Investigação da microbiota e dos processos envolvidos na degradação de óleo em reservatórios de petróleo

Author(s)

Isabel Natalia Sierra Garcia

• Document type: Doctoral Thesis
• Institution: Universidade Estadual de Campinas, Instituto de Biologia
• Defense date: 2016
• Advisor: Valéria Maia Merzel

Abstract

Petroleum reservoirs are deep subsurface environments of global importance as energy resources and in biogeochemical cycles. Microorganisms living in petroleum reservoirs are able to use petroleum hydrocarbons as carbon sources, leading to biodegradation and negatively affecting the quality and economic value of oil. Previous studies suggest that anaerobic microorganisms are responsible for in-reservoir oil biodegradation. However, little is known about the actual microbial diversity and metabolic processes involved in biodegradation, mainly because of the difficulty in recovering the complex microbial community present in such extreme environments. This work aimed to characterize the microbiota of two petroleum reservoir samples using culture-independent approaches and assess the anaerobic hydrocarbon degradation potential of the indigenous microorganisms under different physicochemical conditions. The study revealed clear differences in the phylogenetic diversity between the degraded (BA-1) and non-degraded (BA-2) oil samples based on the analysis of bacterial and archaeal 16S rRNA gene clone libraries. The taxonomic and functional differences were also evident in the metagenomic profiles of the two petroleum reservoir samples. The metagenome from the BA-1 sample showed high abundance of genes related with the anaerobic hydrocarbon degradation, methanogenesis and syntrophic associations, while the BA-2 sample showed abundance of aerobic hydrocarbon degradation genes. Correspondingly, a microbial anaerobic active consortium was successfully cultivated from the BA-1 oil sample capable of metabolizing the crude oil components to methane. Higher rates of methane production were observed at the lowest salinity and at the in situ reservoir temperature. Together, the highest salt concentration (120 gl-1) and temperature (70 ºC) tested showed to inhibit the methanogenic activity of the consortium. Data obtained demonstrate that crude oil can harbour an indigenous microbiota with the ability to degrade petroleum hydrocarbons predominantly via methanogenic metabolism. Results gathered herein, and the ongoing work, will help us to understand the potential roles of microbes in hydrocarbon biodegradation and how such organisms respond to the environmental conditions in the petroliferous subsurface. In addition, the unveiled potential of the BA-1 microbiota to convert oil components to methane has an important contribution to the petroleum industry, as methane might be the future for energy production from deep or depleted reservoirs (AU)

• FAPESP's process: 11/14501-6 - Investigation of the microbiota and microbial processes involved in the anaerobic degradation of oil in Brazilian reservoirs
• Grantee: Isabel Natalia Sierra García
• Support type: Scholarships in Brazil - Doctorate