The microbial flora of sugary kefir grain (the gingerbeer plant): biosynthesis of the grain fromLactobacillus hilgardii producing a polysaccharide gel

The microflora of sugary kefir grains was principally mesophilic and consisted chiefly of lactic acid bacteria [Lactobacillus casei, Lactobacillus hilgardii (=brevis),Leuconostoc mesenteroides ssp.dextranicum, Streptococcus lactis] and a small proportion of yeasts (Zygosaccharomyces florentinus, Torulospora pretoriensis, Kloeckera apiculata, Candida lambica andC. valida). Few coliforms and faecal streptococci were observed. Observation by scanning electron microscopy revealed that the filamentous yeasts adhered to the bacteria on the periphery of the grain.Lactobacillus hilgardii, the single microorganism isolated which was able to produce a gelling polysaccharide, was important in the biosynthesis of the grain. Pieces of gel produced by this strain, and transferred in a yeast extract-sucrose solution, grew and resembled the household kefir grains. This represents a new, cheap way of producing immobilized cells by self-embedding in a neutral polysaccharide.