乳酸菌产胞外多糖的发酵条件优化及其抗氧化活性研究

Optimization of fermentation condition of lactic acid bacteria with high-yield exopolysaccharides andits antioxidant activity

该研究从实验室保藏的17株乳酸菌中筛选高产胞外多糖(EPS)菌株,结合形态学观察与分子生物学技术对其进行鉴定,采用单因素试验和响应面法对其产胞外多糖发酵条件进行优化,并分析胞外多糖结构和抗氧化活性。结果表明,筛选得到一株高产EPS菌株E8,经鉴定其为戊糖片球菌(Pediococcus pentosaceus)。菌株E8最佳发酵工艺条件为:蔗糖添加量5%,蛋白胨和大豆蛋白胨(1∶1)添加量2.5%,发酵时间58 h,接种量3.7%,初始p H值5.85。在此优化条件下,胞外多糖产量为1 516.62 mg/L。结构表征结果表明,胞外多糖中存在吡喃糖环,糖苷键构型为α-型,微观结构呈片状。抗氧化结果表明,当EPS质量浓度为9 mg/m L时,对1,1二苯基-2-三硝基苯肼(DPPH)、2,2-联氮-双-3-乙基苯并噻唑啉-6-磺酸(ABTS)和羟基自由基的清除能力分别为(62.62±1.52)%、(55.17±1.44)%和(63.91±2.71)%。

The high-yield exopolysaccharides(EPS)strain was screened from 17 lactic acid bacteria strains deposited in the laboratory,and identified by morphological observation and molecular biology.The fermentation condition of exopolysaccharides was optimized by single factor tests and response surface methodology,and its structure and antioxidant activity were analyzed.The results showed that the screened high-yield EPS strain E8 was screened and identified as Pediococcus pentosaceus.The optimal fermentation conditions of the strain E8 were as follows:sucrose addition 5%,peptone and soybean peptone(1∶1)addition 2.5%,fermentation time 58 h,inoculum 3.7%,initial pH 5.85.Under the conditions,the yield of EPS could reach 1516.62 mg/L.Structural characterizations results showed that the pyranose ring was presented in EPS,presented asα-anomeric configuration,and the microstructure showed a sheet-like structure.The antioxidant results showed at EPS mass concentration of 9 mg/ml,the scavenge capacities of 1,1-diphenyl-2-picrylhydrazyl(DPPH),2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS)and OH free radical were(62.62±1.52)%,(55.17±1.44)%and(63.91±2.71)%,respectively.