Microalgae culture is crucial for marine hatcheries, serving as feed for shellfish and greenwater for larval finfish. Unlike commercial freeze-dried or non-viable algae products, many hatchery operations require live microalgae. Maintaining these cultures is resource-intensive and prone to crashes. To address this, an open-source microalgae ultrafiltration method is being developed to provide a reliable backup of live cells. Proper storage of these concentrates is essential for preserving cell viability.
When placed in cold storage, microalgae cells tend to settle over time, with some species settling more rapidly than others. Preliminary observations indicate that flagellates settle faster than diatoms and may not actively swim at low temperatures. However, they show increased motility as they warm to ambient air, suggesting the potential to "re-animate" live microalgae concentrates, a critical characteristic for some plankton that rely on consuming live algae.
In culture, microalgae cells are typically kept in suspension through aeration or swirling of the vessels. However, introducing aeration into cold storage, such as refrigeration, is often impractical and can introduce contamination risks. Therefore, alternative methods to maintain cell suspension are needed. This study investigates the use of sodium alginate and xanthan gum, two cost-effective food-grade thickeners, to prolong the suspension of concentrated microalgae during cold storage. By increasing the viscosity of the storage medium, these thickeners aim to reduce the sedimentation rate of algae cells, reflected in decreased Reynolds numbers within the fluid, thereby improving storage time without aeration.
The study’s goal is to identify the optimal thickening agent, concentration, and preparation method to maximize cell viability and ensure easy resuspension for feeding in hatcheries. Preliminary data indicate that increasing water viscosity with thickeners reduces microalgae settlement, potentially extending their usable storage time. By understanding the dynamics of cell suspension and settling through Reynolds numbers and fluid dynamics, this research aims to develop practical solutions for the long-term storage of live microalgae in marine hatcheries and laboratories, where viable algae are essential.