Messastrum gracile (Chlorophyceae) growth using sugarcane molasses-based macrophyte extract culture media

Abstract

The current study investigated whether untreated and pretreated molasses is suitable for Messastrum gracile growth and the influence of extracts of macrophyte species used as culture media. There was a difference in nutrient composition of the macrophyte culture media with high concentrations of P and N (60 mg L-1) in Salvinia auriculata extract culture medium. When exposed to sugarcane molasses, the availability of these nutrients in the culture medium did not directly affect microalgae growth, since the highest growth rate (k = 0.22) and cell density (204 x 10(5) cells mL(-1)) were observed in Lemna minor culture medium, where N and P concentrations were below 0.3 mg L-1. In macrophyte culture media, total inorganic nitrogen concentrations were higher than total phosphorous. Lipid contents were different under both mixotrophic conditions; they were higher under untreated molasses, except S. auriculata culture medium; however, protein contents under two conditions were lower than 24% biomass dry weight. Low-cost production with annual costs of US$ 961.62 and annual biomass production of US$ 5.20 per tonne dry biomass was observed. Current analysis shows that sugarcane molasses (under untreated and pretreated) is not a good alternative to improve and maintain M. gracile, although the opposite occurred with macrophyte culture media that have low cost and high nutrient concentrations enabling the cultivation of this microalga in laboratory.