Influence of the physiological state on the freezing of freshwater microalgae: obtaining the best viability rates and measurement of functional stability of the samples after freezing

• Grant number: 19/01930-8
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: July 01, 2019
• End date: February 14, 2021
• Field of knowledge: Biological Sciences - Botany - Applied Botany
• Principal Investigator: Ana Teresa Lombardi
• Grantee: Letícia Piton Tessarolli
• Host Institution: Centro de Ciências Biológicas e da Saúde (CCBS). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated research grant: 18/07988-5 - Bioprospecting, characterization and optimization of Brazilian microalgal strains for CO2 biofixation and bioproducts of commercial importance, AP.TEM

Abstract

The group of microalgae is diverse in phylogeny, morphology and ecology. Although fundamental processes, such as photosynthesis, are common to all algae, there is great diversity in relation to basic constituents, morphological and cellular structure, and chemical composition. Thus, this group has potential in the biotechnology related to food for humans and animals, pharmaceuticals, pigments, and even biofuels due to its high growth rate and conversion of solar energy.The exploration of the economic and commercial potential of microalgae is directly linked to the maintenance of organisms in culture collections and to the constant offering of stable and standardized inocula, establishing a standard of productivity and consistency of the desired final products. Since microalgae in metabolically active cultures also undergo evolutionary (genetic) changes, leading to small changes in their physiology that can lead to major changes in the production of chemical compounds, the maintenance of stable inocula is of great importance in the management of large scale production. In such cases, the use of cryopreservation as a method of maintaining microalgae cultures in the long term is recommended, since cells kept in liquid nitrogen can be stored for a long period without genetic variations in frozen cells. In this way, it is possible to restart the cultures periodically from an inoculum with the same characteristics.Frozen collections reduce the interference of contaminants, since they require minimal maintenance, avoiding the constant handling of the samples. However, several factors affect algae survival and stability after freezing and maintenance in liquid nitrogen, including its physiological characteristics, such as microalgae culture conditions (age, incubation temperature and osmotic potential of the medium and nutritional limitation). Active-growing cultures generally survive cryopreservation with viability greater than those at stationary phase, or even those growing under limiting conditions. In this project, we will study the influences of variations in the physiological state of algal cells and their direct effect on the viability and recovery of microalgae cultures. Factors determining the functionality of organisms will be studied for the maintenance of biotechnological potential after freezing and the continued exploitation of microalgae cultures.