Searching for microalgal species producing extracellular biopolymers

Abstract

Microalgae have been used in human applications for centuries, but in the mid-twentieth century, an industrial cultivation of some species began. In this study, 17 different microalgal species were screened for the production of extracellular polymeric substances (EPSs). EPS yields (16–1064 mg/L), carbohydrate (1–88%) and protein (0–16%) contents were found to vary greatly. Uronic acids have been identified in most EPSs, indicating their ionic nature. Monosaccharide compositions revealed the heteropolysaccharide type of all EPSs. Monosaccharide compositions revealed a high number of sugar units (6–8) in all EPSs. Besides, hexoses were found as the dominant sugar components in most species. Some EPSs were rich in deoxy-hexoses, i.e. rhamnose or fucose, and some had high pentose content, i.e. xylose or arabinose. In many EPSs partially methylated sugars have been determined. Of the 17 species of microalgae studied, six strains differed significantly in the production of EPSs from others and had a relatively high content of carbohydrates. Screening revealed the following major EPS producers: Chlorosarcinopsis sp. (Lukesova 1996/401), Klebsormidium flaccidum (Lukesova 1997/320), K. flaccidum (Kastovska 1995/02), Dictyosphaerium chlorelloides (Kovacik 1978/11), Dictyosphaerium cf. tetrachotomum Printz (Fott 1959/1), and Dictyosphaerium cf. tetrachotomum Printz Růžicka 1962/50). Dominant producers are selected for cultivation on a larger scale to obtain EPSs for detailed chemical studies and potential biological activities.