The extensive growth of installed wind energy plants lead to increasing balancing problems in the power grid due to the nature of wind fields and diurnal variations in consumption. One way to overcome these problems is to move consumption to times where wind power otherwise cause overproduction and large fluctuations in prices. The paper presents a method which takes advantage of heat capacity in single-family houses using heat pumps which are anticipated to be installed in large numbers in Denmark in next decade. This type of heating gives a large time constant and it is shown possible to move consumption without compromising the comfort of house residents. In the paper an optimization exploiting forecasts of weather and energy prices combined with prediction models of house dynamics is presented. The results show that with the presented method it will be possible to move a substantial amount of energy from one time to another.
Bacteriophages attacking Leuconostoc species may significantly influence the quality of the final product. There is however limited knowledge of this group of phages in the literature. We have determined the complete genome sequences of nine Leuconostoc bacteriophages virulent to either Leuconostoc mesenteroides or Leuconostoc pseudomesenteroides strains. The phages have dsDNA genomes with sizes ranging from 25.7 to 28.4 kb. Comparative genomics analysis helped classify the 9 phages into two classes, which correlates with the host species. High percentage of similarity within the classes on both nucleotide and protein levels was observed. Genome comparison also revealed very high conservation of the overall genomic organization between the classes. The genes were organized in functional modules responsible for replication, packaging, head and tail morphogenesis, cell lysis and regulation and modification, respectively. No lysogeny modules were detected. To our knowledge this report provides the first comparative genomic work done on Leuconostoc dairy phages.
The discovery of heme-induced respiration in Lactococcus lactis has radically improved the industrial processes used for the biomass production of this species. Here, we show that inhibition of the lactate dehydrogenase activity of L. lactis during growth under respiration-permissive conditions can stimulate aerobic respiration, thereby increasing not only growth efficiency but also the robustness of this organism.
Since the first observation of the growth behavior induced by heme in multiple lactic acid bacterial species (1-3), several studies have been carried out to describe this metabolic process in the dairy species Lactococcus lactis (4-9). In the presence of heme and oxygen, initial lactococcal growth occurs via fermentation, and when the external pH reduces to approximately 5.3, the transition to respiration occurs (4). It was hypothesized that the physiological reprogramming that occurs during respiration might be a consequence of the shift in the NAD ϩ /NADH ratio, which allosterically redirects metabolism in favor of enzymes that use either NAD or pyruvate as a substrate (10). The respiration induced by heme ultimately determines the increase in biomass production, due to the improvement of growth efficiency and an extraordinary increase in long-term survival and resistance to oxidative stress (5). These remarkable phenotypes are of industrial relevance, as made apparent by patent applications that are focused on improving the production of starter cultures (11). By analyzing the energy metabolism of L. lactis ( Fig. 1), it can be hypothesized that the inhibition of fermentative metabolism (normally homolactic fermentation) under respiration-permissive conditions (heme plus oxygen) promotes oxidation of NADH by the electron transport chain via cytochrome bd oxidase. In this study, the inhibition of fermentation was achieved by inhibiting the activity of lactate dehydrogenase by using sodium oxamate, an analogue of pyruvate. We used the laboratory strain L. lactis subsp. lactis IL1403. Unlike other L. lactis strains, IL1403 does not demonstrate an observable shift from homolactic to mixed-acid fermentation, which is governed by the sugar consumption rate (12, 13). Nevertheless, the genes of the mixed-acid pathway are present and expressed at higher levels when the IL1403 strain is cultured in the presence of high levels of galactose (13,14). We hypothesized that under aerobic conditions, in the presence of heme, the inhibition of lactate dehydrogenase by the glycolytic inhibitor sodium oxamate (15, 16) causes a shift in IL1403 metabolism in favor of NAD ϩ regeneration by the respiratory chain enzyme NADH oxidase and to a lesser extent by mixed-acid fermentation. An excess of pyruvate should then be directed to acetoin/diacetyl production ( Fig. 1) or mixed-acid fermentation, although the latter is less favored under aerobic conditions (12,17).Sodium oxamate improves the aerobic growth of L. lactis IL1403. L. lactis IL1403 was cultivated at 30°C for 10 h in M17 broth (Difco) containing glucose (20 g/lit...
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