Mannitol-enhanced survival of Lactococcus lactis subjected to drying

Survival of Lactococcus lactis subjected to different drying conditions was investigated. Mannitol most remarkably enhanced the survival of dried cells to a level almost equalling that of viable cells [log₁₀ (cfu ml⁻¹) = 9.42] as was found prior to the drying process (log₁₀ = 9.6). In the absence of mannitol, a survival was reduced by a factor of 10⁴. Drying of cells at 20 °C led to higher survival rates than drying at 30 °C. Mannitol enhanced the survival rate at both temperatures, and at both 20 °C and 30 °C the highest reduction in survival occurred when cells were dried at a water activity of 0.76. In the presence of mannitol, differences in survival after drying at different water activities were less pronounced. Rehydration of cells dried in the presence of mannitol resulted in an extended lag phase of 4 h compared to fresh cells. No growth or acidification of the culture medium was observed for 12 h in the case of rehydrated cells dried in the absence of mannitol. It was hypothesized that a radical scavenging activity of mannitol could partly explain these observations. Received: 28 August 1998 / Accepted: 2 October 1998     

The influences of ecto- and endoderm in determining the axial polarity ofHydra attenuata Pall. (Cnidaria,Hydrozoa)

Summary Ectoderm and endoderm of the gastric column ofHydra attenuata Pall. were separated from each other and reassembled with either the same (controls) or opposite polar orientation. The controls always regenerated a head and basal disc according to the original polarity. In those specimens in which the polarity of ecta- and endoderm was opposite 33 specimens out of 41 reconstituted a single polyp whose body axis was clearly identifiable. Of these cases 8 followed the polarity of the ectoderm, 3 obeyed that of the endoderm, and 22 formed axes perpendicular to the original longitudinal axis. In 5 cases 2 specimens regenerated from the reassembled specimens. It is thus demonstrated that axial polarity ofHydra is determined by both the ecto- and the endoderm.This work was carried out with the support of the Swiss National Science Foundation (Grant Nr. 3.317-0.78)     

A general method for selection of riboflavin-overproducing food grade micro-organisms

Background  

This study describes a strategy to select and isolate spontaneous riboflavin-overproducing strains of Lactobacillus (Lb.) plantarum, Leuconostoc (Lc.) mesenteroides and Propionibacterium (P.) freudenreichii.     

Functional implications of the microbial community structure of undefined mesophilic starter cultures

This review describes the recent advances made in the studies of the microbial community of complex and undefined cheese starter cultures. We report on work related to the composition of the cultures at the level of genetic lineages, on the presence and activity of bacteriophages and on the population dynamics during cheese making and during starter culture propagation. Furthermore, the link between starter composition and starter functionality will be discussed. Finally, recent advances in predictive metabolic modelling of the multi-strain cultures will be discussed in the context of microbe-microbe interactions.