Chemical and Biological Engineering PhD Thesis Defense by Ehsan Sarayloo

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KOÇ UNIVERSITY

GRADUATE SCHOOL OF SCIENCES & ENGINEERING

CHEMICAL AND BIOLOGICAL ENGINEERING

PhD THESIS DEFENSE BY EHSAN SARAYLOO

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Title: Increasing Lipid Productivity of Chlorella Vulgaris by Optimization and Random Mutation-Establishment of Algae Cultivation in Koc University From Single Colony to Large Scale Open Pond

Speaker: Ehsan Sarayloo

Time: November 07, 2017, 14:00

Place: ENG B42

Koç University

Rumeli Feneri Yolu

Sariyer, Istanbul

Thesis Committee Members:

Prof. I. Halil Kavakli (Advisor, Koc University)

Prof. Can Erkey (Koc University)

Assoc. Prof. Nurhan Özlü (Koc University)

Prof. Gül Öz (Istanbul University)

Asst. Prof. Mahmut Altinbaş (Istanbul Technical University)

Abstract:

Algal biofuel is considered a strong candidate as an alternative for fossil fuels, but despite of all advantages, commercial production of microalgae biofuel is not still economically feasible due to the low lipid productivities and high production costs. This study was aimed to increase the lipid productivity of Chlorella vulgaris to make it more feasible for biodiesel production. Several methods including chemical and physical random mutation and optimization of growth conditions were applied. In the first step concentration of CO₂ and nitrogen was optimized to increase the lipid productivity of C. vulgaris, cultivated in stirred tank photobioreactor. According to the results the best initial nitrate concentration is 0.25 g/l and the best CO₂ concentration is 2%. In the next part physical and chemical mutagenesis methods were applied to enhance lipid productivity in Chlorella vulgaris. Then, de novo RNA-seq was performed to observe lipid metabolism changes at the genome-wide level. Characterization of two mutants, UV-715 and EMS-25, showed marked increases in lipid contents, i.e., 42% and 45%, respectively. In addition, the biomass productivity of the UV-715 cells was 9% higher than that of wild-type cells. Then chemical mutagenesis was applied on previously physically mutagenized C. vulgaris strain (UV-715). After screening a mutant (UV-715_EMS25) was selected on the basis of lipid productivity and then cultivated in 25 L bench scale flat panel photobioreactor (FPBR). Lipid content and biomass of mutant was respectively 67% and 35% higher than wild type (WT) which resulted in 2.25 folds increase in lipid productivity of mutant. The highest lipid productivity achieved was 91 mg L^-1 d^-1. Gas chromatography mass spectrophotometry analysis results showed that both fatty acid methyl ester (FAME) content and composition of mutant were enhanced rather than wild type. Finally, after performing studies in pilot scale photobioreactor, mutant UV715-EMS25 was cultivated in large scale outdoor open ponds. Results showed that mutant UV715-EMS25 was able to survive and grow in outdoor large-scale conditions. Sedimentation, filtration and sunlight were found as the most suitable methods for harvesting, dewatering and drying, respectively. Results showed that the lipid content was reached up to 17% of dry biomass and FAME analysis results revealed that the lipid of cultivated biomass in open pond was mainly composed of hexadecanoic acid (C16:0) (41%), linoleic acid (C18:2) (27%) and oleic acid (C18:1) (24%).