Optimization of Fermentation Conditions and Rheological Properties of Exopolysaccharide Produced by Deep-Sea Bacterium Zunongwangia profunda SM-A87

Abstract

Zunongwangia profunda SM-A87 isolated from deep-sea sediment can secrete large quantity of exopolysaccharide (EPS). Response surface methodology was applied to optimize the culture conditions for EPS production. Single-factor experiment showed that lactose was the best carbon source. Based on the Plackett–Burman design, lactose, peptone and temperature were selected as significant variables, which were further optimized by the steepest ascent (descent) method and central composite design. The optimal culture conditions for EPS production and broth viscosity were determined as 32.21 g/L lactose, 8.87 g/L peptone and an incubation temperature of 9.8°C. Under these conditions, the maximum EPS yield and broth viscosity were 8.90 g/L and 6551 mPa•s, respectively, which is the first report of such high yield of EPS from a marine bacterium. The aqueous solution of the EPS displayed high viscosity, interesting shearing thinning property and great tolerance to high temperature, a wide range of pH, and high salinity.

Whey-derived valuable products obtained by microbial fermentation

“…Several authors have shown that several bacterial strains could produce EPS when grown in whey or whey derivatives. Sun et al (2014) reported that the strain Zunongwangia profunda SM-A87 could grow in whey and produce the highest amount of EPS (17.2 g/L) reported for a marine bacterium; this polymer displays antioxidant activity and is of industrial interest since it has optimum biosorption capacities for Cu(II) and Cd(II) and has good rheological properties to enhance oil recovery (Liu et al 2011). Also, the strain Rhizobium radiobacter S10, isolated from kefir grains, is able to produce 2.8 g/L of a 3.03−10 6 Da polymer with interesting thickener or stabilizer properties during its growth in whey ).…”

Rheological and emulsifying properties of a gel-like exopolysaccharide produced by Pseudomonas stutzeri AS22

“…According to previous studies dealing with the influence of pH on the viscosity of 209 polysaccharide solutions, the increase of viscosity at pH 4.0 and 6.0 may be due to an increase 210 of the ionization degree of carboxyl groups in EPS22 polysaccharide (Maalej,Boisset,et al,211 2014) leading to the extension of the polymer molecules (Liu et al, 2011). However, the 212 decrease of the EPS22 viscosity at very acidic (pH 1.0) or alkaline conditions (pH 10.0) may 213 be attributed to the screening effect of excess alkali on the negatively charged polysaccharide 214 molecules (Liu et al, 2011).…”

“…However, the 212 decrease of the EPS22 viscosity at very acidic (pH 1.0) or alkaline conditions (pH 10.0) may 213 be attributed to the screening effect of excess alkali on the negatively charged polysaccharide 214 molecules (Liu et al, 2011). Another explanation was reported by Li and Hou (2011) who 215 suggested that the good pH stability of the SM-A87 EPS solution may be attributed to the 216 hyper-branched structure of the polymer's molecules.…”

Characterization of Bacterial Polysaccharide Capsules and Detection in the Presence of Deliquescent Water by Atomic Force Microscopy

“…The strain was cultured as previously described (11). Briefly, the strain was first cultured on a marine agar medium (10 g/liter peptone, 5 g/liter yeast extract, 15 g/liter agar, and artificial seawater) at 30°C for 1 day.…”