Deconstruction of Kappaphycus alvarezii biomass by pressurized solvents to increase the carrageenan purity

Kappaphycus alvarezii (KA) is a natural renewable resource of valuable products with a high concentration in κ-carrageenan and other bioactive components that can be recovered applying the biorefinery approach. This study aimed to sequentially extract components from KA biomass, including phenolic compounds, carrageenan, low molecular weight compounds, and cellulose, using high-pressure methods. The first step on the KA deconstruction is to recovery of phenolics with ethanol using Soxhlet and Pressurized Liquid Extraction (PLE) methods. KOH was applied for the KA biomass pretreatment. Sequentially, the carrageenan fraction was extracted by low- and high-pressure methods, and the recovered carrageenan samples were characterized by Fourier transform infrared spectroscopy (FTIR), viscosity, gel strength, Gel Permeation Chromatography (GPC), and chemical composition. Scanning electron microscope (SEM) analysis detected the KOH influence and the separation of carrageenan and cellulose materials. Although both extraction routes (low- and high-pressure methods) presented similar recovery yields in phenolics, carrageenan, and cellulosic fractions, the high-pressure route was more efficient in terms of processing time, solvent, and energy consumption. Besides, the novelty of this study was the use of high-pressure sequential procedures for the fractionation of KA, highlighting the effect of the process on the carrageenan characteristics.