Production and Growth Performance of Nannochloropsis oculata (Droop) Hibberd in the Helical Photobioreactor

Abstract

Phytoplankton species preferred in marine fish farming are the primary food source in the larval and young stages of bivalve mollusks, along with some fish and shellfish larvae. For this reason, selecting the appropriate phytoplankton and production technique for feeding marine fish larvae is crucial. Nannochloripsis oculata microalgae species, widely used in rearing sea bream and sea bass larvae and feeding rotifers, has an essential place in our country. N. oculata microalgae species, which is used in rearing sea bream and sea bass larvae and feeding rotifers, was produced in a helical photobioreactor by applying a continuous production technique at 30 ‰ salinity, and its growth performance was aimed to be investigated. In the study, N. oculata was grown in a helical photobioreactor at 30‰ salinity by applying the continuous production technique for two weeks, and the daily cell number and specific growth rate were determined. The study was repeated three times. The supply of live feed for marine fish fry and hatcheries established for this purpose is one of the most critical problems. The latest technology in the production of microalgae, which is the primary link of the live feed chain in this sector, is continuous algae production in helical tubular reactors. The helical tubular reactor used in the study consists of a transparent hose system consisting of a completely tubular helical reactor designed for microalgae production. The helical tubular continuous production system offers more efficient and economically more convenient alternatives than existing production systems. One of the most essential advantages of this system is that the system can be designed without requiring significant capital. The continuous culture technique allows the application of long-term and safe algae cultures. With this system, besides providing continuity in production, the negativities in batch production can be eliminated with adequate light. Since the algae production with the continuous method in the spiral photobioreactor remains in the maximum growth phase for a longer time than the batch production, it is a system with high production efficiency and quality, and production capacity is guaranteed. In addition, the algae product harvesting in the continuous system ensures the daily harvesting of algae as much as half of the system volume. A helical reactor enables automation in algae production and high-quality production over long periods. In the study, the sowing density of N. oculata was determined as 1.068x106 ±0.006 cells/mL. Algin cell growth increased logarithmically during the first five days. From the 5th day to the 15th day, the increase in the number of cells was determined as 12.35x106±0.165 cells/mL at the highest and 8.76x106±0.709 cells/mL at the lowest. However, on the 13th day, it was determined that the increase in algin cells was 12.35x106±0.165 cells/mL, and the specific growth rate decreased by 0.189±0.016 divisions/day. As a result of the study, the number of cells of N. oculata algae 5-15 increased. It was determined that it increased 10 times between days. In this context, it was possible to harvest half of the reactor volume of algae daily at maximum cell density for long periods in the helical reactor.