Scientists from the School of Marine and Tropical Biology at the James Cook University in Australia report that those two microalgae species produced concentrates that lasted two months of storage without significant change in the fatty acid profile or protein content, thereby spanning the typical four to six week hatchery rearing cycle.
On the other hand, concentrates of Entomoneis punctulata and Melosira dubia did not have good shelf-life, indicating that they may not be suitable commercially.
“The findings of this study are directly applicable to the aquaculture industry, which could potentially benefit from using microalgal concentrates to replace or supplement fresh microalgal cultures,” wrote the researchers in the journal Aquaculture.
“Nannochloropsis sp. and D. tertiolecta, which are well-studied, with established growth and nutrient parameters, exhibited excellent fatty acid and protein retention and are thus good candidates for off-the-shelf products.”
Heather Welladsen, Megan Kent, Arnold Mangott, and Yan Li explained that there is a rising demand for microalgae from the booming aquaculture sector, but fresh/live microalgae is a bottleneck for the industry because of the cost and sensitivity of the cultures.
“Mass culture of microalgae for rearing larval and juvenile aquaculture species can represent 30-40% of the hatchery operating costs, whilst culture crashes at critical points in hatchery runs can be devastating for production,” they said.
While dried or concentrated microalgae have been extensively studied as alternatives to fresh microalgal cultures, their wider acceptance has been limited, they said. There are some notable exceptions, such as the North American Pacific oyster industry, which uses Skeletonema costatum and Thalassiosira pseudonana concentrates.
“Algal concentrates have good potential as supplements or replacements of fresh cultures […] and demand for a cost effective ‘off the shelf’ alternative to fresh cultures is driving research in this direction.”
In order to test the applicability of microalgal concentrates the Australian researchers analyzed four species of microalgae: Nannochloropsis sp., Dunaliella tertiolecta, Entomoneis punctulata and Melosira dubia.
Results showed that, while Nannochloropsis sp. and D. tertiolecta showed good stability, M. dubia and E. punctulata were less robust.
“These findings suggest that Nannochloropsis sp. and D. tertiolecta concentrates could be used in aquaculture industries as a replacement or supplement to fresh cultures, whilst E. punctulata may be more suited to short-term storage, and M. dubia would perform better as a fresh culture,” wrote Welladsen, Kent, Mangott, and Li.
“The species-specific effect seen in this study highlights the importance of assessing the shelf-life of microalgal concentrates used in aquaculture,” they concluded.
Volume 430, 20 June 2014, Pages 241–247, doi: 10.1016/j.aquaculture.2014.04.016
“Shelf-life assessment of microalgae concentrates: Effect of cold preservation on microalgal nutrition profiles”
Authors: H. Welladsen, M. Kent, A. Mangott, Y. Li