Acetic acid

About: Acetic acid is a research topic. Over the lifetime, 33996 publications have been published within this topic receiving 458353 citations. The topic is also known as: ethanoic acid & methanecarboxylic acid.

Effects of volatile fatty acid concentrations on methane yield and methanogenic bacteria

Abstract: Volatile fatty acids (VFAs) are important mid-products in the production of methane, and their concentrations affect the efficiency of fermentation. However, their effects on methane yield and methanogenic bacteria growth have been less extensively studied. To address these effects, acetic acid, propionic acid, butyric acid and ethanol were used as substrates and an L9(34) orthogonal table was adopted to design anaerobic digestion tests. When the highest concentrations of ethanol, acetic acid and butyric acid were 2400, 2400 and 1800 mg L−1, respectively, there was no significant inhibition of the activity of methanogenic bacteria. However, when the propionic acid concentration was increased to 900 mg L−1, significant inhibition appeared, the bacteria concentration decreased from 6 × 107 to 0.6–1 × 107 ml−1 and their activity would not reconvert. These effects resulted in the accumulation of ethanol and VFAs, and the total methane yield consequently became very low (<321 ml). The original propionic acid concentration had a significant inhibitory effect on methanogenic bacteria growth (P < 0.01). An optimization analysis showed that ethanol, acetic acid, propionic acid and butyric acid at concentrations of 1600, 1600, 300 and 1800 mg L−1, respectively, led to the maximum accumulative methane yield of 1620 ml and the maximum methanogenic bacteria concentration of 7.3 × 108 ml−1.

Physiology of Saccharomyces cerevisiae in anaerobic glucose-limited chemostat cultures

Abstract: The physiology of Saccharomyces cerevisiae CBS 8066 was studied in anaerobic glucose-limited chemostat cultures in a mineral medium supplemented with ergosterol and Tween 80 The organism had a mu max of 031 h-1 and a Ks for glucose of 055 mM At a dilution rate of 010 h-1, a maximal yield of 010 g biomass (g glucose)-1 was observed The yield steadily declined with increasing dilution rates, so a maintenance coefficient for anaerobic growth could not be estimated At a dilution rate of 010 h-1, the yield of the S cerevisiae strain H1022 was considerably higher than for CBS 8066, despite a similar cell composition The major difference between the two yeast strains was that S cerevisiae H1022 did not produce acetate, suggesting that the observed difference in cell yield may be ascribed to an uncoupling effect of acetic acid The absence of acetate formation in H1022 correlated with a relatively high level of acetyl-CoA synthetase The uncoupling effect of weak acids on anaerobic growth was confirmed in experiments in which a weak acid (acetate or propionate) was added to the medium feed This resulted in a reduction in yield and an increase in specific ethanol production Both yeasts required approximately 35 mg oleic acid (g biomass)-1 for optimal growth Lower or higher concentrations of this fatty acid, supplied as Tween 80, resulted in uncoupling of dissimilatory and assimilatory processes