??????????????? ????????? ????????? ?????? ??? ????????????

??????????????? ????????? ???????????? ???????????? ?????? ?????????????????? ??????????????? ?????? ???????????? ??????. ??? ??????????????? ??????????????? ??? ?????? ????????? ???????????? ????????? ??????????????? ????????? ???????????????. ?????? ??????????????? ????????? ??? ?????? ????????? ???????????????, ??? ?????? ????????? diethylnitrosamine (DEN)??? C3H/HeN ?????? ?????? ?????? ???????????? ??? ?????? ????????? ????????? ???????????????. DEN?????? ????????? ???????????? ?????? alkaline phosphatase (ALP) ??????, TUNEL positive ???????????? ??????, ??? ???????????? ?????? ???????????? duct??? ??????, ?????????????????? ????????????, Masson???s trichrome ???????????? ????????? ???????????? ???, ?????? ?????? ?????? ??? ????????? ????????? ???????????? ?????? ???????????? ?????? ?????? ????????? ??? ?????????. ?????????, ??????????????? ?????? ???????????? ????????? ?????? ?????????????????? ??????, ?????? ?????? ??? ????????? ???????????? ??????????????? ???????????? ???????????? ???????????? ?????? ?????? ????????? ??? ?????????. ???????????? ???????????? ????????? ???????????? ??????, ???????????? ???????????? ???????????? ?????? ????????? ???, solvent partition ????????? ???????????? ????????? ???????????? hexane, ethyl acetate, water ???????????? ???????????????. ?????? ??????????????? ?????? ????????? ??????????????? ??????????????? ???, ethyl acetate ???????????? ??????????????? ????????? ?????????????????? ??????????????? ?????? ??????????????? ???????????? ????????? ????????? ????????? ??? ?????????. ????????? ethyl acetate???????????? ???????????? ????????? ????????? ??? ?????????, ??????????????? ????????? ??? ?????? ????????? ????????? ?????????. ???????????????, ??????????????? ????????? ????????????????????? ?????? ????????? ??? ?????? ????????? ???????????? ?????? ??????????????? ????????? ??? ?????? ????????? ????????? ????????? ?????? ???????????????. ?????????, ?????? ??????????????? ?????? ???????????? ?????? ??? ?????? ?????? ???????????? ??????????????? ?????? ????????? ????????? ??? ?????? ????????? ???????????? ??????.clos

Metabolic characterisation of E. coli citrate synthase and phosphoenolpyruvate carboxylase mutants in aerobic cultures

E. coli is still one of the most commonly used hosts for protein production. However, when it is grown with excess glucose, acetate accumulation occurs. Elevated acetate concentrations have an inhibitory effect on growth rate and recombinant protein yield, and thus elimination of acetate formation is an important aim towards industrial production of recombinant proteins. Here we examine if over-expression of citrate synthase (gltA) or phosphoenolpyruvate carboxylase (ppc) can eliminate acetate production. Knock-out as well as over-expression mutants were constructed and characterized. Knocking out ppc or gltA decreased the maximum cell density by 14% and increased the acetate excretion by 7%, respectively decreased it by 10%. Over-expression of ppc or gltA increased the maximum cell dry weight by 91% and 23%, respectively. No acetate excretion was detected at these increased cell densities (35 and 23 g/l, respectively)

Pyrophosphate-Dependent ATP Formation from Acetyl Coenzyme A in Syntrophus aciditrophicus, a New Twist on ATP Formation.

UnlabelledSyntrophus aciditrophicus is a model syntrophic bacterium that degrades key intermediates in anaerobic decomposition, such as benzoate, cyclohexane-1-carboxylate, and certain fatty acids, to acetate when grown with hydrogen-/formate-consuming microorganisms. ATP formation coupled to acetate production is the main source for energy conservation by S. aciditrophicus However, the absence of homologs for phosphate acetyltransferase and acetate kinase in the genome of S. aciditrophicus leaves it unclear as to how ATP is formed, as most fermentative bacteria rely on these two enzymes to synthesize ATP from acetyl coenzyme A (CoA) and phosphate. Here, we combine transcriptomic, proteomic, metabolite, and enzymatic approaches to show that S. aciditrophicus uses AMP-forming, acetyl-CoA synthetase (Acs1) for ATP synthesis from acetyl-CoA. acs1 mRNA and Acs1 were abundant in transcriptomes and proteomes, respectively, of S. aciditrophicus grown in pure culture and coculture. Cell extracts of S. aciditrophicus had low or undetectable acetate kinase and phosphate acetyltransferase activities but had high acetyl-CoA synthetase activity under all growth conditions tested. Both Acs1 purified from S. aciditrophicus and recombinantly produced Acs1 catalyzed ATP and acetate formation from acetyl-CoA, AMP, and pyrophosphate. High pyrophosphate levels and a high AMP-to-ATP ratio (5.9 ± 1.4) in S. aciditrophicus cells support the operation of Acs1 in the acetate-forming direction. Thus, S. aciditrophicus has a unique approach to conserve energy involving pyrophosphate, AMP, acetyl-CoA, and an AMP-forming, acetyl-CoA synthetase.ImportanceBacteria use two enzymes, phosphate acetyltransferase and acetate kinase, to make ATP from acetyl-CoA, while acetate-forming archaea use a single enzyme, an ADP-forming, acetyl-CoA synthetase, to synthesize ATP and acetate from acetyl-CoA. Syntrophus aciditrophicus apparently relies on a different approach to conserve energy during acetyl-CoA metabolism, as its genome does not have homologs to the genes for phosphate acetyltransferase and acetate kinase. Here, we show that S. aciditrophicus uses an alternative approach, an AMP-forming, acetyl-CoA synthetase, to make ATP from acetyl-CoA. AMP-forming, acetyl-CoA synthetases were previously thought to function only in the activation of acetate to acetyl-CoA

Effect of Nitrate, Acetate and Hydrogen on Native Perchlorate-reducing Microbial Communities and Their Activity in Vadose Soil

The effect of nitrate, acetate, and hydrogen on native perchlorate-reducing bacteria (PRB) was examined by conducting microcosm tests using vadose soil collected from a perchlorate-contaminated site. The rate of perchlorate reduction was enhanced by hydrogen amendment and inhibited by acetate amendment, compared with unamendment. Nitrate was reduced before perchlorate in all amendments. In hydrogen-amended and unamended soils, nitrate delayed perchlorate reduction, suggesting that the PRB preferentially use nitrate as an electron acceptor. In contrast, nitrate eliminated the inhibitory effect of acetate amendment on perchlorate reduction and increased the rate and the extent, possibly because the preceding nitrate reduction/denitrification decreased the acetate concentration that was inhibitory to the native PRB. In hydrogen-amended and unamended soils, perchlorate reductase gene (pcrA) copies, representing PRB densities, increased with either perchlorate or nitrate reduction, suggesting that either perchlorate or nitrate stimulates the growth of the PRB. In contrast, in acetate-amended soil pcrA increased only when perchlorate was depleted: a large portion of the PRB may have not utilized nitrate in this amendment. Nitrate addition did not alter the distribution of the dominant pcrA clones in hydrogen-amended soil, likely because of the functional redundancy of PRB as nitrate-reducers/denitrifiers, whereas acetate selected different pcrA clones from those with hydrogen amendment

Geabacter species enhances pit depth on 304L stainless steel in a medium lacking with electron donor

Geobacter sulfurreducens bacteria increased the open circuit potential of 304L stainless steel by around 320 mV in only a few hours after inoculation. This represents a significant increase in the corrosion risk. In contrast, the oxidation of acetate, which is catalysed by well-established biofilms, shifted the pitting potential towards positive values. In acetate-lacking media, pitting occurred with and without bacteria in the same range of potential values, but the presence of bacteria drastically increased the size of pits. AFM showed pits more than 10 times broader and deeper due to the presence of bacteria. In the absence of acetate, the masking effect due to acetate oxidation disappeared and the full corrosive effect of the biofilm was revealed. This also fully explains why pitting was predominantly observed close to surface areas where bacterial settlement was the densest

Minimizing acetate formation in E. coli fermentations

Escherichia coli remains the best established production organisms in industrial biotechnology. However, during aerobic fermentation runs at high growth rates, considerable amounts of acetate are accumulated as by-product. This by-product has negative effects on growth and protein production. Over the last 20 years, substantial research efforts have been spent to reduce acetate accumulation during aerobic growth of E. coli on glucose. From the onset it was clear that this quest should not be a simple nor uncomplicated one. Simple deletion of the acetate pathway, reduced the acetate accumulation, but instead other by-products were formed. This minireview gives a clear outline of these research efforts and the outcome of them, including bioprocess level approaches and genetic approaches. Recently, the latter seems to have some promising results

Laser-induced prenucleation of alumina for electroless plating

This paper deals with the deposition of palladium from decomposition of a thin palladium acetate layer on rough and porous alumina ceramic surfaces by irradiating it with a UV excimer laser. The palladium acetate layer was formed from a combination of propyl glycol methyl ether acetate solvent and photoresist, and the undecomposed material was removed with the photoresist remover. The discontinuous palladium cluster film formed by the technique was used as seed for electroless coatings. Different patterns were obtained using point focus as well as projection pattering method and subsequently plated with adhesive layers of electroless Ni-B coating