The focus of this study is to elucidate the photosynthetic activity of microalga Chlorella vulgaris using pulse amplitude modulation (PAM) fluorometry. C. vulgaris is a species of microalga that is currently being studied for its use in biodiesel production. In addition, it has many of the advantages of other algal based biofuel feedstock such as being noncompetitive for arable land, its ability to grow on waste water, and it produces high concentrations of short chain fatty acids. C. vulgaris also has the ability to grow mixotrophically (simultaneous heterotrophic and photoautotrophic growth), which can allow for cultures to be grown in the dark; however, the extent of heterotrophic versus photoautotrophic activity in C. vulgaris grown in light conditions has not yet been determined. PAM fluorometry is a reliable and sensitive method of measuring photosynthetic activity in whole cells. By measuring the fluorescence emitted by the algae when the cells are subjected to continuous illumination or flashes of actinic light, the mode of photosynthesis can be determined (linear vs. cyclic). This investigation used PAM fluorometry on C. vulgaris, grown in both light (photomixotrophically) and dark conditions (heterotrophically), in order to evaluate the OJIP curve and the S-states cycle of the algae in both conditions. Cells grown in the light ultimately yield the same biomass as cells grown in the dark while consuming equivalent amounts of glucose; however, they have a higher abundance of lipids. One hypothesis is that the cells are using cyclic electron transfer instead of linear photosynthesis. The purpose of this experiment is to determine which mode of photosynthesis the cells are using under the different growth conditions. The results may also give insight into the extent of the mixotrophy exhibited, which will assist in optimizing the photosynthetic efficiency of microalgae in general.

Pulse amplitude modulation fluorometry as a means to determine photosynthetic modes of Chlorella vulgaris

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.