Maximising the photobiological production of hydrogen using leachate, while monitoring algal photosynthesis using pam fluorometry.
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Date
2014
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Abstract
Hydrogen is universally known as the most efficient renewable energy source capable of
meeting global energy demands. Chlamydomonas reinhardtii has the ability to produce
biohydrogen during the metabolic engineering of the photosynthetic pathways. The aim of
this study was to 1) use leachate as a feedstock to enhance microalgal biomass and
subsequent hydrogen production, 2) use Pulse Amplitude Modulated (PAM) Fluorometry to
elucidate the role of photosystem one during hydrogen production, 3) use Nicotinamide
Adenine Dinucleotide Phosphate (NADPH) fluorescence as an indicator of hydrogen
production and 4) design a modular pilot scale biohydrogen bioprocessing system
implementing experimental findings into a conceptual model. This resulted in a cost
effective source of renewable hydrogen produced from waste. The use of 16% landfill
leachate was found to increase biomass production by 26% as compared to using Tris-
Acetate Phosphate (TAP) media alone. Hydrogen induction resulted in an increased gas
synthesis of 37% as well as an increased production period of 8 days compared to the normal
5 days. Landfill leachate further reduced the costs as it acted as a free nutrient source with
the added ecological advantage of leachate treatment. Hydrogen production was induced by
sulphur depletion and physiological parameters were measured using PAM Fluorometry.
Photosystem I was found to be dominant during hydrogen production while photosystem II
was down-regulated due to the sulphur depletion and damaged D1 proteins. NADPH
fluorescence was significantly correlated to hydrogen yields allowing for NADPH to be
utilised as a molecular indicator for hydrogen synthesis. The overall functionality of this
bioprocessing system relies on the optimum physiological functioning of cells. The above
findings were implemented into a pilot scale design, maximising the physiological
performance during hydrogen production. This study has contributed knowledge regarding
the production of hydrogen gas from leachate, the physiological changes of photosystem I
during hydrogen production and the use of NADPH fluorescence as an indicator. The
fundamental theories of bioprocessing incorporate a firm understanding of cellular and
biochemical processes. The use of molecular indicators determined from physiological
studies can be used at pilot scale to improve overall efficiency of hydrogen production.
Description
Ph.D. University of KwaZulu-Natal, Durban 2014.
Keywords
Leachate., Synthesis gas., Biochemical engineering., Photobiology., Theses--Civil engineering.