Date of Award

5-7-2021

Document Type

Open Access Thesis

Department

Biology

First Advisor

Ira "Ike" Levine

Second Advisor

Theresa Theodose Ph.D.

Third Advisor

Rachel Larsen Ph.D.

Abstract

Astaxanthin is a key carotenoid pigment produced primarily in nature by the unicellular microalga Haematococcus pluvialis. This potent antioxidant is produced in response to environmental stressors, such as high light, upon which reactive oxygen species (ROS) are produced. While the presence of ROS has been established in this cascade via carotenogenic genes, its effect has not been defined. The overall goal of this study was to quantify the effect of ROS on the astaxanthin biosynthesis pathway within H. pluvialis. Cellular ROS concentrations and astaxanthin output were quantified in response to environmental variables, redox-sensitive compounds, and ROS-scavengers. All environmental and redox-sensitive conditions tested led to encystment and an increase in astaxanthin output. Initial astaxanthin production rates over days 0-5 were highest in the redox-sensitive variable group, with a subsequent rate peak at days 5-10 for environmental test groups. Cellular ROS concentrations similarly peaked over days 0-5 and 5-10 for redox-sensitive and environmental test groups, respectively. All groups later showed significant decreases in ROS concentration by days 10-15. Furthermore, application of a ROS-scavenger decreased cellular ROS concentrations and induced germination. These results suggest a strong correlation between astaxanthin output and cellular ROS concentrations. By quantifying a relationship between cellular ROS concentration and H. pluvialis astaxanthin production and germination behavior, this work aims to highlight the important role of ROS in the astaxanthin biosynthesis pathway. Further application of this knowledge could be used to design a more cost and resource efficient method of natural astaxanthin production in industrial settings.

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