Scenedesmus dimorphus (Turpin) Kützing growth with digestate from biogas plant in outdoor bag photobioreactors

Isolation and identification of the alga-symbiotic bacterium Gordonia and characterisation of its exopolysaccharide

An exopolysaccharide (EPS)-producing bacterium TD18, isolated from the culture broth of green alga Scenedesmus obliquus, was identified as Gordonia terrae based on the 100% identity of 16S rRNA sequences and designated Gordonia terrae TD18. The results of compositional and structural analyses and physiochemical tests show that (1) the exopolysaccharide produced by G. terrae TD18 (TD18-EPS) is an acidic hetero-polysaccharide with a molecular weight of 23 kDa, consisting of glucose, mannose, galactose and glucuronic acid, and (2) TD18-EPS is of high thermal stability with a degradation temperature of 308 °C, the solution of which is non-Newtonian pseudoplastic fluid exhibiting good emulsifying properties over a wide range of temperatures, pH and NaCl concentrations. Hence, Gordonia terrae TD18 is the first alga-symbiotic Gordonia strain identified thus far, while TD18-EPS is unique in terms of composition and structure, different from the known Gordonia EPS, with excellent physiochemical properties and thus has potential applications in industry.

Green microalgae as a potential source of trypanocide compounds

Due to the limitations of Chagas disease therapy, microalgae can be promising in the search of new trypanocidal compounds, since these organisms produce bioactive compounds with large pharmaceutical applications, including antiparasitic effects. In this work, trypanocidal activity of aqueous extract of Tetradesmus obliquus and, for the first time, aqueous extract of Chlorella vulgaris, were evaluated against trypomastigote forms of Trypanosoma cruzi. In addition, cytotoxic activity in Vero cells was evaluated. Our results showed that C. vulgaris and T. obliquus present trypanocidal activity (IC50 = 32.9 µg ml-1 and 36.4 µg ml-1, respectively), however, C. vulgaris did not present cytotoxic effects in Vero cells (CC50 > 600 µg ml-1) and displayed a higher selectivity against trypomastigotes forms of T. cruzi (SI > 18). Thus, microalgae extracts, such as aqueous extract of C. vulgaris, are promising potential candidates for the development of natural antichagasic drugs.