Acetic acid tolerance

Greenacre, E.J. and Brocklehurst, T.F. 2006. The acetic acid tolerance response induces cross-protection to salt stress in Salmonella typhimurium. International Journal of Food Microbiology 112 62-65. 

Abstract Acetic acid bacteria (AAB) are obligate aerobes that belong to the a-Proteobacteria and are used for industrial vinegar production because of then-remarkable ability to oxidize ethanol by alcohol dehydrogenase, aldehyde dehydrogenase, and terminal oxidase of respiratory chain members on the ceU membrane. Acetic acid tolerance is a crucial abiUty allowing AAB to stably produce large amounts of acetic acid. 

Because acetic acid tolerance in AAB is conferred by several mechanisms, these mechanisms of acetic acid tolerance are reviewed here. 

Keywords Phosphatidylcholine Tetrahydoxy-bacteriohopane Polysaccharide AarA AarC Aconitase ABC transporter Efflux pump Chaperone Acetic acid tolerance... 

Several acetic acid tolerance mechanisms are summarized here. 

These four mechanisms of acetic acid tolerance of AAB are reviewed next. 

In addition, the surface of AarA protein is more basic than that of E. coli, so it is thought that the enzyme functions stably even at lower pH (Francois et al. 2006). Furthermore, citrate synthase purified from Gluconacetobacter europaeus (Komagataeibacter europaeus) was also shown to be stable in the presence of acetic acid (Sievers et al. 1997). It appears reasonable that the enzymes of acetic acid bacteria are intrinsically resistant to inactivation by low pH and functionally adapt to low pH. It was shown by proteomic analysis that aconitase was induced with acetic acid in a medium (Nakano et al. 2004). The transformant that highly expressed aconitase showed higher productivity of acetic acid than the wild-type strain, which has lower acetic acid tolerance (Fig. 10.6). 

Summary of Molecular Basis of Acetic Acid Tolerance in AAB... 

Prevention of acetic acid influx it was suggested that THBH and PC in the membrane lipids and polysaccharide on the surface of the cells are related to acetic acid tolerance. 

A commonly used peroxy acid is peroxyacetic acid (CH3CO2OH) Peroxyacetic acid is normally used m acetic acid as the solvent but epoxidation reactions tolerate a variety of solvents and are often earned out m dichloromethane or chloroform... 

The addition of acetic acid (0.5 equiv. to the substrate) to the catalyst system led to increased activity (doubling of yield) by maintaining the selectivity with 1.2 equiv. H2O2 as terminal oxidant. Advantageously, the system is characterized by a certain tolerance towards functional groups such as amides, esters, ethers, and carbonates. An improvement in conversions and selectivities by a slow addition protocol was shown recently [102]. For the first time, a nonheme iron catalyst system is able to oxidize tertiary C-H bonds in a synthetic applicable and selective manner and therefore should allow for synthetic applications [103]. 

Katsuki et al. have reported that high enantioselectivity can be obtained in the oxidation of nonconjugated cyclic enol ethers by using Mn(salen) (34) as the catalyst.138 The reactions were performed in an alcoholic solvent to obtain a-hydroxy acetals as the products, because a-hydroxy acetals are tolerant to a weak Lewis acid like Mn(salen) and do not racemize during the reaction and the isolation procedure (Scheme 29). 

P.B1.25 is very fast in application it is fast to fats, oils, soap, and paraffin, which makes it a suitable candidate for packaging inks. Its lightfastness, however, is not excellent. In natural rubber, P.B1.25 tolerates curing very well, and it bleeds neither into the rubber nor into the fabric backing (Sec. 1.8.3.6). In rubber, the pigment is fast to cold and hot water, to soap, soda, and alkali solutions, and to acetic acid. 

Methanol is not miscible with hydrocarbons and separation ensues readily in the presence of small quantities of water, particularly with reduction in temperature. On the other hand, anhydrous ethanol is completely miscible in all proportions with gasoline, although separation may be effected by water addition or by cooling. If water is already present, the water tolerance is higher for ethanol than for methanol, and can be improved by the addition of higher alcohols, such as butanol. Also benzene or acetone can be used. The wear problem is believed to be caused by formic acid attack, when methanol is used or acetic acid attack when ethanol is used. 

Similarly, 2-iodoanilides of indolyl acetic acid 15 lead to the corresponding 7,12-dihydroindolo[3,2-d][l]benzazepin-6(5H)-ones 16 (Equation (3) (2005TL8177)). Contrary to N-phenylsulfonyl derivatives lla,b and EOM protected species 13a,c, Boc-derivatives 14b and 15a do not tolerate these reaction conditions, and their fast decomposition has been observed. 

The Fischer indole synthesis is quite tolerant of additional functional groups in the starting material. Thus reaction of 4-dimethylaminocyclohexanone (18-2) with phe-nylhydrazine (18-1) in acetic acid leads directly to cyclindole (18-3) [18], a compound described as an antidepressant. A shghtly different approach is used to prepare the fluorinated analogue. The tricyhc indole (18-5), in this case, is obtained by reaction of 2,4-diiluorophenylhydrazine (18-4) with 4-hydroxy-cyclohexanone. The hydroxyl... 

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