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Modification of characteristics of kefiran by changing the carbon source of Lactobacillus kefiranofaciens

BACKGROUND: Kefiran is an exopolysaccharide that is widely used in the food and pharmaceutical industries. The aim of this study was to demonstrate that kefiran with different chemical structures can be obtained by changing the composition of the Lactobacillus kefiranofaciens fermentation medium. RESULTS: When using maltose as the sole carbon source: (1) the average molecular mass of kefiran was 1.5 × 105 Da, only 62.5% of that of the control (with lactose as the sole carbon source); (2) the glucose/galactose molar ratio of kefiran from the optimised medium was 1:10; (3) two variable-angle CH bonds existed in the structure of kefiran; (4) the maximum viscosity of kefiran was [η] = 73.86 ± 5.3 dL g−1 and its specific rotatory power was [α]D = + 68°. Increasing the proportion of maltose in a mixed carbon source (maltose and lactose) from 20 to 100 g L−1 decreased the average molecular mass and glucose/galactose molar ratio of kefiran by 35 and 60% respectively. CONCLUSION: Kefiran with different chemical structures was obtained by changing the composition of the fermentation medium. The results presented here will facilitate further study of the relationship between the chemical structure and biological role of kefiran. Copyright © 2008 Society of Chemical Industry