Observations on the structure of kefir grains and the distribution of the microflora

Abstract

The mixed flora of yeasts and lactobacilli of kefir is held together in non‐dispersible structures which build up into large grains. The fibrillar extracellular material of the matrix in which the microflora is embedded was stained by ruthenium red and periodic acid‐thiosemicarbazide silver proteinate, indicating that it was largely composed of carbohydrate. It is suggested that the carbohydrate is of bacterial origin and that this is produced by a population of lactobacilli which resides within the matrix and which separates non‐carbohydrate‐producing populations of lactobacilli and yeasts so that sheet‐like structures are formed which show asymmetry, with yeasts predominating on one side and lactobacilli on the other.

Preservation of Kefir Grains, a Comparative Study

“…It is important to note that although differences exist between morphological features of the colonies, these are difficult to detect. The following are among the lactic acid bacteria described in kefir grains of different sources: Lactobacillus brevis (3,(22)(23)(24), Lactobacillus viridescens, Lactobacillus gasseri, Lactobacillus fermentum and Lactobacillus casei (3), Lactobacillus kefir (3,6), Lactobacillus acidophilus (3,17,23), Lactococcus lactis subsp. lactis (3,17,23), Leuconostoc (3,17,24), Lactobacillus kefiranofaciens (25,26).…”

“…They suggested that the population of yeasts and lactobacilli were not randomly distributed in the grain. Lactobacilli were at the periphery of the grain, while the yeasts were located inside the grain (6). For propagation of the starter culture, presence of all the microorganisms composing the kefir grain, in their desirable and adequate proportion, is required.…”

Microbiological Study of Kefir Grains. Isolation and Identification of High Activity Bacteriocin Producing Strains

“…The complex microflora is enclosed in a matrix of 900 g/kg water, 2 glkg lipids, 30 g/kg protein, GO glkg sugars and 7g!kg ash (4). According to Botazzi and Bianchi (5), who used scanning electron microscopy, the LAB are found at the periphery of the grain, while the yeast arc located in-55 side (6). The microbial composition of grains differs according to their origin.…”

Le kéfir. Caractères physico-chimiques, microbiologiques et nutritionnels. Technologie de production. Une revue

“…L'insolubilité du polysaccharide limiterait la diffusion des substances nutritives et des métabolites microbiens. Ainsi, les microorganismes inclus meurent, devenant des parties inséparables de la structure du grain (MARSHALL et COLE, 1984).…”