High-density cultivation of Lactobacillus and Bifidobacterium using an automatic feedback feeding method

Abstract A new automatic feeding system has been developed, to allow the high-density cultivation of homofermentative Lactobacillus and Bifidobacterium species. The system allowed the automatic supplementation of glucose, and neutralization of acidity based on the consumption of glucose and the production of acids in the growth medium through a sophisticated computerized program. During the pH-controlled culturing, the quantity of NaOH was directly related to the quantity of acids produced. The system supplying the glucose was linked to alkali supplementation to achieve the automatic addition of k mL glucose after 1 mL NaOH solution was automatically added. The glucose consumption and acid production patterns of each strain were carefully studied before the application of the automatic feeding system. All strains ( Lactobacillus and Bifidobacterium species) used approximately 90% of the glucose for the production of acids. The NaOH concentration in the alkali bottle and the glucose concentration in the feed bottle were based on the following formulae: C a l k a l i 40 × 2 × 90 % = C g l u c o s e 180 · k (homofermentative Lactobacillus ); C a l k a l i 40 × 5 × 90 % = C g l u c o s e 180 × 2 · k ( Bifidobacterium ). After using this system, the glucose concentration in the fermentation broth remained stable during the culturing of the strains, and the density of the strains was significantly increased, demonstrating the effectiveness of the method.