Optimization of exopolysaccharides production by Weissella confusa NH 02 isolated from Thai fermented sausages

Exoploysaccharides (EPSs) producing lactic acid bacteria (LAB) were isolated from Thai traditional fermented foods. Colonies exhibiting a clear zone and ropiness on modified MRS agar containing 2% (w/v) sucrose and 0.02% (w/v) bromocresol purple were selected for Gram staining and catalase test. From 140 isolates, 120 isolates were identified as LAB. However, only 14 strains were able to produce a large amount of EPSs (>5.9 g/l) when cultivated in modified MRS broth containing 2% (w/v) sucrose at 37oC for 24 hrs. The highest viscosity and yield of EPSs were obtained from isolate NH 02. Based on 16S rDNA analysis, strain NH 02 was identified as Weissella confusa. Sucrose (40 g/l), an initial pH of modified MRS at 7.0, and a cultivation temperature of 37oC were the optimum conditions, in which EPSs were produced at levels up to 18.08 g/l within 12 hrs. EPSs produced by W. confusa NH 02 contained only glucose and had a molecular mass of 1.1310 6 Da.