Long-chain alkyl-modified quaternized laminarin for enhanced antibacterial activity and food preservation

Food safety hazards induced by microorganisms and their contaminants have exert adverse effects on human health. Based on green food concepts, antimicrobial modification to foods is critical. Laminarin (LMA) is a natural functional polysaccharide that lack antibacterial properties. Herein, six long-chain alkyl-modified quaternized laminarin (C8QAS-LMA, C10QAS-LMA, C12QAS-LMA, C14QAS-LMA, C16QAS-LMA, C18QAS-LMA) were synthesized through alkaline-mediated nucleophilic substitution between LMA and quaternary ammonium (QAS). Their structures were characterized by FT-IR, ¹H NMR, elemental analysis, and GPC. Their solubility and antimicrobial properties were enhanced. Among them, C12QAS-LMA was the best. The water solubility of C12QAS-LMA was up to 2.03 g. The inhibitions of C12QAS-LMA were 92% and 88% against E. coli and S. aureus, respectively, at 0.50 mg/mL with non-toxicity. C12QAS-LMA exhibited potential antioxidant activity and biocompatibility relative to native LMA. As novel functional polysaccharides, QAS-LAM has the potential food industry applications, providing innovative solutions for functional food, preservation and packaging development.