Diversidade filogenética da comunidade de procariotos associada à digestão anaeróbica de resíduos orgânicos urbanos e de suínos

Abstract

Cities generation of municipal solid waste (MSW) and wastewater is a society inherent phenomenon. Addressing it is essential and anaerobic digestion (AD) is a promising strategy. The knowledge of prokaryotes diversity, dynamics and quantification is essential in order to optimize this process. In this study, we used a combination of molecular approaches to phylogenetically and quantitatively analyze the prokaryotes communities from: a full-scale anaerobic reactor treating MSW (Madrid-Spain) during start-up and in steady condition; a pilotscalereactor treating domestic wastewater (Belo Horizonte) during the dry and rainy seasons; and an anaerobic pond with pig waste in a refrigerator. Shifts in the prokaryotes communities were observed as a result of operational and environmental changes in these systems. Bacteroidetes and Firmicutes (mainly Clostridia) predominated. In the UASB reactor during the rainy season, Bacteroidetes predominated over Firmicutes, Bacilli class organisms were observed and also identified during start-up reactor treating MSW. Proteobacteria, carbohydrates oxidizers, also prevailed in the UASB reactor, with -proteobacteria predominating among the five identified classes. In addition, this group was identified inconjunction with -proteobacteria in the anaerobic pond. In the MSW reactor, only - proteobacteria was identified during start-up. Chloroflexi, common in wastewater and MSW reactors, was identified only in the anaerobic pond. Some phyla, mainly consisting of hydrolytic and acidogenic bacteria, were specific or more common to certain systems. During MSW reactor operation substitutions in the prokaryotes composition, increase in cell numbers and in the volatile fatty acids (VFAs) concentration occurred as a result of organic loading of the reactor. In contrast, in the UASB reactor during the rainy season, sewage dilution resulted in a decrease of bacterial cells, but their speciation increased the diversity of this group, which was the more abundant than archaea in all the systems. In the MSW reactor and anaerobic pond, theproduction of methane was dominated by hydrogenotrophic archaea and its relationship with the VFAs degrading bacteria. In contrast, in the UASB reactor the methane was produced by the aceticlastic and methylotrophic archaea and a minor fraction by hydrogenotrophic archaea. Crenarchaeota predominated in the anaerobic pond and was identified in the MSW reactor during steady conditions. As noted in the three waste treatment systems, the physical-chemical, environmental or operational parameters are directly related to the composition and dynamics of the prokaryotes communities and their metabolism in the degradation of organic matter and methane production.