Hydrolysis of lignocellulosic materials for ethanol production: a review.

Biofuels produced from various lignocellulosic materials, such as wood, agricultural, or forest residues, have the potential to be a valuable substitute for, or complement to, gasoline. Many physicochemical structural and compositional factors hinder the hydrolysis of cellulose present in biomass to sugars and other organic compounds that can later be converted to fuels. The goal of pretreatment is to make the cellulose accessible to hydrolysis for conversion to fuels. Various pretreatment techniques change the physical and chemical structure of the lignocellulosic biomass and improve hydrolysis rates. During the past few years a large number of pretreatment methods have been developed, including alkali treatment, ammonia explosion, and others. Many methods have been shown to result in high sugar yields, above 90% of the theoretical yield for lignocellulosic biomasses such as woods, grasses, corn, and so on. In this review, we discuss the various pretreatment process methods and the recent literature that...

http://ucce.ucdavis.edu/files/datastore/234-1388.pdf

Methods for Pretreatment of Lignocellulosic Biomass for Efficient Hydrolysis and Biofuel Production

Biodegradation aspects of Polycyclic Aromatic Hydrocarbons (PAHs): A review

Laccases of fungi attract considerable attention due to their possible involvement in the transformation of a wide variety of phenolic compounds including the polymeric lignin and humic substances. So far, more than a 100 enzymes have been purified from fungal cultures and characterized in terms of their biochemical and catalytic properties. Most ligninolytic fungal species produce constitutively at least one laccase isoenzyme and laccases are also dominant among ligninolytic enzymes in the soil environment. The fact that they only require molecular oxygen for catalysis makes them suitable for biotechnological applications for the transformation or immobilization of xenobiotic compounds.

Fungal laccases - occurrence and properties.

http://www.loewenlabs.com/peter/wp-content/themes/atahualpa/Manuscripts/BA_29_675.pdf

Biomass pretreatment: fundamentals toward application

http://www.dzumenvis.nic.in/Biodegradation/pdf/Biodegradation%20of%20lignin.pdf

Biodegradation of lignin in a compost environment: a review

White-rot fungi produce extracellular lignin-modifying enzymes, the best characterized of which are laccase (EC 1.10.3.2), lignin peroxidases (EC 1.11.1.7) and manganese peroxidases (EC 1.11.1.7). Lignin biodegradation studies have been carried out mostly using the white-rot fungus Phanerochaete chrysosporium which produces multiple isoenzymes of lignin peroxidase and manganese peroxidase but does not produce laccase. Many other white-rot fungi produce laccase in addition to lignin and manganese peroxidases and in varying combinations. Based on the enzyme production patterns of an array of white-rot fungi, three categories of fungi are suggested: (i) lignin-manganese peroxidase group (e.g.P. chrysosporium and Phlebia radiata), (ii) manganese peroxidase-laccase group (e.g. Dichomitus squalens and Rigidoporus lignosus), and (iii) lignin peroxidase-laccase group (e.g. Phlebia ochraceofulva and Junghuhnia separabilima). The most efficient lignin degraders, estimated by 14CO2 evolution from 14C-[Ring]-labelled synthetic lignin (DHP), belong to the first group, whereas many of the most selective lignin-degrading fungi belong to the second, although only moderate to good [14C]DHP mineralization is obtained using fungi from this group. The lignin peroxidase-laccase fungi only poorly degrade [14C]DHP.

Lignin-modifying enzymes from selected white-rot fungi: production and role from in lignin degradation

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

Biodegradation of Lignin

SUMMARY Basidiomycete fungi subsist on various types of plant material in diverse environments, from living and dead trees and forest litter to crops and grasses and to decaying plant matter in soils. Due to the variation in their natural carbon sources, basidiomycetes have highly varied plant-polysaccharide-degrading capabilities. This topic is not as well studied for basidiomycetes as for ascomycete fungi, which are the main sources of knowledge on fungal plant polysaccharide degradation. Research on plant-biomass-decaying fungi has focused on isolating enzymes for current and future applications, such as for the production of fuels, the food industry, and waste treatment. More recently, genomic studies of basidiomycete fungi have provided a profound view of the plant-biomass-degrading potential of wood-rotting, litter-decomposing, plant-pathogenic, and ectomycorrhizal (ECM) basidiomycetes. This review summarizes the current knowledge on plant polysaccharide depolymerization by basidiomycete species from diverse habitats. In addition, these data are compared to those for the most broadly studied ascomycete genus, Aspergillus, to provide insight into specific features of basidiomycetes with respect to plant polysaccharide degradation.

Plant-Polysaccharide-Degrading Enzymes from Basidiomycetes

Of 19 white-rot fungi tested, Pleurotus ostreatus, Pleurotus sp. 535, Pycnoporus cinnabarinus 115 and Ischnoderma benzoinum 108 increased the susceptibility of straw to enzymic saccharification, thus indicating that these organisms degraded or modified the lignin component. After pretreatment cultivation with Pycnoporus cinnabarinus 115, as much as 54.6% of the residue was converted to reducing sugars in the enzymic saccharification process. Phanerochaete sordida 37, Phlebia radiata 79 and two unidentified fungi also gave better results than Polyporus versicolor, a non-selective reference fungus. After 5 weeks pretreatment with Pleurotus ostreatus, 35% of the original straw was convertable to reducing sugars, 74% of which was glucose; compared with this, only 12% of the untreated control straw was convertable to reducing sugars, 42% of which was glucose. After an alkali pretreatment (2% NaOH, 0.4 g NaOH/g straw, 10 min at 115°C) enzymic saccharification converted 41% of the straw to reducing sugars, of which only 50% was glucose. In the best cases the efficiency of biological pretreatment was comparable with that of alkali treatment, but resulted in a higher proportion of glucose in the hydrolysates. Pretreatment by the fungi Phanerochaete sordida 37 and Pycnoporus cinnabarinus 115 in an oxygen atmosphere reduced the treatment time by approximately 1 week. However, the economic feasibility of a non-optimized biological pretreatment process is still poor due to the long cultivation times required.

Annele Hatakka

Papers

Biodegradation of lignin in a compost environment: a review

Lignin-modifying enzymes from selected white-rot fungi: production and role from in lignin degradation

Biodegradation of Lignin

Plant-Polysaccharide-Degrading Enzymes from Basidiomycetes

Pretreatment of wheat straw by white-rot fungi for enzymic saccharification of cellulose