| 1. |
- Deraz, Sahar, et al.
(författare)
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Capture of bacteriocins directly from non-clarified fermentation broth using macroporous monolithic cryogels with phenyl ligands
- 2007
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Ingår i: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229. ; 40:4, s. 786-793
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Tidskriftsartikel (refereegranskat)abstract
- The bacteriocin, sakacin P was produced by the bacteriocin-producing strain Lactobacillus sakei CCUG 42687 at 20 degrees C without pH control. The bacteriocin was captured directly from the fermentation broth using macroporous octyl- and phenyl-monolith columns. The large size of the interconnected macropores (up to 100 mu m) in the macroporous monolith allowed for direct fermentation broth processing with no clarification needed. Screening for optimal bacteriocin binding demonstrated that at pH 6.2 about 80% of the bacteriocin activity could be recovered with a purification factor of 150-160 in the cell-free eluate. Capture of bacteriocins from the fermentation broth using macroporous monoliths in the 96-well plate format presents a promising approach for rapid analytical isolation of bacteriocins from numerous samples.
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| 2. |
- Deraz, Sahar, et al.
(författare)
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Mode of action of acidocin D20079, a bacteriocin produced by the potential probiotic strain, Lactobacillus acidophilus DSM 20079
- 2007
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Ingår i: Journal of Industrial Microbiology & Biotechnology. - : Oxford University Press (OUP). - 1367-5435 .- 1476-5535. ; 34:5, s. 373-379
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Tidskriftsartikel (refereegranskat)abstract
- Lactobacillus acidophilus DSM 20079 is the producer of a novel bacteriocin termed acidocin D20079. In this paper, mode of action using three various concentrations of acidocin D20079 (2,048, 128 and 11.3 AU/ml) was determined against an indicator strain L. delbrueckii subsp. lactis DSM 20076. These concentrations all led to marked decreases in both the number of viable cells and in optical density, indicating that the activity of the acidocin D20079 was bactericidal with concomitant cell lysis. Moreover, the probiotic potential of L. acidophilus DSM 20079 was analyzed for its ability to survive and retain viability at conditions (acid and bile concentrations) mimicking the gastrointestinal (GI) tract, under which it survived exposure to pH 2.0 with a 1.2 log cycle reduction in viability and where 45% of the original population survived in a medium containing 0.3% bile for 3 h.
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| 3. |
- Deraz, Sahar, et al.
(författare)
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Production and physicochemical characterization of acidocin D20079, a bacteriocin produced by Lactobacillus acidophilus DSM 20079
- 2007
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Ingår i: World Journal of Microbiology & Biotechnology. - : Springer Science and Business Media LLC. - 0959-3993 .- 1573-0972. ; 23:7, s. 911-921
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Tidskriftsartikel (refereegranskat)abstract
- Lactobacillus acidophilus DSM 20079 is the producer of a novel bacteriocin termed acidocin D20079. In this paper, a partial sequence of this peptide is determined, together with data on its secondary structure. A modification of the MRS-growth medium (replacing the detergent Tween 80 with oleic acid), was shown to improve the production level of the peptide by one order of magnitude, as well as to stabilize the activity level. Addition of a detergent (Tween 20, less interfering in mass spectrometric analysis), was however necessary for solubilization of the purified acidocin D20079. Digestion of the peptide followed by de-novo sequencing of generated fragments, allowed determination of a partial sequence consisting of 39 of the totally estimated 65 residues. Acidocin D20079 has a high content of glycine residues, hydrophobic residues, and acidic residues. No modified amino acids were found. Edman degradation, and C-terminal sequencing failed, suggesting that the peptide may be cyclic, and a novel member of class IIc bacteriocins. Circular dichroism spectroscopy and secondary structure prediction showed random coil conformation in aqueous solution, but secondary structure was induced in the presence of sodium-dodecyl sulfate. The data could be fitted assuming 2-13% of the residues to be in alpha-helix and 23-27% of the residues to be in beta-strand conformation. This indicates that a membrane/membrane-mimicking hydrocarbon-water interface induces an active conformation.
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| 4. |
- Deraz, Sahar
(författare)
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Production, Purification and Characterization of Antimicrobial Biomolecules from Potential Probiotic Lactic Acid Bacteria
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Development and optimization of the production of lactic acid bacteria (LAB) and their attendant 'natural' inhibitors as biopreservatives to control undesirable bacteria currently remains a primary focus of several laboratories involved in research concerning food safety and quality. Strategies utilized to study incorporation of biopreservatives into food include either direct use of LAB-strains or use of a biopreservative preparation in the form of previously fermented product or use of semipurified, purified, or chemically synthesized bacteriocins. Modern concepts or perspectives of the application of LAB include the following selections: i) the best adapted and safely performing LAB strains, ii) strains with probiotic effects and/or health-promoting effects and finally iii) strains with food protective activities. In the study presented in this thesis, three different strains, Lactobacillus acidophilus DSM 20079, Pediococcus damnosus 2.6 and Lactobacillus sakei CCUG 42685, have been chosen to study their biotechnological properties according to one or several of the previously mentioned concepts. Structural and functional characterization of a novel antimicrobial peptide (acidocin 20079) from an LAB with interesting characteristics as producer strain (Lactobacillus acidophilus DSM 20079), has been made, showing that the isolated bacteriocin has a potential for industrial application. Furthermore, the functional properties of selected bacteriocin producing strains (L. acidophilus DSM 20079 and Pediococcus damnosus 2.6) as probiotic have been studied. The strains showed a high tolerance to the main obstacles of the GI-tract in experiments simulating native conditions at 37 °C. Finally, improvements within the field of purification of bacteriocins from non-clarified crude homogenate are needed as the currently published protocols are often cumbersome. An economically reliable process hence has to be developed for bacteriocin purification. A chromatographic matrix based on continuous supermacroporous cryogel was successfully used for the purification of sakacin P (produced by L. sakei CCUG 42685) directly from non-clarified crude. The bound bacteriocin was eluted with 81-87 % recovery in particulate free eluate with more than 60%purity after one purification step.
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| 5. |
- Deraz, Sahar, et al.
(författare)
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Purification and characterisation of acidocin D20079, a bacteriocin produced by Lactobacillus acidophilus DSM 20079
- 2005
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Ingår i: Journal of Biotechnology. - : Elsevier BV. - 1873-4863 .- 0168-1656. ; 117:4, s. 343-354
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Tidskriftsartikel (refereegranskat)abstract
- Bacteriocins are natural antimicrobial agents produced by food fermentative bacteria. Lactobacillus acidophilus DSM 20079 produces a small bacteriocin, with a molecular mass of 6.6 kDa, designated acidocin D20079. This antimicrobial peptide was extremely heat-stable (30 min at 121 degrees C) and was active over a wide pH range. It was found to be sensitive to proteolytic enzymes (trypsin, ficin, pepsin, papain, and proteinase K). Acidocin D20079 has a narrow inhibitory spectrum restricted to the genus Lactobacillus which includes L. sakei NCDO 2714, an organism known to cause anaerobic spoilage of vacuum-packaged meat. Maximum production of acidocin D20079 in MRS broth was detected at pH 6.0, and the peptide was purified by ammonium sulphate precipitation followed by sequential cation exchange and hydrophobic interaction chromatography. Purified acidocin D20079 spontaneously formed spherulite crystals during dialysis. As the N-terminus was found to be blocked for sequencing, matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry was used to determine a partial sequence. and the molecular mass of the bacteriocin in the formed crystals (6.6 kDa). Estimates of the molecular weight of the partially purified peptide, using tricine-SDS-PAGE, in which bacteriocin activity was confirmed by overlayer techniques were in accordance with this value. (c) 2005 Published by Elsevier B.V.
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| 6. |
- Immerstrand, Tina, et al.
(författare)
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Characterization of the properties of Pediococcus parvulus for probiotic or protective culture use.
- 2010
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Ingår i: Journal of Food Protection. - 0362-028X. ; 73:5, s. 960-966
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Tidskriftsartikel (refereegranskat)abstract
- Pediococcus parvulus 2.6 (previously Pediococcus damnosus 2.6, here confirmed as P. parvulus by 16S DNA sequencing) displayed antibacterial activity toward several bacterial species, including isolates found as contaminants in oats, herein genetically identified as Bacillus cereus. No inhibition of Listeria monocytogenes was found under the conditions used. Antibacterial activity was retrieved after ammonium sulfate or acetone precipitation showed it to be peptide mediated. P. parvulus 2.6 has previously shown good technological properties in oat-based products. This, together with the currently found inhibition of food spoilage microorganisms like B. cereus, makes it suitable as a food protective culture. Survival trials of P. parvulus 2.6 at conditions mimicking the gastrointestinal tract were prompted by previously found cholesterol-lowering effects in humans after consumption of oat products cofermented by using P. parvulus 2.6 and Bifidobacterium spp. Viability was measured with in vitro, gutlike simulations at 37 degrees C. High survival was shown under two of three conditions (gastric juice, bile, and small intestine juice), defined as main obstacles of the gastrointestinal tract. The critical step was bile exposure. At a concentration of 20%, viability was low, but 0.3% bile (mean concentration in the intestine) did not have a major influence on growth. Viability of P. parvulus 2.6 was significantly decreased in gastric juice at pH 1.5 (with pepsin), but it was not significantly affected at pH 2.5, and was also improved at a lower pH in 20% oat milk. Viability was judged sufficient for colonization at gutlike conditions, qualifying the strain for further probiotic studies.
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| 7. |
- Plieva, Fatima, et al.
(författare)
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Characterization of supermacroporous monolithic polyacrylamide based matrices designed for chromatography of bioparticles
- 2004
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Ingår i: Journal of Chromatography. B. - : Elsevier BV. - 1873-376X .- 1570-0232. ; 807:1, s. 129-137
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Tidskriftsartikel (refereegranskat)abstract
- Supermacroporous monolithic acrylamide (AAm)-based cryogels were prepared by radical cryo-polymerizaton (polymerization in the moderately frozen system) of AAm with functional monomers and cross-linker N,N'-methylene-bis-acrylamide (MBAAm). Electron microscopy studies revealed supermacroporous structure of the developed cryogels with pore size of 5-100 mum. Cryogel porosity depended on cryo-polymerization conditions. More than 90% of the monolithic bed volume is the interconnected supermacropores filled with water and less than 10% of the monolithic volume is pore walls. The total protein binding capacity (lysozyme in the case of immobilized metal affinity chromatography (IMAC) column and bovine serum albumin (BSA) in the case of anion-exchange (AE) column) was independent of the flow rates till 600 cm/h. Chromatographic behavior of E. coli cells when a cell suspension was applied to ion-exchange cryogel columns depended on both the density of functional ligand and the porosity of the cryogel. (C) 2004 Elsevier B.V. All rights reserved.
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