Bioprocessing in microalgae

Abstract

This thesis is a portfolio of three projects carried out with Scottish Bioenergy Ltd, in the area of microalgae biotechnology. The first small project saw the development of a rapid, simple and relatively low-cost technique based on UV absorbance for measurement of nitrate in two common freshwater and saltwater growth media. The test was successfully demonstrated in batches of Chlorella, measuring nitrate concentration as low as 40 μM and requiring only a 2 mL sample. The second large project investigated the use of a narrow spectrum Light Emitting Diode (LED) with a maximum wavelength (λmax) of 680 nm for the production of the high-value pigment phycocyanin in Arthrospira (Spirulina). The LEDs produced a substantial over 250 % increase in phycocyanin yield with no significant difference in growth rate in comparison to standard white LEDs, initially requiring an extended photoacclimation period. Although photobioreactor (PBR) systems incorporating the λmax 680 nm would require increased investment in capital and operational expenditure, particularly relating to increased LED cooling requirements, increased product yield and profitability makes a powerful case for switching to longer wavelength red LEDs. The third project was a feasibility study for the use of directed microevolution to generate a non-genetically modified copper-tolerant Arthrospira strain that may be used in a multi-process PBR system fed with distillery wastewater. Resistance 200-fold the typical optimal medium concentration was achieved. However, the extent of resistance was 3-fold lower than required and the length and unreliability made the process impractical for industrial use in generating resistant Arthrospira strains. The projects provided a methodology to assist the company in future research and development, knowledge on the feasibility of a strain development technique and identified an exciting new business opportunity for production of a high-value product in artificially illuminated PBR systems.