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Being an abundant renewable source of aromatic compounds, lignin is an important component of future bio-based economy. Currently, biotechnological processing of lignin through low molecular weight compounds is one of the conceptually promising ways for its valorization. To obtain lignin fragments suitable for further inclusion into microbial metabolism, it is proposed to use a ligninolytic system of white-rot fungi, which mainly comprises laccases and peroxidases. However, laccase and peroxidase genes are almost always represented by many non-allelic copies that form multigene families within the genome of white-rot fungi, and the contributions of exact family members to the overall process of lignin degradation has not yet been determined. In this article, the response of the Trametes hirsuta LE-BIN 072 ligninolytic system to the presence of various monolignol-related phenolic compounds (veratryl alcohol, p-coumaric acid, vanillic acid, and syringic acid) in culture media was monitored at the level of gene transcription and protein secretion. By showing which isozymes contribute to the overall functioning of the ligninolytic system of the T. hirsuta LE-BIN 072, the data obtained in this study will greatly contribute to the possible application of this fungus and its ligninolytic enzymes in lignin depolymerization processes. [ABSTRACT FROM AUTHOR]

The physicochemical characteristics and functional properties of pumpkin (Cucurbita maxima D. var. Cabello de Ángel) pectin obtained by cavitation facilitated extraction from pumpkin pulp have been evaluated and compared with commercial citrus and apple pectins. C. maxima pectin had an Mw value of 90 kDa and a high degree (72%) of esterification. The cytoprotective and antioxidant effects of citrus, apple and pumpkin pectin samples with different concentrations were studied in vitro in cell lines HT-29 (human colon adenocarcinoma) and MDCK1 (canine kidney epithelium). All pectin samples exhibited cytoprotective effect in HT-29 and MDCK1 cells after incubation with toxic concentrations of cadmium and mercury for 4 h. Pumpkin pectin increased the proliferation of cadmium-treated MDCK1 cells by 210%. The studied pectins also inhibited oxidative stress induced by 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AAPH) in cell cultures, as determined by measuring the production of intracellular reactive species using dihydrochlorofluorescein diacetate (DCFH-DA). Pectin from pumpkin pomace had the highest (p < 0.05) protective effect against reactive oxygen species generation in MDCK1 cells induced by AAPH. Distinctive features of pumpkin pectin were highly branched RG-I regions, the presence of RG-II regions and the highest galacturonic acid content among the studied samples of pectins. This correlates with a considerable protective effect of C. maxima pectin against oxidative stress and cytotoxicity induced by heavy metal ions. Thus, C. maxima pectin can be considered as a source of new functional foods of agricultural origin. [ABSTRACT FROM AUTHOR]

White-rot basidiomycetes from the poorly studied residual polyporoid clade of Polyporales order Junghuhnia nitida (Pers.) Ryvarden and Steccherinum bourdotii Saliba & A. David grow as secondary xylotrohps on well decomposed woody materials. The main objective of the current study was to compare oxidative potential, growth, production of oxidative enzymes and laccase properties of J. nitida and S. bourdotii with that of typical primary xylotrohps Trametes hirsuta (Wulfen) Lloyd and Coriolopsis caperata (Berk.) Murrill, belonging to the core polyporoid clade. For the first time we report species J. nitida and S. bourdotii as active laccase producers. New laccases from J. nitida and S. bourdotii were purified and characterized. They had an identical molecular weight of 63 kDa and isoelectric points of 3.4 and 3.1, respectively. However, the redox potential of the T1 copper site for both J. nitida (610 mV) and S. bourdotii (640 mV) laccases was lower than those for T. hirsuta and C. caperata laccases. The new laccases showed higher temperature optima and better thermal stability than T. hirsuta and C. caperata laccases. Their half-lives were more than 40 min at 70 °C. The laccases from J. nitida and S. bourdotii showed higher affinity to syringyl-type phenolic compounds than T. hirsuta and C. caperata laccases. The oxidative potential of studied fungi as well as the properties of their laccases are discussed in terms of the fungal life-style. [ABSTRACT FROM AUTHOR]

Laccases are copper-containing oxidases that catalyze a one-electron abstraction from various phenolic and non-phenolic compounds with concomitant reduction of molecular oxygen to water. It is well-known that laccases from various sources have different substrate specificities, but it is not completely clear what exactly provides these differences. The purpose of this work was to study the features of the substrate specificity of four laccases from basidiomycete fungi Trametes hirsuta, Coriolopsis caperata, Antrodiella faginea, and Steccherinum murashkinskyi, which have different redox potentials of the T1 copper center and a different structure of substrate-binding pockets. Enzyme activity toward 20 monophenolic substances and 4 phenolic dyes was measured spectrophotometrically. The kinetic parameters of oxidation of four lignans and lignan-like substrates were determined by monitoring of the oxygen consumption. For the oxidation of the high redox potential (>700 mV) monophenolic substrates and almost all large substrates, such as phenolic dyes and lignans, the redox potential difference between the enzyme and the substrate (ΔE) played the defining role. For the low redox potential monophenolic substrates, ΔE did not directly influence the laccase activity. Also, in the special cases, the structure of the large substrates, such as dyes and lignans, as well as some structural features of the laccases (flexibility of the substrate-binding pocket loops and some amino acid residues in the key positions) affected the resulting catalytic efficiency. [ABSTRACT FROM AUTHOR]