Production of Polyunsaturated Fatty Acids and Lipids from Autotrophic, Mixotrophic and Heterotrophic cultivation of Galdieria sp. strain USBA-GBX-832

Gina López,Mónica P Cala,Camilo Yate,Sandra Baena,Silvia Restrepo,Freddy A Ramos

doi:10.1038/s41598-019-46645-3

Abstract

A search for extremophile organisms producing bioactive compounds led us to isolate a microalga identified as Galdieria sp. USBA-GBX-832 from acidic thermal springs. We have cultured Galdieria sp. USBA-GBX-832 under autotrophic, mixotrophic and heterotrophic conditions and determined variations of its production of biomass, lipids and PUFAs. Greatest biomass and PUFA production occurred under mixotrophic and heterotrophic conditions, but the highest concentration of lipids occurred under autotrophic conditions. Effects of variations of carbon sources and temperature on biomass and lipid production were evaluated and factorial experiments were used to analyze the effects of substrate concentration, temperature, pH, and organic and inorganic nitrogen on biomass production, lipids and PUFAs. Production of biomass and lipids was significantly dependent on temperature and substrate concentration. Greatest accumulation of PUFAs occurred at the lowest temperature tested. PUFA profiles showed trace concentrations of arachidonic acid (C20:4) and eicosapentaenoic acid (C20:5). This is the first time synthesis of these acids has been reported in Galdieria. These findings demonstrate that under heterotrophic conditions this microalga’s lipid profile is significantly different from those observed in other species of this genus which indicates that the culture conditions evaluated are key determinants of these organisms’ responses to stress conditions and accumulation of these metabolites.

Highlights

Lipids fulfill various functions in cell membranes and organelles, lipid reserves are a form of energy storage that is necessary for cellular metabolism[5]
Given the metabolic potential of Galdieria and interest in obtaining PUFAs and lipids from microalgae, this study has evaluated the effects of several different culture conditions on the production of biomass, lipids and especially of PUFAs by Galdieria sp
We isolated USBA-GBX-832 strain from water and sediment samples from a hot spring in the Los Nevados National Natural Park (NNP) in Colombia and subsequently identified it as Galdieria sp. This was the first report of thermoacidophilic microalgae in acidic thermal springs at 3500 m above sea level

Summary

Introduction

Lipids fulfill various functions in cell membranes and organelles, lipid reserves are a form of energy storage that is necessary for cellular metabolism[5]. Thermoacidophilic microalgae of the order Cyanidiales[17,18] are the only eukaryotes capable of living in environments with pH lower than 3.0 and temperatures higher than 40 °C (maximum ∼56 °C) Their habitats are often thermal mineral springs associated with volcanic systems[19]. It is known that organisms’ growth conditions influence accumulation of lipids and that production of fatty acids and lipids in microalgae is associated with stress conditions including temperature, light intensity, nitrogen source, salinity, and concentration of the carbon source[1].

Methods

Results

Conclusion