Detoxification of woody hydrolyzates with activated carbon for bioconversion to ethanol by the thermophilic anaerobic bacterium Thermoanaerobacterium saccharolyticum

Lee, Jung Myoung; Venditti, Richard A.; Jameel, Hasan; Kenealy, William R.

doi:10.1016/j.biombioe.2010.10.021

Cited by 119 publications

(48 citation statements)

References 32 publications

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“…To determine the role of nfnAB in metabolism, nfnAB was deleted in the following T. saccharolyticum strains: wild-type (WT) JW/SL-YS485, M0353 (17), and M1442 (18). The resulting ⌬nfnAB::Kan r strains were LL1144, LL1145, and LL1220, respectively (Table 1).…”

Section: Genetic Manipulation Of Nfnabmentioning

confidence: 99%

Deletion of nfnAB in Thermoanaerobacterium saccharolyticum and Its Effect on Metabolism

Zheng

Olson

et al. 2015

J Bacteriol

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NfnAB catalyzes the reversible transfer of electrons from reduced ferredoxin and NADH to 2 NADP؉ . The NfnAB complex has been hypothesized to be the main enzyme for ferredoxin oxidization in strains of Thermoanaerobacterium saccharolyticum engineered for increased ethanol production. NfnAB complex activity was detectable in crude cell extracts of T. saccharolyticum. Activity was also detected using activity staining of native PAGE gels. The nfnAB gene was deleted in different strains of T. saccharolyticum to determine its effect on end product formation. In wild-type T. saccharolyticum, deletion of nfnAB resulted in a 46% increase in H 2 formation but otherwise little change in other fermentation products. In two engineered strains with 80% theoretical ethanol yield, loss of nfnAB caused two different responses: in one strain, ethanol yield decreased to about 30% of the theoretical value, while another strain had no change in ethanol yield. Biochemical analysis of cell extracts showed that the ⌬nfnAB strain with decreased ethanol yield had NADPH-linked alcohol dehydrogenase (ADH) activity, while the ⌬nfnAB strain with unchanged ethanol yield had NADH-linked ADH activity. Deletion of nfnAB caused loss of NADPH-linked ferredoxin oxidoreductase activity in all cell extracts. Significant NADH-linked ferredoxin oxidoreductase activity was seen in all cell extracts, including those that had lost nfnAB. This suggests that there is an unidentified NADH:ferredoxin oxidoreductase (distinct from nfnAB) playing a role in ethanol formation. The NfnAB complex plays a key role in generating NADPH in a strain that had become reliant on NADPH-ADH activity. IMPORTANCEThermophilic anaerobes that can convert biomass-derived sugars into ethanol have been investigated as candidates for biofuel formation. Many anaerobes have been genetically engineered to increase biofuel formation; however, key aspects of metabolism remain unknown and poorly understood. One example is the mechanism for ferredoxin oxidation and transfer of electrons to NAD(P)؉ . The electron-bifurcating enzyme complex NfnAB is known to catalyze the reversible transfer of electrons from reduced ferredoxin and NADH to 2 NADP ؉ and is thought to play key roles linking NAD(P)(H) metabolism with ferredoxin metabolism. We report the first deletion of nfnAB and demonstrate a role for NfnAB in metabolism and ethanol formation in Thermoanaerobacterium saccharolyticum and show that this may be an important feature among other thermophilic ethanologenic anaerobes. P lant biomass is a sustainable and low-carbon source for biofuels; however, its recalcitrance makes conversion into fuels difficult (1). One of the leading strategies for low-cost conversion of plant biomass into fuels is consolidated bioprocessing (CBP), wherein one or more microbes solubilize plant cell walls and ferment the resulting sugars into fuel without exogenously added enzymes. The thermophilic anaerobe Thermoanaerobacterium saccharolyticum solubilizes components of plant biomass and produces ethano...

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Section: Genetic Manipulation Of Nfnabmentioning

confidence: 99%

Deletion of nfnAB in Thermoanaerobacterium saccharolyticum and Its Effect on Metabolism

Zheng

Olson

et al. 2015

J Bacteriol

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“…As will be seen further in Section 3.6, detoxification with BC or AC seems to be adequate working with yeasts or bacteria because of the high removals of LS, phenolics and acetic acid. This research gave better results in case of furfurals and weak acids in comparison with Guo et al [17] and Lee et al [22] who removed 94%-96% of furfurals, 14%-28% of acetic acid or 88% of total phenolics.…”

Section: Adsorption With Activated Carbon and Black Carbonmentioning

confidence: 78%

“…Despite the fact that sugar losses are inherent to any detoxification technique as they are chemically bonded to the LS structure, sugar losses were lower using BC in comparison with AC under the Once the equilibrium was reached, final concentrations and consequently maximum removals are summarized in Table 1 at different temperatures, adsorbents and ratios. The two adsorbents, AC and BC, at 30 and 50 • C and solid-to-liquid ratios of 1:10 and 1:5 g per mL of SSL were considered based on literature [21,22]. Among the two adsorbents, BC seems to be the most suitable in terms of low molecular phenolic and LS removal.…”

Section: Adsorption With Activated Carbon and Black Carbonmentioning

confidence: 99%

Detoxification of a Lignocellulosic Waste from a Pulp Mill to Enhance Its Fermentation Prospects

2017

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Detoxification is required for sugar bioconversion and hydrolyzate valorization within the biorefining concept for biofuel or bio-product production. In this work, the spent sulfite liquor, which is the main residue provided from a pulp mill, has been detoxified. Evaporation, overliming, ionic exchange resins, and adsorption with activated carbon or black carbon were considered to separate the sugars from the inhibitors in the lignocellulosic residue. Effectiveness in terms of total and individual inhibitor removals, sugar losses and sugar-to-inhibitor removal ratio was determined. The best results were found using the cation exchange Dowex 50WX2 resin in series with the anion exchange Amberlite IRA-96 resin, which resulted in sugar losses of 24.2% with inhibitor removal of 71.3% of lignosulfonates, 84.8% of phenolics, 82.2% acetic acid, and 100% of furfurals. Apart from exchange resins, the results of evaporation, overliming, adsorption with activated carbon and adsorption with black carbon led to total inhibitor removals of 8.6%, 44.9%, 33.6% and 47.6%, respectively. Finally, some fermentation scenarios were proposed in order to evaluate the most suitable technique or combination of techniques that should be implemented in every case.

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“…Carvalheiro et al (2005) achieved similar reductions of furans by treating hemicellulosic hydrolysates from brewery´s spent grain hydrolysates with ion-exchange resins. Lee et al (2011) achieved also nearly complete adsorption of furfural by activated charcoal in woody hydrolysates. Other researchers reported lower reductions of both furfural and HMF concentrations by activated charcoal in switchgrass hydrolysates (Klasson et al, 2013) or woody biomass (Shen et al, 2013).…”

Section: Prehydrolysate Detoxificationmentioning

confidence: 83%

Hemicellulose-derived sugars solubilisation of rape straw. Cofermentation of pentoses and hexoses by Escherichia coli

López-Linares

Cara-Corpas

Ruiz

et al. 2015

Span. j. agric. res.

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Bioconversion of hemicellulose sugars is essential for increasing fuel ethanol yields from lignocellulosic biomass. We report for the first time with rape straw, bioethanol production from hemicellulose sugars. Rape straw was pretreated at mild conditions with sulfuric acid to solubilize the hemicellulose fraction. This pretreatment allows obtaining a prehydrolysate, consisting basically in a solution of monomeric hemicellulosic sugars, with low inhibitor concentrations. The remaining water insoluble solid constitutes a cellulose-enriched, free of extractives material. The influence of temperature (120ºC and 130ºC), acid concentration (2-4% w/v) and pretreatment time (30-180 min) on hemicellulose-derived sugars solubilisation was evaluated. The highest hemicellulosic sugars recovery, 72.3%, was achieved at 130ºC with 2% sulfuric acid and 60 min. At these conditions, a concentrated sugars solution, 52.4 g/L, was obtained after three acid consecutive contacts, with 67% xylose and acetic acid concentration above 4.5 g/L. After a detoxification step by activated charcoal or ion-exchange resin, prehydrolysate was fermented by ethanologenic Escherichia coli. An alcoholic solution of 25 g/L and 86% of theoretical ethanol yield was attained after 144 h when the prehydrolysate was detoxified by ion-exchange resin. The results obtained in the present work show sulfuric acid pretreatment under mild conditions and E. coli as an interesting process to exploit hemicellulosic sugars in rape straw.Additional key words: agricultural residue; acid pretreatment; xylose; E. coli; bioethanol production

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Detoxification of woody hydrolyzates with activated carbon for bioconversion to ethanol by the thermophilic anaerobic bacterium Thermoanaerobacterium saccharolyticum

Cited by 119 publications

References 32 publications

Deletion of nfnAB in Thermoanaerobacterium saccharolyticum and Its Effect on Metabolism

Deletion of nfnAB in Thermoanaerobacterium saccharolyticum and Its Effect on Metabolism

Detoxification of a Lignocellulosic Waste from a Pulp Mill to Enhance Its Fermentation Prospects

Hemicellulose-derived sugars solubilisation of rape straw. Cofermentation of pentoses and hexoses by Escherichia coli

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