AUTHOR=Blažina Maria , Fafanđel Maja , Geček Sunčana , Haberle Ines , Klanjšček Jasminka , Hrustić Enis , Husinec Lana , Žilić Luka , Pritišanac Ena , Klanjscek Tin 

TITLE=Characterization of Pseudochloris wilhelmii  potential for oil refinery wastewater remediation and valuable biomass cogeneration

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 9 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.983395

DOI=10.3389/fmars.2022.983395

ISSN=2296-7745

ABSTRACT=The microalgae of the genus Pseudochloris/Picochlorum are characterized by fast growth, and wide nutrient (type and concentration) and salinity tolerance, all contributing towards exploration of their use in high-density biomass production and wastewater bioremediation. In this study, removal of N and P nutrients from oil refinery wastewater was monitored during growth of the marine eukaryotic microalgae Pseudochloris wilhelmii, with emphasis on biochemical analyses of its biomass quality to evaluate suitability for biodiesel production. A series of growth experiments under various nutrient and light regimes were performed in a temperature range of 20-30ºC to evaluate nutrient removal and biomass growth dependence on temperature. The highest removal rate of dissolved inorganic nitrogen reached under the given experimental conditions was 0.823 mmol/(gday) accompanied by the corresponding biomass productivity of 115.2 mg/(Lday). Depending on light and temperature, the final lipid concentration ranged 181.5 – 319.8 mg/L. Furthermore, increase in nutrient load decreased the maximum specific growth rate, and the maximum specific removal rate of the dissolved inorganic nitrogen. The decrease prolonged the bioremediation process by 2.5 times, with 26% higher maximal specific growth rate and 81% higher maximal biomass production. In contrast, constant light exposure expedited the nitrogen removal, i.e. bioremediation process, by one day, while supporting 60% higher maximal specific growth rate and 100% higher maximal biomass production. The conditions favoring the highest nitrogen removal and highest toxicity reduction in ORWW are met at 24ºC and 130 µmol phot/(m2s).  The highest proportion of carbon-binding to the P. wilhelmii biomass was noticed under the same conditions, thus indicating them as the most favorable conditions for hydrocarbon removal as well as for CO2 sequestration. Pseudochloris wilhelmii therefore represents a promising candidate for oil refinery wastewater remediation and valuable biomass cogeneration on a large-scale.