Short-term deleterious effects of standard isolation and cultivation methods on new tropical freshwater microalgae strains

Abstract

Algae with potential biotechnological applications in different industries are commonly isolated from the environment in order to obtain pure (axenic) stocks that can be safely stored for long periods of time. To obtain axenic cultures, antibiotics are frequently employed, and cryopreservation is applied to preserve standing stocks. However, many of these now standard methods were developed using strains derived from pristine to near-pristine environments and cold to temperate regions. The potential effect of the said methods on the life cycle and biochemical profile of algae isolates from hyper-eutrophic and constant high-temperature tropical regions is not well understood. These effects could potentially render them unsuitable for their intended biotechnological application. In this study, we conducted a genetic characterization (18S rRNA) and evaluated the effect of purification (the use of the antibiotic chloramphenicol, CAP) and cryopreservation (dimethyl sulfoxide; DMSO–sucrose mix and glycerol) on the growth rate and lipid content of three new tropical freshwater algal isolates: Chorella sp. M2, Chlorella sp. M6, and Scenedesmus sp. R3, obtained from the Ecuadorian coast. The genetic and morphological characterization revealed a clear discrimination between these strains. All strains cultured with CAP exhibited a lower growth rate. Subsequent to cryopreservation, Chorella sp. M2, Chlorella sp. M6, and Scenedesmus sp. R3 presented no significant difference in growth rate between the cryopreservants. Further, a significantly higher lipid content was observed in the biomass cryopreserved with glycerol in relation to the DMSO–sucrose, with Chorella sp. M2 and Chlorella sp. M6 having twice as much as they had in the first treatment. These results highlight the relevance of selecting an appropriate method for storage, as the materials used can affect the biological performance of different tropical species, although it is still to be determined if the effects observed in this study are long lasting in subsequent cultures of these algae.

Cryopreservation of Cyanobacteria and Eukaryotic Microalgae Using Exopolysaccharide Extracted from a Glacier Bacterium

“…According to their findings, little or no cryoprotection was observed when these CPAs were used alone. Aray-Andrade et al (2018) found DMSO–sucrose and glycerol to be effective cryoprotective agents while working with the cryopreservation of two Chlorella and one Scenedesmus species [ 38 ].…”

Crecimiento y viabilidad celular de microalgas: efecto del medio de cultivo

“…The adequate concentration of nutrients can favor the physiological processes of the cell to counteract the damaging effects of cryopreservation, allowing its optimization through the formation of aldose type monosaccharides, which increases the osmolarity of the solution, causing cellular dehydration. These aldoses in synergy with cryoprotectors, minimize the damage of intracellular ice by increasing the total concentration of the solute and reducing the amount of ice formed in the cell (Bui et al, 2013;Aray-Andrade et al, 2018).…”

“…Cryopreservation is a biotechnological technique to preserve cell structures or biological material at low temperatures, which inactivates physiological processes for a period of time (Day and Brand, 2005;Smith et al, 2008;Bui et al, 2013;Saadaoui et al, 2016). Cryopreservation optimizes production, maintenance, and genetic stability of microalgae (Day and Brand, 2005;Bui et al, 2013;Aray-Andrade et al, 2018). The main challenge in cryopreservation is to develop techniques to guarantee post-thawing cell viability.…”