Potential of immobilized Chlorella minutissima for the production of biomass, proteins, carotenoids and fatty acids

This work investigated the potential of Chlorella minutissima immobilized in alginate beads for biomass and bioactive compounds production. The effects of nitrogen concentration in the culture medium (48 to 96 mg L-1 N-NO3) and the nitrogen addition profile during fed-batch culture were evaluated. In batch cultures, the initial nitrogen concentration of 96 mg L-1 N-NO3 produced the highest chlorophyll and protein contents in biomass, about 2.8 and 1.5-fold higher than the control (48 mg L-1 N-NO3), respectively. The biomass concentration (1.65 +/- 0.01 g L-1) and carotenoid content (11.0 +/- 0.8 mg g(-1)) were 21.3% and 32.6% higher than the control (48 mg L-1 N-NO3), but similar to the other nitrogen concentrations tested (64 and 80 mg L-1 N-NO3). Fed-batch cultures were performed in order to optimize the productivity of immobilized C. minutissima. The fed-batch culture with three additions of 96 mg L-1 of N-NO3 resulted in the highest biomass concentration (2.13 +/- 0.02 g L-1) and an increase in chlorophylls (1.7-fold), carotenoids (1.3-fold) and proteins (1.6-fold) content in biomass compared to batch culture. The contents of all-trans-lutein and polyunsaturated fatty acids were 5.31 +/- 0.46 mg g(-1) (dry cell weight) and 52.0 +/- 0.9% of total fatty acids, respectively, similar or higher than free cell cultures. The culture of immobilized C. minutissima cells showed to be a promising technique towards decreasing microalgae production costs. Through fed-batch cultures, it was possible to increase the production of biomass and compounds of biotechnological interest.