Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Chemical and Biochemical Engineering

Supervisor

Amarjeet Bassi

Abstract

Microalgae have been recognized as a natural reservoir of the valuable commercial carotenoid lutein due to its high lutein content and fast growth cycle. However, the production of lutein from microalgal sources is not yet sufficiently cost-effective to compete with traditional marigold flower-based processing (Park et al., 2015). This thesis aims to investigate the factors affecting lutein production and recovery from microalgae using a phototrophic cultivation mode.

The closed photobioreactors can offer controlled conditions for faster microalgae growth. A coiled tubular tree photobioreactor (CTPBR) design was first investigated for cultivating the cold tolerant microalgae, Chlorella vulgaris UTEX 265, under various conditions for lutein production. The response surface method by central composite design was used to measure the interaction of light irradiance, photoperiod cycle and temperature on microalgae growth and lutein production. The results demonstrated that the CTPBR was an effective reactor configuration, and 14 h day-light, 120 µmol photons m-2 s-1 and 10oC was the optimal condition for lutein production in experimental ranges.

The lutein extraction from wet microalgae was next investigated. The lutein production was monitored throughout the micro-algal growth phase, and the biomass drying method and the cell disruption method were investigated. The simultaneous lipid and lutein extraction was also studied. The performance of solvent polarity on extraction was compared quantitatively using Nile Red as a solvatochromic polarity probe. An 80% (v/v) ethanol in hexane was recognized as the optimal solvent for lutein and lipid co-extraction, which contributed to a 13.03 mg/g lutein and 7% (w/w) lipid yield.

A single-step simultaneous extraction, saponification and primary purification process for free lutein production from wet microalgae biomass was then investigated using binary solvent mixtures. The extraction kinetics were modeled using Fick’s second law of diffusion. The optimized conditions for the apparent mass transfer rate and yield was found to be pre-treatment with ultrasonication at 0.5s working cycle per second, react 0.5 hour in 160 mL final solvent volume of 1:3 ether/ethanol (v/v) with 2 mL 10% (w/v) ethanolic KOH.

Overall, an effective method was developed for high yield lutein production from wet microalgae.

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