Influence of agitation and aeration in xanthan production by Xanthomonas campestris pv pruni strain 101.

Production, viscosity, and chemical composition of xanthan synthesized by bacterium Xanthomonas campestris pv pruni strain 101 were evaluated in bioreactor systems. During the process, the volumetric oxygen mass transfer coefficient (k(L)a) and the biomass were determined and the pH was monitored. The cultures were grown in a 3 I bioreactor, with aeration and agitation varying as follows: conditions (A) 300 rpm, 3 vvm and (B) 200 rpm, 2 vvm, at 28 degrees C. Our results showed that gum production was dependent on k(L)a, with a maximum yield of 8.15 g/l at 300 rpm, 3 vvm, 54 h of fermentation, k(L)a 21.4/h, while biomass was not affected. All aqueous solutions of 3% (w/v) xanthans synthesized showed a pseudoplastic behavior. The highest viscosity was reached under the strongest aeration/agitation conditions. All xanthan samples contained glucose, mannose, rhamnose, and glucuronic acid as their main components. The highest agitation and aeration rates used under condition A (300 rpm and 3 vvm) favorably influenced the yield and viscosity of the xanthan produced by bacterium X. campestris pv pruni 101 at different fermentation times.

Influence of agitation and aeration in xanthan production by Xanthomonas campestris pv pruni strain 101 / Influencia de la agitación y la aireación en la producción de xantano por Xanthomonas campestris pv. pruni cepa 101

Production, viscosity, and chemical composition of xanthan synthesized by bacterium Xanthomonas campestris pv pruni strain 101 were evaluated in bioreactor systems. During the process, the volumetric oxygen mass transfer coefficient (kLa) and the biomass were determined and the pH was monitored. The cultures were grown in a 3 l bioreactor, with aeration and agitation varying as follows: conditions (A) 300 rpm, 3 vvm and (B) 200 rpm, 2 vvm, at 28 °C. Our results showed that gum production was dependent on kLa, with a maximum yield of 8.15 g/l at 300 rpm, 3 vvm, 54 h of fermentation, kLa 21.4/h, while biomass was not affected. All aqueous solutions of 3% (w/v) xanthans synthesized showed a pseudoplastic behavior. The highest viscosity was reached under the strongest aeration/agitation conditions. All xanthan samples contained glucose, mannose, rhamnose, and glucuronic acid as their main components. The highest agitation and aeration rates used under condition A (300 rpm and 3 vvm) favorably influenced the yield and viscosity of the xanthan produced by bacterium X. campestris pv pruni 101 at different fermentation times.

Se evaluó la producción, viscosidad y composición química del xantano sintetizado por la bacteria Xanthomonas campestris pv. pruni cepa 101 en un fermentador. Durante el proceso se controló el pH y se determinaron el coeficiente de transferencia de masa de oxígeno (kLa) y la producción de masa celular seca. Los cultivos se realizaron en un fermentador de 3 l variando la aireación y la agitación, en las siguientes condiciones: (A) 300 rpm, 3 vvm y (B) 200 rpm, 2 vvm; a 28 °C. Nuestros resultados mostraron que la producción de goma fue dependiente del kLa, con un rendimiento máximo de 8,15 g/l a 300 rpm y 3 vvm a las 54 h de fermentación, kLa de 21,4/h, mientras que la producción de biomasa no se afectó. Todas las soluciones acuosas de xantano al 3% (m/v) sintetizadas presentaron comportamiento pseudoplástico. La mayor viscosidad se alcanzó en la condición de aireación/agitación más intensa. Todas las muestras de xantano contenían glucosa, manosa, ramnosa y ácido glucurónico como constituyentes principales. La mayor tasa de agitación y aireación utilizada en la condición A (300 rpm y 3 vvm) influyó favorablemente en el rendimiento y la viscosidad del xantano producido por la bacteria X. campestris pv. pruni 101 a diferentes tiempos de fermentación.

Assessing and analysing contamination of a dairy products processing plant by Staphylococcus aureus using antibiotic resistance and PFGE.

A dairy product processing plant was studied for 2.5 years to examine contamination with Staphylococcus aureus and try to correlate the source of contamination. Cultures were submitted to an antibiotic susceptibility test (AST) and characterised by Pulsed-field Gel Electrophoresis (PFGE) analysis. Results showed that 35.2% (19/51) of food handlers were asymptomatic carriers of S. aureus, and that 90.4% (19/21) of raw milk sampled was contaminated. Staphylococcus aureus was isolated from only 10 samples among more than 3200 investigated dairy products. No S. aureus contamination was found on machinery. The AST analysis demonstrated sensitivity of tested S. aureus to oxacillin, cephalothin, vancomycin, gentamicin, and sulfamethoxazole/trimethoprim. AST analysis generated eight different phenotypic profiles, but did not allow us to identify the source of contamination in seven of ten final products. PFGE analysis proved to be a sensitive method as it generated 42 different DNA banding profiles among the 48 S. aureus investigated, demonstrating a lack of predominance of endemic strains in the plant, contrary to suggestions raised by antibiotic resistance typing. Based on PFGE genotyping, S. aureus strains isolated from four contaminated final products were similar to four S. aureus isolated from raw milk. Five final products contained S. aureus different from all other strains collected, and one showed similarity to a strain isolated from a food handler. These results suggest contamination by raw milk as the main source of contamination of the final dairy products.

High biodegradetion levels of 4, 5, 6-trichloroguaiacol by "Bacillus" sp. isolates from pupl mill effluent

An aerobic Gram positive spore-forming bacterium was isolated drom cellulose pulp mill effluent. This microorganism, identified as "Bacillus" sp. and named IS13, was able to rapdly degrade the organic chlorinateed compound 4, 5, 6-trichloroguaiacol (4, 5, 6-TCG) from a culture containing 50 mg/l, wich corresponds to about 3,0E4 times the concentration found in the organic chlorinated compound 4, 5, 6-TCG decreasing, the lack of by-products had shown by such analysis lead to verify the possibility of either adsorption of absorption of 4, 5, 6-TCG by the cells, instead of real biodegradation. There were no traces of 4, 5, 6-TCG. Plasmid isolation was attempted by using different protocols. The best results werw reached by CTAB method, but no plamid DNA was found in "Bacillus"sp. IS13. The results suggest that genes located at the bacterial chromossome might mediate the high decrease of 4, 5, 6-TCG. The importance of this work is that, in being a natural ocurring microorganism, "Bacillus" sp. IS13, can be used as inoculum in plant effluents to best organochlorinated compounds biodegradation.

Studies on plasmid stability, cell metabolism and superoxide dismutase production by Pgk- strains of Saccharomyces cerevisiae.

A double mutant sod1/pgk1 strain of Saccharomyces cerevisiae has been constructed in order to investigate the effects of different environmental conditions on yeast physiology, plasmid stability, and superoxide dismutase (SOD) production. Strains were transformed with yeast episomal plasmids (YEp) containing both PGK1 and SOD1 genes and were grown on fermentable carbon sources and under vigorous aeration. Under these conditions, the presence of the PGK1 gene was made essential for growth and both genes were efficiently expressed. However, plasmid-borne PGK1 was found not to increase the stability of YEp vectors in batch cultures of Pgk- cells. Paradoxically, plasmid stability increased during the respiratory phase of growth. An investigation of the metabolism of Pgk- cells demonstrated that these glycolytic pathway mutants do not appreciably metabolize glycerol. Thus Pgk+, plasmid-containing, cells have a selective advantage during the respiratory phase of batch growth since they can utilize both glycerol and ethanol.

Incidencia de angiossarcoma hepatico em relacao a exposicao ao PVC em nosso meio. / Incidence of hepatic angiosarcoma associated with PVC exposition in our enveronment

A partir da decada de 70, comecou-se a estabelecer uma relacao causal entre a incidencia de angiossarcoma de figado e a exposicao cronica de trabalhadores ao cloreto de polivinila. O presente trabalho teve por objetivo a realizacao de estudo sobre eventuais casos registrados em nosso meio, estudo este que consistiu na exploracao de registros medicos industriais e hospitalares que se constitui em pesquisa inedita dada a inexistencia de qualquer referencia bibliografica sobre o problema no Brasil. Devido a uma serie de dificuldades com as quais se defrontaram os autores, foi-lhes impossivel a execucao de uma estatistica eficiente e concreta, fatos estes que analisam no conteudo do texto