The metabolic activity of bacterial microorganisms may influence the growth and metabolic activities of other microbes that are present in any specific niche. Lactic acid bacteria (LAB) are antagonistic to some microbial pathogens by the metabolic production of compounds with antimicrobial activity. Consequently, investigators have measured the effects of those antimicrobials to inhibit specific pathogens. However, the mode(s) of action of LAB against foodborne pathogens on products and/or in broth is not completely understood. Therefore, the objectives of this research were to (i) determine the LAB dose required for inhibition of Escherichia coli O157:H7 and Salmonella enterica in vitro and on spinach, and (ii) identify and quantify the major antimicrobial substances synthesized by LAB as a function of postinoculation storage conditions. Assays were performed at 7 degrees C under aerobic conditions. The foodborne pathogens dose responses were assessed in a liquid microbiological medium (in vitro) and on spinach leaf surfaces. Different levels of foodborne pathogens and LAB cultures were used. The addition of LAB cultures did not reduce E. coli O157:H7 or Salmonella enterica populations when performed in vitro. However, when LAB cultures were sprayed on the surfaces of spinach leaves at 8.0 log10 CFU/g, there were significant reductions on E. coli O157:H7 of 1.62 and 0.73 log10 CFU/g (after 3 days) and on Salmonella enterica of 1.85 and 0.71 log10 CFU/g (after 6 days) for treatments inoculated with an initial level of 2.0 and 4.0 log10 CFU/g, respectively. After quantification of the antimicrobial compounds synthesized by LAB cultures, they were correlated against the population growth of targeted pathogens. The highest Llactic acid (3.71 plus/minus 0.14 micromoles/ml, day 12) and hydrogen peroxide (3.72 plus/minus 3.34 microM, day 6) production were obtained from the in vitro sample inoculated with 8.0 log10 CFU/ml of LAB and 0.0 log10 CFU/ml of pathogens. The highest bacteriocin production (0.1 plus/minus 0.01 mg/ml) was obtained from the in vitro sample with 8.0 log10 CFU/ml of LAB and 2.0 log10 CFU/ml of pathogens. In conclusion, the LAB cultures were able to produce detectable amounts of antimicrobials that may be used as intervention and/or sciencebased practice against foodborne pathogens by producers and the industry.

Whey media, containing 2% (w/v) whey powder, 1% (w/v) glucose, and 0.5% (w/v) yeast extract, were fermented with nine Lactobacillus strains to produce angiotensin I-converting enzyme (ACE) inhibitory peptides. Lb. brevis, Lb. helveticus, and Lb. paracasei were most effective in producing whey hydrolysates that contained potent ACE inhibitors, with the inhibition rate ranging from 93.3 +/- 0.3 to 100%. The hydrolysates of three Lactobacillus strains were partially purified by dialysis (6,000--8,000 Da cut-off) to remove larger molecules, and subsequently subjected to RP-HPLC, equipped with a Delta Pak C18 column. Each chromatogram displayed at least three distinct peaks at the hydrophobic region of the elution profile. Altogether fourteen peaks were purified and assayed for ACE inhibitory activity. All peaks except one exhibited ACE inhibitory activities, with IC50 ranging from 5.3 +/- 0.1 to 2637.8 +/- 366.9mug/ml. Three of these peaks contained pentapeptides, which consisted of mostly hydrophobic or aromatic amino acids at the C-terminal.

Enterococcus faecalis 710C is a lactic acid bacterium that produces two bacterocins, ent7A and ent7B. Both ent7A and ent7B have strong activity against gram-positive food pathogens including Listeria spp., Clostridium spp., vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA). Mass spectrometry analyses revealed that both ent7A (5201 Da) and ent7B (5207 Da) have formylated N-terminal methionine. The amino acid sequences, structural gene sequences of ent7 from nucleotide position 1-275 and immunity gene were determined. Circular dichroism data suggest that in aqueous solution ent7A and ent7B have 20 to 25% alpha-helical region. Addition of membrane-mimicking reagent (trifluoroethanol) did not significantly enhance the alpha-helical content in ent7A and ent7B. Chiral analysis by gas chromatography- mass spectrometry showed that the amino acid residues elucidated in ent7A and ent7B were all in L-configuration. / Food Science and Technology

Graduation date: 1993

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2005. / Härtill 4 uppsatser.

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2005. / Thesis documentation sheet inserted. Appendix reprints four papers and manuscripts co-authored with others. Includes bibliographical references. Also partially issued electronically via World Wide Web in PDF format; online version lacks appendix.

Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 135-141.

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2006. / Includes bibliographical references. Also available on the World Wide Web in PDF format.

Made available in DSpace on 2014-06-11T19:23:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-04-30Bitstream added on 2014-06-13T19:50:11Z : No. of bitstreams: 1 grandi_az_me_sjrp.pdf: 6424714 bytes, checksum: 49930f6eb63282aae8d204a93c4bb882 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os polímeros microbianos possuem propriedades físico-químicas com maior uniformidade do que os obtidos de outras fontes devido à especificidade do microrganismo utilizado e à possibilidade de um rígido controle dos parâmetros de fermentação. Estão entre as bactérias produtoras de polissacarídeos as bactérias ácido-láticas, as quais são capazes de converter açúcares, ácidos orgânicos, proteínas ou gorduras em componentes de sabor e aroma, contribuindo ainda para melhorar a textura e a viscosidade de produtos fermentados por meio da produção de exopolissacarídeos (EPS). Nestes produtos, possuem a função de realçar, atribuir e manter as características desejáveis de corpo, textura, viscosidade e aparência, melhorando dessa forma os atributos sensoriais do produto final. O objetivo deste trabalho foi estudar o comportamento de Lactobacillus helveticus autóctone em meio de cultivo com substâncias estimulantes ao crescimento e produção de exopolissacarídeos. A cultura foi previamente isolada de soro-fermento natural. Utilizou-se leite desnatado reconstituído (LDR 10%) como meio de produção, acrescido de fontes de carbono (glicose e frutose) e nitrogênio (sulfato de amônio, peptona de carne e extrato de levedura), ambas nas concentrações de 1, 2, 3, 4 e 5% (p/v). Inoculou-se os meios de fermentação com 1% (v/v) das culturas reativadas em meio De Man Rogosa Sharpe - MRS, e a produção de EPS foi avaliada depois de 24, 48, 72 e 96 horas de incubação, a 37ºC e 100 rpm. Das duas fontes de carbono testadas, a frutose foi a mais favorável à produção de exopolissacarídeos, proporcionando maiores quantidades (1,23 g/50mL de meio de produção). Para sulfato de amônio 5%, as produções chegaram a 3,63 com glicose e a 4,25g/50mL de meio de produção com frutose. Peptona de carne e extrato de levedura favoreceram a produção do biopolímero... / Microbial polymers have physical and chemical properties with larger uniformity than those obtained from other sources because of specificity microorganism used and possibility of a strict parameters of control fermentation. Among the polysaccharide-producing bacteria are the lactic acid bacteria, which are able to converting sugars, organic acids, proteins or fats in flavor and aroma components, thus contributing to improve the texture and viscosity of fermented products through the production of exopolysaccharides (EPS). These products have a enhance function, assign and maintain desirable characteristics of body, texture, viscosity and appearance, thus improving the sensory attributes of the final product. The aim was to study the behavior Lactobacillus helveticus autochthono, using a medium with substances stimulating the growth and exopolysaccharide production. Such autochthono culture was previously isolated from natural whey. Was used reconstituted skim milk (LDR 10%) as production medium, plus carbon sources (glucose and fructose) and nitrogen (ammonium sulfate, meat peptone and yeast extract), both varying in concentrations 1, 2, 3, 4 and 5% (w/v). Was inoculated the fermentation medium with 1% (v/v) culture reactivated in medium Man Rogosa Sharpe - MRS, and EPS production was evaluated after 24, 48, 72 and 96 hours of incubation at 37°C and 100 rpm. Carbon sources tested fructose was the most favorable, providing greater amounts of EPS (1.23 g/50mL of medium production). For ammonium sulfate 5%, the yield reached 3.63 with glucose, and 4.25 g/50mL of medium production with fructose. Meat peptone and yeast extract favored the biopolymer production in lower concentrations, the concentration 2% of both showed better results

Orientador: Crispin Humberto Garcia-Cruz / Banca: Sandra Garcia / Banca: Daise Aparecida Rossi / Resumo: Os polímeros microbianos possuem propriedades físico-químicas com maior uniformidade do que os obtidos de outras fontes devido à especificidade do microrganismo utilizado e à possibilidade de um rígido controle dos parâmetros de fermentação. Estão entre as bactérias produtoras de polissacarídeos as bactérias ácido-láticas, as quais são capazes de converter açúcares, ácidos orgânicos, proteínas ou gorduras em componentes de sabor e aroma, contribuindo ainda para melhorar a textura e a viscosidade de produtos fermentados por meio da produção de exopolissacarídeos (EPS). Nestes produtos, possuem a função de realçar, atribuir e manter as características desejáveis de corpo, textura, viscosidade e aparência, melhorando dessa forma os atributos sensoriais do produto final. O objetivo deste trabalho foi estudar o comportamento de Lactobacillus helveticus autóctone em meio de cultivo com substâncias estimulantes ao crescimento e produção de exopolissacarídeos. A cultura foi previamente isolada de soro-fermento natural. Utilizou-se leite desnatado reconstituído (LDR 10%) como meio de produção, acrescido de fontes de carbono (glicose e frutose) e nitrogênio (sulfato de amônio, peptona de carne e extrato de levedura), ambas nas concentrações de 1, 2, 3, 4 e 5% (p/v). Inoculou-se os meios de fermentação com 1% (v/v) das culturas reativadas em meio De Man Rogosa Sharpe - MRS, e a produção de EPS foi avaliada depois de 24, 48, 72 e 96 horas de incubação, a 37ºC e 100 rpm. Das duas fontes de carbono testadas, a frutose foi a mais favorável à produção de exopolissacarídeos, proporcionando maiores quantidades (1,23 g/50mL de meio de produção). Para sulfato de amônio 5%, as produções chegaram a 3,63 com glicose e a 4,25g/50mL de meio de produção com frutose. Peptona de carne e extrato de levedura favoreceram a produção do biopolímero... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Microbial polymers have physical and chemical properties with larger uniformity than those obtained from other sources because of specificity microorganism used and possibility of a strict parameters of control fermentation. Among the polysaccharide-producing bacteria are the lactic acid bacteria, which are able to converting sugars, organic acids, proteins or fats in flavor and aroma components, thus contributing to improve the texture and viscosity of fermented products through the production of exopolysaccharides (EPS). These products have a enhance function, assign and maintain desirable characteristics of body, texture, viscosity and appearance, thus improving the sensory attributes of the final product. The aim was to study the behavior Lactobacillus helveticus autochthono, using a medium with substances stimulating the growth and exopolysaccharide production. Such autochthono culture was previously isolated from natural whey. Was used reconstituted skim milk (LDR 10%) as production medium, plus carbon sources (glucose and fructose) and nitrogen (ammonium sulfate, meat peptone and yeast extract), both varying in concentrations 1, 2, 3, 4 and 5% (w/v). Was inoculated the fermentation medium with 1% (v/v) culture reactivated in medium Man Rogosa Sharpe - MRS, and EPS production was evaluated after 24, 48, 72 and 96 hours of incubation at 37°C and 100 rpm. Carbon sources tested fructose was the most favorable, providing greater amounts of EPS (1.23 g/50mL of medium production). For ammonium sulfate 5%, the yield reached 3.63 with glucose, and 4.25 g/50mL of medium production with fructose. Meat peptone and yeast extract favored the biopolymer production in lower concentrations, the concentration 2% of both showed better results / Mestre