Investigation the effect of the light perturbation on Chlorella Vulgaris IG-R-96 microalgae growth using artificially illuminated PBRs

Because of the ever-growing demand for environmentally friendly and high-value bioproducts, researchers have been focused on microalgae for biofuels manufacturing. Chlorella Vulgaris is a photosynthetic unicellular organism being cultured widely for the production of biodiesel because of its high lipid productivity; consequently, it has been selected in our project for further analyses. The growth of this species is highly affected by several factors, one of the most important of which is the quality of light. This paper investigates the alteration in phenotype characteristics of Chlorella Vulgaris when affecting by light perturbation exerted at the beginning of growth. It was postulated that culturing the inoculation step with a different light intensity and/or light wavelength than the main culture can agitate the light environment, thus, excluding this step leads to cell productivity enrichment. In order to check the claim, two methods of cultivation were proposed. Method A (MA), in which colonies passed through an inoculation step and method B (MB) in which colonies were directly transferred from nutrient agar to the main culture. In order to simulate diverse types of main culture light environment, three PBRs with different light intensity and wavelength were constructed, and then in each PBR two experiments using MA and MB performed; while, the light environment of inoculation step was kept constant for these three PBRs. Results indicated that when using MA culture with diverse light environment between inoculation and PBR steps, the trend of growth and cell productivity can be significantly perturbed depending on the light characteristics of the PBR medium; therefore, elimination of inoculation step could enhance efficiency.

Keywords:

Microalgae , Light perturbation , Cell size , Biomass , Lipid