RESUMO
Abstract This study was conducted to isolate an acid-producing, alkaliphilic bacterium to reduce the alkalinity of cement industry waste (cement kiln dust). Gram-positive isolate KG1 grew well at pH values of 6–12, temperatures of 28–50 °C, and NaCl concentrations of 0–16% and thus was further screened for its potential to reduce the pH of an alkaline medium. Phenotypic characteristics of the KG1 isolate were consistent with those of the genus Bacillus, and the highest level of 16S rRNA gene sequence similarity was found with Bacillus halodurans strain DSM 497 (94.7%). On the basis of its phenotypic characteristics and genotypic distinctiveness from other phylogenetic neighbors belonging to alkaliphilic Bacillus species, the isolated strain was designated B. halodurans strain KG1, with GenBank accession number JQ307184 (= NCIM 5439). Isolate KG1 reduced the alkalinity (by 83.64%) and the chloride content (by 86.96%) of cement kiln dust and showed a potential to be used in the cement industry for a variety of applications.
Assuntos
Bacillus/crescimento & desenvolvimento , Bacillus/metabolismo , Biotecnologia/métodos , Resíduos Industriais , Gerenciamento de Resíduos/métodos , Técnicas de Tipagem Bacteriana , Bacillus/classificação , Bacillus/isolamento & purificação , Análise por Conglomerados , Materiais de Construção , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Concentração de Íons de Hidrogênio , Dados de Sequência Molecular , Filogenia , /genética , Análise de Sequência de DNA , Cloreto de Sódio/metabolismo , TemperaturaRESUMO
This study was conducted to isolate an acid-producing, alkaliphilic bacterium to reduce the alkalinity of cement industry waste (cement kiln dust). Gram-positive isolate KG1 grew well at pH values of 6-12, temperatures of 28-50°C, and NaCl concentrations of 0-16% and thus was further screened for its potential to reduce the pH of an alkaline medium. Phenotypic characteristics of the KG1 isolate were consistent with those of the genus Bacillus, and the highest level of 16S rRNA gene sequence similarity was found with Bacillus halodurans strain DSM 497 (94.7%). On the basis of its phenotypic characteristics and genotypic distinctiveness from other phylogenetic neighbors belonging to alkaliphilic Bacillus species, the isolated strain was designated B. halodurans strain KG1, with GenBank accession number JQ307184 (= NCIM 5439). Isolate KG1 reduced the alkalinity (by 83.64%) and the chloride content (by 86.96%) of cement kiln dust and showed a potential to be used in the cement industry for a variety of applications.
Assuntos
Bacillus/crescimento & desenvolvimento , Bacillus/metabolismo , Biotecnologia/métodos , Resíduos Industriais , Gerenciamento de Resíduos/métodos , Bacillus/classificação , Bacillus/isolamento & purificação , Técnicas de Tipagem Bacteriana , Análise por Conglomerados , Materiais de Construção , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Concentração de Íons de Hidrogênio , Dados de Sequência Molecular , Filogenia , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Cloreto de Sódio/metabolismo , TemperaturaRESUMO
This study was conducted to isolate an acid-producing, alkaliphilic bacterium to reduce the alkalinity of cement industry waste (cement kiln dust). Gram-positive isolate KG1 grew well at pH values of 612, temperatures of 2850 °C, and NaCl concentrations of 016% and thus was further screened for its potential to reduce the pH of an alkaline medium. Phenotypic characteristics of the KG1 isolate were consistent with those of the genus Bacillus, and the highest level of 16S rRNA gene sequence similarity was found with Bacillus halodurans strain DSM 497 (94.7%). On the basis of its phenotypic characteristics and genotypic distinctiveness from other phylogenetic neighbors belonging to alkaliphilic Bacillus species, the isolated strain was designated B. halodurans strain KG1, with GenBank accession number JQ307184 (= NCIM 5439). Isolate KG1 reduced the alkalinity (by 83.64%) and the chloride content (by 86.96%) of cement kiln dust and showed a potential to be used in the cement industry for a variety of applications. (AU)
Assuntos
Bactérias , Indústria do Cimento , Bacillus , Álcalis , Concentração de Íons de HidrogênioRESUMO
The present study deals with the isolation and characterization of the moderately halophilic-alkaliphilic bacteria from a saline habitat in western India. Eight different bacterial strains were isolated using enrichment techniques at 20% (w/v) NaCl and pH 10. The isolates exhibited diversity towards gram's reaction, colony and cell morphology. They were able to grow and produce alkaline protease over a broad range of NaCl, 5-20% (w/v) and pH, 8-10. None of the isolates could grow at pH 7, and one could not grow even at pH 8. Crude and partially purified proteases from strain S5 were subjected to characterization with reference to pH, salt stability and protein folding. Optimum protease activity and stability was recorded at 10% salt and pH 9-9.5. Denaturation kinetics of S5 alkaline protease along with a reference protease was studied at 8M urea followed by renaturation. The S5 alkaline protease could be partially renatured up to 32% of the original activity. Despite of the fact that all the 8 isolates were from the same site, they displayed significant diversity with respect to their salt requirement for growth and enzyme secretion. While the effect of pH was less demarcated on growth, the protease production was significantly affected. Isolate S5 produced substantial amount of halotolerant and alkaline protease. The activity and stability of the alkaline protease in a broader range of pH and salt would definitely make this enzyme an important candidate for various industrial applications.
O presente estudo relata o isolamento e caracterização de bactérias moderadamente halofilicas e alcalífilicas de um habitat salino no oeste da Índia. Oito cepas diferentes de bactérias foram isoladas empregando técnicas de enriquecimento em NaCl a 20% (p/v) e pH 10. As cepas apresentaram diversidade em relação à coloração de Gram e à morfologia das colônias e células. As cepas foram capazes de multiplicar e produzir protease alcalina em uma ampla faixa de concentração de NaCl (5 a 20%) e pH (8 a 10). Nenhuma das cepas foi capaz de se multiplicar em pH 7, e uma não se multiplicou nem em pH 8.0. Proteases naturais e parcialmente purificadas da cepa S5 foram submetidas à caracterização com relação ao pH, estabilidade salina, e estrutura protéica. Atividade e estabilidade ótimas da protease foram obtidas com 10% de sal e pH 9-9,5. A cinética de denaturação da protease de S5, juntamente com uma protease de referencia, foi avaliada com uréia 8M seguida de renaturação. A protease alcalina de S5 foi renaturada a 32% da atividade original. Apesar de provenientes do mesmo local, as oito cepas mostraram grande diversidade em relação à exigência de sal para multiplicação e secreção enzimática. Enquanto o efeito do pH na multiplicação foi menos marcante, o efeito na produção de protease foi significativamente afetada. A cepa S5 produziu uma quantidade substancial de protease alcalina e halotolerante. A atividade e estabilidade da protease alcalina em uma faixa mais ampla de pH e sal tornam essa enzima uma importante candidata para diversas aplicações industriais.