Effects of air condition on the viability of probiotic bacteria: Bifidobacterium lactis V9

Abstract:

Bifidobacterium lactis V9 (B. lactis V9) has been demostrated as a probiotic with well properties and stable genetics. The gas composition in environment of industrial manufacturation is positively associated with viable numbers of probiotic and nextly have influence on probiotic properties. [Objective] The influence of different gas environment on the growing of B. lactis V9. [Methods] By MRS agar plate, liquid MRS medium and pasteurized skim milk inoculated with B. lactis V9. [Results] On the MRS agar plate, the numbers of B. lactis V9 forming colonies under mixed gas environment (N2:H2:CO2=80:10:10) was more than nitrogen gas environment (N2: 99.99%) and few colonies formed under normal air environment (N2:O2≈79:21). In the MRS liquid medium for 24 h, the viable counts under mixed gas were 9.11±0.11 log CFU/mL which was significantly higher than growing in normal air condition with 8.04±0.10 log CFU/mL (P<0.01). Moreover, the acetate and lactate production under mixed gas condition were respectively significantly higher than normal air condition (12.79±0.86 mmol/L VS 11.99±0.73 mmol/L, 0.65±0.07 mmol/L VS 2.75±0.57 mmol/L, P<0.01). In addition, the acetate/lactate molar ratio was 1.06:1 and 0.24:1, respectively. After 18 h of pasteurized skim milk fermentation, the reduced pH of fermented milk under mixed gas condition was significantly lower than normal air condition (4.48±0.07 VS 5.03±0.12, P<0.01). The viable counts under mixed gas were 9.02±0.15 log CFU/mL which was significantly higher than growing in normal air condition with 8.53±0.08 log CFU/mL (P<0.01). The acetate and lactate production under mixed gas condition vs. normal air condition in fermented milk were 60.52±2.30 mmol/L and 5.17±1.02 mmol/L VS 16.86±0.34 mmol/L and 5.92±0.81 mmol/L, repectively. The acetate/lactate molar ratio was 11.71:1 and 2.85:1, repectively. [Conclusion] These study suggested that mixed gas condition with N2:H2:CO2=80:10:10 was beneficial for B. lactis V9 growing in liquid medium and pasteurized skim milk fermentation increased by 0.5?1 grade of viable counts during the same time. It can provide instruction for preparation of probiotic fermented milk and viable bacterial counting of B. lactis V9.