Microalgal cultivation for value-added products

BackgroundThe rate of anthropogenic input of CO2 to the atmosphere exceeds the rate at which physicochemical and biological processes remove CO2. The resulting increase in the atmospheric CO2 concentration is widely perceived as a major cause of the present increase in global temperatures.Biological capture of CO2 using microalgae is promising approach for mitigation of excess carbon. Microalgae have recently gained enormous attention worldwide, to be the valuable feedstock for renewable energy production, due to their high growth rates, high lipid productivities and theability to sequester carbon. The aim here was to study the influence of different CO2 (10, 20, and 30% v/v) concentrations as a carbon source on two indigenous isolates of Dunaliella sp. (ABRIINW-CH2 and ABRIINW-SH33) as well as their lipid content, productivity, and fatty acid profile under adjusted pH conditions. Results High CO2 concentrations were favorable for the accumulation of lipids, lipid productivity, and polyunsaturatedfatty acids formation. The highest lipid content and lipid productivity was obtained at 10% CO2. The unsaturated fatty acids (USFA) content increased significantly under 20% CO2 concentrations in ABRIINW-SH33 and ABRIINW-CH2, respectively. The USFA content was enhanced withinapproximately similar progression at 30% and 10% CO2. Polyunsaturated fatty acid (PUFA) amount showed an upward trend with induction of extra CO2 and it was significantly enhanced with CO2 increase up to 20%. Monounsaturated fatty acid (MUFA) production was induced by CO2 increaseand reached the maximum amount in ABRIINW-SH33 and ABRIINW-CH2 at 20% and 30% CO2, respectively.The highest fraction of the fatty acids (FA) profile was allocated to omega-3 FAs at 20% CO2. Accordingly, our data suggested that using Dunaliella sp. can change, the rising universal CO2 from a threat to an opportunity at low cost compared with developed carbon capture and storagetechnologies. Conclusions The results demonstrated that the CO2 biofixation rate improved with our studied isolates under 10% CO2. High CO2concentrations (10-30%) were favorable for the accumulation of total lipids, increase of lipid productivity and polyunsaturated fatty acids. Omega-3 (n-3) fatty acids formed the highest fraction of total fatty acids. The Omega-3: Omega- 6 (n-6) ratio was even higher than the recommended rangewhich maintains human health. Accordingly, CO2 sequestration could be coupled with the transition to valuable biological products by the studied isolates.

کلیدواژه ها:

CO2 capturing ، Dunaliella microalgae ، Omega-3 fatty acid.