Growth kinetics of probiotic lactobacilli strains cultivated in a laboratory bioreactor with stirring

Batch cultivation in a laboratory bioreactor with stirring of the lactobacilli strains with probiotic properties Lacticaseibacillus casei ssp. casei G17 and Lacticaseibacillus casei ssp. rhamnosus G16 isolated from pink blossom of Rosa damascena Mill was conducted. The changes in the concentration of viable cells were monitored. The growth kinetics was modeled applying the classic and modified logistic curve model and the maximum specific growth rate (μm) of the studied strains was determined. The classical model of the logistic curve showed higher μm for Lacticaseibacillus casei ssp. casei G17 - 0.133 h-1, compared to Lacticaseibacillus casei ssp. rhamnosus G16 - 0.120 h-1, while the modified logistic curve model predicted comparable maximum growth rates of 0.105 h-1 and 0.101 h-1 for Lacticaseibacillus casei ssp. casei G17 and Lacticaseibacillus casei ssp. rhamnosus G16, respectively. Lacticaseibacillus casei ssp. casei G17 was characterized by a shorter induction period (τa = 0.72 h) and a higher adaptation rate constant (k0 – 0.390 h-1) compared to Lacticaseibacillus casei ssp. rhamnosus G16 (τa=1.66 h; k0=0.110 h-1). The established kinetic parameters show that Lacticaseibacillus casei ssp. rhamnosus G16 needs the addition of growth factors in the fermentation medium that will help to optimize its composition for scaling up the fermentation process.