Functional, rheological, and antioxidant properties of extracellular polymeric substances produced by a thermophilic cyanobacterium Leptolyngbya sp

Abstract

Extracellular polymeric substances (EPSs) produced by the filamentous cyanobacterium identified as Leptolyngbya sp. IkmLPT16 were isolated and characterized chemically, and their antioxidant, functional, and rheological properties were studied. The strain produces a significant amount of EPSs (2.15 g L−1) conjointly with a biomass production achieved at a maximum of 1.35 g L−1 after nine production days. Chemical analysis of EPSs revealed the presence of mannose (35%), arabinose (24%), glucose (15%), rhamnose (2%), and one uronic acid (8%). Fourier transformed infrared spectrum of EPSs further revealed the presence of νC-N groups indicating the presence of peptide moieties. Elemental analysis of EPSs showed the presence of sulfate groups (S = 0.59%) as inorganic substituents. Functional properties of Leptolyngbya EPSs were determined based on water holding capacity, oil holding capacity, foaming ability, and metal sorption ability. Experimental results showed high water holding capacity (119%), water solubility index (97.43%), and oil holding ability (87.52%), with a strong metal sorption ability and consequent foam stability (22%). The rheological properties of EPSs were comparable with commercial xanthan gum with higher resistance to Temperature. Leptolyngbya sp. EPSs displayed an effective antioxidant activity via directly scavenging free radicals particularly DDPH• (IC50 = 4 mg. mL−1 against 10 mg. mL−1 for l-ascorbic acid) and •OH (IC50 = 10 mg. mL−1 against 20 mg. mL−1 for l-ascorbic acid) and as an iron-chelating agent (IC50 = 40 mg. mL−1 against 60 mg.mL−1 for EDTA). The outcomes of this study demonstrate the potential use of Leptolyngbya sp. EPSs in several food and pharmaceutical applications.