engleski

Microalgae Utilizing Wastewater as Promising Candidates for Biofuel Production

Linking conventional industrial plants to sustainable processes e.g. connecting algal cultivation systems to industrial wastewater (WW) treatment plants of oil refineries is of the uttermost importance for a 'greener future'.Therefore the Project A3-PICO-IIIG is aimed to investigate the potential of the Adriatic microalgae as biorefinery feedstock. The most promising species are selected according to their biomass yield, the feasibility of cells harvest, lipid and carbohydrate productivity, oil extractability, C16 and C18 content, and fatty acid methyl esters (FAME) saturation. For this reason various phytoplankton species were isolated from nutrient-rich waters at the mouths of the rivers Po and Mirna, and in proximity to the INA-Oil Refinery (Urinj). Among these, three cyanobacteria have been identified by 16S rDNA sequencing as Phormidium lucidum, Phormidium sp. and Synechococcus sp., while the two diatom species: Halamphora coffeiformis and Entomoneis pusilla have been confirmed by Scanning Electron Microscopy. In addition, two Adriatic nanoeukaryotic species: Microchloropsis gaditana and Pseudochloris wilhelmii were purchased. The biomass was produced in photobioreactors under standardized growth conditions, with possibility of regulating temperature, pH, light intensity and gas supply, while the yield was monitored gravimetrically. As follows, nutrients were measured spectrophotometrically while biochemical composition by Fourier Transformed Infrared Spectroscopy (FTIR) and gas chromatography (GC/MSD) for FAME. Dried biomass consisted of 21.4% of lipids in Synechococcus sp. and 26% in eukaryotes i.e. H. coffeiformis. Although FAME profiles predominantly consisted of monounsaturated C16–18 chains, P. wilhelmii was richest in polyunsaturated FAME and grew the fastest (152 mg/L·day). In contrast, lipid- rich species with dominant monounsaturated content grew slower, from 25 mg/L·day for Synechococcus sp. to 75 mg/L·day for M. gaditana. Moreover, the addition of WW up to 50% and consequently the NH4+-increase up to 1.2 mM favoured biomass growth and FAME-saturation of Synechococcus species. The FTIR spectra of the lipid-rich species consistently showed higher peaks for ν(C-H) of saturated C-H chains (around 2900 cm- 1) whereas among them P. wilhelmii had the highest peaks in Amide I and II region.

Microalgae ; industrial wastewater ; wastewater treatment ; photobioreactor ; FAME profile

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