Effects of ethanol,octanoic and decanoic acids on fermentation and the passive influx of protons through the plasma membrane of Saccharomyces cerevisiae

Ethanol, octanoic and decanoic acids are known toxic products of alcoholic fermentation and inhibit yeast functions such as growth and fermentation. pH-stat measurements showed that, in a concentration range up to 20 mg/l, octanoic and decanoic acids increase the rate of passive H⁺ influx across the plasma membrane of Saccharomyces cerevisiae IGC 3507. Decanoic acid was more active than octanoic acid, which agrees with its higher liposolubility. The fatty acids probably act as H⁺ carriers, since the magnitude of the effect depended on pH and correlated with the concentration of protonated fatty acids. Esterification of the fatty acids partially abolished the enhancing effect on passive H⁺ influx. Passive H⁺ influx showed saturation kinetics with half-maximal activity at 6.6 M H⁺ (pH 5.2). Contrary to previous findings, ethanol inhibited H⁺ influx exponentially up to a concentration of 8% (v/v). At higher concentrations, ethanol reactivated H⁺ influx; the original rate of H⁺ uptake was reached at 14% (v/v) ethanol. In the same concentration ranges that affected passive H⁺ influx, ethanol, octanoic and decanoic acids inhibited the fermentation rate. This inhibitory effect of the fatty acids on fermentation rate depended on liposolubility, pH, and esterification in the same way as that found for their effect on passive H⁺ influx. Inhibition of fermentation by octanoic and decanoic acids could therefore result from their effect on the rate of passive H⁺ influx. Correspondence to: S. Stevens     

Inhibition of Yeast Growth by Octanoic and Decanoic Acids Produced during Ethanolic Fermentation

The inhibition of growth by octanoic or decanoic acids, two subproducts of ethanolic fermentation, was evaluated in Saccharomyces cerevisiae and Kluyveromyces marxianus in association with ethanol, the main product of fermentation. In both strains, octanoic and decanoic acids, at concentrations up to 16 and 8 mg/liter, respectively, decreased the maximum specific growth rate and the biomass yield at 30°C as an exponential function of the fatty acid concentration and increased the duration of growth latency. These toxic effects increased with a decrease in pH in the range of 5.4 to 3.0, indicating that the undissociated form is the toxic molecule. Decanoic acid was more toxic than octanoic acid. The concentrations of octanoic and decanoic acids were determined during the ethanolic fermentation (30°C) of two laboratory media (mineral and complex) by S. cerevisiae and of Jerusalem artichoke juice by K. marxianus. Based on the concentrations detected (0.7 to 23 mg/liter) and the kinetics of growth inhibition, the presence of octanoic and decanoic acids cannot be ignored in the evaluation of the overall inhibition of ethanolic fermentation.     

Reduction of hydrogen peroxide stress derived from fatty acid beta-oxidation improves fatty acid utilization in Escherichia coli

Fatty acids are a promising raw material for substance production because of their highly reduced and anhydrous nature, which can provide higher fermentation yields than sugars. However, they are insoluble in water and are poorly utilized by microbes in industrial fermentation production. We used fatty acids as raw materials for l-lysine fermentation by emulsification and improved the limited fatty acid-utilization ability of Escherichia coli. We obtained a fatty acid-utilizing mutant strain by laboratory evolution and demonstrated that it expressed lower levels of an oxidative-stress marker than wild type. The intracellular hydrogen peroxide (H₂O₂) concentration of a fatty acid-utilizing wild-type E. coli strain was higher than that of a glucose-utilizing wild-type E. coli strain. The novel mutation rpsA ^D210Y identified in our fatty acid-utilizing mutant strain enabled us to promote cell growth, fatty-acid utilization, and l-lysine production from fatty acid. Introduction of this rpsA ^D210Y mutation into a wild-type strain resulted in lower H₂O₂ concentrations. The overexpression of superoxide dismutase (sodA) increased intracellular H₂O₂ concentrations and inhibited E. coli fatty-acid utilization, whereas overexpression of an oxidative-stress regulator (oxyS) decreased intracellular H₂O₂ concentrations and promoted E. coli fatty acid utilization and l-lysine production. Addition of the reactive oxygen species (ROS) scavenger thiourea promoted l-lysine production from fatty acids and decreased intracellular H₂O₂ concentrations. Among the ROS generated by fatty-acid β-oxidation, H₂O₂ critically affected E. coli growth and l-lysine production. This indicates that the regression of ROS stress promotes fatty acid utilization, which is beneficial for fatty acids used as raw materials in industrial production.     

Influence of fatty acids on the growth of wine microorganisms Saccharomyces cerevisiae and Oenococcus oeni

The effects of fatty acids, extracted during prefermentation grape skin-contact on Saccharomyces cerevisiae and Oenococcus oeni, were studied. The influence of skin-contact on total fatty acid content was evaluated both in Chardonnay must and in synthetic medium. Prior to alcoholic fermentation, the skin-contact contributes to a large enrichment of long-chain fatty acids (C₁₆ to C_18:3). These results induced a positive effect on yeast growth and particularly on cell viability. In the skin-contact fermented media, levels of C₁₂ and especially C₁₀ are lower and macromolecules content higher than in controls. This production of extracellular mannoproteins and the reduction of medium-chain fatty acids in media by S. cerevisiae increased growth of O. oeni. The influence of fatty acids (C₁₀ to C_18:3), in their free and esterified forms, on bacterial growth and on malolactic activity was also examined. Only C₁₀ and C₁₂, especially in their esterified forms, always appeared to be toxic to O. oeni. Received 15 May 1997/ Accepted in revised form 02 December 1997     

Biochemical Effects of Fatty Acid and its Derivatives on l-Glutamic Acid Fermentation

In the preceding paper on the interrelation between sucrose ester of fatty acid and biotin, the fatty acid being a mixture of C₁₀ to C₁₈ acid, it was described that carbon chain length of fatty acid has a great influence on the accumulation of l-glutamic acid. Fatty acids with C₁₂ to C₁₈ chain length, particularly myristic, palmitic and margaric acids were effective on the accumulation of l-glutamic acid in the culture medium containing sufficient biotin, whereas lower and higher length acids were ineffective. In the form of polyoxyethylene sorbitan or polyethylene glycol ester, C₁₆ and C₁₈ acids were remarkably effective. However, the ester of C₁₂ acid and polyoxyethylene ethers of C₁₂ to C₁₈ alcohols had little or no effect.     

In vivo biosynthesis of -linolenic acid in plants

[1-¹⁴C]acetate was readily incorporated into unsaturated fatty acids by leaf slices of spinach, barley and whole cells of $\text{Chlorella}\text{pyrenoidosa}$ and $\text{Candida}\text{bogoriensis}$. In these systems the [¹⁴C] label in newly synthesized oleate and linoleate was approximately equally distributed in the C_1–9 and the C_10–18 fragments obtained by reductive ozonolysis of these acids, whereas in a-linolenic acid over 90% of the total [¹⁴C] was localized in the C_1–9 fragment. While [1-¹⁴C]oleic acid was converted by whole cells of $\text{Chlorella}$ to [1-¹⁴C]linoleic and [1-¹⁴C]linolenic acids, [U-¹⁴C]oleic acid yielded [U-¹⁴C]linoleic acid but a-linolenic acid was labeled only in the carboxyl terminal carbon atoms. When spinach leaf slices were supplied with carboxyl labeled octanoic, decanoic, dodecanoic, tetradecanoic and octadecanoic acids, only the first three acids were converted to a-linolenic acids while the last two acids were ineffective. Thus we suggest that (a) linoleic acid is not the precursor of a-linolenic acid and (b) 12:3(3, 6, 9) is the earliest permissible trienoic acid which is then elongated to a-linolenic acid.     

In vitro synthesis of mycolic acids by the fluffy layer fraction of Bacterionema matruchotii

Biosynthetic activity for mycolic acid occurred in the fluffy layer fraction but not in the 5000g supernatant of Bacterionema matruchotii. With [1-¹⁴C]palmitic acid as precursor for the in vitro system, the predominant product was identified as C_32:0 mycolic acid by radio-gas-liquid chromatographie (radio-GLC) and gas chromatographic/mass spectroscopic analyses; if [1-¹⁴C]stearic acid was used, two major radioactive peaks appeared on GLC: one corresponding to the peak of (C_34:0 + C_34:1) mycolic acids and the other to (C_36:0 + C_36:1) mycolic acids. By pyrolysis/radio-GLC analysis, C_32:0 mycolic acid synthesized by [1-¹⁴C]palmitic acid was pyrolyzed at 300 °C to form palmitaldehyde (the mero moiety) and methyl palmitate (the branch moiety). The pH optimum for the incorporation of [1-¹⁴C]palmitate into bacterionema mycolic acids was 6.4 and the reaction required a divalent cation. The in vitro system utilized myristic, palmitic, stearic and oleic acids (probably via their activated forms) well as precursors, among which myristic and palmitic acids were more effective than the rest. Avidin showed no effect on the biosynthesis of mycolic acid from ¹⁴C-palmitate whereas cerulenin, a specific inhibitor of β-ketoacyl synthetase in de novo fatty acid synthesis, inhibited the reaction at a relatively higher concentration. Thin-layer chromatographic analysis of lipids extracted from the reacting mixture without alkaline hydrolysis showed that both exogenous [1-¹⁴] fatty acid and synthesized mycolic acids were bound to an unknown compound by an alkali-labile linkage and this association seemed to occur prior to the condensation of two molecules of fatty acid.     

Levels of short-chain fatty acids and of abscisic acid in water-stressed and non-stressed leaves and their effects on stomata in epidermal strips and excised leaves

Straight-chain saturated fatty acids (C6-C11) and abscisic acid (ABA) accumulate in the leaves of Phaseolus vulgaris L. and Hordeum vulgare L. under water stress. ABA and certain of the fatty acids, particularly decanoic and undecanoic acid, can inhibit stomatal opening and cause stomatal closure in epidermal strips of Commelina communis L. depending on the incubating medium used. 10^-4 M (±)-ABA inhibits opening in media containing either high or relatively low concentrations of KCl but causes closure only in the latter medium. The fatty acids (at 10^-4 M) prevent opening in both media while significant closure of open stomata was caused only by undecanoic acid in both media and, additionally, by decanoic acid in the low-KCl medium. 10^-4 M formic acid also caused stomatal closure and prevented opening to significant extents in the low-KCl medium (it was not tested in the high-KCl medium). The efficacy of undecanoic acid in causing 50% inhibition of opening is about three orders of magnitude lower than that of ABA. At a concentration of 10^-3 M, nonanoic, decanoic and particularly undecanoic acid and all-trans-farnesol cause increased cell leakage in Beta vulgaris L. root tissue. Undecanoic acid (10^-4 M) also causes some loss of guard cell integrity in C. communis within 1.5 h of treatment. ABA (10^-4 M) reduces transpiration rates in barley and C. communis leaves when applied via the transpiration stream but decanoic and undecanoic acids did not have this effect. Transpiration was not affected when ABA or the fatty acids were applied to the leaf surfaces.Abbreviations ABA abscisic acid - RWC relative water content - SCFA short-chain fatty acids Deceased May 1977     

ACTIVATION OF GUANYLATE CYCLASE IN SYNAPTIC PLASMA MEMBRANES OF CEREBRAL CORTEX BY FREE FATTY ACIDS

Guanylate cyclase (EC 4.6.1.2) of synaptic plasma membranes of rat cerebral cortex was stimulated about 6-fold by several unsaturated fatty acids (arachidonic, linolenic, linoleic, oleic, palmitoleic and myristoleic acid). Ricinoleic acid (12-hydroxyoleic acid) was much less effective. Saturated fatty acids (C₁₀ and C₁₄-C₂₀) and the methylester of linoleic acid were ineffective. Stimulation by linoleic acid was influenced by the concentration of enzyme protein. At 480 μg/ml of protein 0.6 mm -linoleic acid produced maximal activation of 6-fold_ Activity stimulated by linoleic acid examined with 1.0 mm -GTP was maximal at pH 7.8-7.9 and with 2 mm -MnCl₂, whereas basal activity showed broad optimal pH and Mn²⁺-concentration dependence. Activation of the enzyme by linoleic acid was only partially reversed by washing. Particulate guanylate cyclase of heart, small intestine, adrenal medulla, liver and lung was also activated by linoleic acid. The extents of activation (1.5-14.7-fold) by linoleic acid and the concentrations (0.2-1.0 mat) required for maximal activation depended on the tissues.     

Further evidence for an elongation-decarboxylation mechanism in the biosynthesis of paraffins in leaves

In isolated tobacco leaves l-valine-U-¹⁴C gave rise to labeled even-numbered isobranched fatty acids containing 16 to 26 carbon atoms and iso C₂₉, iso C₃₁, and iso C₃₃ paraffins. l-Isoleucine-U-¹⁴C on the other hand produced labeled odd-numbered anteiso C₁₇ to C₂₇ fatty acids and anteiso C₃₀ and C₃₂ paraffins. Trichloroacetic acid inhibited the incorporation of isobutyrate into C₂₀ and higher fatty acids and paraffins without affecting the synthesis of the C₁₆ and C₁₈ fatty acids. Thus the very long branched fatty acids are biosynthetically related to the paraffins. In Senecio odoris leaves acetate-1-¹⁴C was incorporated into the paraffins (mainly n-C₃₁) only in the epidermis although acetate was readily incorporated into fatty acids in the mesophyll tissue. Similarly only the epidermal tissue incorporated acetate into fatty acids longer than C₁₈ suggesting that the epidermis is the site of synthesis of both paraffins and the very long fatty acids. In broccoli leaves n-C₁₂ acid labeled with ¹⁴C in the carboxyl carbon and ³H in the methylene carbons was incorporated into C₂₉ paraffin without the loss of ¹⁴C relative to ³H. Since n-C₁₈ acid is known to be incorporated into the paraffin without loss of carboxyl carbon these results suggest that the condensation of C₁₂ acid with C₁₈ acid is not responsible for n-C₂₉ paraffin synthesis in this tissue. Thus all the experimental evidence thus far obtained strongly suggests that elongation of fatty acids followed by decarboxylation is the most likely pathway for paraffin biosynthesis in leaves.     

Study of the acyl transfer activity of a recombinant amidase overproduced in an Escherichia coli strain. Application for short-chain hydroxamic acid and acid hydrazide synthesis

The study of acyl transfer activity of a wide spectrum amidase from Rhodococcus sp. R312, overproduced in an Escherichia coli strain, revealed that the ‘bi-bi-ping-pong’ type reaction was efficient with only four very-short chain (C₂–C₃) aliphatic amides as substrates. The optimum working pH was 7.0 for all neutral amides. Very short-chain aliphatic carboxylic acids were 10–1000-fold less efficient and the corresponding optimum working pH values depended on the acid used. Very polar molecules, such as water, hydroxylamine and hydrazine, were good acyl acceptors. An [acyl donor]/[acyl acceptor] ratio lower than 0.3-0.5 had to be maintained to avoid enzyme inhibition by excess acyl donor. The different acyl-enzyme complexes generally exhibited high affinity for hydroxylamine or hydrazine (except the propionyl-enzyme complex), so that the residual hydrolysis activities were almost totally inhibited at appropriate acyl acceptor concentrations. Molar conversion yields were higher with hydrazine as acyl acceptor (e.g., 97% with acetamide as acyl donor) because of the higher V_max values, but in all cases, interesting quantities of short-chain hydroxamic acids (2.9-6.5 g l⁻¹) and acid hydrazides (6.4–7.8 g l⁻¹) could be quickly obtained (10–60 min) with small amounts of enzyme (0.04-0.20 g l⁻¹).     

Tests Whether a Head to Head Condensation Mechanism Occurs in the Biosynthesis of n-Hentriacontane, the Paraffin of Spinach and Pea Leaves

Isobutyrate-1-¹⁴C and l-isoleucine-U-¹⁴C fed through the petiole labeled the surface lipids of broccoli leaves, but the incorporation was much less than from straight chain precursors. Not more than one-third of the ¹⁴C incorporated into the surface lipids was found in the C₂₉ paraffin and derivatives, whereas more than two-thirds of the ¹⁴C from straight chain precursors are usually found in these compounds. The small amount of ¹⁴C incorporated into the paraffin fraction was found in the n-C₂₉ paraffin rather than branched paraffins showing that the ¹⁴C in the paraffin must have come from degradation products. Radio gas-liquid chromatography of the saturated fatty acids showed that, in addition to the n-C₁₆ acid which was formed from both branched precursors, isoleucine-U-¹⁴C gave rise to branched C₁₅, C₁₇, and C₁₉ fatty acids, and isobutyrate-1-¹⁴C gave rise to branched C₁₆ and C₁₈ acids. Thus the reason for the failure of broccoli leaf to incorporate branched precursors into branched paraffins is not the unavailability of branched fatty acids, but the absolute specificity of the system that synthesizes paraffins, probably the elongation-decar-boxylation enzyme complex. Consistent with this view, no labeled branched fatty acids longer than C₁₉ could be found in the broccoli leaf. The branched fatty acids were also found in the surface lipids indicating that the epidermal layer of cells did have access to branched chains. Thus the paraffin synthesizing enzyme system is specific for straight chains in broccoli, but the fatty acid synthetase is not.     

Organic acids and prolonged nitrogenase activity by non-growing,free-living Rhizobium japonicum

Rhizobium japonicum 61-A-101 grew and fixed nitrogen more effectively on media containing an organic acid and a pentose sugar than on media containing only one of these carbon sources. Peak specific activities in the range 10–15 nmol C₂H₄ · h^-1 · mg protein^-1 were found for these organisms in a spot of growth about 1 cm diameter on agar surfaces exposed to air. Increasing concentrations of the organic acids (succinate or malonate) in a medium containing arabinose resulted in longer lasting activity. The inclusion of a third carbon source, glycerol, gave activity which remained at the maximum from about the 8 to the 18 day after inoculation although no growth of the bacteria occurs during the last 8 or 10 days. At low concentration of organic acid l-arabinose was a much better carbon source for supporting nitrogenase activity of these organisms that the d-form. Both organic acids affected the morphology of the bacteria. Higher concentrations, especially of malonate, gave swollen and distorted cells. When bacteria growing on organic acid-containing agar plates were suspended and plated after appropriate dilution on yeast extract — mannitolglycerol agar there was heterogeneity of colony form, with up to 90% microcolonies after growth on high malonate concentrations. The effects of malonate may be correlated with characteristics of the bacteroid form inside the nodule which contains relatively high concentrations of organic acids, especially malonate.     

Effect of Vitamin E and Its Analogues Having Various Molecular Structures on the Growth and Lipid Composition of Pythium debaryanum

The effect of exogenously added vitamin E and its synthetic analogues (the hydrophilic form of vitamin E and chromans C₁₃and C₁) at a concentration of 9.86 × 10^–5M on the growth, lipogenic activity, and the fatty acid composition of the eicosapolyenoic acid–synthesizing oomycete Pythium debaryanumwas studied. The effect was found to depend on the molecular structure of particular compounds. For instance, vitamin E and chroman C₁₃stimulated fungal growth, whereas chroman C₁inhibited it. The hydrophilic form of vitamin E enhanced the lipogenic activity of the oomycete. The studied compounds, which possess antioxidant activity, did not exert any noticeable effect on the content of eicosapolyenoic acids and the degree of the unsaturation of fungal lipids.     

Fatty acid exchange of phospholipids in membranes of rat heart

Incorporation of ¹⁴C fatty acids in phospholipids of plasma membranes and sarcoplasmic reticulum of rat heart was studied. Mainly phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were labelled. Our studies showed that the incorporation of unsaturated fatty acids (oleic and linoleic acid) was higher than for saturated fatty acids (palmitic and stearic acid). The range of uptake was between 0.2 and 2.2 nmol·mg⁻¹ protein·h⁻¹ and 0.5–7.4 nmol·μgatom⁻¹ P₁·h⁻¹, respectively. Uptake of activity in individual phospholipids (measured after separation on TLC) was calculated as percentage of total activity. Incorporation in phosphatidylcholine was higher than in phosphatidylethanolamine. Phosphatidylcholine showed an increasing sequence for the following fatty acids: C_18:0 < C_16:0 < C_18:0 < C_18:2. However, phosphatidylethanolamine showed a decreasing sequence for the incorporation of the same fatty acids. Labelling of PC was always greater than for PE, except for stearic acid which was better incorporated into phosphatidylethanolamine. Uptake of the same fatty acid into phospholipids of sarcoplasmic reticulum was always higher than uptake into plasma membranes. As incorporation of fatty acids bound to albumin was studied in isolated membranes of rat heart, the addition of ATP and CoASH was an absolute requirement.     

Oxalic acid production from lipids by a mutant of Aspergillus niger at different pH

Crude rapeseed oil and post-refining fatty acids were used as substrates for oxalic acid production by a mutant of Aspergillus niger. Both the final concentration and the yield of the product were highest at pH 4 to 5. With a medium containing 50 g lipids l^–1, production reached a maximum of 68 g oxalic acid l^–1 after 7 d. A high yield of the product (up to 1.4 g oxalic acid g^–1 lipids consumed) was achieved with oil and fatty acids combined.     

Evaluation of Malolactic Bacteria Isolated from Oregon Wines

Oregon is a cool wine-producing region where grapes characteristically contain high concentrations of organic acids. To reduce the natural acidity and increase the microbiological stability and flavor complexity of the wine, malolactic fermentation is encouraged. In this study, strains of Leuconostoc oenos indigenous to Oregon wines were evaluated for their suitability to conduct malolactic fermentation in Oregon wines. Tests determined the malolactic activity of the Oregon isolates in comparison with commercial strains ML-34, PSU-1, MLT-kli, and ens 44-40 under various temperature and pH conditions. Sensitivities to sulfur dioxide, ethanol, and fumaric acid also were determined. Two Oregon strains, Er-1a and Ey-2d, were selected for commercial winemaking tests because they had greater malolactic activity under conditions of low pH (3.0) and low temperature (15 and 8°C), respectively.     

The effect of temperature, water activity and sorbic acid on ketone rancidity produced by Penicillium crustosum Thom in coconut and palm kernel oils

In a model system medium-chain fatty acids (MCFA) C₆–C₁₂ in coconut and palm kernel oil are converted to methyl ketones, one carbon atom less than the parent fatty acids, by two strains of Penicillium crustosum Thom. Conversion rates of up to 32% were seen for decanoic acid at 25°C. The optimum temperature for ketone production was 25°C in liquid suspension culture. Coconut oil contains 3.23 mmol/g MCFAs compared with 2.34 mmol/g for palm kernel oil. Coconut oil is more prone to fungal spoilage (growth and ketone production) than palm kernel oil. The main end product of fermentation was 2-undecanone reflecting the high concentration of dodecanoic acid in the substrates. Ketonic rancidity is fungal engendered. The reaction can be controlled by reducing the temperature (4°C), reducing the water activity (0.91) or by addition of sorbic acid (20 mmol/l).     

A comparative study of an intensive malolactic transformation of cider using <Emphasis Type="Italic">Lactobacillus brevis </Emphasis>and<Emphasis Type="Italic"> Oenococcus oeni</Emphasis> in a membrane bioreactor

The aim of this study was to investigate the secondary fermentation of alcoholic green cider by Lactobacillus brevis and Oenococcus oeni in a membrane bioreactor so as to compare the performance of the two organisms to rapidly carry out the malolactic fermentation (MLF), an important step in reducing acidity and enhancing the flavor characteristics of the beverages. First, the growth of both organisms was intensified by using perfusion culture in a membrane bioreactor (MBR). O. oeni and L. brevis were grown up to 12.8 g dry cell weight (DCW) l⁻¹ and 15.5 g DCW l⁻¹ in the MBR. Secondly, the resultant cells were then used for the malolactic transformation of green cider in the MBR. The influences of the residence time in the MBR and the ethanol concentration of the green cider on the organic acid transformation were investigated. Both organisms showed a good tolerance against the acidic conditions (pH 3.0–4.0) and ethanol (90 g l⁻¹). Good levels of malate removal in the MBR were achieved by both organisms but O. oeni was more tolerant to high ethanol concentrations and was capable of growth and malate removal in 130 g ethanol l⁻¹ green cider. L. brevis malate removal was significantly inhibited above 110 g ethanol l⁻¹. The MBR allowed the development of high concentrations of active cells capable of rapid MLF and could be achieved over a prolonged period and over a wide range of conditions thus allowing the control of malate transformation rate. Organism selection for the transformation will be governed by the desired beverage characteristics. There is considerable scope to optimize the process further both with the choice of organisms and the design and operation of the reactor. Rapid beverage maturation on a commercial scale may be possible using MBR and pure cultures of MLF lactic acid bacteria.     

Effects of phenolic compounds on the growth and the fatty acid composition of Lactobacillus plantarum

The effects of different phenolic compound concentrations on the fatty acid composition of Lactobacillus plantarum isolated from traditional home-made olive brines were determined. Increasing amounts of caffeic and ferulic acids induced a gradual increase in the amounts of myristic, palmitoleic, stearic and 9,10-methylenehexadecanoic (C17Δ, where Δ represents the cyclopropane group) acid with a concomitant decrease of lactobacillic acid (C₁₉Δ). On the other hand, the addition of tannins induced an increase in the C₁₉Δ level at the expense of vaccenic acid content. The presence of acidic phenols and tannins also affected bacterial growth, inducing the most obvious effect with tannin at 1 g l⁻¹. Received: 1 July 1997 / Received revision: 9 September 1997 / Accepted: 15 September 1997