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. 2019 Dec 13;17(12):703.
doi: 10.3390/md17120703.

Isolation, Optimization of Fermentation Conditions, and Characterization of an Exopolysaccharide from Pseudoalteromonas agarivorans Hao 2018

Lujiang Hao  1   2 , Wenlin Liu  1 , Kai Liu  1 , Kai Shan  1 , Chunlei Wang  1 , Chenxiang Xi  1 , Jianbang Liu  1 , Qiuping Fan  1 , Xiaofei Zhang  1 , Xiaoping Lu  1 , Yanrui Xu  1 , RuiWen Cao  1 , Yaohong Ma  3 , Lan Zheng  3 , Bo Cui  4
Affiliations

Isolation, Optimization of Fermentation Conditions, and Characterization of an Exopolysaccharide from Pseudoalteromonas agarivorans Hao 2018

Lujiang Hao et al. Mar Drugs. .

Abstract

In recent years, the wide application of exopolysaccharides (EPSs) in food, cosmetics, medicine, and other fields has drawn tremendous attention. In this study, an EPS produced by Pseudoalteromonas agarivorans Hao 2018 was isolated and purified, and its fermentation conditions were optimized. Its structure and biological functions were also studied. The purity and molecular weight of EPS were determined by high performance liquid chromatography (HPLC), and the EPS exhibited a number average of 2.26 × 105 and a weight average of 2.84 × 105. EPS has good adsorption for Cu2+ and Pb2+. The adsorption rates can reach up to 69.79% and 82.46%, respectively. The hygroscopic property of EPS was higher than that of chitosan, but slightly lower than that of sodium hyaluronate. However, the water-retaining activity of EPS was similar to that of chitosan and sodium hyaluronate. EPS has strong ability to scavenge free radicals, including OH radical and O2- radical. Further, its activity on O2- radicals has similarities with that of vitamin C. EPS has broad application prospects in many fields, such as cosmetics, environmental protection.

Keywords: fermentation optimization; marine bacteria; oxidation resistance; structural analysis.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Purification of EPS. The MW distribution of EPS was determined by high performance liquid gel filtration chromatography (HPGFC) using a Shodex SB-806 HQ column with 0.2 M NaCl solution at a flow rate of 0.5 mL/min (A). The ultraviolet (UV) visible spectrum of EPS was measured at 200–600 nm in H2O at 25 °C (B).
Figure 2
Figure 2
Effects of glucose concentration (A.1), yeast extract concentration (A.2) and sea salt concentration (A.3) on EPS Yield in Medium. Effect of glucose concentration: Sea salt concentration 35 g/L, Yeast extract concentration 4.5 g/L, Temperature 25 °C, Fermentation time 35 h, Seed volume 10%, Shaker speed 230 rpm. Effect of sea salt concentration: glucose concentration 30 g/L, Yeast extract concentration 4.5 g/L, other conditions are the same as above. Effect of yeast extract concentration: glucose concentration 30 g/L, sea salt concentration 35 g/L. Other conditions are the same as above.
Figure 3
Figure 3
Based on the optimal medium composition of the above experiment (Sea salt concentration 35 g/L, yeast extract concentration 4.5 g/L, glucose concentration 30 g/L), the optimal temperature (B.1), fermentation time (B.2), seed volume (B.3), and shaker speed (B.4) are further studied.
Figure 4
Figure 4
Effect of different liquid volume (C.1) and pH (C.2) on polysaccharide yield at 25 °C.
Figure 5
Figure 5
Response surface diagram of two-factor interaction: (A) correspondence between the interaction of seed volume and fermentation time; (B) correspondence between the interaction of shaker speed and fermentation time; (C) correspondence between the interaction of Shaker speed and seed volume.
Figure 6
Figure 6
HPLC chromatograms of seven PMP-labeled standard monosaccharides (A) and PMP-labeled monosaccharides released from EPS (B). Peaks: 1. d-Mannose; 2. d-Rhamnose; 3. d-Glucuronic acid; 4. d-Galacturonic acid; 5. d-Glucose; 6. d-Galactose; 7. d-Xylose.
Figure 7
Figure 7
FT-IR spectra of EPS. The dry polysaccharides were crushed and granulated by the KBr method. The ultraviolet-visible spectra of EPS were recorded by a 500–4000 cm spectrophotometer.
Figure 8
Figure 8
Adsorption rate of EPS for different concentrations of Cu2+ (A) and Pb2+ (B).
Figure 9
Figure 9
Moisturizing curve under silica gel environment (A) and 32% relative humidity (B). Moisture retention of EPS was determined by measuring the reserved weight of H2O by EPS. Chitosan and sodium hyaluronate were used as controls. The value at the beginning was set 100%.
Figure 10
Figure 10
The scavenging effect of EPS on hydroxyl (A) and superoxide anions (B). The scavenging activities of different concentrations of EPS on –OH and O2− were determined by removing –OH from FeSO4 and H2O2 and O2− from pyrogallol removal. Vitamin C was used as a control and the activity of 100 µg/mL Vitamin C was set 100%.
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