Degradation of lignin during the overgrowth of pleurotus ostreatus mushrooms on the lignocellulosic substrate

Lignocelulozni substrati so v večji meri sestavljeni iz lignina, vsebujejo pa tudi hemicelulozo in celulozo. Če želimo lignocelulozne materiale uporabljati v različne industrijske namene, je razgradnja lignina pomemben predkorak. Lignin se lahko razgrajuje v fazi preraščanja z določeno gobo. Gobe izločajo specifične encime, ki pomagajo razgrajevati lignin do te mere, da se lahko nadalje vršijo reakcije s celulozo in hemicelulozo. Razgradnja lignina je v naravi počasen proces. V laboratorijskem merilu smo želeli preveriti vpliv prisotnosti gobe Pleurotus ostreatus na razgradnjo lignina. Zanimala nas je razlika med razgradnjo lignina dveh substatov in sicer slame ter miskantusa. Oba substrata spadata med lignocelulozne materiale, vendar ima pšenična slama v osnovi večji delež lignina, kot pa miskantus. Eksperiment je temeljil na različnih substratih, ki so bili predobdelani z isto gobo. Inkubacijski čas vzorcev je bil 30 dni. Merili smo razliko v vsebnosti lignina na začetku in na koncu preraščanja, ter v različnih vmesnih časovnih intervalih. Vzorci so bili predhodno pripravljene mešanice piščančjega gnoja z žagovino in substatom, preraščenim z gobo v različnih razmerjih. Kot kontrolne vzorce smo pripravili tudi mešanice substrata, ki ni bil predobdelan z gobo P. ostreatus ter piščančjega gnoja z žagovino v enakih razmerjih. Opazovali smo razliko v razgradnji lignina. Da bi rezultate podkrepili, smo kvantificirali nekatere monosaharide, ki bi morali nastajati, medtem ko se lignin razgraja. Ugotovitve diplomskega dela so, da je inkubacijski čas 30 dni bistveno prekratek za znatno zmanšanje koncentracije lignina v lignoceluloznih substratih. Žal nismo dokazali niti, da goba pozitivno vpliva na razgradnjo lignina. Rezultati, ki smo jih pridobili s pomočjo Klasonove metode, so razpršeni in ne dajejo jasnega vpogleda, kako in koliko lignina je moč razgraditi na izbranih substratih. Z raziskavami nismo uspeli dokazati neposredne korelacije med razgradnjo lignina in vsebnostjo monosaharodov, saj dobljeni rezultati nakazujejo na to, da gobe nastale monosaharide porabijo kot vir enegije za svojo nadaljno rast.Lignocellulosic substrates are largely composed of lignin and contain hemicellulose and cellulose. If lignocellulosic materials are used for various industrial purposes, lignin degradation is an important step forward. Lignin can be broken down in the process of overgrowing with a certain mushroom. Mushrooms secrete specific enzymes that help at break down lignin to such an extent that further reactions can occur with cellulose and hemicellulose. The decomposition of lignin is a slow process in nature. At the laboratory scale, we wanted to check the effect of the presence of Pleurotus ostreatus on the degradation of lignin. We investigated the difference in the decomposition of lignin in two substrates, namely wheat straw and miscanthus. Both substrates are lignocellulosic materials, but wheat straw has basically higher lignin content than miscanthus. The incubation time of the samples was 30 d. We measured the difference in lignin content at the beginning and at end of the overgrowing, and at different intermediate time intervals. Samples were pre-prepared mixtures of chicken manure with sawdust and a substrate overgrown with mushroom at different mass ratios. Mixtures of un-treated substrates and chicken manure with sawdust in equal mass ratios were also prepared as control samples. The difference in lignin degradation was observed. To confirm the results, we identified and determined the concentrations of some monosaccharides that would have to be generated while lignin decomposes. The incubation time of 30 d is found to be significantly too short for reducing the concentration of lignin in lignocellulosic substrates. Unfortunately, we have not shown that mushroom has a positive effect on lignin degradation. The results obtained by means of the Klason method are scattered and do not give clear insight into how and how much lignin can be degraded on selected substrates. Research has not been able to demonstrate a direct correlation between lignin degradation and monosaccharide content, as the results indicate that mushroom-derived monosaccharides are probably consumed as a source of energy for their continued growth