Marcia Nitschke

Biosurfactants as Agents to Reduce Adhesion of Pathogenic Bacteria to Polystyrene Surfaces: Effect of Temperature and Hydrophobicity

Polystyrene surfaces were conditioned with surfactin and rhamnolipid biosurfactants and then assessed regarding the attachment of Staphylococcus aureus, Listeria monocytogenes, and Micrococcus luteus. The effect of different temperatures (35, 25, and 4°C) on the anti-adhesive activity was also studied. Microbial adhesion to solvents and contact angle measurements were performed to characterize bacteria and material surfaces. The results showed that surfactin was able to inhibit bacterial adhesion in all the conditions analyzed, giving a 63–66% adhesion reduction in the bacterial strains at 4°C. Rhamnolipid promoted a slight decrease in the attachment of S. aureus. The anti-adhesive activity of surfactin increased with the decrease in temperature, showing that this is an important parameter to be considered in surface conditioning tests. Surfactin showed good potential as an anti-adhesive compound that can be explored to protect surfaces from microbial contamination.

Surfactin reduces the adhesion of food‐borne pathogenic bacteria to solid surfaces

Aims:  To investigate the effect of the biosurfactants surfactin and rhamnolipids on the adhesion of the food pathogens Listeria monocytogenes, Enterobacter sakazakii and Salmonella Enteritidis to stainless steel and polypropylene surfaces.

Influence of growth media and temperature on bacterial adhesion to polystyrene surfaces

Bacterial adhesion to inert surfaces is a complex process influenced by environmental conditions. In this work, the influence of growth medium and temperature on the adhesion of Pseudomonas aeruginosa, Serratia marcescens, Staphylococcus aureus, Micrococcus luteus and Listeria monocytogenes to polystyrene surfaces was studied. Most bacteria demonstrated the highest adhesion when cultured in TSYEA, except S. marcescens, which showed to be positively influenced by the pigment production, favored in poor nutrient media (lactose and peptone agar). P. aeruginosa adhesion to polystyrene increased at low temperatures whatever the medium used. The culture medium influenced the surface properties of the bacteria as assessed by the MATS test.

Purification and characterization of a surfactin-like molecule produced by Bacillus sp. H2O-1 and its antagonistic effect against sulfate reducing bacteria

BackgroundBacillus sp. H2O-1, isolated from the connate water of a Brazilian reservoir, produces an antimicrobial substance (denoted as AMS H2O-1) that is active against sulfate reducing bacteria, which are the major bacterial group responsible for biogenic souring and biocorrosion in petroleum reservoirs. Thus, the use of AMS H2O-1 for sulfate reducing bacteria control in the petroleum industry is a promising alternative to chemical biocides. However, prior to the large-scale production of AMS H2O-1 for industrial applications, its chemical structure must be elucidated. This study also analyzed the changes in the wetting properties of different surfaces conditioned with AMS H2O-1 and demonstrated the effect of AMS H2O-1 on sulfate reducing bacteria cells.ResultsA lipopeptide mixture from AMS H2O-1 was partially purified on a silica gel column and identified via mass spectrometry (ESI-MS). It comprises four major components that range in size from 1007 to 1049 Da. The lipid moiety contains linear and branched β-hydroxy fatty acids that range in length from C13 to C16. The peptide moiety contains seven amino acids identified as Glu-Leu-Leu-Val-Asp-Leu-Leu.Transmission electron microscopy revealed cell membrane alteration of sulfate reducing bacteria after AMS H2O-1 treatment at the minimum inhibitory concentration (5 μg/ml). Cytoplasmic electron dense inclusions were observed in treated cells but not in untreated cells. AMS H2O-1 enhanced the osmosis of sulfate reducing bacteria cells and caused the leakage of the intracellular contents. In addition, contact angle measurements indicated that different surfaces conditioned by AMS H2O-1 were less hydrophobic and more electron-donor than untreated surfaces.ConclusionAMS H2O-1 is a mixture of four surfactin-like homologues, and its biocidal activity and surfactant properties suggest that this compound may be a good candidate for sulfate reducing bacteria control. Thus, it is a potential alternative to the chemical biocides or surface coating agents currently used to prevent SRB growth in petroleum industries.

Recent food applications of microbial surfactants

ABSTRACT Owing to their natural origin and environmental compatibility, interest in microbial surfactants or biosurfactants has gained attention during last few years. These characteristics fulfill the demand of regulatory agencies and society to use more sustained and green chemicals. Microbial-derived surfactants can replace synthetic surfactants in a great variety of industrial applications as detergents, foaming, emulsifiers, solubilizers, and wetting agents. Change in the trend of consumers toward natural from synthetic additives and the increasing health and environmental concerns have created demand for new “green” additives in foods. Apart from their inherent surface-active properties, biosurfactants have shown antimicrobial and anti-biofilm activities against food pathogens; therefore, biosurfactants can be versatile additives or ingredients of food processing. These interesting applications will be discussed in this review.

Biossurfactantes: propriedades anticorrosivas, antibiofilmes e antimicrobianas

Due to the importance of biofilms in the food industry, new products are being developed to enhance the efficiency of cleaning food-contact surfaces. Biosurfactants could be an alternative to synthetic products. The major advantages of biosurfactants over synthetic detergents are their low toxicity and highly biodegradable nature. Biosurfactants may also exhibit antimicrobial, anti-adhesive and anticorrosive activity concomitantly. In this review, we emphasize the potential application of biosurfactants as surface coating agents to prevent corrosion and decrease planktonic and sessile microbial growth.

Produção de biotensoativos a partir de resíduos de óleos e gorduras

O presente trabalho visou a selecao de microrganismos com capacidade de produzir biotensoativos a partir de residuos de oleos e gorduras gerados em restaurantes e industrias alimenticias. Borra de soja, gordura de frango, gordura vegetal hidrogenada e oleo de soja usado em frituras foram estudados como fonte de carbono. Os isolados LMI 6c e LMI 7a, ambos pertencentes ao genero Pseudomonas, foram selecionados como potenciais produtores de biotensoativos. Dentre os residuos propostos, a borra de soja foi considerada o melhor substrato, gerando 9,69 g.L-1 de ramnolipidios e uma tensao superficial de 31 mN/m.

Biodegradation of Chlorpyrifos by Whole Cells of Marine-Derived Fungi Aspergillus sydowii and Trichoderma sp

This paper describes the screening of the growth of seven marine-derived fungi strains in the presence of chlorpyrifos in solid medium. The strains that showed best growth were A. sydowii CBMAI 935 and Trichoderma sp. CBMAI 932. Biodegradation reactions were performed in 10, 20 and 30 d in liquid medium containing commercial chlorpyrifos and mycelia from the selected strains. In 30 d, A. sydowii CBMAI 935 and Trichoderma sp. CBMAI 932 were able to degrade on average 63% and 72% of chlorpyrifos, respectively, and reduce the concentration of 3,5,6-trichloro-2-pyridinol, the metabolite formed by the enzymatic hydrolysis of chlorpyrifos. In 30 d, A. sydowii CBMAI 935 and Trichoderma sp. CBMAI 932 could use chlorpyrifos as sole source of carbon with low biodegradation percentages, 24% and 5%, respectively. Spontaneous hydrolysis was evaluated in malt medium, with the complete disappearance of chlorpyrifos. In distilled water, 61% of chlorpyrifos was hydrolyzed in 30 d.

Biodegradação bacteriana de compostos organoclorados

BACTERIAL BIODEGRADATION OF ORGANOCHLORIDE COMPOUNDS. Due to their recalcitrant nature, organochlorides are already found in environment and the search for alternatives to eliminate these compounds such as biodegradation using native microorganisms is of great interest. A screening trial to select environmental bacteria able to degrade DDD, PCP and dieldrin was conducted. Among 14 isolates, the soil bacteria Pseudomonas aeruginosa L2-1 showed the highest tolerance to increasing concentrations of the organochlorides and was selected for further studies. Biodegradation was assessed in liquid medium, varying the concentrations of glucose and the presence of rhamnolipids (RL). The best medium for the occurrence of biodegradation of the compounds contained 0.5% glucose, giving approximately 50% yield after three days of incubation. Results showed that the biodegradation rates of the organochlorides by P. aeruginosa L2-1 were greater at low concentrations of glucose and in the presence of rhamnolipids.

The antibacterial activity of rhamnolipid biosurfactant is pH dependent

Rhamnolipid (RL) biosurfactants have been studied as agents to control the growth of food pathogens however, to be successful applied as antimicrobial agent in food, is important to determine the effect of environmental conditions on RL activity. Once pH is a determinant factor to the development of microorganisms in food, we investigated the antimicrobial activity of RL under different pH values. The antimicrobial activity of RL against the Gram-positive pathogens L. monocytogenes, B. cereus and S. aureus was pH dependent and favored at more acidic conditions while the Gram-negative Salmonella enterica and E. coli (EHEC) showed resistance at all pH levels studied. Bacillus cereus was the most sensitive bacteria showing MIC of 19.5 μg/mL and eradication of the population was observed after 30 min with 39.1 μg/mL of RL. The sensitivity to RL was associated with reduction on cell surface hydrophobicity and cytoplasmic membrane damage. Scanning Electron Microscopy images evidenced the cell damage promoted by RL on sensitive strains. The pH is an important factor to be considered on developing RL-based strategies to the control of food pathogens.