Validação de um sistema de tanques piloto para avaliação do efeito de um coquetel de bacteriófagos sobre o biofilme e produção de H₂S por bactérias redutoras de sulfato
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2022-03-07
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Universidade Federal de Viçosa
Resumo
A corrosão é um processo físico-químico capaz de alterar as propriedades do material exposto a condições corrosivas. O setor de exploração de petróleo é um dos principais setores da economia que sofre com esse processo devido à deterioração de equipamentos, como tanques e oleodutos, que podem acarretar em vazamento de óleo. As bactérias redutoras de sulfato (BRS) constituem o principal grupo relacionado à corrosão microbiologicamente induzida (CMI), gerando prejuízos anuais à indústria do petróleo devido à formação de biofilme e a produção de sulfeto de hidrogênio (H₂S), um gás tóxico e corrosivo. Neste trabalho, um sistema de tanques piloto foi utilizado para simular o armazenamento de fluidos industrial, e inseridos cupons de aço carbono AISI 1020 para formação de biofilme. Nesse sistema, foi avaliado o efeito de um coquetel de bacteriófagos inespecíficos (10^7 UFP/mL), isolados de amostra de água residuais, sobre o biofilme e produção de H₂S de duas culturas mistas de BRS, denominadas AI e AP. Além do coquetel fágico, foi aplicado à cultura AP o biocida comercial sulfato de tetrakis(hidroximetil)fosfônico (THPS), de modo a reproduzir nos tanques o método de rotina empregado na indústria para inibir a biocorrosão. Em células planctônicas, a eficiência dos fagos foi avaliada pela quantificação de H₂S, leitura de DO600nm, contagem do número mais provável de células (NMP) e concentração de ATP total. Para as células do biofilme, foi avaliada a quantificação por NMP de células aderidas, concentração de ATP, perda da massa e taxa de corrosão ocorridas nos cupons, além do efeito sobre a estrutura do biofilme, o que foi verificado por Microscopia Eletrônica de Varredura (MEV) e pela da rugosidade da superfície obtida por perfilometria óptica. De maneira similar, com exceção à MEV, as mesmas análises foram conduzidas quando THPS estava sob estudo. Os resultados iniciais demonstraram redução de 77,8% na produção de H₂S pela cultura mista AI na presença do coquetel fágico, além de menor perda de massa e taxa de corrosão dos cupons avaliados. A população da cultura mista AP teve o crescimento interrompido pelo biocida, mas com surgimento de células resistentes após 12 dias. Com o coquetel fágico, a cultura mista AP apresentou redução de 26,1% na produção de H₂S, redução da matriz do biofilme formado e menor extensão dos vales desencadeados por pites de corrosão. Os dados obtidos sugerem o potencial biotecnológico do coquetel de bacteriófagos em um sistema piloto, além de propor alterações futuras como concentração, tempo de aplicação e composição do coquetel de modo a abranger os eventuais problemas de biocorrosão. Palavras-chave: Biofilme. Bactérias Redutoras de Sulfato. Bacteriófagos. Corrosão Microbiologicamente Induzida. Tanques piloto
Corrosion is a physical-chemical process capable of changing the properties of material exposed to corrosive conditions. The oil exploration sector is one of the main sectors of the economy that suffers from that process due to the deterioration of equipment, such as tanks and pipelines, which can lead to oil leakage. Sulfate reducing bacteria (SRB) are the main group related to microbiologically induced corrosion (MIC), causing annual losses to the oil industry due to biofilm formation and the production of hydrogen sulfide (H₂S), a toxic and corrosive gas. In this work, a pilot tank system was used to simulate industrial fluid storage, and AISI 1020 carbon steel coupons were inserted for biofilm formation. In this system, the effect of a cocktail of nonspecific bacteriophages (10^7 PFU/mL), isolated from a wastewater sample, was evaluated on the biofilm and H₂S production of two mixed cultures of SRB, named AI and AP. Moreover, the commercial biocide tetrakis(hydroxymethyl)phosphonic sulfate (THPS) was applied to culture AP, in order to reproduce in the tanks the routine method used in the industry to inhibit biocorrosion. In planktonic cells, phage efficiency was evaluated by H₂S quantification, optical density (OD 600nm), most probable number (MPN) and total ATP concentration. For the biofilm cells, MPN quantification of adhered cells, ATP concentration, mass loss and corrosion rate occurred in the coupons were evaluated, in addition to the effect on the biofilm structure, which was verified by Scanning Electron Microscopy (SEM) and surface roughness obtained by optical profilometry. Similarly, with the exception of SEM, the same analyzes were conducted when THPS was under study. The initial results showed a reduction of 77.8% in the production of H₂S by the mixed culture AI in the presence of the phage cocktail, in addition to lower mass loss and corrosion rate of the evaluated coupons. The population of mixed culture AP had its growth interrupted by the biocide, but with emergence of resistant cells after 12 days. For the phage cocktail, the mixed culture AP showed a 26,1% reduction in the production of H₂S, reduction in the biofilm matrix formed and a smaller extension of the valleys triggered by corrosion pits. The data obtained suggest the biotechnological potential of the bacteriophage cocktail in a pilot system, in addition to proposing future changes such as concentration, application time and cocktail composition in order to cover possible biocorrosion problems. Keywords: Biofilm. Sulfate-reducing Bacteria. Bacteriophages. Microbiologically Induced Corrosion. Pilot tanks.
Corrosion is a physical-chemical process capable of changing the properties of material exposed to corrosive conditions. The oil exploration sector is one of the main sectors of the economy that suffers from that process due to the deterioration of equipment, such as tanks and pipelines, which can lead to oil leakage. Sulfate reducing bacteria (SRB) are the main group related to microbiologically induced corrosion (MIC), causing annual losses to the oil industry due to biofilm formation and the production of hydrogen sulfide (H₂S), a toxic and corrosive gas. In this work, a pilot tank system was used to simulate industrial fluid storage, and AISI 1020 carbon steel coupons were inserted for biofilm formation. In this system, the effect of a cocktail of nonspecific bacteriophages (10^7 PFU/mL), isolated from a wastewater sample, was evaluated on the biofilm and H₂S production of two mixed cultures of SRB, named AI and AP. Moreover, the commercial biocide tetrakis(hydroxymethyl)phosphonic sulfate (THPS) was applied to culture AP, in order to reproduce in the tanks the routine method used in the industry to inhibit biocorrosion. In planktonic cells, phage efficiency was evaluated by H₂S quantification, optical density (OD 600nm), most probable number (MPN) and total ATP concentration. For the biofilm cells, MPN quantification of adhered cells, ATP concentration, mass loss and corrosion rate occurred in the coupons were evaluated, in addition to the effect on the biofilm structure, which was verified by Scanning Electron Microscopy (SEM) and surface roughness obtained by optical profilometry. Similarly, with the exception of SEM, the same analyzes were conducted when THPS was under study. The initial results showed a reduction of 77.8% in the production of H₂S by the mixed culture AI in the presence of the phage cocktail, in addition to lower mass loss and corrosion rate of the evaluated coupons. The population of mixed culture AP had its growth interrupted by the biocide, but with emergence of resistant cells after 12 days. For the phage cocktail, the mixed culture AP showed a 26,1% reduction in the production of H₂S, reduction in the biofilm matrix formed and a smaller extension of the valleys triggered by corrosion pits. The data obtained suggest the biotechnological potential of the bacteriophage cocktail in a pilot system, in addition to proposing future changes such as concentration, application time and cocktail composition in order to cover possible biocorrosion problems. Keywords: Biofilm. Sulfate-reducing Bacteria. Bacteriophages. Microbiologically Induced Corrosion. Pilot tanks.
Descrição
Palavras-chave
Biofilmes, Bactérias redutoras de sulfato, Bacteriófagos, Corrosão microbiologicamente induzida
Citação
VIEIRA, Marcella Silva. Validação de um sistema de tanques piloto para avaliação do efeito de um coquetel de bacteriófagos sobre o biofilme e produção de H₂S por bactérias redutoras de sulfato. 2022. 73 f. Dissertação (Mestrado em Microbiologia Agrícola) - Universidade Federal de Viçosa, Viçosa. 2022.