Growth-promoting effects of marine microalgae species using tropical forest soil extracts

Abstract

Microalgae are a source of high-value substances beneficial for industrial applications. To augment the mass production of microalgae in an artificial culture medium, growth-promoting nutrients are essential. The effect of soil extracts (SEs) on four microalgae species was investigated in this study. Artificial Conway media were supplemented with SE collected from the Ayer Hitam Forest Reserve and Raja Musa Forest Reserve (RM), tested using a microplate-incubation technique. The samples were cultured for nine days at 25°C and 30°C, with a light intensity of 33.75 mol photons m −2 seconds −1 and a 12-hour light/dark cycle. Incubation at 25°C showed a higher specific growth rate (SGR) for Nannochloropsis oculata (0.32-0.39 d −1 ), while, at 30°C, a higher SGR was observed for Dunaliella tertiolecta in all soil treatments (0.31-0.34 d −1 ). In terms of SEs, media + RM SE showed a higher SGR from 0.25 to 0.39 d −1 for four microalgae. Chlorella sorokiniana and N. oculata grew well at 25°C in all soil treatments, while D. tertiolecta and Dunaliella primolecta grew well at 30°C. This study shows that the RM medium was the optimum soil treatment for all microalgae tested due to the higher concentration of organic matter.