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.
Highlights
The cultivation of wild microalgae under defined/controlled conditions has received considerable interest due to their potential as sources of various compounds that have biotechnological and commercial for the nutraceutical, cosmetic, and pharmaceutical industries (Dogaris et al, 2015; Encarnacao et al, 2015; Gellenbeck, 2012; Maurya et al, 2016; Rodrigues et al, 2015)
The aim of the present study was to evaluate the effect of traditional isolation and cultivation processes used to obtain axenic cultures and their cryopreservation (DMSO–sucrose and glycerol) on the growth rate and lipid content of four new algae isolates obtained from wastewater in the tropical Ecuadorian coast region
The genetic identification conducted with 18S rRNA partial sequences and the SILVA database corresponded with the morphological identification, with the most probable genera being Chorella sp
Summary
The cultivation of wild microalgae under defined/controlled conditions has received considerable interest due to their potential as sources of various compounds that have biotechnological and commercial for the nutraceutical, cosmetic, and pharmaceutical industries (Dogaris et al, 2015; Encarnacao et al, 2015; Gellenbeck, 2012; Maurya et al, 2016; Rodrigues et al, 2015). Some microalgae serve as essential raw materials in biofuel production due to their ability to accumulate a high lipid content. Some Chlorella species are known to produce lipids such that 10–39% of dried biomass is lipids (Chiu et al, 2015), showing a huge potential as a lipid sources in biotechnology. The isolation and characterization of high-temperature-tolerant microalgal species is important for mitigating these effects, as has been demonstrated with the temperature-tolerant strain Chlorella sorokiniana (Bechet et al, 2013)
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