Influence of Carbon Source Pre-Adaptation on Clostridium ljungdahlii Growth and Product Formation

Tirado-Acevedo, Oscar; Cotter, Jacqueline L.; Chinn, Mari S.; Grunden, Amy M.

doi:10.4172/2155-9821.s2-001

Cited by 9 publications

(9 citation statements)

References 22 publications

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“…lostridium ljungdahlii is a promising chassis for the production of organic commodities and biofuels from syngas and carbon monoxide wastes (1)(2)(3)(4)(5) as well as for microbial electrosynthesis, a process in which electrical energy powers the microbial reduction of carbon dioxide to multicarbon organic compounds (6)(7)(8)(9). One reason that C. ljungdahlii is an attractive catalyst for these processes is that it uses carbon dioxide as an electron acceptor for anaerobic respiration via the Wood-Ljungdahl pathway (7,(10)(11)(12).…”

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confidence: 99%

Lactose-Inducible System for Metabolic Engineering of Clostridium ljungdahlii

Banerjee

Leang

Ueki

et al. 2014

Appl Environ Microbiol

105

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The development of tools for genetic manipulation of Clostridium ljungdahlii has increased its attractiveness as a chassis for autotrophic production of organic commodities and biofuels from syngas and microbial electrosynthesis and established it as a model organism for the study of the basic physiology of acetogenesis. In an attempt to expand the genetic toolbox for C. ljungdahlii, the possibility of adapting a lactose-inducible system for gene expression, previously reported for Clostridium perfringens, was investigated. The plasmid pAH2, originally developed for C. perfringens with a gusA reporter gene, functioned as an effective lactose-inducible system in C. ljungdahlii. Lactose induction of C. ljungdahlii containing pB1, in which the gene for the aldehyde/alcohol dehydrogenase AdhE1 was downstream of the lactose-inducible promoter, increased expression of adhE1 30-fold over the wild-type level, increasing ethanol production 1.5-fold, with a corresponding decrease in acetate production. Lactose-inducible expression of adhE1 in a strain in which adhE1 and the adhE1 homolog adhE2 had been deleted from the chromosome restored ethanol production to levels comparable to those in the wild-type strain. Inducing expression of adhE2 similarly failed to restore ethanol production, suggesting that adhE1 is the homolog responsible for ethanol production. Lactose-inducible expression of the four heterologous genes necessary to convert acetyl coenzyme A (acetyl-CoA) to acetone diverted ca. 60% of carbon flow to acetone production during growth on fructose, and 25% of carbon flow went to acetone when carbon monoxide was the electron donor. These studies demonstrate that the lactose-inducible system described here will be useful for redirecting carbon and electron flow for the biosynthesis of products more valuable than acetate. Furthermore, this tool should aid in optimizing microbial electrosynthesis and for basic studies on the physiology of acetogenesis.

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confidence: 99%

Lactose-Inducible System for Metabolic Engineering of Clostridium ljungdahlii

Banerjee

Leang

Ueki

et al. 2014

Appl Environ Microbiol

105

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“…In addition to tolerating various amounts of oxygen, it has been suggested that exposing acetogens to microaerobic conditions triggers a shift in electron flow toward more reduced products, such as ethanol, lactate, H 2 , and/or NH 4 ϩ production instead of acetate formation (51,59,61). C. ljungdahlii was previously shown to grow well and coferment fructose and artificial syngas in a complex medium (5,6,62). Upon exposure to low concentrations of oxygen (Ͻ10%) in the headspace of batch cultures at early log phase, C. ljungdahlii continued to grow and coferment fructose and artificial synthesis gas components while showing an increase in ethanol/acetate ratios (63).…”

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confidence: 99%

Metabolic Response of Clostridium ljungdahlii to Oxygen Exposure

Whitham

Tirado-Acevedo

Chinn

et al. 2015

Appl Environ Microbiol

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cClostridium ljungdahlii is an important synthesis gas-fermenting bacterium used in the biofuels industry, and a preliminary investigation showed that it has some tolerance to oxygen when cultured in rich mixotrophic medium. Batch cultures not only continue to grow and consume H 2 , CO, and fructose after 8% O 2 exposure, but fermentation product analysis revealed an increase in ethanol concentration and decreased acetate concentration compared to non-oxygen-exposed cultures. In this study, the mechanisms for higher ethanol production and oxygen/reactive oxygen species (ROS) detoxification were identified using a combination of fermentation, transcriptome sequencing (RNA-seq) differential expression, and enzyme activity analyses. The results indicate that the higher ethanol and lower acetate concentrations were due to the carboxylic acid reductase activity of a more highly expressed predicted aldehyde oxidoreductase (CLJU_c24130) and that C. ljungdahlii's primary defense upon oxygen exposure is a predicted rubrerythrin (CLJU_c39340). The metabolic responses of higher ethanol production and oxygen/ ROS detoxification were found to be linked by cofactor management and substrate and energy metabolism. This study contributes new insights into the physiology and metabolism of C. ljungdahlii and provides new genetic targets to generate C. ljungdahlii strains that produce more ethanol and are more tolerant to syngas contaminants. Clostridium ljungdahlii is an anaerobic, motile, endosporeforming, Gram-positive, rod-shaped, acetogenic bacterium isolated from chicken yard waste and has application as a biocatalyst to transform syngas components (CO, CO 2 , and H 2 ) into more valuable chemicals (1-4). It was the first bacterium discovered to metabolize these syngas components and to produce ethanol with acetate as its primary fermentation product (1, 4). To reduce the amount of acetate and increase the amount of ethanol produced by C. ljungdahlii for its use in industrial solvent production, different reactor designs and agitation parameters, varied syngas component concentrations, increased gas flow rates and pressures, reduced nitrogen sources, addition of reducing agents to media, adjustment of growth medium pH, and addition of nanoparticles have all been evaluated (1,(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). Some of these efforts have reportedly improved ethanol/ acetate product ratios from 1:20 to 2:1 in batch cultures and from 1:1 to 21:1 for cultures grown in continuously stirred reactors (8,9,16). More recent sequencing and genetic modification techniques have greatly enhanced our understanding of C. ljungdahlii's metabolism and increased production of ethanol as well as enabled production of other chemicals (e.g., acetone, butyrate, and butanol) (2, 3, 17-21).Despite these advancements, for C. ljungdahlii to be effectively used for industrial syngas transformation, some of its catalytic limitations related to gaseous headspace composition still require evaluation. Although steel mill waste gas was recently used as...

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“…For instance, in the acetogen Clostridium ljungdahlii, it has been demonstrated that an adaptation phase, reached by exposing the pre-cultures to CO, could enhance CO stress tolerance. Moreover, in the same study, it was also demonstrated that the combination of CO and a reducing sugar could positively affect the accumulation of both the biomass and the end products, such as ethanol or acetate, due to a higher accumulation of energy (e.g., ATP and GTP), and to the reducing equivalents (e.g., NADH) provided by the sugar metabolism [27].…”

Section: Introductionmentioning

confidence: 80%

Carbon monoxide fermentation to bioplastic: the effect of substrate adaptation on Rhodospirillum rubrum

Mongili

Fino

2020

Biomass Conv. Bioref.

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Rhodospirillum rubrum is a gram-negative bacterium that naturally takes advantage of CO and which, in the presence of acetate, accumulates carbon and energy units as polyhydroxybutyrate (PHB). Since the conversion of CO depends on a large protein membrane complex that is expressed after the exposure to carbon monoxide, this study presents the effects of a CO-based acclimation in R. rubrum on the growth trend and on the production of PHB. The strain was cultured in two consecutive fermentation cycles on 15% of CO, and the behaviour of this species, in the presence of acetate or a reducing sugar, such as fructose, was compared. The exposure of R. rubrum to CO during the first adaptation phase led to the development of a metabolically active population characterised by a greater biomass growth. The supply of fructose ensured a shorter lag-phase and a higher biomass titre, but it also determined a decrease in the biopolymer accumulation. However, R. rubrum showed the best carbon utilisation in the absence of fructose, with a growth molar yield of 48 mg mol −1 , compared to the 12 mg mol −1 obtained for fructose feeding.

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Influence of Carbon Source Pre-Adaptation on Clostridium ljungdahlii Growth and Product Formation

Cited by 9 publications

References 22 publications

Lactose-Inducible System for Metabolic Engineering of Clostridium ljungdahlii

Lactose-Inducible System for Metabolic Engineering of Clostridium ljungdahlii

Metabolic Response of Clostridium ljungdahlii to Oxygen Exposure

Carbon monoxide fermentation to bioplastic: the effect of substrate adaptation on Rhodospirillum rubrum

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