Enzymatic digestion of paper industry waste sludge

Primarni cilj magistrskega dela je bila študija možnosti koristne uporabe odpadnega mulja obstoječe papirnice. Ta material med drugim vsebuje tudi celulozo, za katero je znano, da ob ustrezni predobdelavi hidrolizira najprej do enostavnih sladkorjev, ti pa v naslednjem koraku fermentirajo do bioetanola. Hidrolizo celuloze smo izvajali ob prisotnosti specifičnega encima celulaze in iskali optimalne pogoje za njen najučinkovitejši potek. Reakcije alkoholne fermentacije v okviru tega dela nismo izvajali, saj so predhodne raziskave pokazale, da gre za dokaj enostavno reakcijo s 100-odstotnim izkoristkom. Za izvajanje reakcije hidrolize smo uporabljali šaržni reaktorski sistem EasyMax 102. Sistem je bil izbran zaradi njegove enostavne uporabe, avtomatizacije, natančnosti in majhnih reaktorskih volumnov. Vse te lastnosti sistema smo ob eksperimentalnem delu dodatno potrdili. Pri encimski hidrolizi smo zaradi majhnega izkoristka reakcije odpadni mulj predhodno obdelali z različnimi tehnikami predobdelave. Uporabili smo mletje, kislinsko predobdelavo z orto – fosforjevo kislino, alkalno hidrolizo z NaOH in oksidacijo s H2O2. S temi tehnikami smo spreminjali kristalinično strukturo celuloze na več amorfnih področjih. Z eksperimentalnim delom smo določili in potrdili optimalne reakcijske pogoje encimske hidrolize odpadnega mulja (volumen encima, pH raztopine, čas reakcije in vrsto topila). Kot optimalno tehniko predobdelave smo izbrali kislinsko predobdelavo z orto – fosforjevo kislino. Pri tej je teoretično izračunana dnevna količina bioetanola znašala za bolj razredčeno raztopino ( = 1 g/L) 316 kg in za manj razredčeno raztopino ( = 3,5 g/L) 151 kg. The primary goal of the master's work was the study of possible re-use of waste sludge from the paper mill. This material also includes cellulose, for which it is known than if properly treated it can hydrolyze into simple sugars, which in the next step ferment to bioethanol. We performed the hydrolysis of cellulose with a specific enzyme celullase and searched for optimal reaction conditions. Alcohol fermentation was not carried out, since previous research shows it is a fairly simple reaction with 100 % efficiency. For implementation of hydrolysis reaction we have used batch reactor system EasyMax 102. It was selected because of its ease of use, automation, precision and small reactor volume. All these preferences of the system were confirmed during experiments and were used accordingly. Due to small yield of reaction, the waste sludge was pretreated with different preatretment technics. We used grinding of the material, pretreatment with ortho – phosphoric acid, alkaline hydrolysis with NaOH and oxidation with H2O2. With these technics we changed the crystalline structure of cellulose to different amorfic areas. With this experimental work we have determined and confirmed optimal reaction conditions of enzyme hydrolysis of cellulose from the waste sludge (volume of enzyme, pH of the solution, reaction time and solvent type). As optimal pretreatment technic we chose pretreatment with ortho – phosphoric acid. The theoretical calculated daily value of bioethanol was 316 kg for the case of more diluted solution ( = 1 g/L) and 151 kg for the case of less diluted solution ( = 3,5 g/L).