Culture medium optimization of a new bacterial extracellular polysaccharide with excellent moisture retention activity

摘要

A new kind of extracellular polysaccharide (EPS) from Pseudomonas fluorescens PGM37 was obtained and culture media was optimized using the statistical methods single factor experiments and response surface methodology (RSM) design. As a result, the optimum cultivation conditions initial pH value, medium volume, inoculum size, temperature, and rotation speed were 7.5, 100 mL/250 mL, 5 %, 28 °C, and 180 rpm, respectively. The optimized media: sucrose 36.23 g L~(-1), yeast extract 3.32 g L~(-1), sodium chloride 1.13 g L~(-1), and calcium chloride 0.20 g L~(-1). The maximum predicted yield of EPS was 10.1163 g L~(-1) under these conditions. The validation data was 10.012 g L~(-1), which could strongly confirm the correlation between the experimental and theoretical values. Gas Chromatography analysis revealed that the polymer was made up of mannose and glucose in the ratio of 1:1. Infrared spectroscopy showed that the polysaccharide had β-D-pyranoid configuration and contained no other substituent. Graded by different multiples of alcohol after specific degradation by enzyme and then detected by LC-ESI-MS, the EPS structure was β-D-Glcp-(1, 4)-β-D-Manp-(1, 4)-β-D-Glcp-(1, 4)-β-D-Manp. The moisture retention ability of the EPS was found to be superior to glycerol and only a little inferior to hyaluronic acid (HA), which presented potential application value in cosmetics and clinical medicine fields.