Authors : Pavels Semjonovs and Peteris Zikmanis
Abstract: The effects of high molecular weight (2000 kDa) levan from Zymomonas mobilis 13S on the fermentation of lactose in milk and lactose containing medium by dairy starter ABT-5 and constituent cultures (Bifidobacterium lactis, Lactobacillus acidophilus, Streptococcus thermophilus) were estimated in this study. An increase of biomass concentration (120-134% to control), sugar consumption and acidification power of starter association ABT-5 were observed in the presence of levan in milk and MRS medium. Bifidobacterium lactis Bb12 within the starter association exhibited the most pronounced response to levan in respect to cell growth (almost 2 times to control). The activity of constitutive -fructanhydrolases was detected in cell free extract on sucrose or levan as a substrate. In the presence of inulin or levan as inductors the activities of extracellular -fructanhidrolase were established for ABT-5 dairy starter and constituent cultures. The presence of more specific extracellular endo-fructanhydrolase was detected which might contribute to catabolism of levan. This study indicate certain prospects for application of polyfructans, particularly -2.6 linked fructan polymers (levan) as a potent source of prebiotics to modify and improve the processes of lactose fermentation by ABT-5 type starter cultures.
Pavels Semjonovs and Peteris Zikmanis , 2007. An Influence of Levan on the Fermentation of Milk by a Probiotic ABT-Type Starter . Journal of Food Technology, 5: 123-130.