The effects of temperature and light intensity on growth, reproduction and EPS synthesis of a thermophilic strain related to the genus Graesiella

Abstract

Tunisian microalgae are diverse and rarely been studied. This study reports a first investigation of thermophile Chlorophyta isolated from mats community colonizing the geothermal springs in the north of Tunisia at water temperature 60 °C. In the study, the combined effect of temperature and light intensity was investigated on the cell growth, the mother and daughter cells abundance and the extracellular polymeric substances synthesis in batch culture of the isolated species. Three levels were tested for each factor, 20, 30, 40 °C for temperature; and 20, 70, 120 μmol photons m(-2) s(-1) for light intensity, using full factorial design and response surface methodology. The thermophile strain was identified as a genus Graesiella and showed 99.8% similarity with two Graesiella species: Graesiella emersonii and Graesiella vacuolata based on the 18S rDNA molecular identification. The optimal growth condition was found at 30 °C and 120 µmol photons m(-2) s(-1) (7 MC mL(-1) day(-1)), with the abundance of vegetative cells (daughter cells). In contrast, the number of mother cells increased significantly as the growth decreased; consequently, the highest ratio of auto spore mother cells versus daughter cells (19.4) was obtained at 20 °C and 20 µmol photons m(-2) s(-1). The highest yield of EPS production (11.7 mg L(-1) day(-1)) was recorded at the highest temperature (40 °C) and lowest light intensity (20 µmol photons m(-2)s(-1)). These results revealed how the species respond to high and low temperatures and suggest that the species should be considered as facultative thermophile.

Study on dyeing wastewater treatment at high temperature by MBBR and the thermotolerant mechanism based on its microbial analysis

“…Previous studies demonstrated that the optimum (relative higher) temperature was 35-40 • C for some specific microorganisms on producing highest amount of EPS [24,26]. Nevertheless, in this study, 45 • C was the optimum temperature for EPS production.…”

Sulfated exopolysaccharide production and nutrient removal by the marine diatom Phaeodactylum tricornutum growing on palm oil mill effluent

“…An explanation for this could be that P. tricornutum accumulates sEPS when the culture is in a stressed condition to protect cells from damage (Delattre et al 2016). Previous studies using the green alga Graesiella revealed that total EPS production increased with temperature (Mezhoud et al 2014).…”

Non-surface Attached Bacterial Aggregates: A Ubiquitous Third Lifestyle

“…Together, the whole consortium substantially remove the organic matter and nutrients in wastewater, with excellent settling characteristics allowing for biomass harvesting by gravity sedimentation (Quijano et al, 2017). While the genera such as Chlorella and Scenedesmus have been reported to be a suitable algal species (Gutzeit et al, 2005;Lee et al, 2013;Mezhoud et al, 2014;Vandamme et al, 2014;Shen et al, 2015;Kinnunen and Rintala, 2016;Arcila and Buitrón, 2017), so far, most bacteria identified in wastewater treatment using microalgal-bacterial systems belong to the phyla Bacteroidetes and Proteobacteria, such as Betaproteobacteria, Bacteroidia, Flavobacteria,Gammaproteobacteria (Su et al, 2011), Sphingobacteria, Terrimonas, and Hyphomon-as (Lee et al, 2013). More detailed knowledge on the interaction between different algal-bacteria species would facilitate better design.…”