RESUMOA técnica da compostagem é um recurso empregado com o objetivo de reciclar resíduos orgânicos domésticos e sanitizar o lodo produzido nas estações de tratamento de efluentes de esgoto (ETE) podendose obter um composto com propriedades de fertilizante agrícola e/ou corretor de solos degradados. A alta temperatura atingida pelo sistema deve ser responsável pela redução de micro-organismos patogênicos presentes no início do processo assegurando, desta forma, a qualidade microbiológica do composto sem oferecer riscos de contaminação, conforme preconiza a Resolução 354/2006 do CONAMA. Objetivouse, com o trabalho, avaliar a influência da temperatura sobre a redução de Escherichia coli, Salmonella sp., ovos de helmintos e vírus entéricos durante o processo de compostagem, além da contagem de bactérias heterotróficas. Foram realizados testes colimétricos, semeaduras em meios de cultivo, testes de visualização de ovos de helmintos e detecção molecular de vírus entéricos. Os resultados indicaram oscilação nas contagens de E. coli e de bactérias heterotróficas, mesmo após a fase termofílica. Por outro lado, não foi detectada a presença de Salmonella sp., vírus entéricos nem de ovos viáveis de helmintos, ao final do processo. Palavras-chave: lodo de esgoto, coliformes, matéria orgânicaEvaluation of degradation temperature of compounds in a composting process and microbiological quality of the compost ABSTRACT The composting technique is a promising alternative for the treatment of solid organic residues, along with the sludge produced in sewage treatment plants. The final compost might show fertilizer properties, which can be used to recover poor soils. The high temperatures that the composting process can achieve are responsible for the reduction of the pathogenic microbial population, helminth eggs and virus present in the beginning of the process. This behavior assures the microbial quality of the compost according to the 375/2006 Resolution of the CONAMA. The aim of this study was to evaluate the influence of temperature on Escherichia coli, Salmonella sp., helminth egg and enteric virus presence in the final product from a composting process. For this matter colimetric assays were performed together with the seedling of the samples in different culture media, the assay for helminth eggs visualization under the microscope and the identification of enteric virus. The results showed an oscillation on E. coli and heterotrophic bacteria counts, even after the thermophilic phase. On the other hand, Salmonella sp., helminth eggs and enteric virus were not found in the final compost.
During composting processes, the degradation of organic waste is accomplished and driven by a succession of microbial populations exhibiting a broad range of functional competencies. A total of 183 bacteria, isolated from a composting process, were evaluated for cellulase activity at different temperatures (37, 50, 60, and 70°C) and pH values. Out of the 22 isolates that showed activity, isolate 380 showed the highest cellulase activity. Its ability to produce cellulase was evaluated in culture medium supplemented with carboxymethyl cellulose, microcrystalline cellulose, wheat straw, and rice husk. The culture medium supplemented with carboxymethyl cellulose induced higher enzyme activity after 6 hours of incubation (0.12 UEA mL -1 min -1 ). For wheat straw and rice husk, the results were 0.08 UEA mL -1 min -1 for both, while for microcrystalline cellulose, 0.04 UEA mL -1 min -1 were observed. The highest carboxymethyl cellulase activity was observed at 60°C (0.14 UEA mL -1 min -1 ) for both crude and partially purified enzyme after 30 and 120 min of incubation, respectively. Alkalinization of the medium was observed during cultivation in all substrates. The cellulase had a molecular mass of 20 kDa determined by SDS-Page. Isolate 380 was identified as Bacillus licheniformis. This work provides a basis for further studies on composting optimization.
Cyanobacteria are commonly found in association with other microorganisms, which constitutes a great challenge during the isolation of cyanobacterial strains. Although several methods have been published for obtaining axenic cyanobacterial cultures, their efficiency is usually evaluated by observing the growth of non-cyanobacteria in culture media. In order to verify whether uncultured bacteria should be a concern during cyanobacterial isolation, this work aimed to detect by molecular methods sequences from cyanobacteria and other bacteria present before and after a technique for obtaining axenic cultures from plating and exposure of Fischerella sp. CENA161 akinetes to the Extran detergent and sodium hypochlorite. Solutions containing 0.5, 1, and 2% sodium hypochlorite were able to remove contaminant bacterial CFUs from the culture. However, qPCR pointed that the quantity of sequences amplified with universal bacteria primers was higher than the number of cyanobacteria-specific sequences before and after treatments. The presence of uncultured bacteria in post-hypochlorite cultures was confirmed by high-throughput Illumina sequencing. These results suggest that culturing may overlook the presence of uncultured bacteria associated to cyanobacterial strains and is not sufficient for monitoring the success of cyanobacterial isolation by itself. Molecular methods such as qPCR could be employed as an additional measure for evaluating axenity in cyanobacterial strains.
Microcystins (MCs) are serine/threonine phosphatase inhibitors synthesized by several members of the phylum Cyanobacteria. Mining the draft genome sequence of the nostocalean MC-producing Fischerella sp. strain CENA161 led to the identification of three contigs containing mcy genes. Subsequent PCR and Sanger sequencing allowed the assembling of its complete biosynthetic mcy gene cluster with 55,016 bases in length. The cluster encoding ten genes (mcyA-J) with a central bidirectional promoter was organized in a similar manner as found in other genera of nostocalean cyanobacteria. However, the nucleotide sequence of the mcy gene cluster of Fischerella sp. CENA161 showed significant differences from all the other MC-producing cyanobacterial genera, sharing only 85.2 to 74.1% identities. Potential MC variants produced by Fischerella sp. CENA161 were predicted by the analysis of the adenylation domain binding pockets and further investigated by LC-MS/MS analysis. To our knowledge, this study presents the first complete mcy cluster characterization from a strain of the genus Fischerella, providing new insight into the distribution and evolution of MCs in the phylum Cyanobacteria.
Microcystis aeruginosa strain SPC777 is an important toxin-producing cyanobacterium, isolated from a water bloom of the Billings reservoir (São Paulo State, Brazil). Here, we report the draft genome sequence and initial findings from a preliminary analysis of strain SPC777, including several gene clusters involved in nonribosomal and ribosomal synthesis of secondary metabolites.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.