{"references": ["A. A. Keller, S. McFerran, A. Lazareva, and S. Suh, \"Global life cycle releases of engineered nanomaterials,\" Journal of Nanoparticle Research, vol. 15, pp. 1-17, 2013, pp. 1-17.", "Z.-Y. Zhou, N. Tian, J.-T. Li, I. Broadwell, and S.-G. Sun, \"Nanomaterials of high surface energy with exceptional properties in catalysis and energy storage,\" Chemical Society Reviews, vol. 40, pp. 4167-4185, 2011, pp. 4167-4185.", "T. M. Benn and P. Westerhoff, \"Nanoparticle silver released into water from commercially available sock fabrics,\" Environmental science & technology, vol. 42, pp. 4133-4139, 2008, pp. 4133-4139.", "H.-J. Kim, T. Phenrat, R. D. Tilton, and G. V. Lowry, \"Fe0 nanoparticles remain mobile in porous media after aging due to slow desorption of polymeric surface modifiers,\" Environmental Science & Technology, vol. 43, pp. 3824-3830, 2009, pp. 3824-3830.", "A. P. Roberts, A. S. Mount, B. Seda, J. Souther, R. Qiao, S. Lin, et al., \"In vivo biomodification of lipid-coated carbon nanotubes by Daphnia magna,\" Environmental science & technology, vol. 41, pp. 3025-3029, 2007, pp. 3025-3029.", "J. N. Mwangi, N. Wang, C. G. Ingersoll, D. K. Hardesty, E. L. Brunson, H. Li, et al., \"Toxicity of carbon nanotubes to freshwater aquatic invertebrates,\" Environmental Toxicology and Chemistry, vol. 31, pp. 1823-1830, 2012, pp. 1823-1830.", "A. D. Maynard, R. J. Aitken, T. Butz, V. Colvin, K. Donaldson, G. Oberd\u00f6rster, et al., \"Safe handling of nanotechnology,\" Nature, vol. 444, pp. 267-269, 2006, pp. 267-269.", "T. Satterfield, M. Kandlikar, C. E. Beaudrie, J. Conti, and B. H. Harthorn, \"Anticipating the perceived risk of nanotechnologies,\" Nature nanotechnology, vol. 4, pp. 752-758, 2009, pp. 752-758.", "L. H. Alvarez and F. J. Cervantes, \"Assessing the impact of alumina nanoparticles in an anaerobic consortium: methanogenic and humus reducing activity,\" Applied microbiology and biotechnology, vol. 95, pp. 1323-1331, 2012, pp. 1323-1331.\n[10]\tA. Distaso, \"For an integrated and sustainable management of solid urban waste: an approach based on the theory of social costs,\" International Journal of Sustainable Development, vol. 15, pp. 220-248, 2012, pp. 220-248.\n[11]\t\tC. Wolfram, O. Shelef, and P. Gertler, \"How will energy demand develop in the developing world?,\" The Journal of Economic Perspectives, vol. 26, pp. 119-137, 2012, pp. 119-137.\n[12]\tL. Adelard, T. G. Poulsen, and V. Rakotoniaina, \"Biogas and methane yield in response to co-and separate digestion of biomass wastes,\" Waste Management & Research, vol. 33, pp. 55-62, 2015, pp. 55-62.\n[13]\tC. Mao, Y. Feng, X. Wang, and G. Ren, \"Review on research achievements of biogas from anaerobic digestion,\" Renewable and Sustainable Energy Reviews, vol. 45, pp. 540-555, 2015, pp. 540-555.\n[14]\tM. Hoogwijk, A. Faaij, R. Van Den Broek, G. Berndes, D. Gielen, and W. Turkenburg, \"Exploration of the ranges of the global potential of biomass for energy,\" Biomass and bioenergy, vol. 25, pp. 119-133, 2003, pp. 119-133.\n[15]\tB. Wang, J. Sui, R. Liu, G. Yang, and P. Qi, \"Anaerobic reactors treating beet sugar effluents,\" Effluent & water treatment journal, vol. 26, pp. 150-162, 1986, pp. 150-162.\n[16]\tA. J. Justo, L. Junfeng, S. Lili, W. Haiman, M. R. Lorivi, M. O. Mohammed, et al., \"Integrated expanded granular sludge bed and sequential batch reactor treating beet sugar industrial wastewater and recovering bioenergy,\" Environmental Science and Pollution Research, pp. 1-9, 2016, pp. 1-9.\n[17]\tE. Casals, R. Barrena, A. Garc\u00eda, E. Gonz\u00e1lez, L. Delgado, M. Busquets\u2010Fit\u00e9, et al., \"Programmed iron oxide nanoparticles disintegration in anaerobic digesters boosts biogas production,\" Small, vol. 10, pp. 2801-2808, 2014, pp. 2801-2808.\n[18]\tS. Kato, K. Hashimoto, and K. Watanabe, \"Methanogenesis facilitated by electric syntrophy via (semi) conductive iron\u2010oxide minerals,\" Environmental microbiology, vol. 14, pp. 1646-1654, 2012, pp. 1646-1654.\n[19]\tT. Wang, D. Zhang, L. Dai, Y. Chen, and X. Dai, \"Effects of Metal Nanoparticles on Methane Production from Waste-Activated Sludge and Microorganism Community Shift in Anaerobic Granular Sludge,\" Scientific reports, vol. 6, 2016.\n[20]\tT. W. Odom, J.-L. Huang, P. Kim, and C. M. Lieber, \"Atomic structure and electronic properties of single-walled carbon nanotubes,\" Nature, vol. 391, pp. 62-64, 1998, pp. 62-64.\n[21]\tA. Simon-Deckers, S. Loo, M. Mayne-L'hermite, N. Herlin-Boime, N. Menguy, C. Reynaud, et al., \"Size-, composition-and shape-dependent toxicological impact of metal oxide nanoparticles and carbon nanotubes toward bacteria,\" Environmental science & technology, vol. 43, pp. 8423-8429, 2009, pp. 8423-8429.\n[22]\tT. Yadav, A. A. Mungray, and A. K. Mungray, \"Effect of multiwalled carbon nanotubes on UASB microbial consortium,\" Environmental Science and Pollution Research, pp. 1-10, 2015, pp. 1-10.\n[23]\tL.-L. Li, Z.-H. Tong, C.-Y. Fang, J. Chu, and H.-Q. Yu, \"Response of anaerobic granular sludge to single-wall carbon nanotube exposure,\" Water research, vol. 70, pp. 1-8, 2015, pp. 1-8.\n[24]\tW. Jin, Z.-j. Zhang, Z.-f. Zhang, M. Qaisar, and P. Zheng, \"Production and application of anaerobic granular sludge produced by landfill,\" Journal of Environmental Sciences, vol. 19, pp. 1454-1460, 2007, pp. 1454-1460.\n[25]\tG.-P. Sheng, H.-Q. Yu, and X.-Y. Li, \"Extracellular polymeric substances (EPS) of microbial aggregates in biological wastewater treatment systems: a review,\" Biotechnology advances, vol. 28, pp. 882-894, 2010, pp. 882-894.\n[26]\tY. Chen, J. J. Cheng, and K. S. Creamer, \"Inhibition of anaerobic digestion process: a review,\" Bioresource technology, vol. 99, pp. 4044-4064, 2008, pp. 4044-4064.\n[27]\tH. Mu, X. Zheng, Y. Chen, H. Chen, and K. Liu, \"Response of anaerobic granular sludge to a shock load of zinc oxide nanoparticles during biological wastewater treatment,\" Environmental science & technology, vol. 46, pp. 5997-6003, 2012, pp. 5997-6003.\n[28]\tL. R. Lynd, P. J. Weimer, W. H. Van Zyl, and I. S. Pretorius, \"Microbial cellulose utilization: fundamentals and biotechnology,\" Microbiology and molecular biology reviews, vol. 66, pp. 506-577, 2002, pp. 506-577."]}

Quick development and usage of nanotechnology have resulted to massive use of various nanoparticles, such as iron oxide nanoparticles (IONPs) and multi-wall carbon nanotubes (MWCNTs). Thus, this study investigated the role of IONPs and MWCNTs in enhancing bioenergy recovery. Results show that IONPs at a concentration of 750 mg/L and MWCNTs at a concentration of 1500 mg/L induced faster substrate utilization and biogas production rates than the control. IONPs exhibited higher carbon oxygen demand (COD) removal efficiency than MWCNTs while on the contrary, MWCNT performance on biogas generation was remarkable than IONPs. Furthermore, scanning electron microscopy (SEM) investigation revealed extracellular polymeric substances (EPS) excretion from AGS had an interaction with nanoparticles. This interaction created a protective barrier to microbial consortia hence reducing their cytotoxicity. Microbial community analyses revealed genus predominance of bacteria of Anaerolineaceae and Longilinea. Their role in biodegradation of the substrate could have highly been boosted by nanoparticles. The archaea predominance of the genus level of Methanosaeta and Methanobacterium enhanced methanation process. The presence of bacteria of genus Geobacter was also reported. Their presence might have significantly contributed to direct interspecies electron transfer in the system. Exposure of AGS to nanoparticles promoted direct interspecies electron transfer among the anaerobic fermenting bacteria and their counterpart methanogens during the anaerobic digestion process. This results provide useful insightful information in understanding the response of microorganisms to IONPs and MWCNTs in the complex natural environment.