• microalgae in response to Uv-B

Although only a few species are currently cultivated in relevant applications field, many studies in the literature have aimed at evaluating other newly characterized species as possible candidates for functional foods, high-value products and other use such us feedstock production and bioremediation. As like plants, microalgae use photosynthetic pathway activated by sunlight to fix atmospheric CO2 and convert it in biomass. Microalgae are eukaryotic unicellular cells, are ubiquitous in all environments such as lake, river, sea but also present in wasted water, soil and air, thus able to grow in different conditions thanks to their flexibility to adapt. In this work two autochthonous and two newly isolated microalgal strains from freshwater were evaluated for their capability to live under oxidative stress situation (UV-B 18 h in continuous) compared to control (at normal spectrum light) at room temperature and also tested on photosynthetic pigments, total polyphenols at different time of exposition in triplicate. Moreover, in vitro antioxidant activity of each microalgal strain was screened by DPPH (2,2-diphenyl-1-picrylhydrazyl) assay. Total polyphenols were expressed as µg of gallic acid equivalents (GAE) ml-1, according to the standard curve and the standard deviation (SD) calculated on three biological replicates, and showed a large variability among individuals. Indeed, phenolic substances are strongly influenced by both solvent methods and environmental/ growing conditions, which greatly affect, respectively, their extraction/solubility and production by microalgae.
Our data revealed the presence of variable contents of both biochemical parameters
and antioxidant activities, depending on light treatment and manly referable on the isolation sources or the phylogenetic attribution of the microalgal strains. Moreover, this study also stimulate further studies aimed to evaluate genetic differences and characterize the enzyme activity and the response of this microalgae in extreme condition of life.
Among these strains, this work aimed to select and use of species, showing the most promising features for massive growth and bioactive compound production.
The Chlorella-like clade, one named F4, was isolated from a water sample collected in the Fucecchio Marshland and the other LG1 was isolated from the surface of a recycled CB filter substrate used in the preliminary experiments of a previous study and it also is taxonomically related to Chlorella sorokiniana Shihira & R.W. Krauss species, which is the largest inland Italian swamp are affected differently in the capability to survive and this is also may due to the different growing condition. The Andino strains, were isolated in the Andean Yahuarcocha lake at Imbabura Province of Ecuador, were collected in the deep point reference of the lake, at 0.50 m depth using a Van Dorn bottle and there are called ETI and PEC, related to the identification that was obtained by molecular identification using ITS regions (Ettlia pseudoalveolaris and Pectinodesmus pectinatus) ,until the 18 hour, maybe due to the environment than they usually live and their physiology. ETI was the only one than has got significant increasing in the phenolic constitution related to the time of exposition, and never decrease in all of the time tested, also showed a powerful difference between the control line, that produce a non-detectable results until the 12th hour. Nevertheless this date still be a input for further studies, ETI sems to be stimulated by UV-B radiation in the production of phenols. At least, no one of the strains are able to produce a significant amount of biomass at this extreme oxidative conditions but all the Andino strains are able to survive and growth. Furthermore, the genes ChlL, chlN, and chlB and UV RESISTANCE LOCUS 8 need to be tested in the ETI and PEC to establish if the resistance it also depending by their activity. As, SOD, CAT and POD require to be tested to validate these application. Although, Andino strains are the best putative candidates, future studies on LG1 between F4 need to be done to explicate how two very similar strains had got such a different results.
The characterization of the antioxidant compound and the phenolic fraction, at least, need to be tested due to searching if there is a most compound produced and if it is important for its application in industry fields.
To confirm this results, this microalgae should be tested in various filed, also bioremediation apply.