Rapid evaluation of optimal growth substrates and improvement of industrial production of Bifidobacterium adolescentis based on the automatic feedback feeding method

This study aimed to improve the industrial production of Bifidobacterium adolescentis strain Z25 by establishing a method that could rapidly evaluate proliferation efficiency in response to different carbon, and nitrogen sources, inorganic salts, trace elements. Notably, glucose, yeast extract, fish peptone, Mg were the optimum substrates for high-efficient proliferation of the strain. The inorganic salts were not required in a pH-controlled culture. Both batch culture and automatic feedback feeding culture methods were optimized and compared. The maximum proliferation efficiency was achieved when the carbon-nitrogen ratio was equivalent to the carbon-nitrogen consumption ratio at the point of growth rate inhibition and the osmotic pressure of the medium was lower than 550 mOsm kg(-1). Within a certain concentration range, the maximum biomass was positively correlated with the concentration of Mg2+. The automatic feedback feeding method was more conducive for a high-density bifidobacterial culture. Finally, at the optimum pH of 5.5 and the initial medium osmotic pressure of 312 +/- 6 mOsm kg(-1), the viable bacterial count reached (1.6 +/- 0.1) x 10(10) CFU mL(-1) after 15 h with a feed liquid containing 320 g L-1 glucose, a 20-fold increase compared to the yield obtained with the original culture method and MRS medium.

Automated summary

This study aimed to improve the industrial production of Bifidobacterium adolescentis strain Z25 by optimizing substrate materials and culture conditions. Glucose, yeast extract, fish peptone were identified as the optimal substrates for efficient proliferation of the strain, while Mg2+ concentration was positively correlated with maximum biomass within a certain range. The use of automatic feedback feeding method was found to be more conducive for high-density bifidobacterial culture.