Cellulosic ethanol production via consolidated bioprocessing by a novel thermophilic anaerobic bacterium isolated from a Himalayan hot spring

Nisha Singh, Anshu S. Mathur, Deepak K. Tuli, Ravi P. Gupta, Colin J. Barrow, Munish Puri

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    31 Citations (Scopus)

    Abstract

    Background: Cellulose-degrading thermophilic anaerobic bacterium as a suitable host for consolidated bioprocessing (CBP) has been proposed as an economically suited platform for the production of second-generation biofuels. To recognize the overall objective of CBP, fermentation using co-culture of different cellulolytic and sugar-fermenting thermophilic anaerobic bacteria has been widely studied as an approach to achieving improved ethanol production. We assessed monoculture and co-culture fermentation of novel thermophilic anaerobic bacterium for ethanol production from real substrates under controlled conditions. Results: In this study, Clostridium sp. DBT-IOC-C19, a cellulose-degrading thermophilic anaerobic bacterium, was isolated from the cellulolytic enrichment cultures obtained from a Himalayan hot spring. Strain DBT-IOC-C19 exhibited a broad substrate spectrum and presented single-step conversion of various cellulosic and hemicellulosic substrates to ethanol, acetate, and lactate with ethanol being the major fermentation product. Additionally, the effect of varying cellulose concentrations on the fermentation performance of the strain was studied, indicating a maximum cellulose utilization ability of 10 g L-1 cellulose. Avicel degradation kinetics of the strain DBT-IOC-C19 displayed 94.6% degradation at 5 g L-1 and 82.74% degradation at 10 g L-1 avicel concentration within 96 h of fermentation. In a comparative study with Clostridium thermocellum DSM 1313, the ethanol and total product concentrations were higher by the newly isolated strain on pretreated rice straw at an equivalent substrate loading. Three different co-culture combinations were used on various substrates that presented two-fold yield improvement than the monoculture during batch fermentation. Conclusions: This study demonstrated the direct fermentation ability of the novel thermophilic anaerobic bacteria on various cellulosic and hemicellulosic substrates into ethanol without the aid of any exogenous enzymes, representing CBP-based fermentation approach. Here, the broad substrate utilization spectrum of isolated cellulolytic thermophilic anaerobic bacterium was shown to be of potential utility. We demonstrated that the co-culture strategy involving novel strains is efficient in improving ethanol production from real substrate.

    Original languageEnglish
    Article number73
    Number of pages18
    JournalBiotechnology for Biofuels
    Volume10
    DOIs
    Publication statusPublished - 21 Mar 2017

    Bibliographical note

    © The Author(s) 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License
    (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium,
    provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license,
    and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/
    publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

    Keywords

    • Cellulosic ethanol
    • Co-culture fermentation
    • Dilute acid pretreatment
    • Rice straw

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