Cell enumeration and visualisation by transmission electron microscopy of Lactobacillus rhamnosus treated with cinnamon (Cinnamomum zeylanicum B.) essential oil

The use of essential oils (EOs) in functional foods containing probiotic microorganisms must consider the antimicrobial activity of these oils against beneficial bacteria such as Lactobacillus rhamnosus. This study aimed to evaluate the sensitivity of L. rhamnosus cultures treated with cinnamon EO through viable cell counts and visualisation by transmission electron microscopy. Cinnamon EO at a concentration of 0.04% had a bacteriostatic activity after 2 h of incubation. Although slight alterations were detected in the cell structure, this concentration was considered to be bactericidal, since it led to a significant reduction in cell numbers after 24 h. on the other hand, cinnamon EO at a 1.00% concentration decreased cell counts by 3 log units after 2 h incubation and no viable cell count was detected after 24 h. Transmission electron microscopy indicated that cells treated with 1.00% cinnamon EO were severely damaged and presented cell membrane disruption and cytoplasmic leakage.

Lactic acid production by new Lactobacillus plantarum LMISM6 grown in molasses: optimization of medium composition

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Improvement of L(+)-lactic acid production from cassava wastewater by Lactobacillus rhamnosus B 103

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Response surface optimization of D(-)-lactic acid production by Lactobacillus SMI8 using corn steep liquor and yeast autolysate as an alternative nitrogen source

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Floculação de leveduras por Lactobacillus fermentum em processos industriais de fermentação alcoólica avaliada por técnica fotométrica

Na produção de álcool por fermentação com leveduras, a floculação manifesta-se como um mecanismo natural de agregação de células. Essa condição pode ser induzida por vários fatores, entre eles, a interação entre bactérias floculentas como Lactobacillus fermentum e as leveduras. Esse fato torna-se prejudicial para o processo, pois tanto nas unidades que se utilizam do sistema de recuperação de células por centrifugação, como nas que não o utilizam, ocorrem perdas excessivas de fermento, em conseqüência dos problemas operacionais decorrentes da floculação, comprometendo seriamente o desempenho industrial. No presente trabalho, avaliou-se a floculação em vinho proveniente de fermentação experimental, sob duas condições de pH de fermento tratado utilizadas como inóculo e temperaturas de fermentação, não se observando diferenças significativas entre elas. Com este estudo, pôde-se ainda avaliar a capacidade de dispersão dos flocos em três condições de pH no tratamento do fermento em fase industrial, mostrando diferenças altamente significativas entre elas. A maior capacidade de dispersão no tratamento do fermento é desejável para o controle da floculação industrial, permitindo a sua centrifugação, com conseqüente separação das bactérias contaminantes do fermento. Essas constatações tornaram-se possíveis pelo emprego da técnica usual de determinação da floculação por espectrofotometria, modificada pela desfloculação prévia das amostras de vinho e fermento, o que conferiu maior estabilidade nas leituras.

Perfil fermentativo de silagens de cana-de-açúcar in natura ou queimada e tratadas ou não com Lactobacillus buchneri

Objetivou-se comparar as perdas, a dinâmica microbiológica e as alterações fermentativas e nutritivas de silagens de cana-de-açúcar in natura ou queimada e tratadas ou não com Lactobacillus buchneri durante o período de armazenamento. Os tratamentos foram cana-de-açúcar in natura ou tratada com L. buchneri e cana-de-açúcar queimada ou tratada com L. buchneri, avaliadas com 0, 1, 4, 7, 14, 28 e 56 dias de fermentação, em três repetições por tratamento. Apenas antes da ensilagem foi constatada diferença significativa na população de leveduras entre cana-de-açúcar in natura e queimada, cujos valores foram de 4,85 e 5,43 log ufc/g de forragem, respectivamente. No decorrer do tempo de fermentação, ocorreu redução da recuperação de matéria seca e as perdas se prolongaram até o dia 56. A concentração de etanol foi alta até o dia 28 e estável até o dia 56, sem diferença entre tratamentos. A digestibilidade verdadeira in vitro da matéria seca sofreu severa redução já no primeiro dia de armazenamento, chegando a reduzir cerca de 20 unidades percentuais aos 56 dias de armazenamento. Silagens de cana-de-açúcar queimada apresentam maiores perdas e alterações fermentativas e nutricionais que silagens de cana-de-açúcar in natura. O L. buchneri deve ser utilizado em silagens de cana-de-açúcar queimada, mas nas de cana-de-açúcar in natura seu uso é dispensável.

Effects of nutritional factors on growth of Lactobacillus fermentum mixed with Saccharomyces cerevisiae in alcoholic fermentation

The growth of Lactobacillus fermentum was studied in mixed culture with Saccharomyces cerevisiae during alcoholic fermentation of high test molasses (HTM). Yeast extract or a group of 17 amino acids caused a strong and fast decrease in yeast viability due to the strong increase of acidity produced by bacteria. Pure culture of Lactobacillus fermentum in dry sugar cane broth confirmed amino acids as the main nutrients needed to stimulate the growth of bacterial contaminant during alcoholic fermentation. The absence of L. fermentum growth was obtained when leucine: isoleucine or valine were not added to the medium. Phenylalanine, alanine, glutamic acid, cystine, proline, histidine, arginine, threonine, tryptophane, serine and methionine inhibited the bacterial growth at least in one of the cultures of L. fermentum tested.

Antibiosis associated to Lactobacillus acidophilus growth .1. Strain selection and study of an alternative medium using whey

The production of antimicrobial compounds of some strains of Lactobacillus acidophilus has been studied. They have been grown in whey supplemented with soy milk. It has been found that the production of compounds is able to inhibit the growing of both target bacteria analysed: Staphylococcus aureus and Escherichia coli. The results showed a significant variation (p>0.05) depending on the strain of L. acidophilus and on the level of supplementation utilized. Most of the inhibition observed resulted from the presence of the lactic acid produced. It has also been found the production of other antimicrobial compounds showing inhibitory capacity. The action of these compounds was influenced by the substract pH.

Evaluation in vitro of the antagonistic substances produced by Lactobacillus spp. isolated from chickens

To determine the inhibitory capacity of lactic acid bacteria due to the action of antagonistic substances, we tested 474 isolates of Lactobacillus from the crop and cecum of chickens against gram-positive and gram-negative indicator microorganisms by the spot-on-the-lawn and well-diffusion antagonism methods. of the 474 isolates, 265 demonstrated antimicrobial activity against the indicator microorganisms. Isolates identified as L. reuteri, L. salivarius, or Lactobacillus spp. inhibited Enterococcus faecalis, E. faecium, Listeria monocytogenes, and Salmonella spp. but not L. casei, L. delbrueckii, L. fermentum, or L. helveticus by the well-diffusion simultaneous antagonism method under anaerobic incubation conditions. The antagonistic substances produced by some of the Lactobacillus isolates were inactivated after treatment by proteolytic enzymes, which suggested that the substances could be antimicrobial peptides or bacteriocins.

Atividade antimicrobiana de Lactobacillus acidophilus, contra microrganismos patogênicos veiculados por alimentos

The antimicrobial activity of a commercial probiotic culture, Lactobacillus acidophilus (La5), was tested against two foodborne pathogens, Escherichia coli and Staphylococcus aureus. The antagonistic effect of the probiotic culture in vitro was performed by applying both Multilayer Agar Plate and Agar Well Diffusion methods. The results indicated that the inhibitory substance present on 72 hours culture broth supernatant was extracellular and diffusible. The incubation period of the lactic acid bacteria on MRS Broth, at 3 7 degrees C in aerobic conditions, for the highest lactic acid production (1,08 g/%) was 72 hours, which gave a minimum pH value of the supernatant (3,90) and the best inhibition results by the Well Diffusion Agar Assay, showing inhibition zone diameters of 14,75mm and 15,0mm for E. coli and S. aureus, respectively. The inhibitor compound was not sensitive to proteolytic enzyme and freezing, but was totally inactivated when the supernatant was neutralized with NaOH 1 N solution. The results suggest that the inhibitory activity was due to the lactic acid concentration and the low pH of the probiotic culture broth.

Haemagglutination induced by Bordetella pertussis filamentous haemagglutinin adhesin (FHA) is inhibited by antibodies produced against FHA(430-873) fragment expressed in Lactobacillus casei

Filamentous haemagglutinin adhesin (FHA) is an important virulence factor from Bordetella pertussis related to the adhesion and spread of the bacteria through the respiratory tract. Three distinct domains have been characterized in mature FHA, and among them, the FHA(442-863) fragment was suggested to be responsible for the heparin-binding activity. In this study, we cloned the gene encoding the HEP fragment (FHA(430-873)) in a Lactobacillus casei-inducible expression vector based on the lactose operon. The recombinant bacteria, transformed with the resulting construct (L. casei-HEP), were able to express the heterologous protein depending on the sugar added to the culture. Subcutaneous inoculation of L. casei-HEP in Balb/C mice, using the cholera toxin B subunit as adjuvant, induced systemic anti-HEP antibodies that were able to inhibit in vitro erythrocyte haemagglutination induced by FHA. This is the first example of a B. pertussis antigen produced in lactic acid bacteria and opens new perspectives for alternative vaccine strategies against whooping cough.

Antibiosis associated to Lactobacillus acidophilus growth .2. Optimization of some culture parameters in whey and soy milk medium

Whey supplemented with soy milk has been used as a low-cost alternative in the growth of Lactobacillus acidophilus for the production of antimicrobial compounds. Response Surface Metodology has been employed in order to study the effects of initial pH, incubation temperature and soy milk rate for supplementation in the production of antimicrobial substance. It has been observed that both tested microrganisms used (S. aureus and E. coli) were inhibited by antimicrobial substance produced by L. acidophilus. The results obtained with E. coli inhibition did not follow the employed statistical model. on the other hand, when the tested microorganism S. aureus was used, the best inhibition results have been obtained when L. acidophilus was incubated at 36.80 degrees C in whey with 5.6 initial pH and 31,90% (v/v) rate supplemented with soy milk. The analysed antimicrobial substances were nor acids neither hidrogen peroxid.