Suzana Cláudia Silveira Martins

Immobilization of microbial cells: A promising tool for treatment of toxic pollutants in industrial wastewater

The review articles on cell immobilization have been published since 1980 and reflect the general interest in this topic. Immobilized microbial cells create opportunities in a wide range of sectors including environmental pollution control. Compared with suspended microorganism technology, cell immobilization shows many advantages, such as resistance to toxic chemicals. This review presents the potential of immobilized microbial cells for treatment of toxic pollutants in industrial wastewater, the fundamentals, history and advantages of immobilized cells compared with suspended cells, characteristics of support materials and the principal methods of immobilization, with special emphasis for natural immobilization by cell adsorption. Keywords : Cell immobilization, microorganisms, adsorption, toxic pollutants, wastewater African Journal of Biotechnology Vol. 12(28), pp. 4412-4418

Influence of the copepod Mesocyclops longisetus (Crustacea: Cyclopidae) on the survival of Vibrio cholerae O1 in fresh water

In an experimental microcosm, an analysis was performed of the influence exerted by freshwater Mesocyclops longisetus copepods on the survival of Vibrio cholerae O1 serovar Inaba. In the State of Ceará, copepods are used in the control of Aedes aegypti larvae. The system consisted of water with a salinity of 0.27 per 10,000 habitants and pH 7.5, which after sterilizing filtration was distributed into seven flasks with a volume of 400 ml; in each of six flasks, 10 live copepods were inoculated along with 1 ml of an 8-hour culture of Vibrio cholerae O1 at 37oC in Alkaline Peptone Water, resulting in a concentration of 3.80x10(4) colony-forming units. The control flask contained only the water with the same bacterial suspension. The system was maintained for six days at room temperature (25-28oC), and daily duplicate counts were performed in TCBS Agar. Results confirmed a clear association between Vibrio cholerae O1 and the live copepods, based on survival of the bacteria at compatible levels with the initial inoculation until the sixth day of the analysis.

Selection of culturable environmental microbial strains for cellular immobilization: Association of phenotypic adhesive characteristics and quantitative cellular retention

Environmental pollution by organic compounds is a global problem. Biological treatment methods are used to restore polluted environments. Microbial immobilization on abiotic surfaces is a recent strategy to improve the efficiency of these processes. In this technique, cell adhesion is a fundamental step for subsequent colonization and biofilm formation. Therefore, the use of strains with adhesive properties is a critical factor for successful immobilization. In this work, culturable environmental microbial strains were phenotypically characterized regarding their hydrophobicity, adhesion to polystyrene and production of exopolysaccharides and amyloid fibers. The cell retention was quantified by counting viable cells using polyurethane foam as material support. The degree of hydrophobicity varied from moderately hydrophobic to hydrophilic, while the adhesion to polystyrene and production of exopolysaccharides and amyloid fibers ranged from strong to negative. The results of qualitative tests were transformed into scores and a direct relationship between the qualitative characteristics and number of adhered cells on polyurethane foam was observed. The Gram-negative bacterium Serratia marcescens and the yeast Candida rugosa showed the best results and were selected for further immobilization tests. Key words : Hydrophobicity, cell adhesion, cell immobilization, Serratia marcescens, Candida rugosa.

Facilitation as Attenuating of Environmental Stress among Structured Microbial Populations

There is currently an intense debate in microbial societies on whether evolution in complex communities is driven by competition or cooperation. Since Darwin, competition for scarce food resources has been considered the main ecological interaction shaping population dynamics and community structure both in vivo and in vitro. However, facilitation may be widespread across several animal and plant species. This could also be true in microbial strains growing under environmental stress. Pure and mixed strains of Serratia marcescens and Candida rugosa were grown in mineral culture media containing phenol. Growth rates were estimated as the angular coefficients computed from linearized growth curves. Fitness index was estimated as the quotient between growth rates computed for lineages grown in isolation and in mixed cultures. The growth rates were significantly higher in associated cultures than in pure cultures and fitness index was greater than 1 for both microbial species showing that the interaction between Serratia marcescens and Candida rugosa yielded more efficient phenol utilization by both lineages. This result corroborates the hypothesis that facilitation between microbial strains can increase their fitness and performance in environmental bioremediation.

PRODUÇÃO DE ENZIMAS HIDROLÍTICAS EXTRACELULARES POR ACTINOBACTÉRIAS ORIUNDAS DO SOLO E SERRAPILHEIRA DE REGIÃO SEMIÁRIDA

Actinobacteria are microorganisms that produce a remarkable variety of secondary metabolites. Among these products, the enzymes stand out due to their wide biotechnological and industrial applicability. In addition, these bacteria are responsible for important ecological interactions in soils. The production of hydrolytic enzymes, amylase and cellulase was analyzed and compared to 58 strains of actinobacteria from the soil and litter collected at the Aiuaba Ecological Station (Ce), ENCICLOPÉDIA BIOSFERA, Centro Científico Conhecer Goiânia, v.15 n.27; p. 2018 35 a semi-arid region of northeastern Brazil. The degradation halo in the amylase test was observed in 98.27% of the strains while in the cellulolytic test was 75.86%. Statistical tests showed that there was no significant difference in the enzymatic activity of soil and litter strains. It was concluded that the production of the amylase was higher than the cellulase and that the origin of actinobacteria did not affect significantly its enzymatic activity.

PRODUÇÃO DE CELULASE E AMILASE POR ACTINOBACTÉRIAS DO SEMIÁRIDO BRASILEIRO

Soils are the basis of all terrestrial ecosystems housing a wide diversity of organisms that have vital role in maintaining their biological characteristics. As part of this diverse environment are the actinobcteria, a microbial group that have important ecological functions such as recycling of organic compounds cellulose and starch of high chemical complexity and wide availability in soil. In view of the biological and

Enzymatic activity of actinobacteria from semiarid

Actinobacterias are Gram-positive bacterias found in soil and are distinguished by their production of hydrolytic enzymes, such as amylase and cellulase. These enzymes degrade starch and cellulose, respectively, which are abundant substrates in soil, but that are unavailable for use by other organisms due to their chemical complexity. These bacteria grow in extreme conditions, such as those prevalent in the Brazilian semi-arid northeast, where there are also few studies about this microbial group. Thus, due to the growing interest in the biological functioning of the soil, together with the biotechnology aspect, this work aimed to evaluate the enzymatic activity of twenty eight strains of actinobacteria of the genus Streptomyces, Terrabacter, Nocardia, and Micromonospora obtained from the soil samples of the Ubajara National Park in the state of Ceará. The amylolytic and cellulolytic activities were determined by the enzymatic index corresponding to the relation between the diameter of hydrolysis halo, in millimeters, and the diameter in millimeters of the colony of each strain. The cellulolytic and amylolytic indexes were detected in 75% and 85% of the evaluated strains, respectively. One of the strains evaluated stood out with an enzyme cellulase index equal to 6.90 while the highest rate for amylase was 6.23. The results indicated the ecological and biotechnological potential of actinobacteria from the soil of analyzed region.