Strategy for Carbohydrate-Starch Production Enhancement by Chlorella fusca Using Seawater as Culture Medium

This study was aimed at evaluating the growth of Chlorella fusca LEB 111 in 100% undiluted seawater (SW), both with and without nutrient supplementation. In order to do so, 100% SW was supplemented with 50% (50) and 100% (100) of all nutrients from the BG-11 medium. The use of 100% SW as a culture medium without added nutrients (SW100) was also evaluated, and a control assay was carried out in a standard BG-11 culture medium with distilled water. Microalgal biomass carbohydrate content was evaluated to verify the potential application of this raw material for biofuel production. In both with (50) and without nutrient supplementation (SW100), C . fusca cultured in SW showed better maximum biomass productivity (0.15 and 0.14 g/L.d, respectively) and total carbohydrate concentration (44.6% and 60.0% w/w, respectively) than the control assay (0.12 g/L.d and 22.5% w/w, respectively). Fourier transform infrared (FT-IR) spectroscopy highlighted starch as the major carbohydrate. Furthermore, the concentrations of calcium, potassium, phosphorus, and nitrogen sources present in SW100 were reduced by 42.6%, 61.9%, 99.2%, and 98.6%, respectively, after cultivation. The use of SW is a sustainable and economical way to promote the growth of C. fusca ; it reduces culture medium nutrient costs while stimulating carbohydrate-starch accumulation in the biomass and has the potential for bioethanol production. Graphical Abstract