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Item Sodium bicarbonate amendment for enhanced astaxanthin production from Haematococcus pluvialis(Montana State University - Bozeman, College of Engineering, 2019) Erturk, Berrak; Chairperson, Graduate Committee: Brent M. Peyton; Christian Lewis and Brent M. Peyton were co-authors of the article, 'Sodium bicarbonate amendment for enhanced astaxanthin production from Haematococcus pluvialis' submitted to the journal 'Algal research' which is contained within this thesis.Haematococcus pluvialis is a freshwater green microalga that is widely considered to be the richest natural source of the high value carotenoid astaxanthin. The use of bicarbonate salts as a means of efficiently delivering inorganic carbon in microalgal cultivation is a relatively new concept and its application is continuously growing. Previous studies have largely focused on increasing the lipid content in microalgae via the use of high concentrations of sodium bicarbonate under nitrogen deplete culture conditions. Lipid accumulation is directly related to astaxanthin production as astaxanthin is dissolved and stored in lipid bodies in H. pluvialis. Because of this relationship in H. pluvialis, the effects of sodium bicarbonate addition on astaxanthin production was investigated in this study. Due to its complex life cycle, H. pluvialis is commonly cultivated in two stages called the 'green' and 'red' stage. Different approaches have been proposed in each stage to increase the astaxanthin production, namely by growing microalgae under nutrient-limited conditions or resuspending the cells into nutrient deplete conditions. In this study, H. pluvialis (UTEX 2505) was cultivated in stirred (120 rpm) batch reactors containing MES-Volvox medium with a 12 h:12 h light/dark cycle. Sodium bicarbonate (2.5 mM) was used as an additional inorganic carbon source in the green stage and 50 mM of sodium bicarbonate was used as a trigger mechanism to induce astaxanthin production in the red stage. Following the trigger, the astaxanthin accumulation rate increased from 0.13 mg L ^-1 day ^-1 to 0.64 mg L ^-1 day ^-1 with an astaxanthin concentration of 1.56 + or - 0.01 mg L ^-1 and 3.95 + or - 1.25 mg L ^-1 respectively. Whereas, an addition of 2.5 mM sodium bicarbonate at the green stage increased the final astaxanthin accumulation rate up to 2.12 mg L ^-1 day ^-1 and the astaxanthin concentration to 11.2 + or - 0.56 mg L ^-1. Increasing biomass in the green stage resulted in higher astaxanthin content at the end of the red stage. In addition to increasing the total astaxanthin content, 2.5 mM of sodium bicarbonate led to faster nitrogen utilization during the green stage. With this faster utilization of nitrogen, the cultures were grown with a one-stage cultivation approach, where the astaxanthin production occurred in continuous mode.Item Use of bicarbonate salts in algal growth for enhancement of lipid content(Montana State University - Bozeman, College of Engineering, 2016) Pedersen, Todd Christian; Chairperson, Graduate Committee: Brent M. Peyton; Robert D. Gardner, Robin Gerlach and Brent M. Peyton were co-authors of the article, 'Assesment of Nannochloropsis gaditana growth and lipid accumulation with enhanced inorganic carbon delivery' submitted to the journal 'Journal of applied phycology' which is contained within this thesis.; Robin Gerlach, Brent M. Peyton, Gregory L. Helms and Robert D. Gardner were co-authors of the article, 'Monitoring chlorella vulgaris metabolism during bicarbonate induced lipid accumulation using 1 H high-resolution magic angle spinning (HR-MAS) nuclear magnetic resonance (NMR) spectroscopy' submitted to the journal 'Algal research' which is contained within this thesis.Production of biofuel from microalgae has thus far been cost prohibitive due in part to expenses associated with providing the necessary nutritional requirements for growth of the algal culture. In particular, inorganic carbon must be supplied in higher concentrations than available atmospherically to achieve high density cultures necessary for biofuel production strategies. Cost of algal biomass, as a feedstock, will be the limiting factor to the realization of algal biofuels moving forward. Prior research has demonstrated bicarbonate to enhance lipid content in select algal cultures grown under stress conditions, such as nitrogen depletion. This phenomenon has come to be known as bicarbonate-induced lipid accumulation, colloquially known as 'bicarbonate triggering', and has unrealized potential in executing economical and productive algal biofuel. Still, this method has only been demonstrated in select microalgal species and relatively little metabolic information is available regarding its use. Here, two species were investigated with the use of bicarbonate salts for algal growth and lipid accumulation. Nannochloropsis gaditana is a marine microalga which produces relatively high lipid content under nutrient stressed conditions, and has not been thoroughly studied under use of bicarbonate. This organism was studied under bicarbonate supplementation in batch photobioreactor systems. Chlorella vulgaris is a fresh water green alga which has received attention as a biofuel candidate, due to high growth rates and lipid content. This organism was investigated under bicarbonate supplementation during nitrogen depletion with the use of high resolution-magic angle spinning (HR-MAS) nuclear magnetic resonance (NMR) spectroscopy over 38 hours with a 14:10 diel cycle. N. gaditana showed best growth rates under pH controlled growth strategies during nitrogen replete conditions, and bicarbonate was seen to increase lipid content following nitrogen depletion when paired with this growth strategy. However, N. gaditana may not be an ideal candidate for biofuel production as it has relatively low growth rates compared to other industrially relevant organisms, and demonstrated low productivity in batch systems. Metabolite investigation in C. vulgaris revealed large incorporation of inorganic carbon from bicarbonate amendments into biomass, specifically monitored as increases to the biological sucrose pool and subsequent synthesis of fatty acids as carbon storage compounds.