Scholarship & Research
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/1
Browse
3 results
Search Results
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 The determination of the beta-carotene and vitamin A content of Montana butter from different areas at various seasons and after storage(Montana State University - Bozeman, College of Agriculture, 1944) Brence, John L.Item Functional studies of type II heterodimeric phytochromes and end-modified type I phyAs in arabidopsis(Montana State University - Bozeman, College of Agriculture, 2011) Liu, Peng; Chairperson, Graduate Committee: Robert Sharrock.Phytochromes (phys) are a family of dimeric chromoprotein photoreceptors that modulate plant physiological and developmental processes in response to red (R) and far-red (FR) light. In Arabidopsis thaliana, these fall into two functional groups, type I phyA and type II phyB-E. Previous findings have shown that heterodimerization occurs in type II phytochromes and suggest that diverse dimer forms may have specific functions. The first objective of this study was to characterize the activities of individual phytochrome dimer combinations by developing a novel in vivo protein engineering system. Either obligate homodimers or heterodimers of phytochrome N-terminal regions were produced in phyB mutant plants. With this system, a highly active phyB/D heterodimeric form was shown to rescue the phyB mutant phenotype. Dimers of phyB/achromo-phyB, phyB/C, and phyB/E mediated organ-specific growth in de-etiolation by functioning differentially in cotyledons but not in hypocotyls. Light labile phyA is critical in the plant transition from skotomorphogenic to photomorphogenic growth. To investigate possible in vivo phyA heterodimerization with type II phys and the relationship between phy quaternary structure and signaling mechanisms, transgenic plants were generated that express different myc- tagged N- or C-terminal end fusion phyA proteins in a Landsberg erecta (Ler) phyA mutant or a wild-type background. Co-immunoprecipitation showed that phyA only forms homodimers with itself. Compared with fully active one myc epitope (myc1)-tagged phyAs, six myc epitopes attached to the ends of the N- or C- terminus of phyA impaired phyA-mediated far-red high irradiance (FR-HIR) signaling and also attenuated degradation in the light, indicating that alteration of phyA architecture may damage protein-protein interaction both in phyA downstream signaling and in its protein turnover. Overall, these findings have expanded the structurally complex R/FR sensing systems in plants and have implications for how plant growth and development may be fine-tuned through phy heterodimer-mediated tissue-specific growth or phy-modified activity.