Microalgae Unicellular photosynthetic microorganisms Similar - - PowerPoint PPT Presentation

Chemical mutation of Stichococcus sp. for the selection of strains with reduced chlorophyll content

• G. Makaroglou1, E. Syranidou2, K. Pantelidaki1, N. Kalogerakis2, P

. Gikas1

1Design of Environmental Process Laboratory, School of Environmental Engineering,

T echnical University of Crete, Chania, Crete, 73100, Greece

2Biochemical Engineering and Environmental Biotechnology Laboratory, School of

Environmental Engineering, T echnical University of Crete, Chania, Crete, 73100, Greece Correspondence email: gmakaroglou@isc.tuc.gr; petros.gikas@enveng.tuc.gr

Microalgae

• Unicellular photosynthetic

microorganisms

• Similar growth mechanisms

as terrestrial plants, without having roots, shoots, stems

• r leaves
• Require smaller cultivation

areas

• Growth parameters: Inorganic

nutrients, CO2, Light, Water, pH, T emperature

Benefjts of Microalgae Removal of pollutants from wastewater Sequester CO2 from fmue gas of electric powerplants

T ypes of photobioreactors

CO2 CO2 CO2

Microalgae and climate change

CO2 as a carbon source Bioproducts Sunlight

Closed Photobioreactor

Bioproducts of microalgae

Biopolymers Lipids Proteins Carbohydrates Polyunsaturated Fatty acids Photosynthetic pigments Vitamins

Selected strain

• Stichococcus sp. strain

was used throughout the experiments

• It is a rod-shaped green

microalgae

• It is able to withstand

extreme pH, temperature and salinity variations

Mutation methods

Chemical (Ethyl Methyl Sulphonate, EMS) Radiation (UV-, γ-, X- rays) Heavy ion irradiation

Aim of the experiment

• Reduced chlorophyll content decreases the “shadow

efgect” in photobioreactors, allowing more light to penetrate into the culture

• Mutant strains of Stichococcus sp. with reduced

chlorophyll content and high biomass will be later cultivated in closed fmat photobioreactors, supplied with a combination of gasses (CO2, N2, O2, SO2, NO)

Cultivation of Stichococcus sp.

• Culture medium:

Sterile Seawater + F/2 Medium (inorganic nutrients, mainly 0.015 g/L NaNO3, trace metals, vitamins)

• Treatments:
• Wild, EMS1, EMS3 with 0.015 g/L NaNO3
• Wild, EMS1, EMS3 with 0.75 g/L NaNO3
• Illumination:

2x18 W warm-light fmuorescent lamps

• T

emperature: 23 oC

• pH: 7.50 – 8.00

Experimental set up

Mutation of Stichococcus sp.

• EMS Concentrations: 1%, 1.25%, 1.5%, 1.75%, 2% with

an objective to induce 95% lethality

• Appropriate dilutions, plated in duplicates
• Light green colonies cultivated for 3 generations to

establish successful mutation

Biomass measurements

Vacuum fjltration system Filters

Wild EMS1 EMS3

Optical density, Photosynthetic Pigments measurements

UV-Vis Spectrophotomete r Spectrophotomete r cuvettes Chlorophyll a (mg/l) = 16.72∙A665.2 - 9.16∙A652.4 Chlorophyll b (mg/l) = 34.09∙A652.4 - 15.28∙A665.2 Total Chlorophylls (mg/L) = Chl a +

Wild and Mutant strain in petri dishes

Wild strain Mutant strain

Wild and Mutant strains

Wild EMS1 EMS3

T

• tal Chlorophyll of Wild and

Mutants

0.3 0.5 0.6 0.7 0.8 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 Wild EMS1 EMS3 Optical Density T

• tal Chlorophyll (μg/mg)

Strain Treatm ent Wild With 0.75 g/L NaNO3 EMS1 With 0.015 g/L NaNO3 EMS3 With 0.75 g/L NaNO3

Growth curves and biomass production of Wild and Mutants

7 8 9 10 11 12 13 6 6,5 7 7,5 8 8,5 9 9,5 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 Biomass_Wild Biomass_EMS1 Biomass_EMS3 OD_Wild OD_EMS1 OD_EMS3 Biomass dry basis (mg/mL) Days Optical Density

Strain Treatm ent Wild With 0.75 g/L NaNO3 EMS1 With 0.015 g/L NaNO3 EMS3 With 0.75 g/L NaNO3

Conclusions

• Mutant (EMS1) Stichococcus sp. has greater biomass

production at a lower chlorophyll content

• EMS1 seems to have great growth even though it does

not have additional NaNO3

• Stichococcus sp. is suitable for fmat photobioreactors due

to its tendency to adhere to fmat surfaces, thus making it easier to extract

Future experimental set up

Thank you for your attention

Correspondence email: gmakaroglou@isc.tuc.gr; petros.gikas@enveng.tuc.gr