DETERMINATION OF ALGAE BIOMASS AND CHLOROPHYLL IN CULTIVATION MEDIA

Namen diplomske naloge je bil ugotoviti vpliv dodatka vira ogljika na donos algne biomase in koncentracije klorofila. Mikroalge Chlorella sorokiniana smo inkubirali v tekočem gojišču ter v posameznih poskusih dodali vir ogljika, za kar smo uporabili grozdni sok in med. Omenjeno algno suspenzijo smo poskušali gojiti pri avtotrofnem, heterotrofnem in miksotrofnem rastnem režimu. Glavni parametri, ki smo jih spremljali so pH, temperatura in koncentracija raztopljenega kisika. Prirast mikroalg smo določali z merjenjem optične gostote pri različnih valovnih dolžinah, z direktnim štetjem algnih celic pod mikroskopom, z določanjem suhe mase alg ter z vsebnostjo klorofila. Mikroalge, ki so rastle na gojišču, brez dodatka vira ogljika, smo v eksperimentih uporabili kot kontrolni vzorec. Ugotovili smo, da uporaba grozdnega soka ni bila primerna, saj je v vzorcu, ki je bil izpostavljen viru sončne svetlobe na okenski polici, potekel proces fermentacije. Posledica je bila odmiranje algnih celic. V naslednjem eksperimentu smo kot vir ogljika dodali med in vzorce izpostavili različnim rastnim pogojem. Rezultati kažejo, da smo dobili največji celični donos v miksotrofnem rastnem režimu, kjer smo vzorec z dodatkom medu izpostavili viru sončne svetlobe. Nižji donos algne biomase smo dobili pri gojenju alg pod avtotrofnimi pogoji. Heterotrofni rastni režim, kjer smo celično suspenzijo z dodatkom medu postavili v temen prostor, ni bil uspešen, saj se celice niso uspele prilagoditi nižji intenziteti svetlobe. Ugotovili smo, da z višanjem koncentracije medu kot vira ogljika, narašča donos biomase in klorofila.The purpose of thesis was to establish the influence of carbon source on growth of algae biomass and concentration of chlorophyll. Microalgae Chlorella sorokiniana were incubated in liquid medium and in individual experiments carbon source was added by using grape juice and honey. The algae suspensions were exposed to autotrophic, heterotrophic and mixotrophic growth regime, respectively. Main observed parameters were pH, temperature and concentration of dissolved oxygen. The growth of algae was determined by measuring optical density at different wavelengths, by direct counting of algae cells under the microscope, by defining dry weight and by content of chlorophyll. Microalgae that grew in medium without carbon source additive were used in experiments as a control sample. We have established that using grape juice was inappropriate since in the sample which was exposed to source of sunlight on window shelf, the fermentation process started. The consequence was the dying off of algae cells. In the next experiment we added honey as a source of carbon and then we exposed the samples to different growth conditions. The results showed the highest cell growth in mixotrophic growth regime, when sample was exposed to the sunlight and honey was added. Lower growth of algae biomass was observed under autotrophic conditions. Heterotrophic growth regime, in which the cell suspension with addition of honey was kept in the dark, was not appropriate since the cells could not adjust to lower light intensity. With higher honey concentrations, we observed higher growth of biomass and chlorophyll