Biochimica et biophysica acta.

[36]  K. Eriksson,et al.  Influence of carbohydrates on lignin degradation by the white-rot fungus Sporotrichum pulverulentum , 1975 .