Morphological and ultrastructural characterization of the acidophilic and lipid-producer strain Chlamydomonas acidophila LAFIC-004 (Chlorophyta) under different culture conditions

Abstract

Chlamydomonas acidophila LAFIC-004 is an acidophilic strain of green microalgae isolated from coal mining drainage. In the present work, this strain was cultivated in acidic medium (pH 3.6) under phototrophic, mixotrophic, and heterotrophic regimes to determine the best condition for growth and lipid production, simultaneously assessing possible morphological and ultrastructural alterations in the cells. For heterotrophic and mixotrophic treatments, two organic carbon sources were tested: 1 % glucose and 1 % sodium acetate. Lipid content and fatty acid profiles were only determined in phototrophic condition. The higher growth rates were achieved in phototrophic conditions, varying from 0.18 to 0.82 day. Glucose did not result in significant growth increase in either mixotrophic or heterotrophic conditions, and acetate proved to be toxic to the strain in both conditions. Oil content under phototrophic condition was 15.9 % at exponential growth phase and increased to 54.63 % at stationary phase. Based on cell morphology (flow cytometry and light microscopy) and ultrastructure (transmission electron microscopy), similar characteristics were observed between phototrophic and mixotrophic conditions with glucose evidencing many lipid bodies, starch granules, and intense fluorescence. Under the tested conditions, mixotrophic and heterotrophic modes did not result in increased neutral lipid fluorescence. It can be concluded that the strain is a promising lipid producer when grown until stationary phase in acidic medium and under a phototrophic regime, presenting a fatty acid profile suitable for biodiesel production. The ability to grow this strain in acidic mining residues suggests a potential for bioremediation with production of useful biomass.

Toxicity, Physiological, and Ultrastructural Effects of Arsenic and Cadmium on the Extremophilic Microalga Chlamydomonas acidophila

“…Another remarkable change was a drastic increment of starch reserves; these accumulations appeared distributed randomly in the cytoplasm, especially around the pyrenoid. An increase in carbohydrate reserves, as a consequence of metal or other stresses, has been reported in other microalgae [45,73,74]. Unlike in other species, we have only observed an increment in lipid reserves after As(III) exposure.…”

“…Previously, it has been suggested that Cr produced severe ultrastructural alterations and decomposition of the overall absorption spectra in pigment constituents of both structures in C. reinhardtii and other species [78,79]. Degradation of stigma under metal exposure has been reported in microalgae previously, although without the publication of micrographs or other evidence [73,74]. Mitochondrial ultrastructure was irreversibly damaged by As(III), due to the high toxicity of this cation for C. acidophila, similar to other organisms [24,80].…”

Evaluation of microalgae growth in a mixed‐type photobioreactor system for the phycoremediation of wastewater

“…The extraction of lipids was performed based on the classic method described by Bligh and Dyer adapted and used previously by Souza et al . and Gressler et al .…”

“…The extraction of lipids was performed based on the classic method described by Bligh and Dyer 40 adapted and used previously by Souza et al 41 and Gressler et al 38 To analyze the dry biomass, the biomass was ground and sieved through a 250-μm diameter mesh. The lipid content was measured as a percentage of dry weight (%DW) biomass and lipid extracts were stored under refrigeration for 24 h.…”

Extremophile Microalgae: the potential for biotechnological application

“…, D'Alessandro and Antoniosi Filho , Souza et al. ). The aim of this review is to discuss the most important inherent features of extremophile microalgae and their possible biotechnology applications.…”