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Evaluation of bambara groundnuts (Vigna subterrenea (L.) Verdc.) milk fermented with lactic acid bacteria as a probiotic beverageMurevanhema, Yvonne, Yeukai January 2012 (has links)
Thesis presented in partial fulfilment of the requirements for the degree
of
Master of Technology (Food Technology)
Department of Food Technology
Faculty of Applied Sciences
Cape Peninsula University of Technology, 2012 / The aim of this study was to evaluate bambara groundnut milk (BGNM) subjected to fermentation with lactic acid bacteria (LAB) as a probiotic beverage with a view to developing value-added product. Central Composite Rotatable Design (CCRD) was used to optimise the hydration time and temperature of BGN flour for optimum BGN milk (BGNM) production. The optimum time and temperature was 2 h at 25oC. The effect of variety was assessed on the quality and consumer acceptability of BGNM prepared from five varieties of BGN (black, red, brown, brown-eye, and black-eye) which were representatives of the BGN available in South Africa. BGNM from the five varieties differed significantly (p<0.05) in, lightness, chroma, redness, yellowness, hue and antioxidative activity, while the pH were not significantly different. The four BGNM samples were significantly different (p < 0.05) in appearance, colour, mouthfeel and overall acceptability but not in aroma and taste. A three factor design (4 x 3 x 3) consisting of probiotics (Lactobacillus acidophilus, L. bulgaricus, L. casei and L. plantarum), temperature and fermentation time, were used to estimate the optimal conditions for the production of BGN probiotic beverage (BGNPB). The optimal condition for the production of BGNPB was estimated to be 35oC for 24 h with a desirability of 0.854 for L. bulgaricus. The next promising probiotic was L. plantarum that could be fermented at 35oC for 24 h with 0.843 desirability. BGNM from the red variety were fermented with L. bulgaricus and L. plantarum and L bulgaricus (in combination), making plain and sweetened BGNPB which were evaluated for their quality and consumer acceptability. The four BGNPB samples were significantly different (p < 0.05) in aroma, taste, mouthfeel and overall acceptability but not in appearance and colour. The plain BGNPB were assessed for their proximate composition, antioxidant activity, in vitro probiotic tolerance to simulated gastric juices and bile and a 28 days shelf life study at 5, 15 and 25oC. The protein, total dietary fibre (TDF), ash and antioxidative activity of the BGNPB were significantly different while the fat and carbohydrates were not significantly different. Time and concentration of the gastric juice and bile had significant effects on the percentage bacterial survival of probiotics in the BGNPB. However, the probiotics did survive, in low numbers, in the simulated gastric juice and bile after 180 and 240 minutes of incubation. Titratable acidity, pH, microbial load and colour of the BGNPB were
significantly affected by the storage time and temperature during the shelf life study. At the 5oC storage temperature the BGNPB had a right censored shelf life on day 28. At 15oC the shelf life was 18 and 10 days for L bulgaricus and L. plantarum and L. bulgaricus respectively. The outcome of this research showed that a novel BGNPB product can be made from fermenting BGNM with LAB.
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Lactic acid bacteria as bio-preservatives in bakery : role of sourdough systems in the quality, safety and shelf life of breadKoy, Rebaz January 2017 (has links)
Microbial contamination and survival during storage of bread are a cause of both health concerns and economic losses. Traditional fermentation systems were studied as sources of lactic acid bacteria (LAB) with antagonistic potential against foodborne pathogens and spoilage organisms, with the aim to improve the safety and shelf life of bakery products. The antagonistic activity of four types of buttermilk (BM) products fermented with Lactococcus lactis subsp. lactis was evaluated against a number of pathogenic bacteria to select the best fermented-BM for application as bio-preservatives in bread crumpets, showing up to 9 µg/ml of nisin equivalent antimicrobial activity. These food ingredients could be suitable to be used in crumpet formulations, BM fermented with Lc. lactis subsp. lactis and nisin influenced the quality and shelf life of crumpets; the pH value and firmness of products with fermented BM was lower and the acidity and springiness was higher than for unfermented BM treatment and control withouth additive. The nisin and fermented BM treatment had beneficial effects on the pore size and colour in comparison with the control, and improved microbial shelf life by 2 days. Commercial and traditional sourdough and bread samples (n=18) were collected to assess the diversity of LAB strains and potential properties when applied to dough and bread. DGGE followed by sequencing showed that Lactobacillus was the predominant genus in the studied sourdoughs. Lb. plantarum and Lb. brevis strains accounted for 69% of the 32 isolates, out of which 10 were amylolytic and 12 had proteolytic activity. Most were also good acid producers after 24 h at 30°C. Some LAB strains presented a strong in vitro inhibitory activity against five indicator strains, showing potential as starter cultures to ferment sourdough. In subsequent experiments, the properties of 24 sourdoughs were evaluated, and one of them, fermented with Lb. plantarum (SIN3) yielded low pH value, high lactic acid production, and suitable microbial growth, and was selected for further bread making performance trials. The bread with fast fermentation and high sourdough concentration (FFHSD) had a lower pH, higher acidity and increased the quality attributes with significantly better shelf life comparing to the other treatments during the storage period. Sensory evaluation demonstrated that fast-fermented breads were more acceptable than the slow-fermented counterparts. Bread prepared with high level (18%) of sourdough fast-fermented with the selected culture (SIN3) had a good eating quality and shelf life. The approach of this study is likely to yield feasible improvements of the current methods of preparation of baking goods.
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Avaliação da eficiência de bactérias ácido-láticas para descontaminação de aflotoxina M1 / Evaluation of the efficiency of lactic acid bacteria for the decontamination of aflatoxin M1Bovo, Fernanda 01 March 2011 (has links)
O objetivo do trabalho foi avaliar a capacidade de cepas de bactérias ácido-láticas (BAL) em remover a aflatoxina M1 (AFM1) em solução tampão fosfato salina (TFS) e em amostras de leite. Nos ensaios com TFS, verificou-se a influência do tempo de contato (15 min. ou 24 horas) entre as células de sete cepas de BAL e AFM1, as diferenças entre a eficiência de remoção das bactérias viáveis e inviabilizadas termicamente, e a estabilidade do complexo BAL/AFM1 formado. As três cepas de BAL com maior percentual (> 33%) de remoção da AFM1 nos ensaios com TFS foram re-avaliadas utilizando-se leite UHT (ultra-high-temperature) desnatado artificialmente contaminado com AFM1. Para isso, foram utilizadas somente células inviabilizadas termicamente, verificando-se o efeito da temperatura (4ºC ou 37ºC) sobre a capacidade de remoção da toxina por 15 minutos. A remoção média da AFM1 pelas cepas de BAL em TFS variou entre 5,60±0,45 e 45,67±1,65% (n=3), sendo que as células inviáveis obtiveram percentuais de remoção de AFM1 significativamente maiores que as células viáveis, em ambos os tempos de contato analisados (15 min. ou 24 horas), não havendo diferença significativa entre os tempos. Observou-se que o complexo BAL/AFM1 obtido nos ensaios com TFS é instável, pois 40,57±4,66 a 87,37±1,82% da AFM1 retida pela bactéria foram recuperados em solução após a lavagem do complexo com TFS. As três cepas de BAL com maior percentual de remoção da AFM1 em TFS (Lactobacillus rhamnosus, Lactobacillus delbrueckii spp. bulgaricus e Bifidobacterium lactis) não apresentaram diferenças significativas nos ensaios com leite UHT a 37ºC. Somente B. lactis apresentou maior capacidade de remover a AFM1 do leite UHT a 4ºC. Os resultados demonstraram que a remoção de AFM1 empregando-se as BAL em alimentos é viável para reduzir as concentrações da toxina a níveis seguros. Entretanto, estudos adicionais são necessários a fim de investigar os mecanismos envolvidos na remoção da toxina pelas BAL com vistas à aplicação em indústrias de alimentos. / The purpose of this study was to evaluate the ability of strains of lactic acid bacteria (LAB) to remove aflatoxin M1 (AFM1) in phosphate buffer saline (PBS) and in milk samples. In the assays with PBS, the influence of contact time (15 min. or 24 hours) between the cells of seven LAB strains and AFM1 was evaluated, as well as the differences between the removal efficiency of viable and non-viable (heat-killed) bacteria, and the stability of AFM1/LAB complex produced. The three LAB strains with the highest percentage (> 33%) of AFM1 removal in the tests with PBS were reevaluated using UHT (ultra-high-temperature) skimmed milk spiked with AFM1. For these assays, only non-viable bacterial cells were used for checking the effect of temperature (4ºC or 37ºC) on the toxin removal capacity during 15 min. The mean AFM1 removal by LAB strains in PBS ranged from 5.60±0.45 and 45.67±1.65% (n=3). Non-viable cells showed AFM1 removal percentages significantly higher than viable cells in both contact times (15 min. or 24 hours), although there were not significant differences between these contact times. The AFM1/LAB complex resulted from the tests with PBS was unstable, as 40.57±4.66 to 87.37±1.82% of AFM1 retained by the bacteria were recovered in solution after washing the complex with PBS. The three LAB strains with the highest percentage of AFM1 removal in the PBS assays (Lactobacillus rhamnosus, Lactobacillus delbrueckii spp. bulgaricus and Bifidobacterium lactis) showed no significant differences in the UHT skimmed milk assays at 37ºC. Only B. lactis had greater ability to remove AFM1 in UHT milk at 4ºC. The results demonstrated that the removal of AFM1 by using LAB in foods is viable to reduce the toxin concentrations until safe levels. However, additional studies are needed to investigate the mechanisms involved in the toxin removal by LAB aiming its application in food industries.
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Investigation of yeast Grown in SSF Dring Biothanol Production from Lignocellusosic MaterialBabapour, Ayda Barid, Gavitar, Maryam Nadalipour January 2012 (has links)
Ethanol produced from lignocellulosic biomass has the potential to become a promisingalternative to gasoline. In this work the simultaneous saccharification and fermentation (SSF)technology was applied for ethanol production from hardwood with focus on cell growth,ethanol production and contamination.The SSF was performed at PH 5.5 and 35°C for different suspended solid concentrations(8%, 10% and 12%) of pretreated birch slurry which contained 16 % total suspended solids.Two different hexose fermenting yeast strain (Ethanol Red) and pentose fermenting yeaststrain were used.Quantifying the concentration of chemical components and metabolites in the fermentationmedium demonstrated that glucose and xylose are the major fermentable sugars in the slurry.The higher load of slurry (12%) represents a higher content of carbohydrates and potentiallyhigher end concentration of ethanol. Moreover, more lactic acid is produced with the lowerload of slurry (8 % or 10 %), presumably due to a result of a less inhibitory environment forbacterial growth. In this context, acetic acid sticks out as the most important inhibitor withconcentrations of 15.2 and 12.5 and 9.7 g/l respectively in the 12 %, 10 % and 8 % (ofsuspended solids) trials. Using pentose fermenting yeast may lead to higher ethanolproduction, lower xylose uptake and lower lactic acid formation. Cell viability and cellvitality determination from fermentation media in all the trails represented a sharplydecreasing trend during the fermentation for both Ethanol Red yeast strain and the pentosefermenting strain yeast strain apparently due to cell decomposition. / Program: MSc in Resource Recovery - Industrial Biotechnology
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Construction of hpRNA expression vector for silencing a gene in Rhizopus oryzaePenmatsa, Kiran Kumar, Balu, Bharat January 2012 (has links)
Depending on the previous research on LDHA gene silencing in Rhizopus oryzae CCUG 28959 through introduction of siRNA, a integral vector was constructed by inserting two copies of LDHA gene (by PCR cloning) in a fashion that it can express hpRNA in the transformed fungi, which will trigger the post transcriptional degradation of targeted mRNA through RNA degradation pathway which is known to be quelling in fungi.The vector was successfully designed with the LDHA gene, transformed in to the host organism, and also transferred to its progeny. This helps in maintaining stability of the transformed cell lines. This created vector will be advantageous at this point when compared to the use of siRNA for gene silencing, which is not a stable way. In the future, this vector can be used for down regulating other genes of interest in R. oryzae and can also be used for studying its effect on other metabolic pathways.In this study, Hygromycin resistance to the R. oryzae CCUG 28959 was shown at levels up to 1000 μg/ml, which has not been reported previously. / Program: MSc in Resource Recovery - Industrial Biotechnology
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Eco Friendly Composites Prepared from Lactic Acid Based Resin and Natural FiberEsmaeili, Nima, Javanshir, Shahrzad January 2014 (has links)
Lactic acid based thermoset were synthesised by reacting lactic acid with glycerol andfunctionalizing lactic acid branches by methacrylic anhydride. Resins with different chainlength were prepared and their thermo mechanical properties were examined through DMAanalysis and their molecular structures were analyzed by NMR method and their viscositywere investigated through rheometry analysis and three monomers were selected as the bestchain length. Degree of reaction in different reaction times was evaluated by a modifiedtitration method and bulk preparation of resin was performed by optimal process condition.DSC analysis was conducted in order to evaluate curing behaviour of resin with benzoylperoxide as cross-linking initiator. TGA analysis was performed to check thermo stability ofthe resin. Bio composites by viscose unidirectional and bidirectional knitted fabrics and alsonon woven viscose fiber with different fiber loads were prepared by ordinary hand layupimpregnation followed by compress moulding and their mechanical and thermo mechanicalproperties were characterized by tensile, flexural, charpy and DMA analysis and optimumfiber loads were identified for each fiber type. Ageing properties of prepared composites wereexamined by placing samples in climate chamber to simulate long time ageing and ageingexperiment was followed by tensile and flexural test to evaluate mechanical properties afterageing simulation. Composite`s swelling properties for water and some other solvents wereinvestigated and also their chemical resistance were evaluated by immersing them in 1M HCland KOH. The resin was also compared with a commercial oil based thermoset by preparingglass fiber reinforced composites and also effect of adding styrene to the resin were evaluated.Results of this work demonstrated that the novel synthesised have very high mechanical andthermo mechanical properties surpassing commercial oil based poly esters but ageingbehaviour is not very good however adding styrene can improve ageing properties. Also theresin is compatible with cellulosic natural fibers and forms strong composites. / Program: Masterutbildning i energi- och material
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RNA Silencing of Lactate Dehydrogenase Gene in Rhizopus oryzaeHaghayegh Jahromi, Neda, Hashemi Gheinani, Ali January 2011 (has links)
RNA silencing with direct delivery of siRNA has been used to suppress ldhA gene expression in filamentous fungus Rhizopus oryzae. Here, for the first time we show that, introducing small interfering RNA which consequently forms silencing complexes can alter the gene expression and we report a significant reduction of lactic acid production for isolates containing short (25 nt) synthetic siRNA. In all samples lactic acid production was reduced comparing with wild types. The average concentration of lactic acid production by Rhizopus oryzae during batch fermentation process where glucose has been used as a sole carbon source, diminished from 2.06 g/l in wild types to 0.36 g/l in knockdown samples which signify 5.7 times decrease. Interestingly, the average concentration of ethanol production was increased from 0.38 g/l in wild types to 0.45 g/l in knockdown samples. In some samples we were able to report even a 10 fold decrease in lactic acid production. Since R.oryzae is capable to assimilate a wide range of carbohydrates hydrolysed from lignocellulosic material in order to produce many economically valuable bulk material such as ethanol, these results suggest that RNA silencing is a useful method for industrial biotechnology to be applied in fungus Rhizopus oryzae in order to trigger the metabolism and gene expression toward a desired product.
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Isolamento e seleção de micro-organismos e desenvolvimento de tecnologia para produção de ácido lático /Coelho, Luciana Fontes. January 2011 (has links)
Orientador: Jonas Contiero / Banca: Clóvis Parazzi / Banca: Luiz Carlos Basso / Banca: Pedro de Oliva Neto / Banca: Cíntia Duarte de Freitas Milagre / Resumo: O objetivo deste trabalho foi isolar micro-organismos produtores de D-(-) e L-(+) ácido lático, os quais são utilizados na síntese de polímeros empregados na produção de diversos materiais resistentes e biodegradáveis, além de otimizar a produção de ácido lático, a partir da utilização de diversos resíduos agro-industriais. Os micro-organismos mais promissores para produção de L-(+) ácido lático foram os isolados de Keffir (Ke6, Ke11, Ke8 e Ke24) e o Lactobacillus rhamnosus B103, já para a produção de D-(-) ácido lático, os mais promissores foram os isolados de iogurte (Y15C e Y15A) e o Leuconostoc mesenteroides B512. Pode-se afirmar que os micro-organismos selecionados apresentaram grande potencial para utilização na indústria de biopolímeros e indústria de alimentos. O soro de queijo e a manipueira foram os melhores resíduos para produção de L-(+) ácido lático por Lactobacillus rhamnosus B103. Quando se utilizou 160 g/L de lactose de soro de queijo, 60 mL/L de água de maceração de milho (AMM), 2 mL/L de Tween 80 e 0,10 g/L de MnSO4, observou-se alta produção de L- (+) ácido lático (142 g/L) e baixo residual de lactose (3,2 g/L). Para a otimização com manipueira, foi obtido 41,58 g/L de L-(+) ácido lático, a partir de 50 g/L de açúcar redutor total (ART), 65,40 mL/L de AMM e 1,27 mL/L de Tween 80. Nas otimizações com Leuconostoc mesenteroides B512 foi observado produção de 60,20 g/L de D-(-) ácido lático, utilizando 116,90 g/L de ART de caldo de cana e 44,25 g/L de autolisado de levedura. Nas otimizações com L. plantarum Lmism6 observou-se uma produção de 63,40 g/L de ácido lático, 0,40 g/L de ART residual e alta conversão de substrato (99,40%), quando se utilizou 70 g/L de ART de melaço, 30,00 mL/L de AMM, 2 g/L de K2HPO4 e 1 mL/L de Tween 80 / Abstract: The aim of this study was to isolate D-(-) and L-(+) lactic acid producers micro-organisms, which are used in the synthesis of polymers used in the production of many resistant and biodegradable materials and optimize the lactic acid production, from agro-industrial residues. The most promising micro-organisms for L-(+) lactic acid production were Lactobacillus rhamnosus B103, as well as, the isolated from Keffir (Ke6, Ke11, Ke8 Ke24) and the most promising D-(-) lactic acid producers were strains of yogurt (Y15C and Y15A) and Leuconostoc mesenteroides B512. Cheese whey and cassava wastewater (CW) were the best residues for L-(+) lactic acid production by Lactobacillus rhamnosus B103. Using 160 g/L of lactose from whey, 60 mL/L of CSL, 2 mL/L of Tween 80 and 0.10 g/L of MnSO4, there was higher production of L-(+) lactic acid (142 g/L) and low lactose residual (3.20 g/L). For optimizations with CW, it was obtained 41.58 g/L of L-(+) lactic acid from 50 g/L of reducing sugar, 65.40 mL/L and 1.27 mL of corn steep liquor (CSL) and Tween 80 respectively. Leuconostoc mesenteroides B512 produced 60.20 g/L of D-(-) lactic acid, using 116.90 g/L of sugarcane juice and 44.25 g/L of yeast autolysate. L. plantarum Lmism6 produced 63.40 g/L of lactic acid, with less residual reducing sugar (0.41 g/L) and higher substrate conversion (99.41%), by using 70 g/L of sugar reducing from molasses, 30 mL/L of CSL, 2 g/L of K2HPO4, and 1 mL/L of Tween 80 / Doutor
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Expressão dos antígenos PspA1 e PspA3 de Streptococcus pneumoniae em bactérias lácticas. / Expression of Streptococcus pneumoniae PspA1 and PspA3 antigens in lactic bacteria.Campos, Ivana Barros de 20 March 2006 (has links)
Streptococcus pneumoniae é um importante patógeno respiratório que causa pneumonia, meningite e otite média. A vacina atualmente utilizada, composta de polissacarídeos capsulares (PS) derivados de 23 sorotipos diferentes, tem pouca eficácia em crianças, idosos e em pacientes imunocomprometidos. Vacinas com PS conjugados à proteína são mais eficientes, mas sua produção tem alto custo para ser amplamente utilizada. Além disso, o aumento de isolados clínicos de S. pneumoniae resistentes à antibióticos suporta o desenvolvimento de uma nova e mais eficiente vacina. O uso de bactérias ácido-lácticas (LAB) recombinantes vivas, como um sistema de apresentação do antígeno, representa uma estratégia promissora de vacinação de mucosa, já que são bactérias geralmente consideradas seguras (GRAS-status) e capazes de induzir resposta imune sistêmica e de mucosa. Neste trabalho, Lactococcus lactis, Lactobacillus casei e Lactobacillus helveticus foram engenheirados para expressão constitutiva de PspA (proteína A de superfície de pneumococo), um importante fator de virulência de S. pneumoniae. As bactérias recombinantes foram capazes de expressar PspA em duas localizações celulares: intracelular ou ancorada à parede celular, como analisado por Western-blot, utilizando anticorpos policlonais produzidos contra PspA recombinante purificada de E. coli. A estimulação humoral do sistema imune foi avaliada em termos de produção de anticorpos anti-PspA do tipo IgG no soro ou do tipo IgA na saliva, após administração intranasal de LABs recombinantes em camundongos. / Streptococcus pneumoniae is an important respiratory pathogen that causes pneumonia, meningitis and otitis media. The current vaccine in use is composed of capsular polysaccharides (PS) derived from 23 different serotypes, and has little efficacy in young children, elderly and in patients with immunodeficiencies. PS-protein conjugate vaccines are more effective, but their production is expensive for widespread use. Moreover, the increase in antibiotic-resistant S. pneumoniae clinical isolates supports the development of new and more effective vaccines. The use of live recombinant lactic acid bacteria (LAB) as antigen delivery and presentation systems represents a promising strategy for mucosal vaccination, since they are generally regarded as safe bacteria (GRAS-status) and are able to elicit both systemic and mucosal immune responses. In this work, Lactococcus lactis, Lactobacillus casei and Lactobacillus helveticus were engineered for constitutive expression of PspA (Pneumococcal Surface Protein A), an important S. pneumoniae virulence factor. Recombinant bacteria were able to express PspA in two cellular locations: intracellular or cell-surface exposed, as analyzed by Western-blot, using polyclonal antibodies produced against recombinant PspA purified from E. coli. Stimulation of humoral immune system was evaluated in terms of production of anti-PspA IgG in the sera or IgA in saliva, after intranasal administration of recombinant LAB in mice.
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Bactérias láticas produtoras de bacteriocinas em salame: isolamento, caracterização, encapsulação e aplicação no controle de Listeria monocytogenes em salame experimentalmente contaminado / Bacteriocin-producing lactic acid bacteria in salami: isolation, characterization, encapsulation and application for the control of listeria monocytogenes in experimentally contaminated salamiBarbosa, Matheus de Souza 20 September 2013 (has links)
A tecnologia da microencapsulação apresenta várias aplicações na indústria de alimentos. Sabendo-se que diferentes fatores intrínsecos e extrínsecos dos alimentos podem influenciar a produção e atividade antimicrobiana das bacteriocinas produzidas pelas bactérias láticas, este estudo teve como principal objetivo avaliar a funcionalidade da encapsulação de bactérias láticas (BAL) bacteriocinogênicas em alginato de cálcio no controle de Listeria monocytogenes em salame experimentalmente contaminado. Para atingir este objetivo, foram isoladas novas cepas de BAL a partir de salame, que foram identificadas e caracterizadas quanto às propriedades das bacteriocinas produzidas, avaliando-se a influência do processo de encapsulação na produção de bacteriocinas. Foram isoladas quatro cepas produtoras de bacteriocinas, identificadas como Lactobacillus sakei (uma cepa), Lactobacillus curvatus (duas cepas) e Lactobacillus plantarum (uma cepa), nomeadas MBSa1, MBSa2, MBSa3 e MBSa4, respectivamente. As bacteriocinas produzidas pelas quatro cepas foram termoestáveis e com exceção da cepa MBSa2, sensíveis a pH acima de 8. Todas inibiram todas as cepas de Listeria monocytogenes testadas e várias espécies de BAL, mas foram inativas contra bactérias Gram negativas. As bacteriocinas foram purificadas por cromatografia de troca iônica seguida de cromatografia de interação hidrofóbica sequencial e cromatografia de fase reversa, observando-se que L. sakei MBSa1 produz um peptídeo de 4303 Da, com uma sequência parcial de aminoacidos idêntica à sequência presente em sakacina A. As cepas MBSa2 e MBSa3 produzem dois peptídeos ativos cada, idênticos nas duas cepas, um de 4457 Da e outro de 4360 Da, que apresentam sequências parciais idênticas às presentes na sakacina P e na sakacina X, respectivamente. Aparentemente, a cepa L. plantarum MBSa4 produz uma bacteriocina composta por duas sub-unidades. O DNA genômico da cepa L. sakei MBSa1 contém os genes da sakacina A e curvacina A, enquanto o DNA da cepa L. plantarum MBSa4 foi positivo para o gene da plantaricina W. A cepa L. curvatus MBSa2 foi encapsulada em alginato de cálcio e testada quanto à produção de bacteriocinas in vitro, observando-se que o processo de encapsulação não influenciou a produção de bacteriocina. Quando testada in situ, ou seja, no salame experimentalmente contaminado com Listeria monocytogenes, não foi observada ação anti-Listeria por L. curvatus MBSa2 encapsulado e não encapsulado, durante o 30 dias de fabricação do salame. / The microencapsulation technology has several applications in the food industry. Knowing that different intrinsic and extrinsic factors can influence production and antimicrobial activity of bacteriocins produced by lactic acid bacteria in foods, this study aimed at evaluating the functionality of the encapsulation of bacteriocinogenic lactic acid bacteria (LAB) in calcium alginate in the control of Listeria monocytogenes in experimentally contaminated salami. To achieve this goal, new strains of LAB were isolated from salami, identified and characterized for the properties of the produced bacteriocins, evaluating the influence of the encapsulation process in the bacteriocins production. Four bacteriocin producing strains were isolated and identified as Lactobacillus sakei (one strain), Lactobacillus curvatus (two strains) and Lactobacillus plantarum (one strain), named MBSa1, MBSa2, MBSa3 and MBSa4 respectively. The bacteriocins produced by the four strains were thermostable and with the exception of strain MBSa2, sensitive to pH above 8. All inhibited all tested Listeria monocytogenes strains and various species of LAB but were inactive against Gram-negative bacteria. The bacteriocins were purified by cation-exchange followed by sequential hydrophobic-interaction and reversed-phase chromatography, indicating that L. sakei MBSa1 produces a peptide of 4303 Da, with a partial amino acid sequence identical to the sequence present in sakacin A. L. curvatus MBSa2 and MBSa3 produce two active peptides, identical in the two strains, one of 4457 Da and the other of 4360 Da, with partial aminoacid sequences identical to those present in sakacin X and sakacin P, respectively. Apparently, L. plantarum MBSa4 produces a bacteriocin composed of two subunits. Genomic DNA of L. sakei MBSa1indicated that this strain contains genes for sakacin A and curvacin A, while the DNA of L. plantarum MBSa4 was positive for the plantaricin W gene. The strain L. curvatus MBSa2 was encapsulated in calcium alginate and tested for bacteriocin production in vitro, observing that the encapsulation process did not affect the production of bacteriocin. When tested in situ, i.e. in the salami experimentally contaminated with L. monocytogenes was not observed anti-Listeria<i/> action by L. curvatus MBSa2 encapsulated and non-encapsulated during the 30 day manufacture of salami.
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