Extracellular polymeric substances with high radical scavenging ability produced in outdoor cultivation of the thermotolerant chlorophyte Graesiella sp.

Abstract

The present study developed a two-step strategy to enhance the production of extracellular polymeric substances (EPSs) by a thermotolerant chlorophyte, Graesiella sp., in view to their industrial valorisation. In the first step, Graesiella sp. was grown in outdoor conditions in pilot-scale photobioreactors of 100 L culture volumes. In the second step, the biomass collected in the exponential growth phase was submitted to heat stress (50°C). A joint production of biomass reaching 0.50 g dw L −1 day −1 and of EPS production reaching 1.30 g dw L −1 in 2 days was obtained. EPSs mainly contained polysaccharides (80%) and proteins (14%). FTIR and 1 HNMR revealed the presence of primary amine and sulfated groups. The EPSs contained antioxidant enzymes (SOD, CAT, and APX) maintained in an active state by the microenvironment offered by the EPSs. The EPSs were found to have a potent antioxidant activity via directly scavenging free radicals when compared to L-ascorbic acid.

Extracellular Polymeric Substances Produced by the Thermophilic Cyanobacterium Gloeocapsa gelatinosa: Characterization and Assessment of Their Antioxidant and Metal-Chelating Activities

“…EPSs are a complex mixture of macromolecular polyelectrolytes, mainly consisting of polysaccharides, amine-group, halide-group, aliphatic alkyl group, aromatic compounds, and nucleic acids [2,3]. They have been identified as a new rich source of bioactive compounds, such as antiviral and anti-inflammatory, antitumor, anticancer [1], and wound healing [4] agents.…”

Elaboration and Characterization of a New Heavy Metal Sensor Functionalized by Extracellular Polymeric Substances Isolated from a Tunisian Thermophilic Microalga Strain Graesiella sp.

“…The zeta potential was evaluated at −40 ± 2 mV. The negative charge may be due to the presence of anionic groups and to the presence of uronic acids [ 24 ]. Consequently, the EPS solution could be quite reactive with chemical species such as cadmium and mercury [ 25 ].…”

“…The SEM top view and cross-section ( Figure 7 ) confirmed a homogeneous character and revealed a microstructural lamellar arrangement of the EPS-functionalized membrane. Regarding the homogenous and compact structure, the surface morphology appeared without protrusions and with irregular blocks with similar features to that of native Graesiella EPS [ 24 ].…”

“…FTIR spectroscopy showed little change in functional groups with respect to Graesiella sp. native EPS [ 24 ]. Broadband between 2900 and 3000 cm −1 is attributed to the stretching vibration (ν) of O-H or νC-H groups, characteristic of the hydroxyl and alkyl functionality of carbohydrates.…”

A Novel Impedimetric Sensor Based on Cyanobacterial Extracellular Polymeric Substances for Microplastics Detection

“…Extracellular Polymeric Substances (EPS) were extracted from the culture cultivation of the cyanobacteria Gloecapsa gelationosa. The EPS was concentrated using a tangential ultra-filtration cell (Vivaflow 50) in Millipore membranes with 5 kDa pore size and then washed with deionized water until constant conductivity to eliminate low molecular weight substances [ 48 , 49 ]. Lastly, the recovery filtrate was freeze-dried, lyophilized, and weighed for EPS content determination.…”