Developing Next Generation Algae Bioplastic Technology
- Publication Type:
- Thesis
- Issue Date:
- 2022
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Cyanobacteria are microscopic photosynthetic organisms capable of converting atmospheric CO₂ into a bioplastic, PHB (poly-hydroxy-butyrate). Unfortunately, the industrial production of cyanobacterial PHB is still not economically viable due to lower PHB productivity rates and high cultivation equipment costs compared to fermentation. Thus, four areas were explored as separate data chapters in this thesis:
𝗖𝗵𝗮𝗽𝘁𝗲𝗿 𝟮: 𝗥𝗮𝗻𝗱𝗼𝗺 𝗺𝘂𝘁𝗮𝗴𝗲𝗻𝗲𝘀𝗶𝘀 𝗳𝗼𝗿 𝘀𝘂𝗽𝗲𝗿𝗶𝗼𝗿 𝗰𝘆𝗮𝗻𝗼𝗯𝗮𝗰𝘁𝗲𝗿𝗶𝗮𝗹 𝗣𝗛𝗕 𝗽𝗿𝗼𝗱𝘂𝗰𝘁𝗶𝘃𝗶𝘁𝘆
Ethyl methane sulfonate (EMS) was used to create a mutant library which was screened using fluorescent activated cell sorting (FACS) to sort single cells with BODIPY 493/503 (a neutral lipid dye) into well plates. Mutants were screened for growth rate and PHB productivity with two mutant strains found to have enhanced PHB yields (29% and 26% higher than wild type), biomass densities (36% and 33% higher than wild type) and PHB volumetric densities (75% and 67% higher than wild type).
𝗖𝗵𝗮𝗽𝘁𝗲𝗿 𝟯: 𝗖𝗵𝗲𝗺𝗶𝗰𝗮𝗹 𝗲𝗻𝗵𝗮𝗻𝗰𝗲𝗿𝘀 𝗮𝗻𝗱 𝗶𝗻𝗵𝗶𝗯𝗶𝘁𝗼𝗿𝘀 𝗼𝗳 𝗰𝘆𝗮𝗻𝗼𝗯𝗮𝗰𝘁𝗲𝗿𝗶𝗮𝗹 𝗣𝗛𝗕
10 different compounds (including oxidants, antioxidants, phytohormones) were screened at 3 concentrations (0.1 µM, 1 µM and 10 µM) to identify compounds which boosted and reduced PHB production. Two treatments, 0.1 µM IAA and 1 µM methyl jasmonate were found to increase PHB yield (55% and 19% compared to control). Two treatments, 10 µM allopurinol and 10 µM ethynylestradiol, were found to decrease biomass density, PHB yield and PHB density.
𝗖𝗵𝗮𝗽𝘁𝗲𝗿 𝟰: 𝗠𝘂𝗻𝗶𝗰𝗶𝗽𝗮𝗹 𝘄𝗮𝘀𝘁𝗲𝘄𝗮𝘁𝗲𝗿 𝗮𝘀 𝗮 𝗺𝗲𝗱𝗶𝗮 𝗳𝗼𝗿 𝗰𝘆𝗮𝗻𝗼𝗯𝗮𝗰𝘁𝗲𝗿𝗶𝗮𝗹 𝗣𝗛𝗕 𝗽𝗿𝗼𝗱𝘂𝗰𝘁𝗶𝗼𝗻
This study demonstrated the potential for primary domestic wastewater as a nutrient source of cyanobacterial biomass cultivation with no significant difference between biomass densities compared to the control culture. However, PHB yield was significantly inhibited (85% lower than control) which may have been linked to non-cyanobacterial biomass.
𝗖𝗵𝗮𝗽𝘁𝗲𝗿 𝟱: 𝗧𝗲𝗰𝗵𝗻𝗼-𝗲𝗰𝗼𝗻𝗼𝗺𝗶𝗰 𝗺𝗼𝗱𝗲𝗹𝗹𝗶𝗻𝗴 𝗼𝗳 𝗰𝘆𝗮𝗻𝗼𝗯𝗮𝗰𝘁𝗲𝗿𝗶𝗮𝗹 𝗣𝗛𝗕 𝗽𝗿𝗼𝗳𝗶𝘁𝗮𝗯𝗶𝗹𝗶𝘁𝘆
This techno-economic modelling study breaks down the key capital and operating costs and identifies the major financial barriers to profitability. For a base case scenario, a 10,000 tonnes of PHB bioplastic resin per year facility in Australia was used with breakeven and sensitivity analysis to assess economic viability. The results revealed that the cost of production was $18.1k USD/tonne which is over four times the current market price of PHB. However, through the combination of several optimistic scenarios, the breakeven price could potentially reach $7.7k USD/tonne.
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