Augmented growth of haematococcus pluvialis using nutrients from post hydrothermal liquefaction wastewater (PHWW)

Post Hydrothermal Liquefaction Wastewater, Haematococcus Pluvialis, Astaxanthin, Nutrient Recovery

Stablein, Michael James ; Gates, Richard, ; ,Schideman, Lance C. ; Zhang ; Yuanhui

关键词: Post Hydrothermal Liquefaction Wastewater, Haematococcus Pluvialis, Astaxanthin, Nutrient Recovery;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/101610/STABLEIN-THESIS-2018.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

This study was conducted to evaluate if a high-value algae species, Haematococcus Pluvialis, could be successfully cultivated utilizing nutrients derived from a concentrated wastewater source and produce the potent antioxidant astaxanthin at similar quantities to when it is grown on conventional media and nutrient sources. The primary wastewater used in this study was the aqueous product of hydrothermal liquefaction (HTL), which is an attractive process for the conversion of wet biomass to bio-crude oil. Using recycled nutrients from the post HTL wastewater (PHWW) or other wastewater sources for growing algae can reduce costs and synthetic nutrient inputs, which improves the sustainability of algae cultivation operations. In the first part of this work, we determined an appropriate dilution of PHWW to support algal growth and astaxanthin production, while avoiding significant inhibitory effects of PHWW that have been previously reported in the literature. PHWW, was characterized for nitrogen and phosphorus content and compared with other wastewater sources and conventional algal media. Then, H. Pluvialis cells acclimated on Bold’s Basal Media (BBM) were inoculated across a 0-2% PHWW gradient in a well plate to identify the algae’s tolerance for the PHWW. This result determined that H. Pluvialis cells were able to grow well at concentrations of PHWW up to 0.25% when mixed with BBM. In a second experiment designed to investigate algal preferences for different chemical forms of nutrients, H Pluvialis was inoculated in BBM having only nitrate or only ammoniacal nitrogen as the nitrogen source. The cell counts were measured daily with a hemocytometer, and nutrient removal was also measured. This experiment showed no significant differences in algal growth based on the chemical form of nitrogen provided.Using the concentrations of 0.125% and 0.25% PHWW that were determined in the first experiment to support good algal growth, another larger scale cultivation experiment was performed in three 1L flasks to confirm algal growth results in comparison to the BBM only control. In each of the respective media compositions, the total amount of inorganic nitrogen was held constant by removing only nitrate from the baseline BBM media recipe, replacing it with the corresponding concentration of total ammoniacal nitrogen (TAN) from PHWW. For the 0.125% and 0.25% PHWW treatments, the corresponding amount of nitrogen replaced was 5 and 10%, respectively. During this experiment, nutrient concentrations were measured daily, and the algae were able to reduce nitrogen concentrations from the various media mixes by at least 80%. Based on cell counts, the PHWW at 0.125% and 0.25% augmented the algae growth by 44% and 17%, respectively.The algae biomass from the BBM control media and the alternative media blends with PHWW nutrients was harvested and subjected to stress conditions of elevated light and salinity. Stressing the cells was intended to induce increased production of carotenogenic antioxidants, including astaxanthin, which was confirmed by a gradual reduction of the chlorophyll: carotenoid ratio. After encystment, astaxanthin production was quantified using high performance liquid chromatography (HPLC), and these data showed that it was reduced by 47.3% and 34.1% in the 0.125% and 0.25% PHWW augmented cultures, respectively. Even though the amount of astaxanthin was reduced for the PHWW treatments, the final harvest extracts of algae grown with PHWW presented a more diverse and complex carotenogenic profile. In conclusion, this study demonstrates that PHWW nutrients can enhance H. Pluvialis cell growth, but further work is needed to better understand and control the amount and types of carotenoids produced by H. Pluvialis. The long-term effects of acclimation and adaptation were not studied, and provide additional opportunities for improving overall system performance. In particular, acclimation could help mitigate inhibitory effects of the PHWW that were observed even when PHWW was added at very low levels. Finally, other sources of sustainable nutrients from wastewater with less inhibitory contaminants should be investigated to hopefully provide replacement of a larger fraction of the nutrients needed for large scale algae cultivation.