Aleksandar Knežević

Lignin degradation by selected fungal species.

As biological decomposition of plant biomass represents a popular alternative environmental-friendly and economically justified process, screening of ligninolytic enzyme systems of various fungal species is a topical study area. The goal of the study was to obtain clear insight into the dynamics of laccase, Mn-dependent peroxidase, and Mn-independent peroxidase activity and levels of wheat straw lignin degradation in seven wood-rotting fungi. The best laccase producers were Pleurotus ostreatus and Pleurotus eryngii. Lenzites betulinus and Fomitopsis pinicola were the best Mn-dependent peroxidase producers, and P. ostreatus the weakest one. The peak of Mn-independent peroxidase was noted in Dichomytus squalens, and the minimum value in P. ostreatus. The profiles of the three enzymes, obtained by isoelectric focusing, were variable depending on the species and cultivation period. D. squalens was the best lignin degrader (34.1% of total lignin amount), and P. ostreatus and P. eryngii the weakest ones (7.1% and 14.5%, respectively).

Potential of Pleurotus ostreatus Mycelium for Selenium Absorption

The aim of this study was to evaluate the effect of high selenium (Se) concentrations on morphophysiological and ultrastructural properties of Pleurotus ostreatus. Mycelium growth was good in media enriched with 5.0, 10.0, and 20.0 mg L−1 of Se, concentration of 500.0 mg L−1 strongly inhibited growth, and 1000.0 mg L−1 was the minimum inhibitory concentration. Contrary to thin-walled, hyaline, branched, and anastomized hyphae with clamp-connections in the control, at Se concentrations of 100.0 and 500.0 mg L−1, they were noticeably short, frequently septed and branched, with a more intensive extracellular matrix, and without clamp-connections. At high Se concentrations, hyphae with intact membrane, without cellular contents, with a high level of vacuolization, and with numerous proteinaceous bodies were observed. Biomass yield ranged between 11.8 g L−1, in the control, and 6.8 g L−1, at an Se concentration of 100.0 mg L−1, while no production was detected at a concentration of 500.0 mg L−1. Se content in the mycelia reached a peak (938.9 μg g−1) after cultivation in the medium enriched with Se at the concentration of 20.0 mg L−1, while the highest absorption level (53.25%) was found in the medium enriched with 5.0 mg L−1 Se.

Induction of wheat straw delignification by Trametes species.

Wheat straw is the major crop residue in European countries which makes it the most promising material for bioconversion into biofuels. However, cellulose and hemicellulose are protected with lignin, so delignification is an inevitable phase in lignocellulose processing. The organisms predominantly responsible for its degradation are white-rot fungi and among them Trametes species represent promising degraders due to a well-developed ligninolytic enzyme system. Although numerous studies have confirmed that low molecular weight compounds can induce the production and activity of ligninolytic enzymes it is not clear how this reflects on the extent of delignification. The aim of the study was to assess the capacity of p-anisidine and veratryl alcohol to induce the production and activity of Mn-oxidizing peroxidases and laccases, and wheat straw delignification by six Trametes species. Significant inter- and intraspecific variations in activity and features of these enzymes were found, as well as differences in the potential of lignocellulose degradation in the presence or absence of inducers. Differences in the catalytic properties of synthesized enzyme isoforms strongly affected lignin degradation. Apart from enhanced lignin degradation, the addition of p-anisidine could significantly improve the selectivity of wheat straw ligninolysis, which was especially evident for T. hirsuta strains.

Antigenotoxic Effect of Trametes spp. Extracts against DNA Damage on Human Peripheral White Blood Cells

Trametes species have been used for thousands of years in traditional and conventional medicine for the treatment of various types of diseases. The goal was to evaluate possible antigenotoxic effects of mycelium and basidiocarp extracts of selected Trametes species and to assess dependence on their antioxidant potential. Trametes versicolor, T. hirsuta, and T. gibbosa were the species studied. Antigenotoxic potentials of extracts were assessed on human peripheral white blood cells with basidiocarp and mycelium extracts of the species. The alkaline comet test was used for detection of DNA strand breaks and alkali-labile sites, as well as the extent of DNA migration. DPPH assay was used to estimate antioxidative properties of extracts. Fruiting body extracts of T. versicolor and T. gibbosa as well as T. hirsuta extracts, except that at 20.0 mg/mL, were not genotoxic agents. T. versicolor extract had at 5.0 mg/mL the greatest antigenotoxic effect in both pre- and posttreatment of leukocytes. The mycelium extracts of the three species had no genotoxic activity and significant antigenotoxic effect against H2O2-induced DNA damage, both in pre- and posttreatment. The results suggest that extracts of these three species could be considered as strong antigenotoxic agents able to stimulate genoprotective response of cells.

Role of Mushroom Mn-Oxidizing Peroxidases in Biomass Conversion

Intensive agricultural and industrial production followed by increased production of lignocellulosic wastes, disruption of environment, and depletion of natural resources are features of the modern society. However, these wastes present sustainable resources of fibers and energy and can be useful raw materials for many industries. Therefore, development of the optimal ways for their environmental and economical friendly biological pretreatment where the main participants will be fungi, owing to their ability to produce lignocellulolytic enzymes, preoccupies scientists. Mn-oxidizing peroxidases play crucial role in the process and based on the substrate specificity, this group is divided into Mn-dependent- and versatile peroxidases. However, delignification capacity depends on fungal species and strain, namely on their potential of lignocellulolytic enzyme production and degradation selectivity, type and composition of lignocellulosic wastes, and fermentation conditions. Species which predominantly degrade lignin and significantly weaker cellulose could have important role in processes of food, feed, paper, and biofuel production.

Composition and biological activities of different extracts of Salvia jurisicii, a rare and endemic Macedonian species

Abstract This is the first report on the phenolic composition and biological activities of endemic species Salvia jurisicii Košanin (Lamiaceae) originating from Macedonia. Aerial parts of S. jurisicii were extracted with dichloromethane, ethyl acetate, methanol, ethanol and water. All extracts were tested spectrophotometrically for total phenolic and flavonoid contents, while their phenolic composition was analyzed using HPLC-DAD. The antioxidant activity of extracts was studied using 2,2-dyphenyl-1-picrylhydrazyl, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), ferric reducing ability of plasma and ß-carotene bleaching assays. Being the most frequently used solvents for extraction of bioactive ingredients from medicinal plants, water and ethanol extracts were chosen for further testing of antimicrobial, cytotoxic and antineurodegenerative activities. More polar solvent extracts showed higher total phenolic content and lower flavonoid content. Ethanol and methanol extracts, followed by water extract exhibited the strongest antioxidant activity. Extracts showed antimicrobial activity against certain bacteria and micromycetes. The cytotoxicity assay showed slight toxicity to HCT-116 cell line. In the antineurodegenerative assays, the extracts performed lower inhibition of acetylcholinesterase and tyrosinase than standards. According to the results of this study, it can be inferred that more polar extracts of S. jurisicii were quantitatively richer in total phenolics, showing stronger antioxidant activity. Ethanol extract showed stronger biological activities comparing to water extract.

Antioxidative, antifungal, cytotoxic and antineurodegenerative activity of selected Trametes species from Serbia

In a last few decades mushrooms are increasingly attracting attention as functional food and sources of biologically active compounds. Several Trametes species have been used for centuries in traditional medicine of East Asia cultures, but only T. versicolor was studied sufficiently while there are less substantial data about medicinal properties of other species. Trametes versicolor, T. hirsuta and T. gibbosa were the species tested for biological activities. Antifungal potentials of extracts were assessed for clinical strains of selected Candida and Aspergillus species. ABTS and FRAP assays were used to evaluate antioxidant capacities of studied extracts. Cytotoxic activity was determined against human cervix and lung adenocarcinoma and colon carcinoma cell lines. Antineurodegenerative activity was assessed by determining the rate of acetylcholinesterase and tyrosinase activity. The presence of metabolites in extracts of mycelia and basidiocarps of studied Trametes species was analyzed by 1H NMR spectroscopy. Studied extracts showed low antifungal potential in comparison with ketoconazole. Basidiocarp extracts were more effective ABTS+ scavengers and Fe2+ reducers than mycelium ones but less effective in comparison with L-ascorbic acid. Results showed that mycelium extracts had stronger cytotoxic effects against three cancer cell lines than basidiocarp ones, and that cervix adenocarcinoma cells were the most sensitive to the extracts and commercial cytostatics. T. versicolor mycelium extract was the most effective inhibitor of acetylcholinesterase activity but double weaker than galantamine, and T. gibbosa mycelium extract was significantly better inhibitor of tyrosinase activity than kojic acid for 40.9%. Chemical analysis indicated strong synergistic action of triterpenes, sugars and polyphenols in applied assays. The results suggest that tested Trametes species have significant medicinal potentials which could be attributed to antioxidative and cytotoxic activity. Additionally both, basidiocarps and mycelia extracts can strongly inhibit activity of acetylcholinesterase and tyrosinase.