Statistical study of growth kinetics and lipid content of microalgae grown in brackish waters for bioenergetic purposes

Abstract

This study aimed to statistically prove the influence of salinity on growth kinetics and intracellular lipid accumulation in microalgae. The species Chlorella sp., Scenedesmus acuminatus, Nannochloropsis sp., Monoraphidium contortum and Pediastrum tetras were studied, which were isolated in the Brazilian semi-arid region and cultivated in synthetic media with the addition of NaCl. From the crops, growth kinetics, dry biomass production and lipid content were analyzed, using the experimental planning for one factor as a tool, with the NaCl concentration as an independent variable. The kinetic parameters maximum growth speed (µ_max) and generation time (t_g), as well as lipid concentration were the response variables studied. The results showed that, in the species Scenedesmus acuminatus, Nannochloropsis sp. and Pediastrum tetras, salt stress contributed to the increase in µ_max and the consequent decrease in t_g. The highest levels of lipid accumulation were obtained in Nannochloropsis sp. (62.04%), in the medium with the highest salinity and Pediastrum tetras (54.04%) in the lowest. Dry biomass production was higher in Scenedesmus acuminatus (1,941.37 mg.L^-1) and Nannochloropsis sp. (1237.05 mg.L^-1), both at a concentration of 4.0 g.L^-1. Therefore, saline stress acted directly on the cell growth and lipid content of the species, which can be used as a device to enhance lipid production for the purpose of producing biofuels.