生物化学与分析生物化学

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Biotechnology Congress 2015 : The influence of growth conditions (temperature and oxygen supply) on manganese(II) sorption by viable and autoclaved Lactococcuslactisvar.lactis NCIMB 6681 - Sandra BorkowskaHeurtaux - Glasgow Caledonian University

Sandra Borkowska-Heurtaux, Colin Hunter and Alistair Sutherland

Manganese (II) is an essential element required for normal growth and development of humans, animals and plants, however it has a tendency to accumulate in some organisms, what leads to higher,potentially toxic, level within the food chain.Mn2+ sorption properties of Lactococcuslactisvar.lactis, a non-pathogenic bacteriumwidely used in the dairy industry were studied as a function of four growth conditions: Cells werecultivated aerobically and with reduced oxygenat 30°C and 37°C. Additionally,biosorption properties of live and autoclaved cells were compared. L. lactis showed very competitive capability to sorb Mn2+ over 5 days and pH drifts in the experimental suspensionsdemonstrated an involvement of ion exchange mechanisms in Mn2+ sorption. Viability of L. lactis during sorption experimentswas studied by serial dilutions and plate count methods with the biggest decrease in a cell numbers observed at 24 and 72 hours contact time. Sorption capacity of live L. lactis cultivated under four different conditions towards Mn(II) ranged 34-50 mg/gdw. Autoclaved biomass showed muchlower sorption capacity (20-39 mg/gdw)but this rangeis among the highest removal capacities towards Mn2+ seen in previous studies using various (non-living) biomasses.The obtained results are the first report showing Mn2+ sorption by viable and autoclaved cells of L. lactis as a function of different growth conditions and metal loadings. It is also among the first work investigating the difference between viable and dead microbial cells. Bacteriocin ST34BR, a little polypeptide of 2.9 kDa delivered by Lactococcus lactis subsp. lactis ST34BR, hinders the development of Enterococcus faecalis , Escherichia coli , Lactobacillus plantarum , Lactobacillus casei , Pseudomonas aeruginosa and Staphylococcus aureus . MRS stock, acclimated to pH 6.0 yielded 6,400 AU/ml, contrasted with 400 AU/ml recorded in BHI stock, M17 stock, 10% (w/v) soy milk, and 8% and 10% (w/v) molasses. At pH of 4.5 just 800 AU/ml was delivered. In view of similar investigations in MRS stock, without natural nitrogen, enhanced with various mixes of tryptone, meat concentrate and yeast separate, tryptone was distinguished as the invigorating nitrogen compound. Development within the sight of 20 g/l glucose, maltose, mannose or sucrose yielded bacteriocin levels of 6,400 AU/ml, though a similar centralization of lactose and fructose yielded 3,200 AU/ml and 1,600 AU/ml, separately. No distinction in bacteriocin ST34BR action was recorded in MRS stock enhanced with 2 g/l K2HPO4 and 2 g/l, 5 g/l, 10 g/l or 50 g/l KH2PO4. Nonetheless, 20 g/l KH2PO4 expanded bacteriocin ST34BR creation to 12,800 AU/ml. Glycerol at 1g/l to 10 g/l in MRS stock decreased bacteriocin movement to 3,200 AU/ml, while 20 g/l and 50 g/l yielded just 1,600 AU/ml. The nearness of cyanocobalamin, L �?�ascorbic corrosive, thiamine and dl �?�6,8�?�thioctic corrosive in MRS stock at 1.0 ppm, individually, didn't bring about expanded action levels. (© 2004 WILEY�?�VCH Verlag GmbH and Co. KGaA, Weinheim)Oxygen is a significant determinant of both endurance and mortality of oxygen consuming life forms. For the facultative anaerobe Lactococcus lactis, oxygen effectsly affects both development and endurance. We appear here that oxygen can be helpful to L. lactis if heme is available during circulated air through development. The development time frame is broadened and long haul endurance is particularly improved contrasted with results acquired under the standard aging conditions. We thought about that improved development and endurance could be because of the limit of L. lactis to experience breath. To test this thought, we affirmed that the metabolic conduct of lactococci within the sight of oxygen and hemin is reliable with breath and is most articulated late in development. We at that point utilized a hereditary way to deal with show the accompanying. (I) The cydA quality, encoding cytochrome d oxidase, is required for breath and assumes an immediate job in oxygen usage. cydA articulation is incited late in development under breath conditions. (ii) The hemZ quality, encoding ferrochelatase, which changes over protoporphyrin IX to heme, is required for breath if the forerunner, as opposed to the last heme item, is available in the medium. Shockingly, endurance improved by breath is seen in a superoxide dismutase-inadequate strain, an outcome which underlines the physiological contrasts among maturing and breathing lactococci. These examinations affirm respiratory digestion in L. lactis and propose that this living being might be preferable adjusted to breath over to customary fermentative digestion. The poisonous cell impacts of oxygen are a central point in maturing and mortality. Oxygen poisonousness is ascribed to the action of receptive oxygen species that assault proteins, lipids, and nucleic acids. Impacts of oxygen have been widely concentrated by utilization of bacterial models, chiefly with the facultatively breathing bacterium Escherichia coli.

 

In this model, breath itself is embroiled as a wellspring of oxidative harm in E. coli. It has been proposed that the shutdown of breath in supplement constrained conditions may diminish responsive oxygen species levels and in this way improve E. coli endurance. Ongoing proof further recommends that endurance is supported by moving cells to anaerobic conditions during passage into fixed stage. Current data on the impacts of oxygen is predominantly founded on breathing living beings. In that capacity, the subject of what anaerobes do within the sight of oxidative pressure has been investigated close to nothing. It is assumed that these creatures adapt to worry similarly as aerobes, then again, actually their barrier frameworks, which may incorporate superoxide dismutases (SODs) and catalases, might be progressively restricted. Be that as it may, there has been no exhibition to date that reactions of anaerobes to an oxidative domain are unsurprising from the conduct of breathing microbes. The impacts of oxygen have been analyzed with Lactococcus lactis, a gram-positive facultative anaerobe with a fermentative digestion that can utilize various sugars to create essentially l-(+)- lactic corrosive. Oxygenation of societies brings about a changed redox state and more prominent NADH oxidase action; as a result, sugar aging is moved toward blended aging, and acidic corrosive, formic corrosive, CO2, ethanol, and acetoin, just as lactic corrosive, are created. Regardless of its grouping as an anaerobe and studies that have concentrated almost altogether on its fermentative digestion, results got around 30 years prior proposed that L. lactis can experience respiratory development, given that heme is added to circulated air through societies; this view was upheld by an exhibition of adjusted metabolic final results, cytochrome arrangement, and hemin-subordinate oxygen take-up. Nonetheless, later investigations of a L. lactis subsp. diacetylactis strain proposed that breath doesn't happen under these conditions, as cytochromes couldn't be recognized.

 

To date this inquiry has not been additionally investigated, and the results of respiratory development have not been examined. The harmful impacts of oxygen on L. lactis development and endurance have been uncovered by a few examinations under maturation conditions. Development is supposedly restrained by oxygen, and delayed air circulation of lactococcal societies can prompt cell passing and DNA corruption. Oxygen harmfulness might be because of development of hydrogen peroxide and hydroxyl radicals. In contrast to E. coli, L. lactis has a solitary SOD and no catalase. It was discovered that the expansion of exogenous catalase improved endurance of L. lactis cells presented to oxygen. These outcomes recommend that L. lactis may not be completely prepared to withstand the poisonous impacts of an oxidative domain.

 

Our investigations on oxygen harmfulness drove us to dismember the constructive outcomes of the expansion of exogenous catalase on development and endurance of L. lactis. As catalase contains a heme core (in which iron is complexed with a porphyrin atom), we originally analyzed the impacts of oxygen within the sight of heme. We affirmed that L. lactis is equipped for respiratory development, in concurrence with prior work. Breath conditions bring about improved development and a breathtaking increment in long haul endurance contrasted with development under customary aging conditions. The watched phenotypes require an unblemished cydA quality, which encodes cytochrome d oxidase. Under breath conditions, maturation happens during beginning development, while breath is most noteworthy during the late exponential stage. (An underlying oral correspondence of breath and its consequences for lactococci was first introduced at the Lactic Acid Conference in Veldhoven, Holland, in September 1999.