Sugary Kefir: Microbial Identification and Biotechnological Properties

Abstract

Background: The aim of the present study was to assess the microecosystem composition of three different fruit kefir grains used for the fermentation of apple juice (NAJ), cherry juice (SCN), and a solution of sugary water, enriched with plums (BSS). Methods: Yeast and bacterial populations were enumerated using classical microbiological techniques, clustered by RAPD-PCR genotyping, and identified by sequencing of the D1/D2 region of 26S-rRNA gene and the V1-V3 region of 16S-rRNA gene, respectively. The caseinolytic/lipolytic activities and the production of antimicrobial compounds were assessed by well diffusion assays. The proteolytic and lipolytic capacity were further assessed by SDS-PAGE and titrimetric assay, respectively. Results: Yeast and bacterial populations were enumerated at 6.28, 6.58, and 6.41 log CFU/g and at 4.32, 4.85, and 4.34 log CFU/g, regarding BSS, NAJ, and SCN, respectively. Saccharomyces cerevisiae dominated all three sugary kefir grains; Kluyveromyces marxianus formed a secondary microbiota in BSS and NAJ. Bacillus amyloliquefaciens dominated NAJ and SCN; Lactobacillus rhamnosus dominated BSS. Four bacteria and nine yeast isolates exhibited proteolytic activity. Forty bacteria and 45 yeast isolates possessed lipolytic activity. No antibacterial activity was detected. Conclusions: Prevalence of yeast over bacterial populations was evident in all samples assessed. Several bacterial and yeast strains exhibited proteolytic and lipolytic activities, making them suitable candidates for inclusion in starter cultures for milk and sugary kefir fermentation.

Technological and Safety Attributes of Lactic Acid Bacteria and Yeasts Isolated from Spontaneously Fermented Greek Wheat Sourdoughs

“…However, the SDS-PAGE confirmed the proteolytic capacity for only three LAB strains. Similar results are often reported and may be attributed to insufficient incubation time [ 36 , 37 , 38 ]. Lancetti et al [ 34 ] have already reported the proteolytic capacity of Lcb.…”

“…Lipolysis has been extensively studied in fermented dairy, non-dairy and meat products [ 38 , 41 , 42 ]. Despite the fact that a certain level of lipolysis is a desirable attribute of microbial strains, in terms of synthesis of flavor precursors, only a few pieces of scientific literature have reported the microbial screening for lipolytic activity of sourdough microorganisms [ 2 ].…”

Prebiotic, Probiotic, Antimicrobial, and Functional Food Applications of Bacillus amyloliquefaciens

“…The applications of probiotic B. amyloliquefaciens plays a major role by producing essential nutrients and also making available the necessary breakdown of complex food components for better digestion. Moreover, the spore-forming B. amyloliquefaciens is resistant to low pH, varying temperatures, and other conditions which give it an advantage over sustaining at intestinal low pH gastric digestion and able to reach the small intestine. ,, In recent publications, the spore-forming B. amyloliquefaciens are being used for the probiotic products including yogurt, kefir, tempeh, kimchi, miso, pickles, natto, cheese, fermented cassava, and some fermented cereals …”

Water kefir grains vs. milk kefir grains: Physical, microbial and chemical comparison

“…There are two types of kefir, known as milk kefir (MK) and water kefir (WK) (Syrokou et al, 2019). The origin of MK was the Caucasian Mountain region (Sanli & Anli, 2020) and usually these are referred to as 'milk kefir grains'.…”

“…The origin of MK was the Caucasian Mountain region (Sanli & Anli, 2020) and usually these are referred to as 'milk kefir grains'. Other names such as 'Kefer', 'Kippi', 'Kanphon' and 'Kiaphur' can be found in the literature (Unal et al, 2020). MK is traditionally made by fermentation of milk with MK grains (Sanli & Anli, 2020).…”