为解决青春双歧杆菌在生产中发酵密度低的问题,该文测定了94株青春双歧杆菌的耐渗能力,同时评价了耐高渗菌株耐渗能力的遗传稳定性,最后通过解析培养基底物和发酵工艺探究了耐高渗菌株的最适发酵条件,从而提高其生产中的发酵活菌数。筛选得到两株最高可耐受1 400 mOsm/kg的菌株CCFM1302和CCFM1066,其最优氮源为复合氮源(胰酪蛋白胨和酵母浸粉FM528以质量比1∶1复合),最优碳氮比分别为(2.71±0.23)∶1和(2.53±0.11)∶1。以达到完全抑制渗透压为发酵终点推算底物最适浓度,进一步优化微量元素的添加量,得到最优培养基:复合氮源21.0 g/L、葡萄糖57.0 g/L(CCFM1302),复合氮源22.4 g/L、葡萄糖56.5 g/L (CCFM1066);此外添加MgSO4·7H2O 0.25 g/L,半胱氨酸1 g/L、吐温80 1 mL/L。恒pH 5.5培养至稳定期发酵液活菌数可达(1.82±0.08)×1010 CFU/mL和(1.70±0.03)×1010 CFU/mL。该文筛选到可产业化的两株青春双歧杆菌,并优化其高密度发酵工艺,对生产和应用都具有重要意义。
In order to solve the problem of low fermentation density of Bifidobacterium adolensentis in industry, 94 strains of B. adolensentis were selected to study their tolerance to the osmotic pressure and the genetic stability of strains with high osmotic pressure resistance was evaluated. The optimal fermentation conditions of B. adolensentis with high osmotic pressure tolerance were explored by analyzing the culture substrates and fermentation process, so as to increase the number of viable bacteria during the industrial fermentation. CCFM 1302 and CCFM 1066 were screened with the highest tolerance of 1 400 mOsm/kg, whose optimal nitrogen source was compound nitrogen source of trypsin peptone and yeast extract FM528 at a ratio of 1∶1. The optimal carbon-nitrogen ratios of B. adolensentis CCFM 1302 and CCFM 1066 were (2.71±0.23)∶1 and (2.53±0.11)∶1, respectively. The optimal concentration of substrate was calculated with the fermentation end point of complete inhibition of osmotic pressure, and the addition amount of trace elements was further optimized. The optimal culture media for CCFM1302 were 21.0 g/L of compound nitrogen source and 57.0 g/L of glucose. The optimal culture media for CCFM1066 were 22.4 g/L of compound nitrogen source and 56.5 g/L of glucose. In addition, MgSO4·7H2O 0.25 g/L, cysteine 1 g/L and Tween-80 1 mL/L were also added in the optimal media. The number of viable bacteria in fermentation broth reached (1.82±0.08)×1010 CFU/mL and (1.70±0.03)×1010 CFU/mL at constant pH of 5.5. In this study, two strains of B. adolesentis that can be industrialized were screened and their high-density fermentation process was optimized, which is of great significance for production and application.
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