Galactomannan-based sustainable functional biopolymeric material for efficient harvesting of Chlorella sorokiniana

Abstract

Microalgae serve as sustainable biofactories for bioenergy and bioproducts, yet their biomass harvesting remains a critical bottleneck because of low culture density and the inherent instability caused by negative zeta potential. Conventional flocculants often contaminate biomass with toxic residues or metallic ions, resulting in difficulties in efficient downstream processing of microalgal biomass. Thus, it is essential to develop natural, non-toxic, and biocompatible materials for efficient microalgal dewatering. A cationic locust bean gum (GLBG) polymer was synthesized via graft copolymerization of [2-(Methacryloyloxy)ethyl] trimethylammonium chloride (METAC) onto locust bean gum. The polymer was characterized using FTIR, NMR, elemental analysis, XRD, and zeta potential measurements. Its harvesting efficiency was evaluated against Chlorella sorokiniana. Also, cytocompatibility was assessed through trypan blue staining, chlorophyll fluorescence, and in vitro fibroblast cell viability assays. The effect of GLBG on metabolite extraction was examined for lipids, proteins, and carbohydrates. GLBG achieved >97% harvesting efficiency at an optimum dosage of 25 ppm. It did not interfere with lipid, protein, or carbohydrate recovery from biomass and preserved microalgal cell integrity and photosynthetic performance. Cytocompatibility assays confirmed non-toxicity, positioning GLBG as a sustainable, biodegradable, and efficient biopolymeric material for microalgal biomass recovery and downstream applications.