BackgroundStructural component of plant biomass, lignocellulose, is the most abundant renewable resource in nature. Lignin is the most recalcitrant natural aromatic polymer and its degradation presents great challenge. Nowadays, the special attention is given to biological delignification, the process where white-rot fungi take the crucial place owing to strong ligninolytic enzyme system. However, fungal species, even strains, differ in potential to produce high active ligninolytic enzymes and consequently to delignify plant biomass. Therefore, the goals of the study were characterization of Mn-oxidizing peroxidases and laccases of numerous mushrooms as well as determination of their potential to delignify wheat straw, the plant raw material that, according to annual yield, takes the first place in Europe and the second one in the world.ResultsDuring wheat straw fermentation, Lentinus edodes HAI 858 produced the most active Mn-dependent and Mn-independent peroxidases (1443.2 U L−1 and 1045.5 U L−1, respectively), while Pleurotus eryngii HAI 711 was the best laccase producer (7804.3 U L−1). Visualized bends on zymogram confirmed these activities and demonstrated that laccases were the dominant ligninolytic enzymes in the studied species. Ganoderma lucidum BEOFB 435 showed considerable ability to degrade lignin (58.5%) and especially hemicellulose (74.8%), while the cellulose remained almost intact (0.7%). Remarkable selectivity in lignocellulose degradation was also noted in Pleurotus pulmonarius HAI 573 where degraded amounts of lignin, hemicellulose and cellulose were in ratio of 50.4%:15.3%:3.8%.ConclusionsAccording to the presented results, it can be concluded that white-rot fungi, due to ligninolytic enzymes features and degradation potential, could be important participants in various biotechnological processes including biotransformation of lignocellulose residues/wastes in food, feed, paper and biofuels.
Biological pretreatment of the lignocellulosic residues, in which white-rot fungi have a crucial role, has many advantages compared to the chemical, physical, and physico-chemical methods of delignification and therefore attracts increasing scientific attention. Regarding the fact that properties and capacities of the ligninolytic enzymes of Daedaleopsis spp. are still unknown, the aim of this study was to research how nitrogen sources and inducers affect the potential of Daedaleopsis confragosa and Daedaleopsis tricolor to degrade cherry sawdust. NHNO, (NH)SO, and peptone were tested as nitrogen sources, while veratryl alcohol, p-anisidine, vanillic acid, and phenylmethylsulfonyl fluoride were the studied inducers. As Mn-dependent peroxidase and laccase were the leader enzymes and cherry sawdust/peptone medium the best stimulator of their activities, the effect of inducers on delignification potential of these species was studied during fermentation of that substrate. Veratryl alcohol was the best stimulator of laccase and phenylmethylsulfonyl fluoride of Mn-dependent peroxidase activity (27,610.0 and 1338.4 U/L, respectively). These inducers also increased cherry sawdust delignification selectivity, particularly in D. tricolor in the presence of phenylmethylsulfonyl fluoride (lignin:hemicellulose:cellulose = 32.1%:0.9%:11.7%). Owing to the presented results, studied species could have an important role in the phase of lignocellulose pretreatment in various biotechnological processes.
Hypsizygus marmoreus is an edible and medicinal commercially cultivated mushroom, whose ligninolytic potential is still insufficiently known. Therefore, the goals of this study were to profile its Mn-oxidizing peroxidases and laccases activity and its potential to depolymerize common agro-forestry residues. Raspberry and blackberry sawdust induced the production of highly active laccases (26006.83 U L-1 and 17576.79 U L-1, respectively), while the activity peaks of Mn-dependent peroxidase (134.47 U L-1) and Mn-independent peroxidase (184.40 U L-1) were recorded on plum sawdust and wheat straw, respectively. The pretreatment of corn stalks resulted in the highest lignin removal (57.15%), while the highest lignin/cellulose removal ratio (selectivity) was noted on oak sawdust (17.69). The maximal (20%) and the minimal (8.30%) dry matter loss were obtained for corn stalks and oak sawdust, respectively. The presented results showed the exceptional potential of the ligninolytic system of H. marmoreus HAI 605 and the possibility of its application in numerous biotechnological processes.
The goals of the present study were to characterize the profile of ligninolytic enzymes in five Pleurotus species and determine their ability to delignify eight common agro-forestry residues. Generally, corn stalks were the optimal inducer of Mn-dependent peroxidase activity, but the activity peak was noted after wheat straw fermentation by P. eryngii (3066.92 U/L). P. florida was the best producer of versatile peroxidase, especially on wheat straw (3028.41 U/L), while apple sawdust induced the highest level of laccase activity in P. ostreatus (49601.82 U/L). Efficiency of the studied enzymes was expressed in terms of substrate dry matter loss, which was more substrate-than species-dependent. Reduction of substrate dry mass ranged between 24.83% in wheat straw and 8.83% in plum sawdust as a result of fermentation with P. florida and P. pulmonarius, respectively. The extent of delignification of the studied substrates was different, ranging from 51.97% after wheat straw fermentation by P. pulmonarius to 4.18% in grapevine sawdust fermented by P. ostreatus. P. pulmonarius was also characterized by the highest cellulose enrichment (6.54) and P. ostreatus by very low one (1.55). The tested biomass is a highly abundant but underutilized source of numerous value-added products, and a cocktail of ligninolytic enzymes of Pleurotus spp. could be useful for its environmentally and economically friendly transformation.
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