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
- Bacterial Proteins MeSH
- Biological Transport MeSH
- Escherichia coli * MeSH
- Membrane Transport Proteins MeSH
- Metabolic Engineering MeSH
- Microbial Viability MeSH
- 1-Butanol * analysis metabolism toxicity MeSH
- Escherichia coli Proteins MeSH
- Pseudomonas putida * MeSH
- Solvents MeSH
- Carrier Proteins MeSH
- Publication type
- Journal Article MeSH
- Review 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
- Bioreactors MeSH
- Biotechnology methods MeSH
- Clostridium cytology metabolism ultrastructure MeSH
- Fermentation MeSH
- Cells, Immobilized cytology metabolism ultrastructure MeSH
- Zea mays chemistry MeSH
- 1-Butanol metabolism MeSH
- Waste Products analysis MeSH
- Batch Cell Culture Techniques MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Changes in membrane lipid composition of Clostridium pasteurianum NRRL B-598 were studied during butanol fermentation by lipidomic analysis, performed by high resolution electrospray ionization tandem mass spectrometry. The highest content of plasmalogen phospholipids correlated with the highest butanol productivity, which indicated a probable role of these compounds in the complex responses of cells toward butanol stress. A difference in the ratio of saturated to unsaturated fatty acids was found between the effect of butanol produced by the cells and butanol added to the medium. A decrease in the proportion of saturated fatty acids during conventional butanol production was observed while a rise in the content of these acids appeared when butanol was added to the culture. The largest change in total plasmalogen content was observed one hour after butanol addition i.e. at the 7th hour of cultivation. When butanol is produced by bacterial cells, then the cells are not subjected to severe stress and responded to it by relatively slowly changing the content of fatty acids and plasmalogens, while after a pulse addition of external butanol (to a final non-lethal concentration of 0.5 % v/v) the cells reacted relatively quickly (within a time span of tens of minutes) by increasing the total plasmalogen content.
- MeSH
- Biomass MeSH
- Clostridium drug effects growth & development metabolism MeSH
- Spectrometry, Mass, Electrospray Ionization MeSH
- Fatty Acids analysis MeSH
- Membrane Lipids chemistry MeSH
- 1-Butanol metabolism pharmacology MeSH
- Fatty Acids, Unsaturated analysis MeSH
- Plasmalogens analysis MeSH
- Batch Cell Culture Techniques MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't 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.
- Keywords
- isobutanol, sec-butanol, 2-ethylhexanol,
- MeSH
- 1-Propanol poisoning toxicity MeSH
- 2-Propanol poisoning toxicity MeSH
- Alcoholism MeSH
- Alcohols * classification poisoning toxicity MeSH
- Butanols poisoning toxicity MeSH
- Ethanol metabolism poisoning toxicity MeSH
- Hexanols poisoning toxicity MeSH
- Environmental Pollutants MeSH
- Humans MeSH
- Methanol metabolism poisoning toxicity MeSH
- 1-Butanol poisoning toxicity MeSH
- Alcoholic Intoxication * etiology metabolism MeSH
- Pentanols poisoning toxicity MeSH
- Alcohol Drinking metabolism adverse effects MeSH
- tert-Butyl Alcohol poisoning toxicity MeSH
- Environmental Pollution MeSH
- Animals MeSH
- Check Tag
- Humans MeSH
- Animals MeSH
- Publication type
- Research Support, Non-U.S. Gov't MeSH
- Review MeSH
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.
Clostridium pasteurianum forms acetic and butyric acids in an initial growth phase, which is a typical feature of clostridial acetone-butanol fermentation where an initial accumulation of acids is followed by production of solvents 1-butanol, acetone and ethanol. The initiation of the solvent production coupled with endospore formation leads to decrease of cell-wall thickness; thinner cell wall is more resistant against solvents and dyes. These changes can be observed by the method based on adaptation of Gram staining. The cell wall of G+ bacteria allows the entry of hexidium iodide and rhodamine 123, whereas the outer membrane of G- bacteria does not allow the uptake and therefore G+ bacteria are stained with higher fluorescence intensity than G- bacteria. The ratio of fluorescence intensity (FI) to forward scatter (FSC) was determined to correspond to G+ bacteria when clostridia were producing less solvents. The significant drop of the ratio FI to FSC to the level corresponding to G- bacteria is detected after initiation of solvent production.
