Bioprospecting of wild microalgae collected in pisciculture ponds

Abstract

The study of freshwater microalgae is important, as it represents a source of knowledge for the development of innovative technologies, whether through bioactive production or their plasticity in inhospitable environments. This study aimed to evaluate isolation techniques and the taxonomic composition of microalgae in pisciculture ponds, as well as analyze their development in a laboratory environment. Water was collected from the ponds using a Van Dorn-type bottle and filtered through a phytoplankton net (20 µm) for densification. Subsequently, the water was incubated in the laboratory for 28 days in a non-axenic system, with constant aeration and controlled temperature and lighting (22 ± 2.0 °C and 12 h light/12 h dark) to evaluate the algal density and ecological succession of taxonomic groups. Four microalgal isolation techniques were adopted after this period: serial dilution, inoculation on solid medium, selection by aging, and micromanipulation. Fifteen species of microalgae were identified after 28 days of cultivation. The species Lacunastrum gracillimum, Scenedesmus quadricauda, and Chlorella sp. maintained constancy in cell density during the successional period. The technique of streaking on a solid medium was more efficient, with five isolated species of microalgae: Scenedesmus acuminatus, S. quadricauda, Chlorella sp., Monoraphidium contortum, and Scenedesmus bernardii. The other techniques isolated at least one species of microalgae. The ex-situ study of microalgae was important to better understand isolation techniques and their development in a controlled environment, providing essential information to advance research on the use and biotechnological application of microalgae.