Integrated Supercritical CO2 and subcritical water extraction of high-value compounds to valorize brown macroalgae (Padina tetrastromatica and Turbinaria conoides) harvested from Indian coastline

Abstract

Abstract This work centred on the valorisation of brown macroalgae by sequentially extracting multiple value-added compounds using developing green extraction techniques. Supercritical fluid extraction (SFE) was used to extract lipids from biomass, which were found to be rich in polyunsaturated fatty acids with multiple nutraceutical applications. Using the subcritical water (ScW) technique, 48% sodium alginate and 11% protein were recovered from the SFE residual biomass. The alginate derived from ScW revealed the presence of mannuronic (M) and guluronic acids (G) with M/G ratio greater than 1, fulfilling WHO and FAO guidelines for the nutraceutical and pharmaceutical industries. Due to high concentration of polyphenolic compounds, alginate exhibited up to 80% invitro 2,2-diphenyl-1-picrylhydrazyl scavenging activity and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activity. Thus, an integrated method has been designed to valorize biomass by extracting commercially relevant valuable compounds from macroalgae utilising green and sustainable technologies, which could be used for the scale-up extraction of these compounds by a variety of industrial sectors.