João Carlos Teixeira Dias

Metabolism of benzonitrile by Cryptococcus sp. UFMG‐Y28

The yeast Cryptococcus sp. UFMG‐Y28 can utilize benzonitrile as a nitrogen and possible additional carbon source. The kinetics of growth on Yeast Carbon Base (YCB) added of benzonitrile as sole nitrogen source showed that benzonitrile was metabolized to benzoic acid and ammonia. Liquid chromatography analysis indicated that Cryptococccus sp. UFMG‐Y28 metabolized 12 mM benzonitrile to 10 mM benzoic acid. Resting cells cultivated on YCB‐propionitrile medium showed nitrilase activity against benzonitrile. This strain appears to be promising for bioconversion of nitriles to high value acids and for bioremediation of sites contaminated with aliphatic and aromatic nitriles.

The use of acetonitrile as the sole nitrogen and carbon source by Geotrichum sp. JR1

A yeast strain identified as Geotrichum sp. JR1 was able to use acetonitrile as the sole carbon and nitrogen source. The strain grew in 0.5 to 2M acetonitrile. Ammonia generation as enzymatic product during the strain growth indicates the presence of an acetonitrile degrading enzyme. Acetic acid and acetamide were detected during assays with the resting cells cultivated in acetonitrile, indicating the presence of nitrile and amide degrading enzymes. This paper is the first to describe the use of acetonitrile as the sole carbon and nitrogen source by a yeast.

Biodegradation of acetonitrile by cells of Candida guilliermondii UFMG-Y65 immobilized in alginate, kappa-carrageenan and citric pectin

Na degradacao de acetonitrila, foram testadas celulas livres de Candida guilliermondii UFMG-Y65 e imobilizadas em diferentes suportes, quais sejam, Ba-alginato, k-carrageno e pectina citrica. A velocidade de degradacao da acetonitrila foi monitorada por 120 h, mediante o crescimento da levedura e geracao de amonia. Diferentes concentracoes de alginato nao afetam a viabilidade das celulas; mas o periodo de incubacao, em solucao de BaCl2, reduziu o numero de celulas vivas. Da mesma forma, a natureza do gel e a estrutura da matriz do suporte, ambas resultantes das condicoes de imobilizacao das celulas, foram de fundamental importância para a atividade catalisadora e sua performance; afetando assim, os padroes de crescimento microbiano e a de atividade enzimatica. As celulas imobilizadas em alginato degradaram acetonitrila com maior eficacia do que as imobilizadas em k-carrageno ou as celulas imobilizadas em pectina citrica.

Gold and silver accumulation by Aspergillus niger from cyanide-containing solution obtained from the gold mining industry

An Aspergillus niger strain accumulated gold and silver from solution containing high cyanide concentrations. Our results show that A. niger is of potential use for the removal of metals and/or the recovery of valuable metals from cyanide-containing solutions.

High prevalence of Salmonella in tegu lizards (Tupinambis merianae), and susceptibility of the serotypes to antibiotics.

Species of tegu (Tupinambis) are the largest lizards in South America. Large numbers of these lizards are hunted; there is a vigorous trade in their skins and the meat is consumed by rural and native peoples. The animals are also bred in captivity, an economic activity for rural populations which can help in the animals’ conservation. Faecal samples from 30 captive‐born tegus were analysed for the presence of Salmonella in two separate samplings. In the first analysis, samples from 26 animals (87%) yielded Salmonella enterica of which 23% were of Rubislaw serotype; 20% Carrau and Agona serotypes; 7% Infantis and Saint‐Paul serotypes; 3% Panama and Brandenburg serotypes; 10% were S. enterica subsp. enterica and 7% were rough form. In the second analysis, four tegus (13%) which had been negative in the first sampling were positive, thus, 100% of the animals studied carried the bacterium. Antibiotic susceptibility showed resistance to sulfonamide in 82% of the isolates, streptomycin in 64%, tetracycline in 6% and Chloramphenicol in 20%. Two animals carried strains of the same serotype with different patterns of antibiotic susceptibility. Although it is well known that reptiles are a significant source of Salmonella, to our knowledge, its prevalence in tegu has not been studied previously.

EFFECTS OF IMMOBILIZATION IN Ba-ALGINATE ON NITRILE-DEPENDENT OXYGEN UPTAKE RATES OF CANDIDA GUILLIERMONDII

Yeast cells immobilized by entrapment in Ba-alginate gel were investigated for growth pattern and respiratory activity. The oxygen uptake rates (OUR) of cells entrapped in gels with 4% alginate were 5.2 and 23% lower than the OUR of 2% alginate and free cells, respectively. The mass-transfer resistance offered by the matrix and growth of the entrapped cells determine a gradient of nutrients throughout the gel which is responsible for both a lower specific growth rate of immobilized cells with respect to that of free ones, and a heterogeneous biomass distribution, with progressively increasing cellular density from the inside to the outside of the matrix. Gel-matrix polymer concentration affected the maximum oxygen uptake of immobilized growing yeast cells.

Cyano-metal complexes uptake by Aspergillus niger

Aspergillus niger was grown in an industrial gold mining solution containing cyano-metal complexes. Gold, silver, copper, iron and zinc were accumulated, and the major mechanism of metal uptake involved metal precipitation on the cell surface. This could be achieved by the extensive application of instrumental analyses combined to the study of the chemical composition of the solutions, before and after contact with the fungus.

Microbial surfactant activities from a petrochemical landfarm in a humid tropical region of Brazil

The goal of this study was to assess the presence and surfactant potential of naturally occurring microbes from a tropical soil with petrochemical contamination. Microorganisms in a soil sample from a Brazilian landfarm were isolated and grown on petroleum as the sole carbon source. Of 60 isolates screened for petroleum-based growth, 7 demonstrated surfactant activities by the drop-collapse methodology over various types of oils. From their growth profiles in liquid culture during 132 h, all had their first detection of surfactant activity after 96 h. Little is currently known about biosurfactant-producing microorganisms in tropical environments contaminated by hydrophobic compounds, and the search for them is essential for bioremediation and for oil recovery enhanced by microbes. Our results indicate that different petroleum-grown microorganisms showing surfactant activity can be recovered from landfarm soil in a tropical environment.

Degradation of thiocyanate by immobilized cells of mixed and pure cultures

Thiocyanate is frequently found in industrial wastewater such as those from coal, gold and silver mining. Although the microbial degradation of thiocyanate has been well documented, scarce information is available on the heterotrophic degradation of thiocyanate. A pure bacteria strain (BMV8) and a mixed culture of bacteria and fungi were isolated by an enrichment method from a fixed bed bioreactor for cyanide and thiocyanate removal and they were able to metabolize thiocyanate heterotrophically as a nitrogen source. The efficiency of thiocyanate biodegradation decreased when the cells were immobilized in citric pectin. The immobilized mixed culture was able to degrade thiocyanate more efficiently than the BMV8 strain.

Aerobic granular sludge to treat paper mill effluent: selection of ideal strains that contribute to the formation of strong aggregates

AbstractThe formation of aerobic granules after the treatment of paper mill effluents was feasible. Granular sludge presented a lower fouling potential than flocculent sludge, allowing a higher flux through the membranes in a membrane bioreactor (MBR). However, it was observed that after filtration many of the biogranules disrupted, which increased the membrane fouling. Therefore, the formation of aggregates that are physically and mechanically more resistant to decomposition would be beneficial to an MBR process. This work determines which of the microorganisms found in the aerobic granular sludge contribute to microbial aggregation, thereby increasing the mechanical resistance of aggregates. Nineteen strains were isolated from granular aerobic sludge. Tests for coaggregation showed that some isolates (E2, E7, E9, E13, and E25) were able to improve the formation of granules, while others (E10, E14, E18, and E26) inhibited the aggregation. The extracellular polymeric substances analyses indicated which su...