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1.
Bioresour Technol ; 137: 153-9, 2013 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-23584415

RESUMO

In this study, the removal of IBE from aqueous solutions by gas stripping has been characterized. The effect of one or more components in the solution on the kinetics of the separation has been studied, both at 37°C and at 70°C. Gas stripping has been applied to batch, repeated batch and continuous cultures of Clostridium beijerinckii grown on a glucose/xylose mixed sugar substrate mimicking lignocellulosic hydrolysates, with the aim of finding optimal conditions for a stable IBE-producing culture with high productivity. An innovative repeated-batch process has been demonstrated in which the gas-stripping is performed at 70°C, resulting in a prolonged stable IBE culture.


Assuntos
2-Propanol/química , Butanóis/química , Fracionamento Químico/métodos , Clostridium beijerinckii/metabolismo , Etanol/química , Fermentação , Reatores Biológicos , Técnicas de Cultura de Células , Glucose/metabolismo , Cinética , Nitrogênio/química
2.
Appl Environ Microbiol ; 70(9): 5238-43, 2004 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-15345405

RESUMO

Clostridium acetobutylicum ATCC 824 is a solventogenic bacterium that grows heterotrophically on a variety of carbohydrates, including glucose, cellobiose, xylose, and lichenan, a linear polymer of beta-1,3- and beta-1,4-linked beta-D-glucose units. C. acetobutylicum does not degrade cellulose, although its genome sequence contains several cellulase-encoding genes and a complete cellulosome cluster of cellulosome genes. In the present study, we demonstrate that a low but significant level of induction of cellulase activity occurs during growth on xylose or lichenan. The celF gene, located in the cellulosome-like gene cluster and coding for a unique cellulase that belongs to glycoside hydrolase family 48, was cloned in Escherichia coli, and antibodies were raised against the overproduced CelF protein. A Western blot analysis suggested a possible catabolite repression by glucose or cellobiose and an up-regulation by lichenan or xylose of the extracellular production of CelF by C. acetobutylicum. Possible reasons for the apparent inability of C. acetobutylicum to degrade cellulose are discussed.


Assuntos
Celulase/metabolismo , Clostridium/enzimologia , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Sequência de Bases , Celulase/biossíntese , Primers do DNA , Reação em Cadeia da Polimerase , Proteínas Recombinantes/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Especificidade por Substrato
3.
Appl Biochem Biotechnol ; 113-116: 497-508, 2004.
Artigo em Inglês | MEDLINE | ID: mdl-15054273

RESUMO

This study addressed the utilization of an industrial waste stream, paper sludge, as a renewable cheap feedstock for the fermentative production of hydrogen by the extreme thermophile Caldicellulosiruptor saccharolyticus. Hydrogen, acetate, and lactate were produced in medium in which paper sludge hydrolysate was added as the sole carbon and energy source and in control medium with the same concentration of analytical grade glucose and xylose. The hydrogen yield was dependent on lactate formation and varied between 50 and 94% of the theoretical maximum. The carbon balance in the medium with glucose and xylose was virtually 100%. The carbon balance was not complete in the paper sludge medium because the measurement of biomass was impaired owing to interfering components in the paper sludge hydrolysate. Nevertheless, >85% of the carbon could be accounted for in the products acetate and lactate. The maximal volumetric hydrogen production rate was 5 to 6 mmol/(L x h), which was lower than the production rate in media with glucose, xylose, or a combination of these sugars (9-11 mmol/[L x h]). The reduced hydrogen production rate suggests the presence of inhibiting components in paper sludge hydrolysate.


Assuntos
Bactérias/metabolismo , Glucose/química , Hidrogênio/química , Xilose/química , Reatores Biológicos , Carboidratos/química , Carbono/química , Relação Dose-Resposta a Droga , Fermentação , Resíduos Industriais , Modelos Químicos , Papel , Temperatura , Fatores de Tempo
4.
Appl Biochem Biotechnol ; 105 -108: 557-66, 2003.
Artigo em Inglês | MEDLINE | ID: mdl-12721435

RESUMO

The main objective of this study was to develop a system for the production of "renewable" hydrogen. Paper sludge is a solid industrial waste yielding mainly cellulose, which can be used, after hydrolysis, as a feedstock in anaerobic fermentation by (hyper)thermophilic organisms, such as Thermotoga elfii and Caldicellulosiruptor saccharolyticus. Tests on different medium compositions showed that both bacteria were able to produce hydrogen from paper sludge hydrolysate, but the amount of produced hydrogen and the requirement for other components differed. Hydrogen production by T. elfii strongly depended on the presence of yeast extract and salts. By contrast, C. saccharolyticus was less dependent on medium components but seemed to be inhibited by a component present in the sludge hydrolysate. Utilization of xylose was preferred over glucose by C. saccharolyticus.


Assuntos
Bactérias/metabolismo , Bacilos Gram-Negativos Anaeróbios Retos, Helicoidais e Curvos/metabolismo , Hidrogênio/isolamento & purificação , Papel , Esgotos/química , Metabolismo dos Carboidratos , Meios de Cultura , Glucose/metabolismo , Hidrólise , Resíduos Industriais , Oligoelementos/análise , Xilose/metabolismo , Leveduras/metabolismo
5.
Appl Environ Microbiol ; 69(2): 869-77, 2003 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-12571006

RESUMO

The genome sequence of Clostridium acetobutylicum ATCC 824, a noncellulolytic solvent-producing strain, predicts the production of various proteins with domains typical for cellulosomal subunits. Most of the genes coding for these proteins are grouped in a cluster similar to that found in cellulolytic clostridial species, such as Clostridium cellulovorans. CAC0916, one of the open reading frames present in the putative cellulosome gene cluster, codes for CelG, a putative endoglucanase belonging to family 9, and it was cloned and overexpressed in Escherichia coli. The overproduced CelG protein was purified by making use of its high affinity for cellulose and was characterized. The biochemical properties of the purified CelG were comparable to those of other known enzymes belonging to the same family. Expression of CelG by C. acetobutylicum grown on different substrates was studied by Western blotting by using antibodies raised against the purified E. coli-produced protein. Whereas the antibodies cross-reacted with CelG-like proteins secreted by cellobiose- or cellulose-grown C. cellulovorans cultures, CelG was not detectable in extracellular medium from C. acetobutylicum grown on cellobiose or glucose. However, notably, when lichenan-grown cultures were used, several bands corresponding to CelG or CelG-like proteins were present, and there was significantly increased extracellular endoglucanase activity.


Assuntos
Proteínas de Bactérias , Celulase/biossíntese , Clostridium/enzimologia , Família Multigênica , Sequência de Aminoácidos , Celulase/genética , Celulose/metabolismo , Clostridium/genética , Meios de Cultura , Glucanos/metabolismo , Glicosídeo Hidrolases/biossíntese , Glicosídeo Hidrolases/genética , Dados de Sequência Molecular , Fases de Leitura Aberta , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Xilose/metabolismo
6.
Biotechnol Bioeng ; 81(3): 255-62, 2003 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-12474247

RESUMO

Substrate and product inhibition of hydrogen production during sucrose fermentation by the extremely thermophilic bacterium Caldicellulosiruptor saccharolyticus was studied. The inhibition kinetics were analyzed with a noncompetitive, nonlinear inhibition model. Hydrogen was the most severe inhibitor when allowed to accumulate in the culture. Concentrations of 5-10 mM H(2) in the gas phase (identical with partial hydrogen pressure (pH(2)) of (1-2) x 10(4) Pa) initiated a metabolic shift to lactate formation. The extent of inhibition by hydrogen was dependent on the density of the culture. The highest tolerance for hydrogen was found at low volumetric hydrogen production rates, as occurred in cultures with low cell densities. Under those conditions the critical hydrogen concentration in the gas phase was 27.7 mM H(2) (identical with pH(2) of 5.6 x 10(4) Pa); above this value hydrogen production ceased completely. With an efficient removal of hydrogen sucrose fermentation was mainly inhibited by sodium acetate. The critical concentrations of sucrose and acetate, at which growth and hydrogen production was completely inhibited (at neutral pH and 70 degrees C), were 292 and 365 mM, respectively. Inorganic salts, such as sodium chloride, mimicked the effect of sodium acetate, implying that ionic strength was responsible for inhibition. Undissociated acetate did not contribute to inhibition of cultures at neutral or slightly acidic pH. Exposure of exponentially growing cultures to concentrations of sodium acetate or sodium chloride higher than ca. 175 mM caused cell lysis, probably due to activation of autolysins.


Assuntos
Bactérias Anaeróbias/crescimento & desenvolvimento , Bactérias Anaeróbias/metabolismo , Hidrogênio/metabolismo , Sacarose/metabolismo , Archaea/efeitos dos fármacos , Archaea/crescimento & desenvolvimento , Archaea/metabolismo , Bactérias Anaeróbias/efeitos dos fármacos , Biodegradação Ambiental , Reatores Biológicos , Células Cultivadas , Cinética , Modelos Biológicos , Sais/farmacologia , Sensibilidade e Especificidade , Acetato de Sódio/farmacologia , Especificidade por Substrato
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