SUMMARYThe aim of this research is to isolate and identify fungi with high lignin-degrading abilities that are autochthonous to southern Serbian region. Two novel fungal isolates identified as Trametes hirsuta F13 and Stereum gausapatum F28 were selected to assess their ligninolytic enzyme activities and the efficiency of lignin removal from beech wood sawdust. Obtained results show that both isolates are good sources of industrially valuable enzymes with a potential for application in various biotechnological and industrial processes. Both isolates showed laccase, manganese-dependent peroxidase, and versatile peroxidase activities, while only S. gausapatum F28 had lignin peroxidase activity. This is the first record of the ability of S. gausapatum species to produce lignin peroxidase. T. hirsuta F13 showed higher laccase activity than S. gausapatum F28, while S. gausapatum F28 had higher manganese peroxidase activity. Also, T. hirsuta F13 exhibited much higher laccase activity under submerged cultivation conditions than solid-state cultivation conditions, which is rare for fungi. This is important for industrial processes since the submerged fermentation is a dominant technique in industry. The test of the efficiency of lignin removal showed that both isolates are efficient lignin decomposers. After five weeks of incubation on beech wood sawdust, the total lignin losses were 33.84% with T. hirsuta F13 and 28.8% with S. gausapatum F28.

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Izvod Predtretman predstavlja neophodan korak u procesu konverzije lignocelulozne biomase do etanola. On unapređuje enzimsku hidrolizu promenama u strukturi lignoceluloze, ali je često utrošak energije za predretman veliki i/ili se primenjuju skupe i toksične hemikalije, što proces čini ekonomski i ekološki nepogodnim. Primena lignocelulolitičkih gljiva (iz klasa Ascomycetes, Deuteromycetes i Basidiomycetes) je atraktivna metoda za predtretman, ekološki prihvatljiva i ne zahteva ulaganje energije. U ovom radu su predstavljeni mehanizmi razgradnje lignoceluloze pomoću gljiva. One proizvode širok spektar enzima i hemijskih supstanci kojima uspešno razgrađuju lignocelulozu, ali i aromatične polimere slične strukture ligninu. U ovom radu je prikazana mogućnost njihove primene u tehnologiji proizvodnje bioetanola, a navedene su i prednosti i nedostaci biološkog predtretmana.

This study provides detailed analysis of the lignocellulolytic activity of a new isolate Stereum gausapatum F28, Serbian autochthonous fungi, on beechwood sawdust supplemented with cheap waste, sugar beet molasses stillage. Advanced multiple response optimization techniques were applied to improve ligninolytic and reduce hydrolytic activity as a requirement for potential biorefinery use. The applied techniques were supposed to select cultivation conditions that would give manganese peroxidase and laccase activities above 0.84 and 0.12 U g-1 substrate, respectively, and cellulase and xylanase activities below 1.12 and 1.4 U g-1 substrate. The optimal cultivation conditions that met the set requirements included molasses stillage concentration of 10 %, substrate moisture content of 53 %, incubation temperature of 23.5?C, and pH 5.2. The research showed that the addition of molasses stillage had positive effect on the enzyme production and that the optimal stillage concentration differed depending on the enzyme type (for laccase it was <5 %, manganese peroxidase ~12 %, cellulase ~21 %, xylanase ~16 %), which should be taken into consideration when optimizing the desired process.

This research examined the potential use of isolated Serbian autochthonous fungi in lignocellulosic biomass pretreatment. Among 12 isolated fungi, the isolates identified as Trametes hirsuta F13 and Stereum gausapatum F28 stood out as ligninolytic enzyme producers and were selected for potential use in the pretreatment of a waste lignocellulosic biomass. An isolate identified as Myrmaecium fulvopruinatum F14 showed high hydrolytic activity, but negligible ligninolytic activity, and it was selected as a potential producer of important industrial hydrolytic enzymes. Further, the breakdown of lignocellulosic waste, beechwood sawdust, by T. hirsuta F13 and S. gausapatum F28 was examined. Both isolates efficiently degraded biomass, but T. hirsuta F13 exhibited greater selectivity (selectivity coefficient of 1.7) than S. gausapatum F28 (1.1). The isolate F13 was considered a better candidate for the pretreatment, and it was selected for further analysis which involved the use of molasses stillage as a supplement to improve the pretreatment.