Molecular diversity of mesophilic and thermophilic bacteria in a membrane bioreactor determined by fluorescent in situ hybridization with mxaF- and rRNA-targeted probes.

An evaluation of the efficiency of treatment of kraft mill foul condensates in a membrane bioreactor was carried out in the laboratory. Efficiency and rate of methanol removal were quantified at operating temperatures of 35, 45 and 55 degrees C. The structure of the bacterial community present in the reactor biomass at the different operating temperatures was evaluated by in situ hybridization of the biomass samples with fluorescently-labelled probes (FISH) targeting the Eubacteria, the alpha, beta and gamma subclasses of the Proteobacteria, the low G + C content Gram-positive bacteria (Bacillus spp.), while community function was evaluated by in situ hybridization with a methanol dehydrogenase gene (mxaF) probe. Methanol removal efficiency decreased from 99.4 to 92%, and removal rate from 2.69 mg MeOH/l x min to 2.49 mg MeOH/l x min when the operating temperature was increased from 35 to 55 degrees C. This decrease in methanol removal was accompanied by a decrease (from 58% to 42%) in the relative proportion of cells that hybridized with the mxaF probe. The relative proportion of Bacillus spp. increased from 5 to 20% while the proportion of members of the alpha subclass of Proteobacteria decreased from 16% to 6% when the bioreactor operating temperature was raised from 35 to 55 degrees C. The relative proportions of bacteria belonging to the beta (22-25%) and gamma (18-20%) subclasses of the Proteobacteria remained relatively constant regardless of operating temperature. Proteobacteria (alpha, beta and gamma subclasses) and Bacillus spp. represented 61, 67 and 71% of the Eubacteria in the biomass sampled at 35, 45 and 55 degrees C, respectively. The FISH technique was shown to be an efficient method for detection of both structural and functional changes in the bacterial communities that could be related to efficiency of methanol removal in a membrane bioreactor operating at different temperatures.

Phenol degradation by a Graphium sp. FIB4 isolated from industrial effluents.

In this work, we show that the fungal strain Graphium sp. FIB4 was able to use phenol as the sole carbon source. Higher degradation of phenol was accomplished by alginate-immobilized mycelial mass than by mycelial suspensions of Graphium sp. FIB4. Free mycelium exhibited higher degradation rates when compared with the alginate-immobilized mycelium in the presence of 14 mM of phenol or less. Above this concentration, degradation rates by free mycelium decreased and the immobilized mycelium showed higher values. The maximum degradation rate for 8 mM phenol was found to be 20.13 mg/l x h by free mycelia and 16.24 mg/l x h by immobilized mycelial mass in the presence of 18 mM phenol. When the fungus was grown on medium without phenol, catechol 1,2-dioxygenase activity was not detected. This enzyme activity was induced at phenol concentrations as low as 0.05 mM and up to 6 mM at 24 h incubation at 30 degrees C, suggesting that catechol was oxidized by the ortho type of ring fission. Addition of glucose reduced phenol consumption rate, and both substrates were used simultaneously. Glucose concentrations higher than 0.075% repressed the induction of phenol oxidation by Graphium sp. FIB4 grown on glucose. But glucose did not fully repress utilization of phenol by phenol-pre-induced cells. Immobilization and addition of calcium and barium ions were detrimental to the stability of catechol 1,2-dioxygenase activity and phenol degradation by Graphium sp. FIB4.

Phenol degradation by yeasts isolated from industrial effluents.

Yeast strains of the genera Aureobasidium, Rhodotorula and Trichosporon were isolated from stainless steel effluents and tested for their ability to utilize phenol as the sole carbon source. Fourteen strains grew in the presence of up to 10 mm phenol. Only the strain Trichosporon sp. LE3 was able to grow in the presence of up to 20 mm phenol. An inhibitory effect was observed at concentrations higher than 11 mm, resulting in reduction of specific growth rates. Phenol degradation was a function of strain, time of incubation and initial phenol concentration. All strains exhibited activity of catechol 1,2-dioxygenase and phenol hydroxylase in free cell extracts from cells grown on phenol, suggesting that catechol was oxidized by the ortho type of ring fission. Addition of glucose and benzoate reduced the phenol consumption rate, and both substrates were used simultaneously. Glucose concentrations higher than 0.25% inhibited the induction of phenol oxidation by non-proliferating cells and inhibited phenol oxidation by pre-induced cells.

Biodegradation of acetonitrile by cells of Candifa Guillermondii UFMG-Y65 immobilized in alginate, kcarrageenan and citric pectin

Different encapsulation matrices were tested for immobilized cells of Candida guillermondii UFMG-Y65 used for acetonitrile degradation. Acetonitrile degradation by free cells and cells immobilized in Ba-alginate, k-carrageenan and citric pectin was studied. The rate of acetonitrile degradation was monitored for 120h by measuring yeast growth and ammonia concentration. Different alginate concentrations did not affect cell viability, but the period of incubation in BaCl(2) solution reduced the number of viable cells. Likewise, the gel nature and the matrix structure of the support resulting from the cell immobilization conditions were of fundamental importance for biocatalyst activity and performance, affecting substantially the patterns of microbial growth and enzymatic activity. Alginate-immobilized cells degraded acetonitrile more efficiently than k-carrageenan or citric pectin-immobilized cells.

Utilization of nitriles by yeasts isolated from a Brazilian gold mine.

Yeast strains from the genera Candida, Debaryomyces, Aureobasidium, Geotrichum, Pichia, Rhodotorula, Tremella, Hanseniaspora, and Cryptococcus were isolated from samples of a gold mine from liquid extraction circuit. These strains were tested for their ability to utilize acetonitrile at 12 mM as the sole nitrogen source. The yeasts that grew using acetonitrile at 12 mM were tested in the presence of acetonitrile, isobutyronitrile, methacrylnitrile, and propionitrile at concentrations of 12, 24, 48, 97, and 120 mM. One strain was selected for each nitrile and the concentration of nitrile in which the best growth occurred. Cryptococcus sp. strain UFMG-Y28 had a better growth on 120 mM propionitrile and 97 mM acetonitrile, Rhodotorula glutinis strain UFMG-Y5 on 48 mM methacrylnitrile, and Cryptococcus flavus strain UFMG-Y61 on 120 mM isobutyronitrile. The utilization of different nitriles and amides by yeast strains involves hydrolysis in a two-step reaction mediated by both inducible and intracellular nitrile hydratase and amidase.