Space mutation was carried out with an exopolysaccharide(EPS)-producing strain,Lactobacillus casei LC2W,by spaceship carried experiment of manned spacecraft Shenzhou-7.Three high-yielding EPS strains,LC2W-1,LC2W-2 and LC2W-3,had been screened out and also showed good genetic stability after cultivated for 10 generations.The fermentation conditions of LC2W-1 were optimized by means of single factor tests and orthogonal tests.The optimum conditions for synthesis of EPS by LC2W-1 were as follows: adding 4% glucose and 0.6% yeast extract into the skimmed milk medium and cultured at 33℃for 26h.Under these conditions,the yield of EPS could reach(276.76±7.34) mg/L,which was increased by 44.54% and 104.93% compared with that produced by the mutant and original strain,respectively.