RESUMO
Arabinoxylan is a major hemicellulose in the sugarcane plant cell wall with arabinose decorations that impose steric restrictions on the activity of xylanases against this substrate. Enzymatic removal of the decorations by arabinofuranosidases can allow a more efficient arabinoxylan degradation by xylanases. Here we produced and characterized a recombinant Bifidobacterium longum arabinofuranosidase from glycoside hydrolase family 43 (BlAbf43) and applied it, together with GH10 and GH11 xylanases, to produce xylooligosaccharides (XOS) from wheat arabinoxylan and alkali pretreated sugarcane bagasse. The enzyme synergistically enhanced XOS production by GH10 and GH11 xylanases, being particularly efficient in combination with the latter family of enzymes, with a degree of synergism of 1.7. We also demonstrated that the enzyme is capable of not only removing arabinose decorations from the arabinoxylan and from the non-reducing end of the oligomeric substrates, but also hydrolyzing the xylan backbone yielding mostly xylobiose and xylose in particular cases. Structural studies of BlAbf43 shed light on the molecular basis of the substrate recognition and allowed hypothesizing on the structural reasons of its multifunctionality.
Assuntos
Bifidobacterium longum , Celulose , Endo-1,4-beta-Xilanases , Glucuronatos , Glicosídeo Hidrolases , Oligossacarídeos , Saccharum , Xilanos , Oligossacarídeos/química , Oligossacarídeos/metabolismo , Glicosídeo Hidrolases/metabolismo , Glicosídeo Hidrolases/química , Glucuronatos/metabolismo , Glucuronatos/química , Endo-1,4-beta-Xilanases/metabolismo , Endo-1,4-beta-Xilanases/química , Xilanos/metabolismo , Xilanos/química , Saccharum/química , Saccharum/metabolismo , Celulose/química , Celulose/metabolismo , Bifidobacterium longum/enzimologia , Bifidobacterium longum/metabolismo , Hidrólise , Especificidade por Substrato , Proteínas Recombinantes/metabolismo , Proteínas Recombinantes/química , DissacarídeosRESUMO
Biocatalytic decolorization of azo dyes is hampered by their recalcitrance and the characteristics of textile effluents. Alkaline pH and heavy metals present in colored wastewaters generally limit the activity of enzymes such as laccases of fungal origin; this has led to an increasing interest in bacterial laccases. In this work, the dye decolorization ability of LAC_2.9, a laccase from the thermophilic bacterial strain Thermus sp. 2.9, was investigated. Its resistance towards different pHs and toxic heavy metals frequently present in wastewaters was also characterized. LAC_2.9 was active and highly stable in the pH range of 5.0 to 9.0. Even at 100 mM Cd+2, As+5 and Ni+2 LAC_2.9 retained 99%, 86% and 75% of its activity, respectively. LAC_2.9 was capable of decolorizing 98% of Xylidine, 54% of RBBR, 40% of Gentian Violet, and 33% of Methyl Orange after 24 h incubation at pH 9, at 60 °C, without the addition of redox mediators. At acidic pH, the presence of the mediator 1-hydroxybenzotriazole generally increased the catalytic effectiveness. We analyzed the degradation products of laccase-treated Xylidine and Methyl Orange by capillary electrophoresis and mass spectrometry, and propose a degradation pathway for these dyes. For its ability to decolorize recalcitrant dyes, at pH 9, and its stability under the tested conditions, LAC_2.9 could be effectively used to decolorize azo dyes in alkaline and heavy metal containing effluents.
Assuntos
Compostos Azo , Lacase , Águas Residuárias , Biodegradação Ambiental , Cor , CorantesRESUMO
Laccases are multicopper oxidases that are being studied for their potential application in pretreatment strategies of lignocellulosic feedstocks for bioethanol production. Here, we report the expression and characterization of a predicted laccase (LAC_2.9) from the thermophilic bacterial strain Thermus sp. 2.9 and investigate its capacity to delignify lignocellulosic biomass. The purified enzyme displayed a blue color typical of laccases, showed strict copper dependence and retained 80% of its activity after 16 h at 70 °C. At 60 °C, the enzyme oxidized 2,2'-azino-di-(3-ethylbenzthiazoline sulfonate) (ABTS) and 2,6-dimethoxyphenol (DMP) at optimal pH of 5 and 6, respectively. LAC_2.9 had higher substrate specificity (kcat/KM) for DMP with a calculated value that accounts for one of the highest reported for laccases. Further, the enzyme oxidized a phenolic lignin model dimer. The incubation of steam-exploded eucalyptus biomass with LAC_2.9 and 1-hydroxybenzotriazole (HBT) as mediator changed the structural properties of the lignocellulose as evidenced by Fourier transform infrared (FTIR) spectroscopy and thermo-gravimetric analysis (TGA). However, this did not increase the yield of sugars released by enzymatic saccharification. In conclusion, LAC_2.9 is a thermostable laccase with potential application in the delignification of lignocellulosic biomass.
RESUMO
We report here the complete annotated 6,035,547-bp draft genome sequence of Bacillus thuringiensis INTA Fr7-4. This strain contains three cry8 and two vip1 and vip2 insecticidal toxin genes.
RESUMO
We report the complete sequence and analysis of pFR260, a novel megaplasmid of 260,595 bp from the Bacillus thuringiensis strain INTA Fr7-4 isolated in Argentina. It carries 7 insecticidal genes: 3 cry8 copies previously reported, 2 vip1, and 2 vip2. Also, it carries a gene encoding a putative atypical Cry protein. These genes are arranged in a region of approximately 105 kbp in size with characteristics of a pathogenicity island with a potential coleopteran-specific insecticide profile. DNA strand composition asymmetry, as determined by GC skew analysis, and the presence of a Rep protein involved in the initiation of replication suggest a bidirectional theta mechanism of replication. In addition, many genes involved in conjugation and a CRISPR-Cas system were detected. The pFR260 sequence was deposited in GenBank under accession number KX258624.
Assuntos
Bacillus thuringiensis/genética , Proteínas de Bactérias/genética , Endotoxinas/genética , Ordem dos Genes , Proteínas Hemolisinas/genética , Plasmídeos , Análise de Sequência de DNA , Argentina , Bacillus thuringiensis/isolamento & purificação , Toxinas de Bacillus thuringiensis , Sistemas CRISPR-Cas , Conjugação Genética , DNA Helicases/genética , Replicação do DNA , DNA Bacteriano/química , DNA Bacteriano/genética , Ilhas GenômicasRESUMO
Geobacillus sp. isolate T6 was collected from a thermal spring in Salta, Argentina. The draft genome sequence (3,767,773 bp) of this isolate is represented by one major scaffold of 3,46 Mbp, a second one of 207 kbp, and 20 scaffolds of <13 kbp. The assembled sequences revealed 3,919 protein-coding genes.
RESUMO
Thermus sp. isolate 2.9 was obtained from a hot water spring in Salta, Argentina. Here, we report the draft genome sequence (2,485,434 bp) of this isolate, which consists of 11 scaffolds of >10 kbp and 2,719 protein-coding sequences.
RESUMO
We found and characterized two cry8 genes from the Bacillus thuringiensis strain INTA Fr7-4 isolated in Argentina. These genes, cry8Kb3 and cry8Pa3, are located in a tandem array within a 13,200-bp DNA segment sequenced from a preparation of total DNA. They encode 1,169- and 1,176-amino-acid proteins, respectively. Both genes were cloned with their promoter sequences and the proteins were expressed separately in an acrystalliferous strain of B. thuringiensis leading to the formation of ovoid crystals in the recombinant strains. The toxicity against larvae of Anthonomus grandis Bh. (Coleoptera: Curculionidae) of a spore-crystal suspension from the recombinant strain containing cry8Pa3 was similar to that of the parent strain INTA Fr7-4.
Assuntos
Bacillus thuringiensis/isolamento & purificação , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Endotoxinas/genética , Endotoxinas/metabolismo , Proteínas Hemolisinas/genética , Proteínas Hemolisinas/metabolismo , Animais , Argentina , Bacillus thuringiensis/genética , Toxinas de Bacillus thuringiensis , Clonagem Molecular , Besouros/efeitos dos fármacos , Expressão Gênica , Regiões Promotoras Genéticas , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Análise de Sequência de DNA , Análise de SobrevidaRESUMO
Insecticidal activity of Bacillus thuringiensis is attributed largely to the crystal proteins. These were found with specific toxic activity against insects in different orders. A novel cry8 gene from B. thuringiensis strain INTA Fr7-4 from Argentina was characterized. The encoded protein, Cry8Qa2, is 1184 amino acids long and its sequence is more similar to those of Cry8F class. We cloned and expressed the protein in an acrystalliferous strain of B. thuringiensis using two differentially regulated promoters. The recombinant strains produced ovoid crystals with low toxicity against larvae of Anticarsia gemmatalis (Lepidoptera: Noctuidae). The morphology and insecticidal properties of these crystals resembled those produced by the native strain INTA Fr7-4.