Extraction and characterization of polysaccharide films prepared from Furcellaria lumbricalis and Gigartina skottsbergii seaweeds

Polysaccharide films prepared using water extraction of red algae represent an important group of environmentally-friendly materials suitable for industrial applications in food processing, medicine or electrical engineering. In this study, we prepared polysaccharide films from Furcellaria lumbricalis (FL) and Gigartina skottsbergii (GS) seaweed extracts and investigated their physical, chemical, and mechanical properties. Following contents of individual isolated fractions were observed by the nuclear magnetic resonance (NMR): ultrasonic water extraction of GS (GSUW) consisted of (1-3)-?-glycan 6-sulfate; ultrasonic carbonate-peroxide extraction (GSUCP) consisted of the same glycan and extra carrageenan hybrids µ-D6S and ?-D2S,6S observed for the first time in this study; extractions of FL and GS in boiling water under reflux (FLW, GSW) contained ?-, ?-, ?-, µ-, ?-, and ?-carrageenans and (1-3)-?-glycan partially sulphated at C or the most complex mixture of ?-, ?-, ?-, ?-, ?-, ?-carrageenans, and (1-3)-?-glycan partially sulfated at C, respectively. Spatially-resolved surface morphology and mechanical properties were evaluated by the atomic force microscopy and PeakForce quantitative nanomechanical mapping and correlated to the other investigated films properties. According to X-ray diffraction analysis, we observed no cellulose content or confirm the crystalline form of carrageenans in none of the studied polysaccharide films.