Microalgae production improvement for the ICCM´s Marine Fish Hatchery

Abstract

In order to improve the microalgae production in the ICCM`s marine fish hatchery one experiment took place in the traditional culture bags inside the microalgae room adding CO2 to avoid carbon limitation, stabilize pH and boost the cell concentration; after 10 days of culture non differences were observed. Microalgae growth could be limited for other factors, such as nutrient and light limitation, so a second experiment took place this time adding twice the regular nutrient dose plus CO2 gas income to the culture bags for 20 days. After the 10th culture day different dilutions (10%, 15% and 20%) were tested to obtain the best dilution rate for a daily microalgae harvest. The best dilution rate was 10% for bags without CO2 and 15% with CO2 for a daily harvest, although cell concentration growth didn`t show any considerable increase which lead to test outdoor photo-bioreactors to improve the cell concentration growth. Two outdoor vertical photo-bioreactors were tested and confronted to a traditional culture bag with twice nutrient dose; both photo-bioreactors (with twice and fourth times nutrient dose)were also confronted to each other. After the 10th culture day, 10% of the volume was daily harvest and replaced with the same volume of enriched water on the three systems. The cell concentration showed significant magnitude increase (P>0.05) in the photo-bioreactors in respect to the culture bag, and also between them but not in magnitude terms. In the last experiment microalgae growth was tested for 30 days with twice nutrient dose in a tubular horizontal photo-bioreactor system whith controlled temperature and pH by adding CO2 gas into the culture medium. After the 10th culture day, 10% of the volume was daily harvest and replaced with the same volume of enriched water. Cell density increased before it collapsed due to diatoms stuck to the methacrylate tubes.