Effect of different irradiance levels on the growth of the cyanobacterium Lyngbya majuscula

ANDREA ROSE V. FRANCO, FRANCIZ LOVELY L. TIANIA, and ANDREA LUCYLE M. BELA-ONG

Philippine Science High School Western Visayas Campus – Department of Science and Technology (DOST-PSHSWVC), Brgy. Bito-on, Jaro, Iloilo City 5000, Philippines

Abstract

Lyngbya majuscula is a prolific producer of secondary metabolites that are used in the pharmaceutical industry. As a photosynthetic organism, the effect of irradiance on its cultivation was studied to maximize algal growth for mass production. The cyanobacterium was subjected to different irradiances of 20, 45, 110, 180, and 320 μmol photons m-2s-1 to determine its specific growth rate (SGR) in each treatment. Results showed the highest SGR under 20 and 45 μmol photons m-2s-1 during the exponential phase, showing a significant difference (p < 0.05) among all other treatments. Minimal growth rates were obtained under 110, 180, and 320 μmol photons m-2s-1 and results showed that the SGRs under these treatments have no significant difference (p > 0.05) with the negative control; however, color changes were observed at these irradiances. These showed that L. majuscula prefers lower irradiances to maximize its growth, while higher irradiances are unideal.

Keywords: Lyngbya majuscula, cyanobacteria, irradiance, specific growth rate, algal growth

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