This study evaluated the potential of a microbial consortium collected from a pulp and paper mill wastewater treatment plant (WWTP) for converting cellulose to hydrogen, biogas and organic acids. Fermentation tests were conducted in batch reactors fed with different concentrations of cellulose as substrate: (C1) 2.0 g L -1; (C2) 5.0 g L -1 and (C3) 10.0 g L -1. The parameters investigated were hydrogen, biogas, organic acids, carbohydrates and pH. The maximum hydrogen production was 14.77, 39.25 and 22.53 mmol L -1, and the maximum methane was 4.40, 3.72 and 9.56 mmol L -1, for C1, C2 and C3, respectively. Butyric acid was the main metabolite generated, with maximum concentrations of 2.2, 1.8 and 2.2 g L -1 for C1, C2 and C3, respectively. The decrease in hydrogen production was accompanied by the production of methane, acetic acid and hydrogen sulfide in the three tests, probably related to hydrogenotrophic methanogenesis, homoacetogenesis and sulfidogenesis, respectively. The phylogenetic characterization of the bacterial community was performed by cloning and sequencing analysis. The microorganisms identified in the consortium were similar (> 95%) to Clostridium sp., Klebsiella sp., Routella sp. and Desulfovibrio sp. These genera were associated with hydrogen production, degradation of cellulosic substrates, and/or hydrogen-consuming microorganisms.

Resumo: Objetivo As comunidades microbianas desempenham papel crucial nos processos ambientais como na mineralização de matéria orgânica e ciclagem de nutrientes em ambientes aquáticos. No entanto, apesar da importância ecológica de archaea e bactéria em ambientes aquáticos, a estrutura destas comunidades permanece pouco estudada. Métodos Neste sentido, nos avaliamos a riqueza e densidade de archaea e bactéria na coluna d’água e no sedimento do reservatório de Itupararanga e avaliamos as relações entre os fatores bióticos e abióticos. Para tanto, amostragens foram realizadas em cinco profundidades na região próxima a barragem e em três profundidades no ponto da entrada. Resultados A partir de PCR-DGGE observou-se que ambas as comunidades distribuíram-se ao logo dos pontos de amostragem, mesmo em condições com presença de oxigênio. Conclusões A densidade bacterianas, avaliada por qPCR foi maior do que a de archaea, provavelmente devido a maior plasticidade metabólica desses microrganismos.

Abstract Aim: Microbial communities play a central role in environmental process such as organic matter mineralization and the nutrient cycling process in aquatic ecosystems. Despite their ecological importance, variability of the structure of archaeal and bacterial communities in freshwater remains understudied. Methods In the present study we investigated the richness and density of archaea and bacteria in the water column and sediments of the Itupararanga Reservoir. We also evaluated the relationship between the communities and the biotic and abiotic characteristics. Samples were taken at five depths in the water column next to the dam and three depths next to the reservoir entrance. Results PCR-DGGE evaluation of the archaeal and bacterial communities showed that both were present in the water column, even in oxygenated conditions. Conclusions The density of the bacteria (qPCR) was greater than that of the archaea, a result of the higher metabolic plasticity of bacteria compared with archaea.