Effect of the culture system and culture technique on biochemical characteristics of Pavlova lutheri and its nutritional value for Crassostrea gigas larvae

Pavlova lutheri was cultivated in carboys using batch technique and in a flat alveolar photobioreactor (FAP), using initially batch and then semi-continuous techniques. Growth and productivity of the cultures were compared and their nutritional quality was assessed by analysing their biochemical composition (gross composition, fatty acids and sterols) and by evaluating their food value for Pacific oyster (Crassostrea gigas) larvae as bispecific diet in association with Chaetoceros calcitrans forma pumilum. The highest productivity was achieved with the FAP operating in semi-continuous mode. Gross composition of P. lutheri was similar in all cultures, while cellular organic matter content of the microalga grown in FAP in semi-continuous mode was lower. Significant differences in fatty acid content were detected with respect to the n-6 polyunsaturated fatty acid fraction, which was lower in cells cultivated in the FAP in semi-continuous mode. As concerns the main individual fatty acids, docosahexaenoic acid (DHA) content was higher in cells cultivated in the photobioreactor in batch mode than in carboys. The neutral lipid fraction contained seven principal sterols and the comparison among the cultures evidenced different proportions and different patterns. No differences were observed among larvae fed diets containing P. lutheri grown in carboys or in the FAP.