RESUMO
Thirteen new Clostridium strains, previously isolated from soil and found to produce high amounts of solvents from glucose, hydrolyzed a great variety of alpha- and beta-glycans, including raw starch, xylan, pectin, inulin and cellulose. The sequences of the PCR-amplified DNA fragments containing the variable 3' part of one of the 16S rRNA genes were 99.5% identical. The macrorestriction pattern of two endonucleolytic digests of chromosomal DNA in the pulsed-field gel electrophoresis (PFGE) confirmed their high homogeneity on the DNA level. The complete 16S rRNA gene sequence of three selected strains was 99.8% identical to the 16S rRNA gene sequence from Clostridium butyricum and separates them from C. acetobutylicum. To the closely related four species of solventogenic clostridia a new group of strains has to be added, which has a great potential for the direct fermentation of biomass.
Assuntos
Clostridium/metabolismo , Polissacarídeos/metabolismo , Solventes/metabolismo , Biomassa , Clostridium/classificação , Clostridium/isolamento & purificação , Fermentação , Hidrólise , Microbiologia Industrial , Dados de Sequência Molecular , RNA Ribossômico 16S/genética , Homologia de Sequência do Ácido Nucleico , Microbiologia do SoloRESUMO
One hundred and seventy-eight new butanol-acetone producing bacteria related to saccharolytic clostridia were isolated from agricultural sources in Colombia and their fermentation potential was evaluated. Thirteen isolates produced more total solvents from glucose than Clostridium acetobutylicum ATCC 824. The isolates with the highest single solvent production were IBUN 125C and IBUN 18A with 0.46 mol butanol and 0.96 mol ethanol formed from 1 mol glucose, yielding 25. 2 and 29.1 g l(-1) total solvents, respectively, which is close to the maximum values described to date. Most of the new isolates produced exoenzymes for the hydrolysis of starch, carboxymethyl cellulose, xylan, polygalacturonic acid, inulin and chitosan. Together with the high efficiency of solvent production, these hydrolytic isolates may be useful for the direct fermentation of biomass. According to their physiological profile, the most solvent-productive isolates could be classified as strains of C. acetobutylicum, Clostridium beijerinckii, and Clostridium NCP262.
Assuntos
Clostridium/metabolismo , Polissacarídeos/metabolismo , Clostridium/efeitos dos fármacos , Hidrólise , Testes de Sensibilidade Microbiana , SolventesRESUMO
Las cepas de Clostridium, productoras de solventes y áci-dos, han sido caracterizados empleando una amplia gama de técnicas fisiológicas, bioquímicas y moleculares. Los trabajos más recientes han clasificado estos mi-croorganismos en cuatro grupos y es de esperarse que mu-chos de los microorganismos anaerobios solventogénicos estén fuera de esta clasificación. El presente trabajo estu-vo orientado a caracterizar molecularmente por 16S rARN trece cepas silvestres de Clostridium seleccionadas por su mayor capacidad para producir solventes con respecto a la cepa patrón de Clostridium acetobutylicum ATCC824. Se hizo la secuenciación parcial del gen 16S rARN, sobre su segmento final (aproximadamente 700 pb). Para anali-zar las secuencias, se calculó p y se construyó el dendograma empleando neighbor-joining. Se pudo obser-var que las cepas silvestres no pertenecen a ninguno de los cuatro grupos de Clostridium solventogénicos sino que están cercanamente relacionadas con Clostridium butyricum.