RESUMO
In the present paper the presence of heptadecanoic acid and C19 cyclopropane fatty acid in Zymomonas mobilis is reported. The former has not been mentioned as a component of the lipid fraction of this microorganism, and the presence of the latter is not well documented.
Assuntos
Ácidos Graxos/análise , Zymomonas/químicaRESUMO
The influence of modifications of the environmental conditions of growth on beta-N-acetyl-D-glucosaminidase (EC 3.2.1.30) activity and on hyphal morphological patterns in pellets of Aspergillus niger was studied. It was found that changes in the degree of branching and, to a lesser extent, in the number of bulbous cells were directly related to the activity of the enzyme. Nevertheless, since beta-N-acetyl-D-glucosaminidase is not the only enzyme involved in the lytic potential of the fungus, these findings do not exclude the possibility that other enzymes may be involved.
Assuntos
Acetilglucosaminidase/metabolismo , Aspergillus niger/citologia , Aspergillus niger/enzimologia , Aspergillus niger/crescimento & desenvolvimento , Cátions/farmacologia , Concentração de Íons de Hidrogênio , TemperaturaRESUMO
Addition of 0.5 g/L CaCl2 to the fermentation medium lowered the final biomass dry mass by 35% and increased the uptake of phosphate and sucrose, and the production of citric acid by 15, 35 and 50%, respectively. In a medium deprived of Ca2+ the microorganism displayed both a pelleted and a filamentous form of growth, the hyphae being scarcely branched, without bulbous cells. An addition of Ca2+ induced a pelleted form of growth, highly branched hyphae and numerous bulbous cells. Bulbous cells growing in the presence of Ca2+ exhibited cell walls composed of laminated layers, and featured vesicles associated with the wall and/or the cell membrane, containing numerous inclusions. The cytotoxic effect of high concentrations of citric acid in the medium as well as an increase of the activity of N-acetyl-beta-D-glucosaminidase, a lytic enzyme, might be involved in these morphological changes.
Assuntos
Aspergillus niger/efeitos dos fármacos , Cloreto de Cálcio/farmacologia , Ácido Cítrico/metabolismo , Aspergillus niger/crescimento & desenvolvimento , Aspergillus niger/metabolismo , Aspergillus niger/ultraestrutura , Membrana Celular/ultraestrutura , Parede Celular/ultraestrutura , Ácido Cítrico/toxicidade , Microscopia Eletrônica , Nitrogênio/metabolismo , Fósforo/metabolismoRESUMO
Pure and mixed cultures of Zymomonas mobilis and Saccharomyces sp. were tested for the production of ethanol using sucrose as the carbon source. Both strains, isolated from spontaneously fermenting sugar-cane juice, are flocculent and alcohol-tolerant. The best results were obtained using a mixed culture, with a yield of 0.5 g ethanol/g sugar consumed and a volumetric productivity of 1.5 g ethanol l-1 h-1. No levan was produced even if a sucrose-based medium was used.
Assuntos
Etanol/metabolismo , Saccharomyces/metabolismo , Zymomonas/metabolismo , Fermentação , Floculação , Saccharomyces/ultraestrutura , Sacarose/metabolismo , Zymomonas/ultraestruturaRESUMO
When Candida utilis was grown in continuous culture, decreasing the concentration of N in the medium affected cell composition, biomass yield, biomass productivity, maximal growth rate and cell morphology. When the dilution rate was low (0.1 h(-1)), reducing N from 1100 to 100 mg/l led to a 40% decrease in RNA content of the cells. Nitrogen-limited growth, which occurred when N<420 mg/l, was associated with significant changes in cell-wall carbohydrates and a significant reduction in the glycogen content of the cells. A set of culture conditions was established which permitted maximal consumption of the main nutrients in the medium and the production of yeast biomass suitable as a source of single-cell protein.
RESUMO
During the production of pectinases by a strain of Aspergillus niger isolated from rotten lemons, methanol was liberated into the medium due to the cleavage of the pectin molecule used as the carbon source. The methanol was subsequently consumed by the microorganism but neither the synthesis nor the activity of pectinesterase and polygalacturonase was affected. Although not studied in detail, the mechanism involved in the utilization of methanol is similar to that described for methylotrophic yeasts.
RESUMO
Rapid ethanol fermentation is defined as a fermentation in which the ethanol content increases from 0 to 94.8 g 1(-1) in 6 horless. To achieve this by the fermentation of glucose withZymomonas mobilis, the initial biomass concentration must be at least 20 g dry wt 1(-1) and that of the substrate must not exceed 150 to 200 g 1(-1) during fermentation. The best results were obtained with a medium containing initielly 16% of the total sugar with the remaining glucose being added continuously, after 20 min of incubation, over 5 h at a rate of 0.21 g/min. After 6 h, ethanol reached 102 g 1(-1), the volumetric productivity was 17g ethanol 1(-1) h(-1) and the yield 79.8 or 88% of the theoretical value, calculated according to the total fed or the consumed glucose, respectively.
RESUMO
Como consecuencia de la crisis energética mundial, se están realizando numerosas investigaciones sobre la obtención de alcohol etílico por fermentación, con el objeto de disminuir su costo de producción. En el campo de la biotecnología se han propuesto diversos sistemas de fermentación, algunos con buenos resultados. Sin embargo en nuestro país se continúa trabajando con el sistema tradicional en lotes, seguramente por la gran inversión que requiere un cambio de tecnología. El objetivo de este trabajo es ponderar las posibilidades de realizar fermentaciones en lotes con alta concentración de levaduras, con el fin de aumentar la productividad volumétrica, es decir la cantidad de etanol producida por litro de mosto y por hora. Se estudió la realción entre la concentración de levaduras en el medio de fermentación y las productividades volumétrica y específica, la primera aumenta y la segunda disminuye a medida que se incrementa la concentración de microorganismos, ambas de manera no lineal. Ensayos de fermentación en lotes con reutilización de levaduras mostraron la dificultad de mantener una población superior a 300 x 10**6 lev/ml. La propagación periódica (cada 13 lotes) de las levaduras recuperadas demostró ser un método sencillo y efectivo para mantener concentraciones altas de microorganismos en el medio de fermentación, lo que se traduce en una productividad mayor que la obtenida en el proceso en lotes convencional con recuperación de levaduras. Las aplicación de estas experiencias a nivel industrial no implicaría ningún tipo de modificación, ni la incorporación de equipos adicionales en las destilerías que actualmente trabajan con el sistema Melle Boinot
Assuntos
Etanol/biossíntese , Fermentação/métodos , Saccharomyces/metabolismoRESUMO
Como consecuencia de la crisis energética mundial, se están realizando numerosas investigaciones sobre la obtención de alcohol etílico por fermentación, con el objeto de disminuir su costo de producción. En el campo de la biotecnología se han propuesto diversos sistemas de fermentación, algunos con buenos resultados. Sin embargo en nuestro país se continúa trabajando con el sistema tradicional en lotes, seguramente por la gran inversión que requiere un cambio de tecnología. El objetivo de este trabajo es ponderar las posibilidades de realizar fermentaciones en lotes con alta concentración de levaduras, con el fin de aumentar la productividad volumétrica, es decir la cantidad de etanol producida por litro de mosto y por hora. Se estudió la realción entre la concentración de levaduras en el medio de fermentación y las productividades volumétrica y específica, la primera aumenta y la segunda disminuye a medida que se incrementa la concentración de microorganismos, ambas de manera no lineal. Ensayos de fermentación en lotes con reutilización de levaduras mostraron la dificultad de mantener una población superior a 300 x 10**6 lev/ml. La propagación periódica (cada 13 lotes) de las levaduras recuperadas demostró ser un método sencillo y efectivo para mantener concentraciones altas de microorganismos en el medio de fermentación, lo que se traduce en una productividad mayor que la obtenida en el proceso en lotes convencional con recuperación de levaduras. Las aplicación de estas experiencias a nivel industrial no implicaría ningún tipo de modificación, ni la incorporación de equipos adicionales en las destilerías que actualmente trabajan con el sistema Melle Boinot (AU)
Assuntos
Etanol/biossíntese , Fermentação/métodos , Saccharomyces/metabolismoRESUMO
Due to the dramatic increase in international oil prices, the ethanol production by fermentation is presently becoming an attractive and feasible project for many countries Argentina has implemented an experimental national program of ethanol use as fuel and the standard procedure of Melle-Boinot is currently employed in sugar cane molasses fermentation. The aim of this work was to improve the overall efficiency of the batch process by recycling high levels of yeast biomass. It was observed that the volumetric productivity increased with biomass concentration, whereas the specific productivity decreased. Both variations were not linear (Fig. 1). It was difficult to keep a yeast concentration higher than 3 x 10(8) cell/ml during batch fermentation assays. Anyhow the periodic subculturing of yeast biomass (every 13 recycling periods) proved to be an effective method to obtain a high cell density in the fermentation medium (Fig. 2). The industrial application of data reported here would not imply additional investment or equipment to distilleries using standard fermentation procedures.
Assuntos
Etanol/biossíntese , Fermentação , Leveduras/metabolismo , Leveduras/crescimento & desenvolvimentoRESUMO
Due to the dramatic increase in international oil prices, the ethanol production by fermentation is presently becoming an attractive and feasible project for many countries Argentina has implemented an experimental national program of ethanol use as fuel and the standard procedure of Melle-Boinot is currently employed in sugar cane molasses fermentation. The aim of this work was to improve the overall efficiency of the batch process by recycling high levels of yeast biomass. It was observed that the volumetric productivity increased with biomass concentration, whereas the specific productivity decreased. Both variations were not linear (Fig. 1). It was difficult to keep a yeast concentration higher than 3 x 10(8) cell/ml during batch fermentation assays. Anyhow the periodic subculturing of yeast biomass (every 13 recycling periods) proved to be an effective method to obtain a high cell density in the fermentation medium (Fig. 2). The industrial application of data reported here would not imply additional investment or equipment to distilleries using standard fermentation procedures.
RESUMO
Para la produccion de proteina unicelular a partir de medula de bagazo de cana de azucar, se uso un cultivo mixto de bacterias identificadas como Cellulomonas sp. y Bacillus subtilis. Los maximos valores de rendimiento (0,17 g proteina/g medula) y de produccion (3,43 g proteina/I) fueron obtenidos a 34 graus C. (pH 7,0) con nitrato de sodio como fuente de nitrogeno.El cultivo mixto mostro un crescimiento satisfactorio con 20% de oxigeno disuelto con respecto a saturacion, condicion esta alcanzada con 400 rpm y 0,15 vvm de aire.El contenido proteico (N x 6,25) del cultivo misto es de 50%, respondiendo la composicion aminoacidica con alto contenido en lisina (6,4%) a los requerimientos de la FAO para aminoacidos esenciales excepto em metionina