Dissecting microbial community structure and acidogenic fermentation pathways of rumen microorganisms fermenting office paper under mesophilic and thermophilic temperatures by massive sequencing

This study aimed the hydrolysis and fermentation of paper with recovery of H2 and VFAs using a natural microbial consortium in lysimeters. Serial dilutions of rumen fluid in natura (F.N.) were performed to obtain the fermentative non-methanogenic purified consortium (F.P.). Then, the consortium was used as inoculum in lysimeters under 2 different conditions of mass of paper (g) and temperature of incubation (oC), under the same paper’s moisture content (80%), at pH 5.5: L1 (500 g; 80%; 35 oC) and L2 (1000 g; 80%; 55 oC). For monitoring the lysimeters in relation to paper hydrolysis and fermentation, analyses of biogas (H2, N2, CO2 e CH4) and the compounds’ concentrations in the leachate, such as, total sugars, chemical oxygen demand, volatile fatty acids (VFA’s) and alcohols were performed. Alcalinity, pH and total solids content of the leachate were also monitored. High-throughput sequencing was used to characterize the phylogenetic composition and functional potential of microbial consortium. The effect of temperature, mass of paper and paper’s moisture content was evaluated on the microbial community and on the metabolisms performed by the microorganisms at each condition. Hydrogen production was detected in lysimeters with 35 mmol (L1) and 3 mmol (L2). In L1, high concentration of acetic acid, of 17.000 mg/L, respectively, were due to the likely occurrence of homoacetogenesis. Under thermophilic condition L2, the hydrogen production was detected in low volume, and the highlight was the production of ethanol and methanol, with concentrations around 2.300 and 5.600 mg/L, respectively. The most abundant microbial genus in each sample sequenced were: Prevotella in the rumen fluid in natura (F.N.) Dysgonomonas in the purified consortium and L1 (35o C) and Thermicanus in L2 (55o C). In conclusion, moisture content of 80% promoted paper hydrolysis and fermentation by microorganisms; temperature was the principal parameter that influenced the structure of microbial community, confirmed by the different metabolic route observed under mesophilic and thermophilic conditions; and the production yields of the compounds were not influenced by the mass of paper added to the lysimeters.