Juke S. Lolkema

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Food-fermenting lactic acid bacteria (LAB) are generally considered to be non-toxic and non-pathogenic. Some species of LAB, however, can produce biogenic amines (BAs). BAs are organic, basic, nitrogenous compounds, mainly formed through decarboxylation of amino acids. BAs are present in a wide range of foods, including dairy products, and can occasionally(More)
Histamine production from histidine in fermented food products by lactic acid bacteria results in food spoilage and is harmful to consumers. We have isolated a histamine-producing lactic acid bacterium, Lactobacillus hilgardii strain IOEB 0006, which could retain or lose the ability to produce histamine depending on culture conditions. The hdcA gene, coding(More)
L-malate transport was studied in membrane vesicles from Leuconostoc oenos MLE(-) (mutant lacking malolactic enzyme) which were fused with liposomes containing beef heart cytochrome c oxidase as a proton-motive-force-generating system. In these hybrid membranes, accumulation of L-malate was observed in response to a pH gradient (delta pH), with the inside(More)
Neuronal and glial glutamate transporters remove the excitatory neurotransmitter glutamate from the synaptic cleft. The proteins belong to a large family of secondary transporters, which includes bacterial glutamate transporters. The C-terminal half of the glutamate transporters is well conserved and thought to contain the translocation path and the binding(More)
The mechanism and energetics of citrate transport in Leuconostoc oenos were investigated. Resting cells of L. oenos generate both a membrane potential (delta psi) and a pH gradient (delta pH) upon addition of citrate. After a lag time, the internal alkalinization is followed by a continuous alkalinization of the external medium, demonstrating the(More)
Microbial growth is analyzed in terms of mosaic and phenomenological non-equilibrium thermodynamics. It turns out that already existing parameters devised to measure bacterial growth, such as YATP, mu, and Q substrate, have as thermodynamic equivalents flow ratio, output flow and input flow. With this characterisation it becomes possible to apply much of(More)
In cells of Leuconostoc oenos, the fermentation of L-malic acid generates both a transmembrane pH gradient, inside alkaline, and an electrical potential gradient, inside negative. In resting cells, the proton motive force ranged from -170 mV to -88 mV between pH 3.1 and 5.6 in the presence Of L-malate. Membrane potentials were calculated by using a model(More)
Integral membrane proteins are found in all cellular membranes and carry out many of the functions that are essential to life. The membrane-embedded domains of integral membrane proteins are structurally quite simple, allowing the use of various prediction methods and biochemical methods to obtain structural information about membrane proteins. A critical(More)
Measurement of the flux through the citrate fermentation pathway in resting cells of Lactococcus lactis CRL264 grown in a pH-controlled fermentor at different pH values showed that the pathway was constitutively expressed, but its activity was significantly enhanced at low pH. The flux through the citrate-degrading pathway correlated with the magnitude of(More)
Neuronal and glial glutamate transporters remove the excitatory neurotransmitter glutamate from the synaptic cleft and thus prevent neurotoxicity. The proteins belong to a large and widespread family of secondary transporters, including bacterial glutamate, serine, and C4-dicarboxylate transporters; mammalian neutral-amino-acid transporters; and an(More)