Isolation and physico-chemical characterisation of extracellular polymeric substances produced by the marine bacterium Vibrio parahaemolyticus

A marine bacterial strain identified as Vibrio parahaemolyticus by 16S rRNA gene (HM355955) sequencing and gas chromatography (GC) coupled with MIDI was selected from a natural biofilm by its capability to produce extracellular polymeric substances (EPS). The EPS had an average molecule size of 15.278 mu m and exhibited characteristic diffraction peaks at 5.985 degrees, 9.150 degrees and 22.823 degrees, with d-spacings of 14.76661, 9.29989 and 3.89650 angstrom, respectively. The Fourier-transform infrared spectroscopy (FTIR) spectrum revealed aliphatic methyl, primary amine, halide groups, uronic acid and saccharides. Gas chromatography mass spectrometry (GCMS) confirmed the presence of arabinose, galactose, glucose and mannose. (HNMR)-H-1 (nuclear magnetic resonance) revealed functional groups characteristic of polysaccharides. The EPS were amorphous in nature (CIxrd 0.092), with a 67.37% emulsifying activity, thermostable up to 250 degrees C and displayed pseudoplastic rheology. MALDI-TOF-TOF analysis revealed a series of masses, exhibiting low-mass peaks (m/z) corresponding to oligosaccharides and higher-mass peaks for polysaccharides consisting of different ratios of pentose and hexose moieties. This is the first report of a detailed characterisation of the EPS produced by V. parahaemolyticus, which could be further explored for biotechnological and industrial use.