Angelidaki, Irini

Campanaro, S.

De Francisci, Davide

Kougias, Panagiotis

Treu, Laura

Online Research Database In Technology

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Downloaded from orbit.dtu.dk on: Dec 20, 2017Microbial diversity and dynamicity of biogas reactors fed with different substratesDe Francisci, Davide; Kougias, Panagiotis; Treu, Laura; Campanaro, S.; Angelidaki, IriniPublished in:Proceedings of the 2nd International Conference on Biogas MicrobiologyPublication date:2014Link back to DTU OrbitCitation (APA):De Francisci, D., Kougias, P., Treu, L., Campanaro, S., & Angelidaki, I. (2014). Microbial diversity anddynamicity of biogas reactors fed with different substrates. In Proceedings of the 2nd International Conferenceon Biogas MicrobiologyMicrobial diversity and dynamicity of biogas reactors fed with different substrates  Davide De Francisci1, Panagiotis G. Kougias1, Laura Treu1, Stefano Campanaro2, Irini Angelidaki1  1Department of Environmental Engineering, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark 2Department of Biology, University of Padua, Via U. Bassi 58/b 35131 Padova, Italy   Anaerobic digestion (AD) is widely applied method for treating different types of wastes. Nowadays, the biogas plants have proliferated and therefore extra biomass is needed in order to meet the surplus needs. In Denmark, most of the biogas plants are co-digesting manure (at an amount of 70%) and other organic residues mainly derived from food industries (at an amount of 30%) (Angelidaki and Ellegaard, 2003). As a consequence, the mixed feedstock is very complex and contains several compounds that could either result in a successful combination for the biomethanation or in contrary could inhibit the AD process. Aim of this study is to gain a deeper understanding on how the microbial ecology of the biogas reactors, mainly constituted by Archaea and Bacteria, responds to radical changes of substrate.  The experimental work was carried out in three continuous stirred tank reactors (CSTR) denoted as R1, R2 and R3, operating under thermophilic conditions (54±1oC). The hydraulic retention time (HRT) of the reactors was kept to 15 days. During the start-up period all the reactors were inoculated with thermophilic inoculum obtained from Hashøj biogas plant, Denmark. The whole experiment was divided in two periods; during the first experimental period all the reactors were fed with cattle manure, while in the second period the substrate contained cattle manure supplemented with proteins (R1), lipids (R2) and carbohydrates (R3).  The amount of the different compounds added to the manure was based according to preliminary experiment in order to maintain the level of organic loading rate (OLR) stable (Kougias et al., 2013). Samples were taken from each reactor prior to the feedstock change and after a time period of one HRT during which the reactors were fed with the corresponding mixed substrate. DNA was extracted from each sample and the corresponding microbial composition was determined via analyses of 16S amplicons. During the experiment the daily biogas production, the composition of methane in biogas, pH and the concentration of volatile fatty acids (VFA) were recorded. Before the substrate change, the microbial composition of the three reactors was found to be extremely similar. The most abundant within the identified genera (excluding < 1% relative abundance) were found to be Methanobrevibacter, Megamonas, Flectobacillus, Bacteroides, Clostridium, Myroides, Flavobacterium and Bacillus. After the substrate composition was modified, taking in consideration only the genera whose relative abundance reached at least 1% before or after the change, the profile of the microbial communities substantially changed within a relatively short period of time, corresponding to one HRT. In the reactor supplemented with carbohydrates, the relative abundance of microorganisms belonging to the genera Methanobravibacter and Bacteroides show the highest decrease (12 and 9 folds, respectively), Myroides 3 folds and Flavobacterium 2 folds. These decrements are compensated by the enormous increase (69 folds) of Lactobacillus and the more moderate of Bacillus (2 folds). In the reactor supplemented with lipids Methanobrevibacter and Bacteroides are again found to decrease of several folds (6 and 4, respectively) together with Myroides (14 folds) Flectobacillus (2 folds) and Bacillus (decrease of 2 folds). Megamonas is the only genus that increased its relative abundance upon the addition of lipids (increase of 2 folds). In contrast with the aforementioned reactors, the one supplemented with proteins did not undergo substantial changes in its microbial composition. Methanobrevibacter is the only genus whose relative abundance varies significantly (decrease of 2 folds). This simple analysis underlines the dynamicity of microbial communities populating biogas reactors showing that by changing the composition of the main substrate the profile of the microbial community undergoes a profound transformation and is significantly altered already after a relatively short period of time corresponding to one HRT.  References  1. Demirel, B., Scherer, P., 2010. The roles of acetotrophic and hydrogenotrophic methanogens     during anaerobic conversion of biomass to methane: a review. Rev Environ Sci Biotechnol 7, 173–190. 2. Morita, M., Sasaki, K., 2012. Factors influencing the degradation of garbage in methanogenic    bioreactors and impacts on biogas formation. Appl Microbiol Biotechnol. 94, 575–582. 3. Hung, C., Chang, Y., Chang Y., 2011. Roles of microorganisms other than Clostridium and Enterobacter in anaerobic fermentative biohydrogen production systems – A review. Bioresource Technology. 102, 8437–8444. 4. Baserba, M., Karakashev, D., Angelidaki, I., 2012. Effect of continuous oleate addition on microbial communities involved in anaerobic digestion process. Bioresource Technology. 106, 74–81. 5. Kanokwan Boe, K., Batstonea, D., Steyera, J. Angelidaki, I., 2010. State indicators for monitoring the anaerobic digestion process. Water Research. 44, 5973-5980. 6. Kougias, P.K., Boe, K., Angelidaki, I., 2013. Effect of organic loading rate and feedstock composition on foaming in manure-based biogas reactors. Bioresource Technology. 144, 1-7. 7. Angelidaki, I., Ellegaard, L.,  2003. Codigestion of manure and organic wastes in centralized biogas plants. Applied Biochemistry and Biotechnology. 109, 95-105.  Conference topic: - Microbial inhibition and adaptation to perturbations ORAL PRESENTATION  

Microbial diversity and dynamicity of biogas reactors fed with different substrates

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Microbial diversity and dynamicity of biogas reactors fed with different substrates

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