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ABSTRACT: The study aimed to analyze the physicochemical properties and starter culture viability of frozen yogurts produced with liquid cheese whey (LCW) and inulin at different proportions (F0: 66% LCW and 0% inulin; F1: 65% LCW and 1% inulin; F2: 64% LCW and 2% inulin; F3: 62% LCW and 4% inulin). Results demonstrated that the frozen yogurt F3 presented higher total solids and carbohydrates levels. LCW and inulin contributed to the overrun increase (11.8-18.2%) but did not interfere significantly in the retardation of the melting rate and range in the samples' hardness. Over the storage time, formulation F3 showed lower pH and higher titratable acidity. However, from the sixtieth day of storage, the formulations of frozen yogurts varied in the pH and titratable acidity profile associated with the decline in the viability of starter cultures. Even so, the inulin supplementation positively affected the strains' viability during storage. Based on our data, the formulation F3 presented better nutritional value, physicochemical characteristics, and stability over the storage period.
RESUMO: O estudo teve como objetivo analisar as propriedades físico-químicas e a viabilidade das culturas starters de frozen yogurts produzidos com soro líquido de queijo (SLQ) e inulina em diferentes proporções (F0: 66% SLQ e 0% inulina; F1: 65% SLQ e 1 % inulina; F2: 64% SLQ e 2% inulina; F3: 62% SLQ e 4% inulina). Os resultados demonstraram que o frozen yogurt F3 apresentou maiores teores de sólidos totais e carboidratos. SLQ e inulina contribuíram para o aumento do overrun (11.8-18.2%), mas não interferiram significativamente no retardo da taxa de derretimento e na variação da dureza das amostras. Ao longo do tempo de armazenamento, a formulação F3 apresentou menor pH e maior acidez titulável. Porém, a partir do sexagésimo dia de armazenamento, as formulações de frozen yogurts variaram o perfil de pH e acidez titulável associado ao declínio da viabilidade das culturas starter. Mesmo assim, a suplementação de inulina afetou positivamente a viabilidade das cepas durante o armazenamento. Com base em nossos dados, a formulação F3 apresentou melhor valor nutricional, características físico-químicas e estabilidade ao longo do período de armazenamento.
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Background: Diabetic wound is a major socioeconomic debilitating problem in this society. Various treatment options are available but still it requires better treatment option. In diabetes mellitus the oxygenation to the tissues is reduced. In this study effects of low level laser therapy were compared with topical application of Streptococcus thermophilus on diabetic wounds that induces formation of new blood vessel and free radical scavenging system, a comparative study to get better treatment option for diabetic wounds.Methods: 18 male rats were selected and divided randomly into three groups. Diabetes was induced in all the rats by using the Alloxan monohydrate at a dose of 120mg/kg of the body weight. Group A was treated with normal saline, group B was treated with low level laser therapy and group C was treated with Streptococcus thermophilus topically. Skin tissues were collected on day three and seven, slides were prepared for microscopic examination to observe the new blood vessels formation.Results: Mean number of new blood vessel formation was observed in group B compared with group A and C. Significant vasculogenesis was seen in group B when treated with Low level laser therapy.Conclusions: In the group of low level laser therapy new blood vessel formation was seen with better wound healing. It means LLLT provides better oxygenation to the tissues by generation of new blood vessels compared with Streptococcus thermophilus and normal saline.
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Background: Diarrhoea is the second most common cause of under-five mortality especially in developing world. Many studies have been conducted so far using different probiotic strains with variable outcome. So, the aim of the present study was to compare the clinical efficacy of Bacillus clausii and multi strain probiotic formulation as adjunct treatment of acute diarrhoea.Methods: This prospective single blind randomized controlled clinical trial included 300 infants and children between 6 months to 6 years of age admitted in a tertiary care hospital Sylhet, Bangladesh with acute watery diarrhoea having varied dehydration status ranging from no to severe dehydration excluding shocked state. Cases were randomly assigned to three groups which were group I (n=100) comprised of children who were treated with standard treatment (according to WHO guideline) only as control group, group II (n=100) who received standard treatment plus Bacillus clausii and group III (n=100) who received standard treatment plus multi strain probiotic formulation (Lactobacillus casei, Lactobacillus rhamnosus, Lactobacillus acidophilus, Lactobacillus bulgaricus, Bifidobacterium breve, Bifidobacterium infantis, Streptococcus thermophilus). Primary outcome variables were duration, frequency of diarrhoea and consistency of stool. Secondary outcome variable was duration of hospital stay.Results: Mean duration of diarrhoea was significantly shorter (p=0.001) in group III (2.62 days) compared to group I (3.26 days) and group II (3.22 days). Frequency of diarrhoea was significantly lower on day 3 of probiotic administration in group III (p <0.05) and on day 5 of treatment in group II (p <0.05). Stool consistency significantly improved on day 3 in group III (p <0.05) while it was on day 4 in group II. The duration of diarrhoea, hospital stay, stool consistency and frequency of stool on day 3 were not statistically significant (p >0.05) in group II in comparison to group I and group III.Conclusions: Multistrain probiotic formulation is effective in reducing the duration, frequency of diarrhoea and duration of hospital stay.
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Functional foods are those that, beyond basic nutrition, promote health benefits. This study aimed to produce a fermented beverage from a water-soluble soybean extract and low-lactose semi-skimmed milk. The beverage was prepared using a blend (v/v) containing 62% water-soluble soybean extract, 33% low-lactose semi-skimmed milk, and 5% of an inoculum containing Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus. The fermentation was carried out with monitoring of the lactic acid bacteria (LAB) counts, pH, and titrable acidity (% lactic acid). The consumption-ready fermented beverage was added of strawberry syrup and posteriorly characterized by its centesimal composition and sensory attributes as appearance, aroma, flavour, texture, overall impression, and purchase intent. Additionally, the LAB count and presence of pathogens in the final product were evaluated. After 14 h of fermentation, the refrigerated product presented L. bulgaricus and S. thermophilus counts of 8.5 × 103 and 7.4 × 107 CFU/mL, respectively. The product contained 14.93% carbohydrates, 0.76% fats, 0.96% ash, 22.76% totalsolids, and 2.19% protein. Because the product did not present any pathogens, it was adequate according to the standards of microbiological safety determined by Brazilian legislation. Regarding the sensory evaluation, the panelists assigned a mean score of 7.0 for the attributes evaluated, indicating 'liked moderately' to the drink. In addition, 61% of the evaluators responded that they 'certainly or probably would buy' the product if it were available on the market.
Alimentos funcionais são aqueles que, além da nutrição básica, promovem benefícios à saúde. Este trabalho teve como objetivo produzir uma bebida fermentada a partir de extrato hidrosolúvel de soja (EHS) e leite semidesnatado com baixa lactose. A bebida foi preparada utilizando uma mistura (v/v) contendo 62% de EHS, 33% de leite semidesnatado com baixa lactose e 5% de inóculo contendo Lactobacillus delbrueckii subsp. Bulgaricus e Streptococcus salivarius subsp. Thermophilus. A fermentação foi acompanhada durante 14 horas, através das contagens das bactérias ácido lácticas, pH e a acidez titulável (% de ácido láctico). A bebida fermentada pronta para consumo foi adicionada de uma calda de morango e caracterizada por sua composição centesimal, bem como por avaliação sensorial para os atributos: aparência, aroma, sabor, impressão global e intenção de compra. Além disso, a contagem das bactérias lácticas e presença de patógenos no produto foi avaliada. Após 14 horas de fermentação, o produto final refrigerado apresentou contagens de 8,5x103 UFC/mL e 7,4x107 UFC/mL para as bactérias L. bulgaricus e S. thermophilus respectivamente. O produto apresentou 14,93% de carboidratos, 0,76% de gordura, 0,96% de cinzas, 22,76% de sólidos totais e 2,19% de proteína. O produto não apresentou quaisquer patógenos, portanto, foi adequado aos padrões determinados pela legislação brasileira quanto à segurança microbiólogica. Com relação à avaliação sensorial, os provadores atribuíram em média nota 7,0 para todos os parâmetros avaliados, indicando que "gostarammoderadamente" da bebida. Ademais 61% dos avaliadores apontaram que "certamente ou provavelmente comprariam" o produto se estivesse disponível no mercado.
Subject(s)
Streptococcus thermophilus , Lactobacillus delbrueckii , Functional Food , Glycine max , Fruit and Vegetable JuicesABSTRACT
Objetivo: Este artigo tem como objetivo avaliar a atividade antifúngica in vitro dos Lactobacillus bulgaricus e Streptococcus thermophilus que estão presentes no iogurte sobre o crescimento da Candida albicans. Método: Foi realizado o repique da Candida albicans, fornecido em um tubo, na placa de petri contendo o ágar sabouraud dextrose para formação de colônias e aumento da população de Candida albicans. As amostras foram diluídas em soro fisiológico e semeada na placa de petri e incubou-se por duas horas. Após as duas horas, realizou-se a semeadura do iogurte, contendo os Lactobacillus bulgaricus e Streptococcus thermophilus, sobre a placa de petri contendo a Candida albicans e incubou-se na estufa a 37º C por 48 horas. Resultado: Após o período de incubação, verificamos que houve a inibição do crescimento da Candida albicans, reduzindo a quantidade de colônias das placas onde foi semeado o iogurte. Conclusão: Os Lactobacillus presentes no iogurte foram eficazes na atividade antifúngica contra a Candida albicans in vitro. Atualmente, poucos estudos foram realizados in vitro, sendo necessário realizar novos experimentos isolando os Lactobacillus bulgaricus e Streptococcus thermophilus presentes no iogurte, para maior certeza da eficácia da atividade antifúngica de cada Lactobacillus.
Objective: this paper aims to assess the antifungal activity in vitro of Lactobacillus bulgaricus and Streptococcus thermophilus that exist in yogurts on the Candida albicans growing. Method: we ringed the Candida albicans, that was provided in a tube and in a Petri´s plate, containing agar Sabouraud dextrose to compose the colonies and increase the Candida albicans population. Samples were diluted in physiological solution and seeded in the Petri´s plate, being incubated for two hours. After this time, we put the yogurt- containing the Lactobacillus bulgaricus and the Streptococcus thermophilus on the Petri´s plate. It was incubated in the heating chamber under 37oC for 48 hours. Results: After the incubation period, we verified that Candida albicans growing was inhibited, reducing the number of colonies in plates where the yogurt was seeded in. Conclusion: the Lactobacillus existent in the yogurt has an effective antifungal activity in vitro. Nowadays, few investigations were conducted in vitro, being necessary another studies to ensure the antifungal activity effectiveness of Lactobacillus present in yogurts
Subject(s)
Candida albicansABSTRACT
The Norwegian Scientific Committee for Food Safety (Vitenskapskomiteen for mattrygghet, VKM) has, at the request of the Norwegian Food Safety Authority (Mattilsynet; NFSA), assessed the risk of "other substances" in food supplements sold in Norway. These risk assessments will provide NFSA with the scientific basis while regulating the addition of “other substances” to food supplements and other foods. "Other substances" are described in the food supplement directive 2002/46/EC as substances other than vitamins or minerals that have a nutritional and/or physiological effect. It is added mainly to food supplements, but also to other foods. VKM has not in this series of risk assessments of "other substances" evaluated any claimed beneficial effects from these substances, only possible adverse effects. The present report is a risk assessment of Streptococcus thermopilus, and it is based on previous risk assessments and articles retrieved from a literature search. The risk of S. thermophilus was assessed for the general population. However, in previous assessments of “probiotics” published by VKM, concerns have been identified for specific groups. Therefore, the risk was assessed for the age group with immature gastro-intestinal flora (age group 0-36 months), population with mature gastro-intestinal flora (>3 years) and vulnerable groups independent of age. VKM has also assessed the risk of S. thermophilus in food supplements independent of the dose and have assessed exposure in general terms. Other sources of S. thermophilus, such as foods, have not been included in the present risk assessment. VKM concludes that it is unlikely that S. thermophilus causes adverse health effects in the general healthy population with mature gastro-intestinal tract. Acquired resistance genes have been detected in this species and the assessment of susceptibility to antibiotics for each single strain is required. However, no data on long-term adverse effects on infants and young children were identified. As evidence is accruing that the early microbial composition of the neonatal gut is important for the development of the gut flora and the immune system of the growing child, it is not possible to exclude that a daily supply of a single particular bacterial strain over a prolonged period of time to an immature gastro-intestinal tract may have long-term, although still unknown, adverse effects on that development.
ABSTRACT
El objetivo principal de esta investigación fue determinar las condiciones adecuadas de crecimiento del Lactobacillus delbrueckii subsp. bulgaricus y Streptococcus thermophilus para la producción de ácido láctico, utilizando como sustrato lactosuero proveniente del departamento del Cesar, Colombia. El ácido láctico es producto de la extracción y purificación de caldos de fermentación donde se usa como bacterias fermentativas el co-cultivo Lactobacillus delbrueckii subsp. bulgaricus y Streptococcus thermophilus, usualmente usadas para la producción de yogurt. El sustrato es suplementado con extracto de levadura, fosfato de amonio como fuente de nitrógeno y carbonato de calcio como neutralizante. Esto con el fin de optimizar el consumo, por parte de las bacterias, del carbohidrato principal presente en el suero (lactosa). Durante la fermentación se controló la concentración del inóculo y temperatura, el tiempo máximo fue 72 h. La purificación se llevó a cabo mediante esterificación, filtración de sólidos formados con la reacción y extracción de agua por evaporación y posterior arrastre con nitrógeno. Finalmente se obtuvo ácido láctico con un 78,0% de pureza (36,7 g/L), el cual se caracterizó a través de espectroscopía infrarroja.
O principal objetivo desta pesquisa foi determinar as condições adequadas de crescimento do Lactobacillus delbrueckii subsp. bulgaricus e Streptococcus thermophilus para a produção de ácido láctico utilizando como substrato soro de leite obtido do Departamento do Cesar, Colômbia. O ácido láctico é um produto da extração e purificação de caldos de fermentação, no qual são usadas como bactérias fermentativas Lactobacillus delbrueckiisubsp. bulgaricus e Streptococcus thermophilus, normalmente usadas para a produção de iogurte. O substrato é suplementado com extrato de levedura, fosfato de amonio como fonte de nitrogênio e de carbonato de cálcio como um neutralizador, para optimizar o consumo, pelas bactérias, do principal hidrato de carbono presente no soro (lactose). Durante a fermentação os seguintes fatores foram controlados: concentração do inóculo e temperatura, e atingiu num máximo de 72 h. A purificação foi efetuada por esterificação, filtração dos sólidos formados com a reação e remoção de água por evaporação e varrimento com nitrogênio. Finalmente o ácido láctico foi obtido com 78,0% de pureza (36,7 g/L), e foi caracterizado por espectroscopia de infravermelho.
The main objective of this research was to determine the proper growth conditions of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus for the production of lactic acid using serum as substract. This serum was obtain from the department of Cesar, Colombia. Lactic acid is the result of the extraction and purification of fermentation broths in which bacteria Lactobacillus delbrueckii subsp bulgaricus and Streptococcus thermophilus are used, which are usually used for the production of yogurt. The substrate was supplemented with yeast extract, ammonium phosphate as a nitrogen source, and calcium carbonate as a neutralizer, in order to optimize the consumption, by the bacteria, of the main carbohydrate present in serum (lactose). During the fermentation (up to 72 h) the inoculums concentration, and temperature were controlled. Purification consisted in esterification, filtration of solids formed during the reaction, and removing of water by evaporation and nitrogen influx. Finally, lactic acid was obtained with 78,0% purity (36.7 g/L), which was characterized by infrared spectroscopy.
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Objective: An investigation of isolation of Lactic acid bacteria was carried out under low temperature for the preparation of Yogurt by using various food supplements like carrot, ground-nut and tomato juices. Methods: Various samples of Cow milk, Skimmed milk were processed along with nutrients like Carrot, ground nut and tomato juices with Tryptone glucose yeast extract agar (TGYA) at different temperatures like 50C, 150C and 220C for the isolation of Lactic acid bacteria for the preparation of yogurt. The characteristic isolates were identified by using various biochemical tests and direct microscopy. Results: Lactic acid bacteria (LAB) dominated the microbial population of Yogurt, and were identified according to their morphological and physiological characteristics. Among these lactobacilli were frequently occurring organisms. The most abundant species were Lactobacillus delbrueckii subspecies Bulgaricus and Streptococcus thermophilus. The Lactic Streptococci was subjected to bio-chemical tests to identify the species. Based on the biochemical reactions the species was identified as Lactococcus Lactis, sub species di-acetylactis. Isolated culture of lactic Streptococci was found to grow at low temperature. When this was used as an inoculum to prepare yogurt at 50C, 150C and 220C curdling took place in 3days time. In order to reduce the setting time, nutrients in the form of carrot, ground-nut and tomato juices were added. The yogurt was found to set at 50C in 30hrs which is considered useful. Acidity of yogurt was found to be 0.53%- 0.55%. The yogurt was found to contain di-acetyl and quality of yogurt was good.
ABSTRACT
O objetivo do presente trabalho foi avaliar as características de físico-químicas e microbiológicas de queijo petit-suisse processado com a adição de duas cepas de Lactobacillus acidophilus: LA-14 (potencialmente probiótica) e La-5 (comprovadamente probiótica), utilizando Streptococcus thermophilus TA040 como cultura starter. Três queijos petit-suisse foram preparados: Q1 (controle:TA040), Q2 (TA040 + LA-14) e Q3 (TA040 +La-5). Foram realizadas análises microbiológicas (determinação das populações dos microrganismos La-5, La-14 e TA040) e físico-químicas (umidade e pH) após 1, 7, 14, 21 e 28 dias de armazenamento dos produtos a 4±1°C. As populações de L. acidophilus oscilaram entre 7,46 e 7,62 log UFC g -1 para La-5 e entre 6,39 e 6,83 log UFC g -1 para LA-14, evidenciando que a sobrevivência de L. acidophilus no produto depende de características particulares da cepa. Populações superiores da cultura starter foram observadas para Q2 (9,58 - 9,68 log UFC g -1 ) e Q3 (9,42 - 9,79 log UFC g -1 ), quando comparadas a Q1 (9,11 - 9,23 log UFC g -1 ), sugerindo sinergismo entre L. acidophilus e o starter. A umidade e o pH permaneceram estáveis e não diferiram entre os queijos após o 1º dia de armazenamento (p>0,05). As características peculiares das cepas de L. acidophilus determinaram os comportamentos distintos observados nos queijos petitsuisse, sendo possível detectar a melhor adaptação da cepa La-5 ao produto, o que resultou em populações significativamente superiores quando comparada a LA-14.
Particular behavior of different Lactobacillus acidophilus strains in petit-suisse cheese. The objective of this study was to evaluate the physico-chemical andmicrobiological characteristics of petit-suisse cheeses manufactured with the addition of two Lactobacillus acidophilus strains: LA-14 (potentially probiotic) and La-5 (probiotic culture), using Streptococcus thermophilus TA040 as starter culture. Three cheese-making trials were prepared: Q1 (control: with TA040), Q2 (with TA040 + LA-14), and Q3 (with TA040 + La-5). Parameters analyzed included microbial counts of probiotic, potentially probiotic and starter microorganisms, and physico-chemical parameters (pH and moisture) after 1, 7, 14, 21, and 28 days of storage of the product at 4±1°C. Viable counts of L. acidophilus remained between 7.46 and 7.62 log CFU g -1 for La-5, and between 6.39 and 6.83 log CFU g -1 for LA-14. As for the starter, higher populations were observed for Q2 (9.58 - 9.68 log CFU g -1 ) and Q3 (9.42 - 9.79 log CFU g -1 ), when compared to Q1, which suggests synergism between L. acidophilus and the starter culture. Moisture and pH values remained stable for cheeses Q1, Q2, and Q3, and no significant differences were detected between cheeses after the first day of storage (p>0.05). Particular features of both L. acidophilus strains determined different behavior in petit-suisse cheese, and the better adaptation of the La-5 to the product environment was perceptible, since higher populations were observed when compared to LA-14.
Subject(s)
Cheese/analysis , Food Technology/methods , Lactobacillus acidophilus/chemistry , Probiotics/chemistry , Streptococcus thermophilus/growth & development , Analysis of Variance , Cheese/microbiology , Food Microbiology , Food Storage/methods , Lactobacillus acidophilus/metabolism , Microbial Interactions/physiology , Time FactorsABSTRACT
The effects of the expression of a small heat shock protein (shsp) gene from Streptococcus thermophilus on stress resistance in Lactococcus lactis under different environmental stresses were investigated in this study. pMG36e-shsp, an expression vector, was first constructed by inserting a shsp open reading frame (ORF) cloned from S. thermophilus strain St-QC into pMG36e. Then, a food-grade expression vector, pMG-shsp, was generated by deleting the erythromycin resistance gene from pMG36e-shsp. The transformation rate of pMG-shsp was comparable to that of pMG36e-shsp when each of these two vectors was introduced into L. lactis. These results demonstrated that the shsp ORF could successfully used as a food-grade selection marker in both pMG-shsp and pMG36e-shsp. Furthermore, the growth characteristics were almost the same between L. lactis ML23 transformants harboring pMG36e or pMG-shsp. The survival rate of L. lactis ML23 expressing the shsp ORF were increased to 0.032%, 0.006%, 0.0027%, 0.03%, and 0.16% under the following environmental stresses: heat, acid, ethanol, bile salt and H2O2, respectively. These results indicated that the expression of the shsp gene in the food-grade vector pMG-shsp conferred resistance to environmental stresses without affecting the growth characteristics of L. lactis ML23.
Subject(s)
Humans , Drug Resistance , Erythromycin/pharmacology , Food Microbiology , Gene Expression , Lactobacillus , Streptococcus thermophilus/genetics , Methods , VirulenceABSTRACT
To analyze the exopolysaccharide (EPS) production by Streptococcus thermophilus ST1, cultures were cultivated in 10 percent (w/v) reconstituted skim milk under different growth conditions including various temperatures and pHs of growth medium, supplementation of the medium with various carbon sources (glucose, lactose, sucrose, galactose and fructose) and nitrogen source (whey protein concentrate, or WPC). The results showed that most EPS production by strain ST1 was obtained at a temperature (42°C) and pH (6.5) optimal for its growth. Supplementation of the skim milk medium with either carbohydrates or WPC increased both growth and polymer formation by different extents, with sucrose being most effective among the carbon sources tested. Under the optimal cultural conditions, i.e. pH 6.5, 42°C with 2 percent (w/v) sucrose and 0.5 percent (w/v) WPC, 135.80 mg l-1 of EPS was produced by strain ST1. The monosaccharide composition of the EPS was determined to be glucose and galactose (2:1), and the molecular mass of the EPS was 3.97 × 10(6) Da. The aqueous solution of the EPS at 1 percent (w/v) showed relatively high viscosity, indicating the potential of this EPS-producing S. thermophilus strain for applications in the improvement of physical properties of fermented milk products.
Subject(s)
/analysis , Yogurt/analysis , Milk , Polysaccharides, Bacterial , Streptococcus thermophilus/growth & development , Streptococcus thermophilus/isolation & purification , Food Microbiology , Food Samples , Methods , MethodsABSTRACT
The present investigation represents the effect of freeze drying on some properties as acid and bile tolerance of Streptococcus thermophilus MTCC 1938 culture isolated from dairy products. The cell paste obtained from milk based medium was freeze dried with a pressure of 50-100 mtorr for 24h at -40ºC. Acid and bile tolerance test exhibited 3.8-4.9 and 3.2-3.8 log counts reduction after freeze drying respectively.
Subject(s)
Lactic Acid/analysis , Cryoprotective Agents/analysis , Yeast, Dried/analysis , Dairy Products/analysis , Milk , Streptococcus thermophilus/isolation & purification , Food Microbiology , Food Samples , Freeze Drying , Methods , MethodsABSTRACT
Exopolysaccharides (EPSs) production was studied by Lactobacillus delbrueckii subsp. bulgaricus (B3, G12) and Streptococcus thermophilus (W22) in the medium containing various carbon sources (glucose, fructose, sucrose or lactose). For all the strains, glucose was the most efficient carbon source and B3, G12 and W22 strains produced 211, 175 and 120 EPS mg/L respectively. Also, the influence of different concentrations of glucose (5,10,15,20,25,30 g/L) on EPS production and growth was studied. The results indicated that EPS production and growth were stimulated by the high glucose concentration (30 g/L).
ABSTRACT
The typical yogurt flavor is caused by acetaldehyde produced through many different pathways by the yogurt starter bacteria L. bulgaricus and S. thermophilus. The attention was focused on one specific reaction for acetaldehyde and folic acid formation catalyzed by serine hydroxymethyltransferase (SHMT), encoded by the glyA gene. In S. thermophilus, this enzyme SHMT also plays the typical role of the enzyme threonine aldolase (TA) that is the interconvertion of threonine into glycine and acetaldehyde. The behavior of engineered S. thermophilus strains in milk fermentation is described, folic acid and acetaldehyde production were measured and pH and counts were followed. The engineered S. thermophilus strains StA2305 and StB2305, have the glyA gene (encoding the enzyme serine hydroxymethyltransferase) overexpressed. These engineered strains showed normal growth in milk when it was supplemented with Casitione. When they were used in milk fermentation it was observed an increase in folic acid and in acetaldehyde production by StA2305 and for StB2305 it was noticed a significative increase in folic acid formation.
O acetaldeído, responsável pelo sabor e aroma característicos de iogurte, é produzido por diferentes vias metabólicas pelas bactérias lácticas: Streptococcus thermophilus (S. thermophilus) e Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus). Neste trabalho, a atenção foi focada especificamente na reação para a formação de acetaldeído e de ácido fólico, catalisada pela enzima serina hidroximetil transferase (SHMT), codificada pelo gene glyA. A enzima SHMT catalisa diversas reações e, no caso da bactéria S. thermophilus, ela exerce também a atividade característica da enzima treonina aldolase (TA), definida como a interconversão do aminoácido treonina em glicina e acetaldeído. Foram construídas linhagens de S. thermophilus (StA2305 e StB2305) com super expressão do gene glyA. Estas linhagens modificadas apresentaram crescimento normal quando o leite foi suplementado com hidrolisado de caseína (Casitione). Quando foram usadas para fermentação de leite, observou-se: aumento na produção de ácido fólico e acetaldeído por StA2305 e aumento significativo na formação de ácido fólico por StB2305.
ABSTRACT
The typical yogurt flavor is caused by acetaldehyde produced through many different pathways by the yogurt starter bacteria L. bulgaricus and S. thermophilus. The attention was focused on one specific reaction for acetaldehyde and folic acid formation catalyzed by serine hydroxymethyltransferase (SHMT), encoded by the glyA gene. In S. thermophilus, this enzyme SHMT also plays the typical role of the enzyme threonine aldolase (TA) that is the interconvertion of threonine into glycine and acetaldehyde. The behavior of engineered S. thermophilus strains in milk fermentation is described, folic acid and acetaldehyde production were measured and pH and counts were followed. The engineered S. thermophilus strains StA2305 and StB2305, have the glyA gene (encoding the enzyme serine hydroxymethyltransferase) overexpressed. These engineered strains showed normal growth in milk when it was supplemented with Casitione. When they were used in milk fermentation it was observed an increase in folic acid and in acetaldehyde production by StA2305 and for StB2305 it was noticed a significative increase in folic acid formation.
O acetaldeído, responsável pelo sabor e aroma característicos de iogurte, é produzido por diferentes vias metabólicas pelas bactérias lácticas: Streptococcus thermophilus (S. thermophilus) e Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus). Neste trabalho, a atenção foi focada especificamente na reação para a formação de acetaldeído e de ácido fólico, catalisada pela enzima serina hidroximetil transferase (SHMT), codificada pelo gene glyA. A enzima SHMT catalisa diversas reações e, no caso da bactéria S. thermophilus, ela exerce também a atividade característica da enzima treonina aldolase (TA), definida como a interconversão do aminoácido treonina em glicina e acetaldeído. Foram construídas linhagens de S. thermophilus (StA2305 e StB2305) com super expressão do gene glyA. Estas linhagens modificadas apresentaram crescimento normal quando o leite foi suplementado com hidrolisado de caseína (Casitione). Quando foram usadas para fermentação de leite, observou-se: aumento na produção de ácido fólico e acetaldeído por StA2305 e aumento significativo na formação de ácido fólico por StB2305.