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The review describes the natural biopolymer lignin, which is second in plant biomass abundance. It is evident now that lignin is considerably undervalued and insufficiently studied in the applied area. The review focuses on the history of the lignin discovery, methods for its extraction from plant objects, its biodegradation by fungi, the enzymes degrading lignin, and the prospects of its application in current biotechnology.

The ability of micromycetes Trichoderma viride and Aspergillus terreus to decompose the cellulose-containing substrates was studied. Office paper and cardboard, as well as a paper mixture, were found to be the most hydrolyzable. The cellulolytic activity of T. viride was 2-3 times higher than that of A. terreus; the highest values of 0.80 and 0.73 U/mLwere obtained from office paper and the paper mixture, respectively. The micromycete cultivation conditions (composition of culture medium, sucrose cosubstrate addition, seeding method) and the conditions of the fungus biomass treatment for its subsequent bioconversion into biogas by anaerobic microbial communities were optimized. It was shown that pretreatment improves the efficiency of biogas production from lignocellulosic materials under seeding with microbial community of bovine animal manure. After pretreatment of the Jerusalem artichoke phytomass (stems and leaves) and its subsequent bioconversion into biogas by methanogenic community, the biogas yield was increased by 1.5 times.

The presence of genes encoding lignin peroxidase, laccase, and manganese peroxidase was assessed in more than 20 types of polypore fungi collected in the woods of Kirov oblast; the fungi studied had not been previously characterized with regard to ligninolytic enzyme production. Fifteen isolates of eleven basidiomycete species were shown to contain genes coding for all three ligninolytic enzymes. Genes coding for these enzymes were detected in D. mollis, D. quercina, F. pinicola, G. trabeum, G. lucidum, H. fasciculare, L. betulina, P. betulinus, P. igniarus, P. pomaceus, P. pini, and P. cinnabarinus for the first time.

The efficiency of the enzymatic hydrolysis of wood polysaccharides ground into ultrafine particles (UFPs) has been investigated. The content of reducing sugars (RS's) in powdered raw materials and the yield of sugars during enzymatic hydrolysis have been shown to depend on the particle size. Laser interference microscopy and dynamic light scattering studies have shown that increasing the grinding time from 20 to 40 min resulted in the formation of particles ranging from 2 to 200 nm in size. Enzymatic hydrolyzates of UFPs mostly contained glucose and galactose. The grinding intensity (mill rotation rate) and time had a significant effect on the extent of the enzymatic hydrolysis of wood.

Inhibition efficiency (antioxidant activity) of 26 oxygen-containing aromatic compounds was studied in methemalbumin-H202-o-phenylenediamine (PDA) or tetramethylbenzidine (TMB) pseudoperoxidase system at 20 degrees C in buffered physiological solution (pH 7.4) containing 6% DM F and 0.25% DMSO. The inhibitor's efficiency was quantitatively characterized by the inhibition constants (Ki, microM) or the inhibition degree (%). Ki values varied in the range of4 to 500 microM and were influenced by a substrate, the structure of an inhibitor, hydroxyl groups, electron-donating substituents in aromatic ring, and steric hindrances. The type of inhibition at cooxidation of eight pairs was noncompetitive, and that of five pairs was mixed and determined by the substrate nature and the inhibitor structure. Lignin phenolic compounds ofguaiacyl and syringal series exhibited high antioxidant activity (Ki in the range of 10-300 microM), and their efficiency decreased in the following order: caffeic acid > synapaldehyde > syringic acid > coniferyl aldehyde > para-hydroxycou maric acid.

Data on comparative investigations of chemical structure of lignins from medical grassy plants Rhodiola rosea and Serratula coronata lignins were obtained. The NMR and ESR spectroscopy, and functional and element analysis were used. The high antioxidant activity of lignins was shown. Experimental evidence of anti-aging activity of Rhodiola rosea lignin on model objects Drosophila melanogaster were presented.

We studied the structure of alcohol-soluble lignin in cognac spirits from Spain (7-year aging) and Azerbaijan (15-year aging). Alcohol-soluble lignin was precipitated and refractionated by means of preparative high-performance liquid chromatography. Lignin was studied by the method of high-performance liquid chromatography and mass spectrometry. Lignin hydrolysis products were assayed by the method of gas-liquid chromatography and mass spectrometry. The structure of lignans was reconstructed from these fragments. Lignans from Spanish and Azeri alcohol were arbitrarily designated as sinapoconiferal triglycoside and glucoferulate flavone diglycoside, respectively.

Antioxidant properties of different botanic origin water soluble lignins are considered. Possibility to develop onco- and geroprotectors on the base of natural lignins is shown.

Commercial and pilot enzyme preparations from fungi of the genera Penicillium and Trichoderma have been compared with regard to their action on conifer wood pretreated with acidified aqueous ethanol (organosolve). In most experiments, enzymes from the genus Penicillium allowed higher yields of reducing sugars and glucose than those from Trichoderma. High beta-glucosidase activity is essential for deep pulp hydrolysis.

Abstract-Physiological and biochemical properties of the strain Penicillium tardum H-2, a degrader of phenolic compounds formed during lignin pyrolysis, have been characterized. The micromycete P. tardum H-2 can consume phenol, pyrocatechol, p-cresol, vanillin, and guaiacum resin. When grown in a medium containing the water-soluble fraction of lignin pyrolysis waste at concentrations from 0.5 to 2%, it consumes 62-72% of the phenolic components of the waste. According to gas-liquid chromatography, cultivation of P. tardum H-2 in a medium with liquid pyrolysis products results in a complete consumption of the phenol-cresol fraction.

This work presents the data on the rate of utilization of phenols formed during lignin pyrolysis by micromycetes of the genera Trichoderma and Penicillium. Trichoderma strains utilized phenols at the concentration of liquid pyrolytic products of 0.5-1%, while representatives of Penicillium degraded over 50% phenols at the concentration of pyrolytic products of 2%. Micromycete cultures completely utilized phenol and the cresol-xylenol fraction. Penicillium strains demonstrated a more active growth on media containing phenol, pcresol, or guaiacolic acid as the source of carbon as compared to Trichoderma. m-Cresol and m-xylenol in micromycete growth media containing products of lignin pyrolysis seem to be utilized by co-oxidation.

Composting of hydrolytic lignin by a microbial association changed its molecular-weight composition, acid-based properties, and supramolecular structure. Specifically, by the end of the third month of composting, an increase was observed in its exchange capacity and the amount of negative charges, as well as in the content of phenyl, hydroxyl, and carboxyl groups. The use of this compost as a fertilizer for barley growth demonstrated that the changes increased the biological activity of hydrolytic lignin.

Considerable differences in lignin degradation by fungi of two ecological groups have been revealed. Xylotrophs cause a twofold decrease in the molecular weight of lignin. The degrading activity of saprotrophs is insignificant. Xylotrophs demethoxylate and oxidize lignin more rapidly than saprotrophs, showing a higher level of antioxidant activity. As follows from the comparison of the degrading and antioxidative effects, measurement of the antioxidant activity can be used in screening of fungi for the ability to degrade lignocellulose substrates.

Microbial assemblages were composed for composting hydrolysed lignin. Data on bioconversion of aromatic compounds with various types of substitution in the ring were used for this purpose. Composting of hydrolysed lignin reduced the contents of lignin, low-hydrolyzable polysaccharides, resins, and low-molecular-weight phenols and resulted in accumulation of humic acids. The resulting compost showed no phytotoxicity.

Conversion of lignins contained in solid parts of Rkatsiteli grapes (crests, seeds, and skin) during alcoholic fermentation by wine yeast in Reader's medium was studied. Various species of wine yeast were used: Saccharomyces oviformis, S. vini Kakhuri 42, S. chodati Teliani 79, and S. uvarum Tsinandali 77. We found that lignins from solid parts of grapes are partially decomposed during alcoholic fermentation, which releases low-molecular-weight aromatic compounds into the medium. A peculiar feature of lignin decomposition during alcoholic fermentation is the formation of reduction products.

Formation of pyrogallol ether during thermal oxidation of oak (Quercus iberica L.) lignin in the presence of air oxygen was investigated. A model reaction demonstrated that the substance identified by us as pyrogallol ether (1,2-dioxy-3-methoxybenzene) is derived from syringic aldehyde.