Metabolite stress and tolerance in the production of biofuels and chemicals: Gene‐expression‐based systems analysis of butanol, butyrate, and acetate stresses in the anaerobe <i>Clostridium acetobutylicum</i>

Alsaker, Keith V.; Paredes, Carlos J.; Papoutsakis, Eleftherios T.

doi:10.1002/bit.22628

Cited by 202 publications

(220 citation statements)

References 99 publications

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“…The metabolic activity of C. acetobutylicum greatly decreases with the age of culture (28), due to metabolite inhibition (1) and/or sporulation. Thus, it was reasoned that alleviating solvent toxicity using gas stripping (6) would allow prolonged solvent production, resulting in the production of more butanol as well as isopropanol and ethanol.…”

Section: Discussionmentioning

confidence: 99%

Metabolic Engineering of Clostridium acetobutylicum ATCC 824 for Isopropanol-Butanol-Ethanol Fermentation

Lee

Jang

Choi

et al. 2012

Appl Environ Microbiol

215

141

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Clostridium acetobutylicum naturally produces acetone as well as butanol and ethanol. Since acetone cannot be used as a biofuel, its production needs to be minimized or suppressed by cell or bioreactor engineering. Thus, there have been attempts to disrupt or inactivate the acetone formation pathway. Here we present another approach, namely, converting acetone to isopropanol by metabolic engineering. Since isopropanol can be used as a fuel additive, the mixture of isopropanol, butanol, and ethanol (IBE) produced by engineered C. acetobutylicum can be directly used as a biofuel. IBE production is achieved by the expression of a primary/secondary alcohol dehydrogenase gene from Clostridium beijerinckii NRRL B-593 (i.e., adh B-593 ) in C. acetobutylicum ATCC 824. To increase the total alcohol titer, a synthetic acetone operon (act operon; adc-ctfA-ctfB) was constructed and expressed to increase the flux toward isopropanol formation. When this engineering strategy was applied to the PJC4BK strain lacking in the buk gene (encoding butyrate kinase), a significantly higher titer and yield of IBE could be achieved. The resulting PJC4BK(pIPA3-Cm2) strain produced 20.4 g/liter of total alcohol. Fermentation could be prolonged by in situ removal of solvents by gas stripping, and 35.6 g/liter of the IBE mixture could be produced in 45 h.

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Section: Discussionmentioning

confidence: 99%

Metabolic Engineering of Clostridium acetobutylicum ATCC 824 for Isopropanol-Butanol-Ethanol Fermentation

Lee

Jang

Choi

et al. 2012

Appl Environ Microbiol

215

141

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“…This included several genes probably in- During host infection, C. difficile is exposed to several stresses and responds to stress stimuli by inducing different mechanisms of defense (62). Among stress-related genes, we observed about 2-fold upregulation of genes encoding heat shock proteins, including groEL (CD0194) and grpE (CD2462) that are induced by clinically relevant heat stress and acid pH conditions in C. difficile (63,64) and by metabolic stresses in Clostridium acetobutylicum (65). Moreover, the expression of several genes that might be involved in the oxygen tolerance response and cell redox balance was altered in the CDIP53 strain compared to the CDIP51 strain.…”

Section: Construction Of a Strain Depleted For Hfq And Analysis Of Itmentioning

confidence: 91%

Pleiotropic Role of the RNA Chaperone Protein Hfq in the Human Pathogen Clostridium difficile

et al. 2014

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cClostridium difficile is an emergent human pathogen and the most common cause of nosocomial diarrhea. Our recent data strongly suggest the importance of RNA-based mechanisms for the control of gene expression in C. difficile. In an effort to understand the function of the RNA chaperone protein Hfq, we constructed and characterized an Hfq-depleted strain in C. difficile. Hfq depletion led to a growth defect, morphological changes, an increased sensitivity to stresses, and a better ability to sporulate and to form biofilms. The transcriptome analysis revealed pleiotropic effects of Hfq depletion on gene expression in C. difficile, including genes encoding proteins involved in sporulation, stress response, metabolic pathways, cell wall-associated proteins, transporters, and transcriptional regulators and genes of unknown function. Remarkably, a great number of genes of the regulon dependent on sporulation-specific sigma factor, SigK, were upregulated in the Hfq-depleted strain. The altered accumulation of several sRNAs and interaction of Hfq with selected sRNAs suggest potential involvement of Hfq in these regulatory RNA functions. Altogether, these results suggest the pleiotropic role of Hfq protein in C. difficile physiology, including processes important for the C. difficile infection cycle, and expand our knowledge of Hfq-dependent regulation in Gram-positive bacteria.

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“…On the other hand, they might play important roles in the stabilities of fermentation performance and community of complex microbial consortiums in anaerobic fermentation systems by reducing VFAs (e.g., acetate, lactate, butyrate, etc.) and hydrogen stress (47,48). Furthermore, Nitrososphaera, an ammonia-oxidizing archaeal genus, plays important roles in nitrification (49).…”

Section: Figmentioning

confidence: 99%

Illuminating Anaerobic Microbial Community and Cooccurrence Patterns across a Quality Gradient in Chinese Liquor Fermentation Pit Muds

Ren

et al. 2016

Appl Environ Microbiol

146

139

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Fermentation pit mud, an important reservoir of diverse anaerobic microorganisms, is essential for Chinese strong-aroma liquor production. Pit mud quality, according to its sensory characteristics, can be divided into three grades: degraded, normal, and high quality. However, the relationship between pit mud microbial community and pit mud quality is poorly understood, as are microbial associations within the pit mud ecosystem. Here, microbial communities at these grades were compared using Illumina MiSeq sequencing of the variable region V4 of the 16S rRNA gene. Our results revealed that the pit mud microbial community was correlated with its quality and environmental factors. Species richness, biodiversity, and relative and/or absolute abundances of Clostridia, Clostridium kluyveri, Bacteroidia, and Methanobacteria significantly increased, with corresponding increases in levels of pH, NH 4 ؉ , and available phosphorus, from degraded to high-quality pit muds, while levels of Lactobacillus, dissolved organic carbon, and lactate significantly decreased, with normal samples in between. Furthermore, 271 pairs of significant and robust correlations (cooccurrence and negative) were identified from 76 genera using network analysis. Thirteen hubs of cooccurrence patterns, mainly under the Clostridia, Bacteroidia, Methanobacteria, and Methanomicrobia, may play important roles in pit mud ecosystem stability, which may be destroyed with rapidly increased levels of lactic acid bacteria (Lactobacillus, Pediococcus, and Streptococcus). This study may help clarify the relationships among microbial community, environmental conditions, and pit mud quality, allow the improvement of pit mud quality by using bioaugmentation and controlling environmental factors, and shed more light on the ecological rules guiding community assembly in pit mud. Chinese strong-aroma liquor (CSAL), a traditional alcoholic beverage, accounts for Ͼ70% of both national liquor industry production (12 billion liters) and sales volume ($80 billion) (1, 2). Its production is a typical recycling process using solid-state fermentation. In brief, fermented grains obtained from the last fermentation round are mixed with crushed raw materials (sorghum, wheat, corn, rice, and sticky rice) for distillation to give CSAL (3). After cooling, the steamed mixture is supplied with a 10 to 20% (wt/wt) Daqu starter. Next, the above-mentioned mixture is placed into a fermentation vessel (underground cuboid soil pit, 2 m wide by 3 m long by 2 m deep), sealed, and anaerobically fermented for about 60 days at 28 to 32°C (2). The inside walls of the pit are covered with fermentation pit mud (FPM), which is prepared initially by incubating the mixture of clay, spent grain, bean cake powder, and fermentation bacteria (e.g., Clostridium spp.) (2). After fermentation, the fermented grains taken out of the pit are distilled to give liquor after new raw materials are supplied, and then the mixture is applied to the next round of fermentation, as described above. It is widely believe...

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Metabolite stress and tolerance in the production of biofuels and chemicals: Gene‐expression‐based systems analysis of butanol, butyrate, and acetate stresses in the anaerobe Clostridium acetobutylicum

Cited by 202 publications

References 99 publications

Metabolic Engineering of Clostridium acetobutylicum ATCC 824 for Isopropanol-Butanol-Ethanol Fermentation

Metabolic Engineering of Clostridium acetobutylicum ATCC 824 for Isopropanol-Butanol-Ethanol Fermentation

Pleiotropic Role of the RNA Chaperone Protein Hfq in the Human Pathogen Clostridium difficile

Illuminating Anaerobic Microbial Community and Cooccurrence Patterns across a Quality Gradient in Chinese Liquor Fermentation Pit Muds

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