Butanol toxicity Dotaz Zobrazit nápovědu
V posledních desetiletích je snahou Evropského společenství snížit závislost svých členských států na ropných zdrojích, což vede k zájmu O procesy, které využívají obnovitelné zdroje energií. Jedním z nich je proces výroby 1-butanolu, který je realizován pomocí různých solventogenních druhů klostridií. Butanol se fermentačním způsobem produkuje při aceton-butanol-ethanolové fermentaci, kdy v první fázi procesu dochází k tvorbě organických kyselin a v druhé fázi procesu, často spojené se sporulací produkčního kmene, se tvoří rozpouštědla. Dvoufázový charakter fermentace výrazně komplikuje regulaci procesu a toxicita produktů brání dosažení jejich vysoké koncentrace. Aby byla zvýšena efektivita tohoto procesu, je prováděn intenzivní výzkum, zaměřený hlavně na zlepšení produkčních vlastností kmenů, zvýšení jejich odolnosti k 1-butanolu, využití levných surovin a zvýšení celkové produktivity procesu. Pokud se podaří výrobní cenu biobutanolu snížit, mohl by díky svým výhodným vlastnostem sloužit jako kosolvent do motorového paliva, do kterého se dnes již přidává ethanol a oddálit tak nevyhnutelné vyčerpání fosilních paliv.
An effort of European Community to reduce its dependence on fossil fuels provokes increased interest on processes using renewable energy resources. One of them is the fermentation process of 1-butanol production using various types of solventogenic clostridia. Biobutanol is produced by aceton-butanol-ethanol fermentation process consisting of two phases - acidogenic and solventogenic, which is associated with sporulation. Biphasic nature of fermentation significantly complicates the process control and product toxicity prevents the achievement of high concentration of solvents. To increase the efficiency of this process, an inventive research focused on improving the production characteristics of strains, increasing their resistance to 1-butanol, the use of cheap raw materials and amelioration of overall productivity of the process is carried out. If the production cost of biobutanol would be reduced, it could be advantageously used as an additive to petrol which could postpone the depletion of fossil fuels.
- MeSH
- bezpečnostní opatření MeSH
- hygiena práce MeSH
- lidé MeSH
- n-butanol chemie škodlivé účinky MeSH
- nebezpečné látky MeSH
- Check Tag
- lidé MeSH
N-butanol, a valued solvent and potential fuel extender, could possibly be produced by fermentation using either native producers, i.e. solventogenic Clostridia, or engineered platform organisms such as Escherichia coli or Pseudomonas species, if the main process obstacle, a low final butanol concentration, could be overcome. A low final concentration of butanol is the result of its high toxicity to production cells. Nevertheless, bacteria have developed several mechanisms to cope with this toxicity and one of them is active butanol efflux. This review presents information about a few well characterized butanol efflux pumps from Gram-negative bacteria (P. putida and E. coli) and summarizes knowledge about putative butanol efflux systems in Gram-positive bacteria.
- MeSH
- bakteriální proteiny MeSH
- biologický transport MeSH
- Escherichia coli * MeSH
- membránové transportní proteiny MeSH
- metabolické inženýrství MeSH
- mikrobiální viabilita MeSH
- n-butanol * analýza metabolismus toxicita MeSH
- proteiny z Escherichia coli MeSH
- Pseudomonas putida * MeSH
- rozpouštědla MeSH
- transportní proteiny MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
For n-butanol production by Clostridium pasteurianum DSM 525, a modified reinforced Clostridium medium was used, where glucose was alternated with glycerol and two kinds of continuous fermentation were tested using suspended and surface immobilized cells on corn stover pieces. A steady state, with butanol productivity of 4.2g/Lh, was reached during the packed-bed continuous fermentation at a dilution rate of 0.44h(-1). The average n-butanol concentration, yield and the ratio of n-butanol/liquid by-products were 10.4g/L, 33 % and 2.5, respectively. Unexpectedly, during continuous fermentation with suspended cells, at a dilution rate of 0.01h(-1), steady-state was not achieved and regular oscillations occurred in all measured variables, i.e. concentrations of glycerol, products and the number of cells stained with the fluorescent dyes carboxy fluorescein diacetate and propidium iodide. A possible explanation for oscillatory/steady-state behavior of suspended/surface-attached cells, respectively, may be specific butanol toxicity (toxicity per cell), which was higher/lower in respective cases, and which might be caused by lower/higher cell numbers respectively in both systems.
- MeSH
- bioreaktory MeSH
- biotechnologie metody MeSH
- Clostridium cytologie metabolismus ultrastruktura MeSH
- fermentace MeSH
- imobilizované buňky cytologie metabolismus ultrastruktura MeSH
- kukuřice setá chemie MeSH
- n-butanol metabolismus MeSH
- odpadní produkty analýza MeSH
- techniky vsádkové kultivace MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Toxic alcohols that clinicians commonly encounter are ethylene glycol, methanol, and isopropanol. Adults ingest these either for suicidal intent or to achieve inebriation, since these substances are readily available and cheaper than alcohol. Nevertheless, assorted alcohols are used very often in many applications and any alcohol can be toxic if ingested in large enough quantities. Toxic alcohols discussed here include all saturated aliphatic alcohols containing from 1 to 6 carbons in their molecules.
- Klíčová slova
- isobutanol, sec-butanol, 2-ethylhexanol,
- MeSH
- 1-propanol otrava toxicita MeSH
- 2-propanol otrava toxicita MeSH
- alkoholismus MeSH
- alkoholy * klasifikace otrava toxicita MeSH
- butanoly otrava toxicita MeSH
- ethanol metabolismus otrava toxicita MeSH
- hexanoly otrava toxicita MeSH
- látky znečišťující životní prostředí MeSH
- lidé MeSH
- methanol metabolismus otrava toxicita MeSH
- n-butanol otrava toxicita MeSH
- otrava alkoholem * etiologie metabolismus MeSH
- pentanoly otrava toxicita MeSH
- pití alkoholu metabolismus škodlivé účinky MeSH
- terc-butanol otrava toxicita MeSH
- znečištění životního prostředí MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- práce podpořená grantem MeSH
- přehledy MeSH
The main bottleneck in the return of industrial butanol production from renewable feedstock through acetone-butanol-ethanol (ABE) fermentation by clostridia, such as Clostridium beijerinckii, is the low final butanol concentration. The problem is caused by the high toxicity of butanol to the production cells, and therefore, understanding the mechanisms by which clostridia react to butanol shock is of key importance. Detailed analyses of transcriptome data that were obtained after butanol shock and their comparison with data from standard ABE fermentation have resulted in new findings, while confirmed expected population responses. Although butanol shock resulted in upregulation of heat shock protein genes, their regulation is different than was assumed based on standard ABE fermentation transcriptome data. While glucose uptake, glycolysis, and acidogenesis genes were downregulated after butanol shock, solventogenesis genes were upregulated. Cyclopropanation of fatty acids and formation of plasmalogens seem to be significant processes involved in cell membrane stabilization in the presence of butanol. Surprisingly, one of the three identified Agr quorum-sensing system genes was upregulated. Upregulation of several putative butanol efflux pumps was described after butanol addition and a large putative polyketide gene cluster was found, the transcription of which seemed to depend on the concentration of butanol.
- MeSH
- biologický transport genetika MeSH
- bioreaktory mikrobiologie MeSH
- buněčná membrána metabolismus MeSH
- butanoly toxicita MeSH
- Clostridium beijerinckii účinky léků genetika metabolismus MeSH
- fyziologický stres genetika MeSH
- glukosa metabolismus MeSH
- glykolýza genetika fyziologie MeSH
- mastné kyseliny metabolismus MeSH
- plasmalogeny biosyntéza MeSH
- proteiny teplotního šoku metabolismus MeSH
- quorum sensing genetika MeSH
- stanovení celkové genové exprese MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
N-Butanol, a valuable solvent and potential fuel extender, can be produced via acetone-butanol-ethanol (ABE) fermentation. One of the main drawbacks of ABE fermentation is the high toxicity of butanol to producing cells, leading to cell membrane disruption, low culture viability and, consequently, low produced concentrations of butanol. The goal of this study was to obtain mutant strains of Clostridium beijerinckii NRRL B-598 with improved butanol tolerance using random chemical mutagenesis, describe changes in their phenotypes compared to the wild-type strain and reveal changes in the genome that explain improved tolerance or other phenotypic changes. Nine mutant strains with stable improved features were obtained by three different approaches and, for two of them, ethidium bromide (EB), a known substrate of efflux pumps, was used for either selection or as a mutagenic agent. It is the first utilization of this approach for the development of butanol-tolerant mutants of solventogenic clostridia, for which generally there is a lack of knowledge about butanol efflux or efflux mechanisms and their regulation. Mutant strains exhibited increase in butanol tolerance from 36% up to 127% and the greatest improvement was achieved for the strains for which EB was used as a mutagenic agent. Additionally, increased tolerance to other substrates of efflux pumps, EB and ethanol, was observed in all mutants and higher antibiotic tolerance in some of the strains. The complete genomes of mutant strains were sequenced and revealed that improved butanol tolerance can be attributed to mutations in genes encoding typical stress responses (chemotaxis, autolysis or changes in cell membrane structure), but, also, to mutations in genes X276_07980 and X276_24400, encoding efflux pump regulators. The latter observation confirms the importance of efflux in butanol stress response of the strain and offers new targets for rational strain engineering.
- Publikační typ
- časopisecké články MeSH
Pumping toxic substances through a cytoplasmic membrane by protein transporters known as efflux pumps represents one bacterial mechanism involved in the stress response to the presence of toxic compounds. The active efflux might also take part in exporting low-molecular-weight alcohols produced by intrinsic cell metabolism; in the case of solventogenic clostridia, predominantly acetone, butanol and ethanol (ABE). However, little is known about this active efflux, even though some evidence exists that membrane pumps might be involved in solvent tolerance. In this study, we investigated changes in overall active efflux during ABE fermentation, employing a flow cytometric protocol adjusted for Clostridia and using ethidium bromide (EB) as a fluorescence marker for quantification of direct efflux. A fluctuation in efflux during the course of standard ABE fermentation was observed, with a maximum reached during late acidogenesis, a high efflux rate during early and mid-solventogenesis and an apparent decrease in EB efflux rate in late solventogenesis. The fluctuation in efflux activity was in accordance with transcriptomic data obtained for various membrane exporters in a former study. Surprisingly, under altered cultivation conditions, when solvent production was attenuated, and extended acidogenesis was promoted, stable low efflux activity was reached after an initial peak that appeared in the stage comparable to standard ABE fermentation. This study confirmed that efflux pump activity is not constant during ABE fermentation and suggests that undisturbed solvent production might be a trigger for activation of pumps involved in solvent efflux. KEY POINTS: • Flow cytometric assay for efflux quantification in Clostridia was established. • Efflux rate peaked in late acidogenesis and in early solventogenesis. • Impaired solventogenesis led to an overall decrease in efflux.
- MeSH
- aceton MeSH
- butanoly MeSH
- Clostridium beijerinckii * MeSH
- Clostridium MeSH
- ethanol MeSH
- fermentace MeSH
- Publikační typ
- časopisecké články MeSH
- MeSH
- diabetes mellitus MeSH
- ethambutol škodlivé účinky toxicita MeSH
- komplikace diabetu MeSH
- lidé MeSH
- neuritida farmakoterapie chemicky indukované MeSH
- plicní tuberkulóza diagnóza terapie MeSH
- Check Tag
- lidé MeSH
- ženské pohlaví MeSH
- Publikační typ
- kazuistiky MeSH
