Abstract: This invention relates to the production of the microorganisms. The operation is conducted in two stages. The first stage is conducted in the absence of ultrafiltration while the pH of the growth medium is maintained within the range of 6-7 by the addition of a neutralizing agent. Nutrient substratum and dilution water are added during the first stage to maintain the growth rate at a constant level, and the volume of growth medium is permitted to increase. When the amount of growth inhibiting agent produced in the fermentation reaches a predetermined maximum level, the second stage is initiated and the growth rate is maintained in a range of 0.10 to 0.50/hr, which is less than the growth rate in the first stage. By increasing the amount of dilution water the concentration of the growth inhibiting agent is maintained so as to achieve the desired moderate growth rate.

Abstract: The process for preparing concentrated amounts of lyophilized micro-organisms employs an ultrafiltration with a supply of nutritive substrates and the supply of a neutralizing agent in the fermenter, and further comprises the following steps:(a) ceasing to supply substrates while cooling;(b) continuing the ultrafiltration until the obtainment of a primary concentrate (40-80 kg dry weight of bacteria/cu. m) and cooling to 15.degree.-20.degree. C.;(c) washing the primary concentrate with mineral salts and amino acids, oligo-elements and vitamins;(d) concentrating by ultrafiltration to 90-220 kg dry weight of bacteria/cu. m;(e) cooling to 5.degree. C. and adding a protector;(f) deep freezing and lyophilizing.The process particularly applies to the preparation of lactic bacteria.