Growth and Metabolism of Lacticaseibacillus casei and Lactobacillus kefiri Isolated from Qymyz, a Traditional Fermented Central Asian Beverage

Abstract

The growth characteristics of two strains of lactic acid bacteria (LAB), Lacticaseibacillus casei and Lactobacillus kefiri, isolated from qymyz, a traditional fermented mare milk beverage, were studied and modeled, including the effect of different carbohydrates, pH, and temperature. Along with population, substrates, and metabolites, lactic acid and ethanol were monitored by HPLC. Growth parameters were obtained from mono- and biphasic logistic growth models that fit the population evolution of L. casei and L. kefiri, respectively. The effect of temperature and pH on the growth rate was represented with the gamma concept model, while the effect of the limiting substrate was evaluated according to the Monod equation. Lastly, a simplified Luedeking and Piret equation was used to represent metabolite production. The optimum values of pH and temperature were 6.69 ± 0.20, 38.63 ± 0.32 °C, 5.93 ± 0.08, and 33.15 ± 0.53 °C, with growth rate values of 0.66 ± 0.01 h−1 and 0.29 ± 0.01 h−1 for L. casei and L. kefiri, respectively. L. casei had a homofermentative pathway, while L. kefiri was heterofermentative, with an ethanol production rate of 2.90 × 10−9 mg·CFU−1. The Monod model showed that L. casei had the lowest Ks value for lactose, while for L. kefiri, it was the highest among milk carbohydrates. These results show that the population of the two LAB strains and therefore the concentrations of acid and ethanol can be controlled by the fermentation conditions and that our model can help to significantly improve the production of qymyz.

Growth Kinetics of Kazachstania unispora and Its Interaction with Lactic Acid Bacteria during Qymyz Production

“…In general, the results showed that the population obtained in a synthetic medium was similar to that obtained in reconstituted mare milk. Figure 5A,C shows that LAB simulated population obtained with the monoculture growth parameters obtained by Kondybayev et al [15] fitted well with the experimental population of LAB in coculture. This means that the LAB population growth rate and final population was not significantly affected by the coculture with K. unispora.…”

“…Lactose consumption in mono-and coculture followed the same trend for L. kefiri. Among the studied LAB, only L. kefiri produces ethanol [15]. The content of ethanol in the L. kefiri coculture reached ~7.8 g•L −1 , which was the same level as in the monoculture of this strain.…”

“…In order to mimic qymyz production, the already characterized bacteria Lactobacillus kefiri (B2) and Lacticaseibacillus casei (B7) were taken from a previous study [15] for use in a coculture.…”

“…Temperature effect experiments were conducted in Minifor Lambda fermenters (LAMBDA Instruments, Brno, Czech Republic) with a working volume of 800 mL and using an infrared radiator to control temperature. Yeast was grown at temperatures ranging from 5 • C to 40 • C (5,10,15,20,25,27,30,32,35,37, and 40 • C). Yeast precultures grown overnight were prepared at 30 • C, and the initial population was set at approximately 10 6 CFU•mL −1 .…”

Fermented Mare Milk and Its Microorganisms for Human Consumption and Health

“…The microbial composition of raw mare milk, like that in other similarly less common milk types, has not been studied in depth: nevertheless, it is known to be widely variable, depending on many factors, such as the breed, season, and region [34]. However, many studies regarding the microbiological composition of fermented mare milk are available.…”