Keywords

Biohydrogen, Microalgae, External proton supply, Proton exchange membrane

Abstract

Green microalgae can naturally produce renewable hydrogen gas (H2) in anaerobic environments by expressing hydrogenase enzymes (HydA). However, H2 production from microalgae remains low and challenging because HydA are only active in low O2 conditions. One practical strategy for creating an anaerobic environment is by adding acetate which can disrupt the oxygen evolving complex (OEC) causing the microalgae to switch to respiration of acetate until O2 is completely depleted. However, by disrupting the OEC, a rich source of protons (H+) from water splitting is lost. This may make H+ into a limiting reactant for H2 production resulting in lower H2 production. In this study, a novel dual chamber design was developed to externally supply H+ from an open photobioreactor (PBR), called the proton supply PBR (PS-PBR), via proton exchange membrane (PEM) to a closed PBR undergoing H2 synthesis. It is hypothesized that microalgae growing in the PS-PBR can provide H+ either by photosynthetic water splitting or respiration of acetate. Therefore, the effect of acetate in the PS-PBR was evaluated. Also, increasing the microalgae biomass in the PS-PBR may result in a higher H+ supply, and thus the effect of initial cell density in the PS-PBR was evaluated as well. Our findings indicated that acetate is necessary for the PS-PBR to provide an external supply of H+, but an excessive amount of acetate diminished this H+ supply. In addition, using higher initial cell density in the PS-PBR in the presence of acetate resulted in an even higher H+ supply. When the optimized PS-PBR condition was used (i.e., 35 mM acetate and 600 mg L-1 initial cell density), H2 production increased 60% compared to the control without PS-PBR. Overall, this novel dual chamber design can be used to improve low biohydrogen production from green microalgae by providing a source of external H+.

Completion Date

2024

Semester

Summer

Committee Chair

Lee, Woo Hyoung

Degree

Master of Science (M.S.)

College

College of Medicine

Department

Burnett School of Biomedical Sciences

Degree Program

Burnett School of Biomedical Sciences

Format

application/pdf

Identifier

DP0028879

URL

https://stars.library.ucf.edu/cgi/viewcontent.cgi?article=1416&context=etd2023

Language

English

Rights

In copyright

Release Date

2-15-2025

Length of Campus-only Access

None

Access Status

Masters Thesis (Open Access)

Campus Location

Orlando (Main) Campus

Accessibility Status

Meets minimum standards for ETDs/HUTs

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