With the rising awareness of microbial exopolysaccharides (EPSs) application in various
With the rising awareness of microbial exopolysaccharides (EPSs) application in various fields, halophilic microorganisms which produce EPSs have received broad attention. 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 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. ZJUQH, exopolysaccharides, optimization, response surface methodology 1. Introduction Halophilic microorganisms are capable of growing and carrying out their metabolism under hypersaline conditions. As a result of adaptation to their environment, they have developed numerous character types and salt acclimation strategies. Halophilic microorganisms can be classified according to the salt concentrations that they need to grow in, as slight halophiles (2C5% NaCl), moderate halophiles (5C20% NaCl), and extreme halophiles (20C30% NaCl) . Extracellular polysaccharides (exopolysaccharides, EPSs) are one of the most important group of substances produced by microorganisms for their survival in hypertonic environment . They occur in two forms: as a capsule closely associated with the cell surface or as slime polysaccharides loosely associated with the cell surface . Those polysaccharides could also be differentiated by their chemical composition. Homopolysaccharides (HoPS) are composed of only one monosaccharide (glucose or fructose, mainly), and heteropolysaccharides (HePS) comprise repeating models of different monosaccharides . Other residues such as sn-glycerol-3-phosphate, N-acetyl-amino sugars, phosphate, and acetyl groups can also be found . EPSs have important ecological and physiological functions and play special functions in protecting the microorganisms that produce them. They are believed to safeguard cells against antimicrobial substances, desiccation, bacteriophages, osmotic stress, and antibodies as well as to permit adhesion to solid surfaces and biofilm formation [6,7,8]. Microbial polysaccharides have found a broad spectrum of applications in industry. In the food industry, these polymers are used as biothickeners to improve food quality and texture because of their stabilizing, gelling or emulsifying properties . As supplemented with dextran, superior AS-605240 cost structural and textural extrudate characteristics were achieved in high dietary fiber extrusion . In the pharmaceutical industry, polysaccharides can be used as a hydrophilic matrix for controlled release of drugs , as an anti HIV agent , and to enhance nonspecific immunity . In the agriculture sector, the fluidity of fungicides, herbicides, and insecticides has been improved by the addition of xanthan, which results in the uniform suspension of solid components in formulations . In addition, their functional properties T also include bioflocculants , biosorption of heavy metals , and chemical products [16,17]. With the industrial development, new water and hypersaline environments are frequently contaminated with organic pollutants . At present, the halophiles show great potential in bioremediation of those organic compounds in hypersaline conditions . In this study, an endophyte halobacterium ZJUQH that was previously AS-605240 cost isolated from Chaka Salt Lake, Tibet was found to produce EPSs during liquid submerged cultivation. This study was carried out on its fermentation character, defining the most significant components in the medium makeup, and then investigating the optimal fermentation medium components for higher EPS production. 2. Results 2.1. Determination of the Salt Tolerance We previously found that the isolated bacterium showed better salt tolerance on the basis of its origin which is a salt lake with very high salinity. The correlation between the salt tolerance and EPS formation is still needed to be made obvious. As shown in Physique 1, ZJUQH is able to survive in the culture environment made up of up to 10% NaCl. Thus, it was considered to be a moderate halophile. Based AS-605240 cost on the record of cell biomass and EPS production, the maximum cell biomass (2.08 g/L) was obtained AS-605240 cost with 6% NaCl. Moreover, it was found that cell growth was in accordance with the EPS formation. Open in a separate window Physique 1 Determination of the salt tolerance by ZJUQH. Different amounts of NaCl at 4%, 6%, 8%, 10% ( 0.05) (Table 3). These results indicated that this optimum point was not in the domain name of our experiment. Thus, we adopted the experiment of steepest ascent path to reach the optimum domain name. KCl (x4) and MgSO4 (x6) were then determined to be the main factors for further optimization. Table 2 Range of values for Fractional Factorial Designs (FFD). ValueZJUQH. ZJUQH was primarily determined by the linear and quadratic terms of KCl (x4) and MgSO4 (x6) concentrations of the model and no significant interaction existed between.