Development and characterization of stable anaerobic thermophilic methanogenic microbiomes fermenting switchgrass at decreasing residence times

Autor: Zamin K. Yang, Vincent Lombard, Liang Tian, James Elkins, Lee R. Lynd, Evert K. Holwerda, Tom L. Richard, Mircea Podar, Dawn M. Klingeman, Xiaoyu Liang, Bernard Henrissat, Steven D. Brown, Yu Wei Wu, Xiongjun Shao, Jason M. Whitham
Přispěvatelé: Thayer School of Engineering, Dartmouth College [Hanover], BioSciences Division [Oak Ridge], Oak Ridge National Laboratory [Oak Ridge] (ORNL), UT-Battelle, LLC-UT-Battelle, LLC, Joint BioEnergy Institute [Emeryville], Architecture et fonction des macromolécules biologiques (AFMB), Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), Pennsylvania State University (Penn State), Penn State System, NOAA Earth System Research Laboratory (ESRL), National Oceanic and Atmospheric Administration (NOAA), BioEnergy Science Center, a US Department of Energy Bioenergy Research Center - Office of Biological and Environmental Research in the DOE Office of Science [DE-AC05-00OR22725], US DOE [DE-AC05-00OR22725], Biomass Research and Development Initiative from the National Institute of Food and Agriculture, US Department of Agriculture [2016-10008-25319], Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Lynd, Lee R
Jazyk: angličtina
Rok vydání: 2018
Předmět:
Zdroj: Biotechnology for Biofuels
Biotechnology for Biofuels, BioMed Central, 2018, 11 (1), pp.243. ⟨10.1186/s13068-018-1238-1⟩
Biotechnology for Biofuels, 2018, 11 (1), pp.243. ⟨10.1186/s13068-018-1238-1⟩
Biotechnology for Biofuels (11), . (2018)
Biotechnology for Biofuels, Vol 11, Iss 1, Pp 1-18 (2018)
ISSN: 1754-6834
DOI: 10.1186/s13068-018-1238-1⟩
Popis: Background Anaerobic fermentation of lignocellulose occurs in both natural and managed environments, and is an essential part of the carbon cycle as well as a promising route to sustainable production of fuels and chemicals. Lignocellulose solubilization by mixed microbiomes is important in these contexts. Results Here, we report the development of stable switchgrass-fermenting enrichment cultures maintained at various residence times and moderately high (55 °C) temperatures. Anaerobic microbiomes derived from a digester inoculum were incubated at 55 °C and fed semi-continuously with medium containing 30 g/L mid-season harvested switchgrass to achieve residence times (RT) of 20, 10, 5, and 3.3 days. Stable, time-invariant cellulolytic methanogenic cultures with minimal accumulation of organic acids were achieved for all RTs. Fractional carbohydrate solubilization was 0.711, 0.654, 0.581 and 0.538 at RT = 20, 10, 5 and 3.3 days, respectively, and glucan solubilization was proportional to xylan solubilization at all RTs. The rate of solubilization was described well by the equation r = k(C − C0fr), where C represents the concentration of unutilized carbohydrate, C0 is the concentration of carbohydrate (cellulose and hemicellulose) entering the bioreactor and fr is the extrapolated fraction of entering carbohydrate that is recalcitrant at infinite residence time. The 3.3 day RT is among the shortest RT reported for stable thermophilic, methanogenic digestion of a lignocellulosic feedstock. 16S rDNA phylotyping and metagenomic analyses were conducted to characterize the effect of RT on community dynamics and to infer functional roles in the switchgrass to biogas conversion to the various microbial taxa. Firmicutes were the dominant phylum, increasing in relative abundance from 54 to 96% as RT decreased. A Clostridium clariflavum strain with genetic markers for xylose metabolism was the most abundant lignocellulose-solubilizing bacterium. A Thermotogae (Defluviitoga tunisiensis) was the most abundant bacterium in switchgrass digesters at RT = 20 days but decreased in abundance at lower RTs as did multiple Chloroflexi. Synergistetes and Euryarchaeota were present at roughly constant levels over the range of RTs examined. Conclusions A system was developed in which stable methanogenic steady-states were readily obtained with a particulate biomass feedstock, mid-season switchgrass, at laboratory (1 L) scale. Characterization of the extent and rate of carbohydrate solubilization in combination with 16S rDNA and metagenomic sequencing provides a multi-dimensional view of performance, species composition, glycoside hydrolases, and metabolic function with varying residence time. These results provide a point of reference and guidance for future studies and organism development efforts involving defined cultures. Electronic supplementary material The online version of this article (10.1186/s13068-018-1238-1) contains supplementary material, which is available to authorized users.
Databáze: OpenAIRE
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