Changes in Microbiota During Multiple Fermentation of Kefir in Different Sugar Solutions Revealed by High-Throughput Sequencing

Abstract

Kefir is a fermented beverage produced through the activity of its grains, which is constituted by lactic acid and acetic acid bacteria and yeasts. We studied the bacterial succession during multiple fermentation of Argentinian kefir in brown sugar, purified molasses or high-test molasses, using 16S high-throughput sequencing. Firmicutes was dominant (up to 98% of total population) in grains and beverages made from various sugar substrates, except in high-test molasses beverage, which was dominated by Proteobacteria (up to 78% of total population). Major bacterial species in Firmicutes were Liquorilactobacillus nagelii, Lentilactobacillus hilgardii/diolivorans and Lacticaseibacillus casei/paracasei, which are active in lactic acid fermentation. Proteobacteria comprised Acetobacter lovaniensis and Gluconobacter oxydans/roseus as major species, which are presumably responsible for the acetic acid formation in sugary kefir beverages. Bacteria differ in abundance depending on the sugar type, as revealed by the competitive dominances between L. nagelii and A. loveniensis. Purified molasses led to scarce acetic acid bacteria during fermentation, indicating that it is not a suitable substrate for their growth. Our results suggest that acetic acid (and/or ethanol) in sugary kefir modulates the succession and dominance of specific lactic acid bacteria. This study will provide valuable information for designing more sophisticated non-dairy fermented beverages with stable microbial properties.

Characterization of Bacterial Diversity in Aguamiel and Two Types of Pulque from the Zacatlán Region, México

“…This phenomenon occurs because, of the total number of microorganisms identified in the seed, 83.37% belonged to the Lactobacillus genus, which has an effect on diversity, but not on abundance (Figure 1). These results are similar to those reported by Gamba et al [36] after evaluating the bacterial richness and diversity in sugary kefir and its grains, since the Chao1 index was similar in all samples after seven fermentation cycles, while diversity was higher during the early stages as a result of changes in growth dynamics after metabolite accumulation and microbial interactions [11].…”

“…Even though aseptic conditions during pulque production have been questioned in the past [35,36], the results of this research confirm the prevalence of beneficial lactic acid bacteria over pathogenic microorganisms, since their presence does not exceed 24, 4, 3, and 2% of the population screened in the seed, aguamiel, artisanal, and commercial pulque, respectively (Figure 5). This is mainly due to the accumulation of various fermentation by-products, such as organic acids, hydrogen peroxide, and bacteriocins, which act as biopreservative agents leading to the eradication of putrefactive and pathogenic bacteria, thus improving food safety [37,38].…”

“…This was demonstrated by Choi et al [25], as they discovered that kimchi could be a vector for pathogens because it is often consumed before sufficient fermentation has taken place, so bacteria such as E. coli O157:H7, Salmonella enteritidis, Staphylococcus aureus, and Listeria monocytogenes can grow and survive on this substrate. Even though aseptic conditions during pulque production have been questioned in the past [35,36], the results of this research confirm the prevalence of beneficial lactic acid bacteria over pathogenic microorganisms, since their presence does not exceed 24, 4, 3, and 2% of the population screened in the seed, aguamiel, artisanal, and commercial pulque, respectively (Figure 5). This is mainly due to the accumulation of various fermentation by-products, such as organic acids, hydrogen peroxide, and bacteriocins, which act as biopreservative agents leading to the eradication of putrefactive and pathogenic bacteria, thus improving food safety [37,38].…”

The complex world of kefir: Structural insights and symbiotic relationships

“…This indicates that yeasts thrive better in milk sources with higher protein content, leading to kefir milk fermentation with a more pronounced alcoholic flavor in a shorter period. Gamba et al (2021) examined the impact of varying carbon sources on the community structure. Adding glucose to milk significantly increases the viscosity and titratable acidity of fermented milk (Kavas, 2015).…”

“…Gamba et al. (2021) examined the impact of varying carbon sources on the community structure. Adding glucose to milk significantly increases the viscosity and titratable acidity of fermented milk (Kavas, 2015).…”