Optimization of EPS Production and Characterization by a Halophilic Bacterium, Kocuria rosea ZJUQH from Chaka Salt Lake with Response Surface Methodology

Abstract

With the rising awareness of microbial exopolysaccharides (EPSs) application in various fields, halophilic microorganisms which produce EPSs have received broad attention. A newly identified Kocuria rosea ZJUQH CCTCC M2016754 was determined to be a moderate halobacterium on account of its successful adaption to the environment containing 10% NaCl. The optimal combination of fermentation medium compositions on EPS production was studied. In this work, a fractional factorial design was adopted to investigate the significant factors that affected EPS production. The factors of KCl and MgSO4 were found to have a profound impact on EPS production. We utilized central composite design and response surface methodology to derive a statistical model for optimizing the submerged culture medium composition. Judging from these experimental results, the optimum culture medium for producing EPSs was composed of 0.50% casein hydrolysate, 1.00% sodium citrate, 0.30% yeast extract, 0.50% KCl, 0.50% peptone, and 5.80% MgSO4 (initial pH 7.0). The maximal EPS was 48.01 g/L, which is close to the predicted value (50.39 g/L). In the validation experiment, the highest concentration of 70.64 g/L EPSs was obtained after 120 h under the optimized culture medium in a 5-L bioreactor. EPS from this bacterium was also characterized by differential scanning calorimetry (DSC) and Fourier transform infrared analysis (FT-IR). The findings in this study imply that Kocuria rosea ZJUQH has great potential to be exploited as a source of EPSs utilized in food, the pharmaceutical and agriculture industry, and in the biotreatment of hypersaline environments.

Metabolic potential of the moderate halophile Yangia sp. ND199 for co‐production of polyhydroxyalkanoates and exopolysaccharides

“…No absorption peaks around the region of 1700–1770 cm −1 attributed to C=O stretching of carbonyls in esters were observed (Kielak et al, 2017). The peak in the region of 1644 cm −1 would represent the absorption band of carboxylic groups, suggesting the presence of acidic sugars (Deshmukh et al, 2017; Kielak et al, 2017), and similarly, the peak at 1219 cm −1 observed in some samples could be attributed to C‐O stretching in ether or alcohol groups (Gu et al, 2017; Kanamarlapudi & Muddada, 2017). The peak at 1051 cm −1 indicates a possible α (1→6) glucosidic bond with certain flexibility (Gu et al, 2017), while the absorption band at 978 cm −1 suggests the vibrations of the glycosidic bonds C‐O‐C and the peak in the region of 840–860 cm ‐1 are characteristic of α‐D‐glucan (Kanamarlapudi & Muddada, 2017).…”

“…to C-O stretching in ether or alcohol groups (Gu et al, 2017;Kanamarlapudi & Muddada, 2017). The peak at 1051 cm −1 indicates a possible α (1→6) glucosidic bond with certain flexibility (Gu et al, 2017), while the absorption band at 978 cm −1 suggests the vibrations of the glycosidic bonds C-O-C and the peak in the region of 840-860 cm -1 are characteristic of α-D-glucan (Kanamarlapudi & Muddada, 2017). The band at 630 cm -1 is due to the out-of-plane bending of -OH groups (Deshmukh et al, 2017).…”

Characterization of Microbial Communities Associated with Ceramic Raw Materials as Potential Contributors for the Improvement of Ceramic Rheological Properties

“…This latter is a halophilic bacterium able to produce a polysaccharide designated as Kocuran [49]. Recent publications claims that certain strains of Kocuria rosea have great potential to be exploited as a source of EPSs utilized in industry, as well as in the biotreatment of hypersaline environments [50]. In addition, the genus Brachybacterium was detected in the isolates of sample 1A with a 100% rate of similarity, represented by the species Brachybacterium rhamnosum.…”

Production, purification, characterization, and biological properties of Rhodosporidium paludigenum polysaccharide

“…Six different fermentation media were used as follows: (1) The yeast peptone dextrose adenine (YPDA) medium: yeast extract 10 g, peptone 20 g, glucose 20 g, and distilled water 1 L [ 15 ]; (2) Czapek medium: sucrose 30 g, sodium nitrate 3 g, dipotassium phosphate 1 g, potassium chloride 0.5 g, magnesium sulfate 0.5 g, ferrous sulfate 0.01 g, and distilled water 1 L [ 16 ]; (3) Medium 1: sucrose 50 g, soybean peptone 40 g, yeast extract 30 g, glycerin 16 g, and distilled water 1 L [ 17 ]; (4) Medium 2: sucrose 50 g, glucose 20 g, yeast extract 50 g, ammonium sulfate 10 g, potassium dihydrogen sulfate 3 g, glycerol 2 g, calcium chloride 1 g, and distilled water 1 L [ 18 ]; (5) Medium 3: sucrose 60 g, yeast paste 40 g, ammonium sulfate 10 g, potassium dihydrogen sulfate 3 g, glycerin 10 g, and distilled water 1 L [ 19 ]; (6) Medium 4: sucrose 50 g, glucose 20 g, peptone 60 g, ammonium sulfate 30 g, glycerin 3 g, calcium chloride 3 g, magnesium sulfate 1 g, calcium D-pantothenate 0.6 g, and distilled water 1 L. All the media were sterilized at 121°C in an autoclave sterilizer for 30 min.…”