Mirjana Stajic

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).

Biology of Pleurotus eryngii and role in biotechnological processes : a review

Pleurotus eryngii is considered a complex species owing to a perplexed structure within species and a wide geographical distribution. Due to its remarkable flavor, high nutritional value, and numerous medicinal features, P. eryngii is commercially cultivated on various raw plant materials. Its efficacy in using nutrients from lignocellulose residues is based on possession of a potent ligninolytic enzyme system, constituted of laccase, Mn-oxidizing peroxidases, and aryl-alcohol oxidase, which successfully degrade different aromatic compounds. Similarly, due to the ability of these enzymes, P. eryngii plays a very important role in many biotechnological processes, such as food production (edible basidiomata), biotransformation of raw plant materials to feed, biopulping and biobleaching of paper pulp, as well as bioremediation of soil and industrial waters.Pleurotus eryngii is considered a complex species owing to a perplexed structure within species and a wide geographical distribution. Due to its remarkable flavor, high nutritional value, and numerous medicinal features, P. eryngii is commercially cultivated on various raw plant materials. Its efficacy in using nutrients from lignocellulose residues is based on possession of a potent ligninolytic enzyme system, constituted of laccase, Mn-oxidizing peroxidases, and aryl-alcohol oxidase, which successfully degrade different aromatic compounds. Similarly, due to the ability of these enzymes, P. eryngii plays a very important role in many biotechnological processes, such as food production (edible basidiomata), biotransformation of raw plant materials to feed, biopulping and biobleaching of paper pulp, as well as bioremediation of soil and industrial waters.

Screening of laccase, manganese peroxidase, and versatile peroxidase activities of the genus Pleurotus in media with some raw plant materials as carbon sources

Species of the genus Pleurotus are among the most efficient natural species in lignin degradation belonging to the subclass of ligninolytic organisms that produce laccase (Lac), Mn-dependent peroxidase (MnP), versatile peroxidase (VP), and the H2O2-generating enzyme aryl-alcohol oxidase, but not lignin peroxidases. Production of Lac and oxidation of 2,6-dimethoxyphenol (DMP) in the presence and absence of Mn2+ were detected both in submerged fermentation (SF) of dry ground mandarine peels and in solid-state fermentation (SSF) of grapevine sawdust in all investigated Pleurotus species and strains. Evidence of cultivation methods having a distinct influence on the level of enzyme activities has been demonstrated. Most of the species and strains had higher Lac activity under SSF conditions than under SF conditions. DMP oxidation in the presence and absence of Mn2+ was detected in all investigated species and strains, but was lower under SF conditions than under SSF conditions for most of them. However, relative activities of DMP oxidation in the absence of Mn2+, as percentages of activity agasint DMP in the presence of Mn2+, were higher under conditions of SF than in SSF cultures in most of the investigated species and strains. The obtained results showed that strains of different origins have different efficiently ligninolytic systems and that conditions of SSF are more favorable for ligninolytic activity than those in SF owing to their similarity to natural conditions on wood substrates.

Biological activity of Ganoderma lucidum basidiocarps cultivated on alternative and commercial substrate

ETHNOPHARMACOLOGICAL RELEVANCE Ganoderma lucidum (W. Curt.:Fr.) P. Karst. has been used for several thousand years in traditional medicine of the Far East for the treatment of a various diseases including: cancer, immunological disorders, hepatitis, arthritis, nephritis, bronchitis, asthma etc. Ganoderma species are natural sources of various antimicrobial, antioxidant and antitumor active compounds which can be alternative to commercial antibiotics, antimycotics, antioxidants and cytostatics. As the amount of wild Ganoderma lucidum basidiocarps is not sufficient, the aim of this study was to compare the bioactivity of basidiaocarps obtained on alternative substrate (wheat straw) with commercially cultivated ones. MATERIALS AND METHODS Antimicrobial potential of the tested Ganoderma lucidum extracts was studied by disc-diffusion and microdilution method. Cytotoxic effect of tested extracts on two cancer cell lines was determined by microculture tetrazolium test. DPPH scavenging ability, total phenols and flavonoids content were measured in order to determine the antioxidative potential of Ganoderma lucidum extracts. RESULTS Ganoderma lucidum BEOFB 434 extract was the most effective antibacterial agent, while commercial strain was the weakest. DPPH· scavenging activity of extracts of basidiocarps from alternative substrate was also significantly higher than that of commercially obtained basidiocarps. The extracts of Ganoderma lucidum BEOFB 431 exhibited the strongest cytotoxic activity significantly higher than those in commercial strain. CONCLUSION The study showed that fruiting bodies produced on one of the most accessible and cheapest crop residue, wheat straw, are better antimicrobial, antioxidant and cytotoxic agents than those obtained on conventional substrate, oak sawdust.

Effect of Copper and Manganese Ions on Activities of Laccase and Peroxidases in Three Pleurotus Species Grown on Agricultural Wastes

Copper (Cu2+) and manganese (Mn2+) ions influenced laccase (Lac) and peroxidase production in Pleurotus eryngii, Pleurotus ostreatus, and Pleurotus pulmonarius. In P. eryngii, the optimum Cu2+ concentration for Lac production was 1 mM and for peroxidases 10mM, and Mn2+ concentration of 5mM led to peaks of Lac and peroxidase activity. In P. ostreatus HAI 493, the highest level of Lac activity was at Cu2+ concentrations of 1 and 10 mM and Mn2+ concentration of 1mM, respectively. The absence of Cu2+ and Mn2+ caused the highest levels of peroxidase production. In P. ostreatus HAI 494, the highest level of Lac activity was at a Cu2+ concentration of 5 mM and at Mn2+ concentration of 1 mM, respectively. High levels of peroxidase activity were found in the medium without and with 1mM Cu2+, and at 1 and 5 mM Mn2+, respectively. In P. pulmonarius, the highest Lac activity was found in the presence of 5 mM Cu2+ and 5 mM Mn2+, respectively. The absence of Cu2+ and Mn2+ as well as their presence at a concentration of 1 mM led to the peaks of peroxidase activities.

Antioxidant protective effects of mushroom metabolites.

Global industrialization and agricultural development are related to the release of various pollutants into the environment including huge amounts of free radicals, which are associated with the occurrence of various destructive diseases and disorders. Due to different rates of metabolic activity and oxygen consumption, organisms, organs and tissues have distinct protective antioxidant systems and defence mechanisms. Although numerous synthetic antioxidants can improve defence system capacity, because of their toxic and mutagenic effects as well as rising awareness of a healthy lifestyle, preference is given to natural antioxidants. Therefore, studies of metabolites of various fungal species and their activity are currently increasing. Antioxidant features of numerous compounds isolated from mushrooms, such as phenolic compounds, vitamins, polysaccharides, peptides, proteins, organic acids, carotenoids, alkaloids, and nucleotides, have been reported. Chemical composition and antioxidant potential of mushrooms are highly-dependent on species, habitat, phase of life cycle (mycelium, young or mature fruiting body), method of processing, extraction solvent, and extract dose. Although around only 5% of fungal species have been well studied and thousands more species have potential benefit for mankind, reports on the antioxidant potentials of fungi are already numerous and these are the subject of this review.

In vitro toxicity of selected fungicides from the groups of benzimidazoles and demethylation inhibitors to Cladobotryum dendroides and Agaricus bisporus

Twenty microfungal isolates were collected from diseased fruiting bodies of Agaricus bisporus sampled from Serbian mushroom farms during 2003–2007. Based on morphological characteristics and pathogenicity tests, the isolates were identified as Cladobotryum dendroides. The isolates of C. dendroides and A. bisporusF56 and U3 were tested for sensitivity to several selected fungicides in vitro. C. dendroides isolates were found to be more sensitive to prochloraz manganese and flusilazole + carbendazim than to the other fungicides tested (EC50 values were 0.09 and 0.11 mg L− 1, respectively) and weakly resistant to thiophanate-methyl (EC50 values ranged between 6.53 and 12.09 mg L− 1). Selectivity indexes of the tested fungicides on both C. dendroidesand A. bisporusindicated that thiophanate-methyl, cyproconazole + carbendazim and flusilazole + carbendazim had much less selective fungitoxicity than benomyl, carbendazim and prochloraz manganese.

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.

Antioxidant and Antifungal Potential of Pleurotus ostreatus and Agrocybe cylindracea Basidiocarps and Mycelia

Basidiocarps of Pleurotus ostreatus and Agrocybe cylindracea are characterized by high nutritional value and numerous medicinal activities, though bioactivities of their mycelia have not been sufficiently studied. The aim of the study was to evaluate antioxidant and antifungal potentials of P. ostreatus and A. cylindracea basidiocarp extracts, as well as those obtained from mycelia cultivated in common synthetic medium and media enriched with various agro-industrial residues. The free radical scavenging activity of the extracts was determined spectrophotometrically, based on DPPH• reduction while antifungal potential was studied by a microdilution method. The highest level of DPPH• scavenging ability was obtained by an extract of P. ostreatus mycelium cultivated in wheat bran-enriched medium, while control medium favoured the antioxidant potential of A. cylindracea mycelium. Phenol compounds were the main carriers of antioxidant activity that was demonstrated by high coefficients for correlations between total phenol contents in extracts and level of DPPH• scavenging (0.94 for P. ostreatus extracts and 0.91 for A. cylindracea extracts). Only the extracts of A. cylindracea basidiocarp and control mycelium, at a concentration of 1.33 mg/mL, inhibited the growth of Microsporum gypseum and Aspergillus flavus, while basidiocarp extract at 1.67 mg/mL also had fungicidal effect against M. gypseum. These results revealed a considerable antioxidant potential of submergedly-cultivated mycelium which showed higher antioxidant activity than basidiocarp extracts. This is very important because significant amounts of mycelium biomass could be obtained more easily, cheaper and in a more controllable way than basidiocarps cultivation.