| Abstract | Medovina je tradicionalno alkoholno piće dobiveno fermentacijom razrijeđene otopine meda pomoću odabrane vrste kvasca. Budući da je med siromašan na nutrijentima koji su potrebni za aktivnost stanica kvasca, uobičajen je dodatak suplemenata s dušikovim spojevima u mednu sladovinu kako bi se skratilo vrijeme trajanja fermentacije i ostvarili bolji pokazatelji uspješnosti bioprocesa. U preliminarnom istraživanju provedenom u tikvicama ispitan je utjecaj dodatka različitih koncentracija kvaščevog ekstrakta (0 g/L, 0,5 g/L i 2 g/L) kao izvora dušika na dinamiku fermentacije sladovine od bagremovog meda uz pomoć kvasca Saccharomyces cerevisiae ph.r. bayanus. Ostvareni prinosi etanola u tikvicama redom su iznosili 8,04 g/L, 15,64 g/L i 50,74 g/L čime je dokazan pozitivan utjecaj dodatka kvaščevog ekstrakta na koncentraciju proizvedenog etanola. Na temelju rezultata preliminarnog eksperimenta, odabrana je koncentracija kvaščevog ekstrakta od 2 g/L pri kojoj je provedena fermentacija u bioreaktoru s miješalom primjenom dvije različite tehnike proizvodnje (šaržni postupak i šaržni postupak s pritokom supstrata) s ciljem usporedbe pokazatelja uspješnosti ta dva postupka. U ovom dijelu istraživanja ostvareni su slični prinosi etanola, 43,28 g/L kod šaržnog postupka te 41,42 g/L kod šaržnog postupka s pritokom supstrata. Koeficijent pretvorbe supstrata u produkt kod šaržnog postupka iznosio je 0,38 g/g, uz produktivnost od 0,65 g/Lh, dok je kod šaržnog postupka s pritokom supstrata postignut koeficijent konverzije od 0,33 g/g, uz produktivnost od 0,42 g/Lh. Iz rezultata dobivenih tijekom izrade ovog diplomskog rada može se zaključiti da dodatak odgovarajuće koncentracije kvaščevog ekstrakta u sladovinu od bagremovog meda znatno utječe na konačni prinos etanola te da se medovina može proizvoditi primjenom obje tehnike proizvodnje. |
| Abstract (english) | Mead is a traditional alcoholic drink obtained by fermenting a diluted solution of honey, using a selected strain of yeast. Since honey is poor in nutrients necessary for yeast activity, it is common to add supplements with nitrogen compounds into the honey wort to accelerate fermentation and achieve better bioprocess efficiency parameters. In the preliminary part of this thesis, carried out in flasks, the effect of adding different initial concentrations of yeast extract (0 g/L, 0,5 g/L, and 2 g/L) as a nitrogen source on the fermentation dynamics of acacia honey wort using the yeast Saccharomyces cerevisiae ph.r. bayanus was studied. The achieved yields of ethanol in these experiments were 8,04 g/L, 15,64 g/L and 50,74 g/L, respectively, which indicates a positive effect of adding yeast extract on the concentration of produced ethanol. Based on the results of the preliminary experiment, a concentration of yeast extract of 2 g/L was selected for fermentation carried out in a stirred tank bioreactor by using two different production techniques (batch process and fed-batch process) with the aim of comparing the bioprocess efficiency parameters between them. Similar results were achieved by using both techniques, where ethanol yield of 43,28 g/L for the batch and 41,42 g/L for the fed-batch process was obtained. The conversion coefficient of substrate to product for the batch process was 0,38 g/g, with a productivity of 0,65 g/Lh, while in the fed-batch process achived conversion coefficient was 0,33 g/g, with a productivity of 0,42 g/Lh. From the results obtained during prepearation of this thesis, it can be concluded that the addition of a suitable concentration of yeast extract to acacia honey mead significantly affects the final yield of ethanol and that both production techniques can be used for mead production in stirred tank bioreactor. |
