Ultrastructure and lipid chemistry of specialized epidermal structure of Indian porcupines and hedgehog

Poddar‐Sarkar, M., Raha, P., Bhar, R., Chakraborty, A. and Brahmachary, R.L. 2011. Ultrastructure and lipid chemistry of specialized epidermal structure of Indian porcupines and hedgehog. —Acta Zoologica (Stockholm) 92 : 134–140. In the present study, we investigated the ultrastructural variations of specialized epidermal structure of Indian porcupines (Hystrix indica and Atherurus macrourus) and hedgehog (Hemiechinus collaris) as well as the variation in the fatty acid composition of total lipid fraction. Scanning electron microscope images reveal the usual scaly structure in surface view and network of channels in cross‐section but with different orientation of partition walls. The lipid profile reveals the presence of free sterol, long‐chain alcohol, free fatty acids, wax ester and sterol ester in all the three cases and trace amount of triglyceride, diglyceride and monoglyceride. Gas chromatography–mass spectrometry analysis of fatty acid methyl ester of total lipid fraction indicates the presence of C₈‐C₂₂ fatty acids in Hystrix indica, C₈‐C₁₈ in Atherurus macrourus and C₈‐C₂₀ fatty acids in Hemiechinus collaris. It is interesting to note that the total lipid fraction of hedgehog shows no branched‐chain, unsaturated and odd‐carbon fatty acids. Odd‐carbon fatty acid and branched‐chain fatty acids detected in the adult H. indica but were absent in juvenile H. indica as well as in A. macrourus. With the exception of C_18:1, the other unsaturated fatty acids were also absent in both juvenile H. indica and A. macrourus.     

Neutral lipids of leaves and stems of Trifolium repens

The neutral lipids of white clover leaves and stems have been separated into wax esters, free fatty acids, free fatty alcohols, free sterols, triglycerides and hydrocarbons. The wax esters were mainly of C₁₈ di- and tri-unsaturated fatty acids and C₃₀ fatty alcohol. Linolenic acid was the predominant free fatty acid and triacontanol was the principal free fatty alcohol. Of the hydrocarbons, C₂₉ and C₃₁ were present in the largest amounts.     

Substrate Specificity and Mode of Action of the Lipase Produced by Pseudomonas fragi22.39 B

The lipase purified from Pseudomonas fragi 22.39 B hydrolyzed not only triglycerides but also synthetic esters such as Tween, Span and methyl oleate. Of the saturated monoacid triglycerides tested, tributyrin was hydrolyzed most quickly. The lipase did not produce 1,3-diolein as a hydrolysis product from triolein. The addition of the Ca²⁺ ion to the reaction mixture promoted the hydrolysis rate for triglycerides and monoesters with longer-chain fatty acids (C₁₄, C₁₆, C₁₈). The enzyme could hydrolyze various kinds of natural fats and oils, and the extent their hydrolysis reached above 90%.     

Surface-Active Lipids from Nocardia erythropolis Grown on Hydrocarbons

Nocardia erythropolis (ATCC 4277) was grown in a 28-liter fermentor on mineral salts medium and 4% hydrocarbon. Extraction of the neutral lipids with pentane removed approximately 90% of the surface activity of the culture medium. The residual surface activity of the culture medium was attributed to the polar lipid fraction which was not extracted with pentane. Analysis of the pentane extracts with thin-layer chromatography showed the presence of four major compounds. A fatty alcohol reached a maximum concentration in the early log phase of growth and then decreased to the end of the fermentation. A monoglyceride, an ester, and a fatty acid appeared during the log phase of growth and continued to increase until the end of the fermentation. The fatty acids isolated from the culture grown on hexadecane had a carbon skeleton with the same length as the substrate, with 70% of the component as the saturated acid and 30% as a monounsaturated homolog. When isolated from a kerosene culture, the fatty acids consisted of a number of homologs from C₁₈ to C₂₀, including branched-chain and unsaturated acids, reflecting the distribution of the branched-chain isomers in the substrate.     

Changes in Cellular Fatty Acid Composition of Cephalosporium acremonium during Cephalosporin C Production

Cephalosporium acremonium was cultivated in fermentation medium containing sucrose or methyl oleate as a carbon source for cephalosporin C production. The level of antibiotic production was 48 g of cephalosporin C per liter under optimum conditions when methyl oleate was used. The C_18:1 (oleic acid) methyl ester appeared to be utilized faster than the C_18:2 (linoleic acid) methyl ester in fermentation broth. Physiological characteristics of C. acremonium were investigated by determining the fatty acid composition of the total cellular free lipid. Significant changes in cellular fatty acid composition occurred during inoculum cultivation and fermentation. The percentage of C_18:1 increased from 19.1 to 38.5%, but the percentage of C_18:2 decreased from 56.7 to 36.1%, and there was an increase in pH during inoculum cultivation. The cellular fatty acid composition of C. acremonium grown in fermentation medium containing methyl oleate (methyl oleate medium) was significantly different from that in fermentation medium containing sucrose (sucrose medium). The major fatty acids detected were C_16:0 (palmitic acid), C_18:1, and C_18:2. In methyl oleate medium, the ratio of C_18:1 to C_18:2 increased from 0.34 to 1.37, while the cell morphology changed from hyphae to arthrospores and conidia. In contrast, in sucrose medium, the ratio of C_18:1 to C_18:2 decreased from 0.70 to 0.43, and most of the cells remained hyphal at the end of fermentation. We observed that hyphae contained a higher proportion of C_18:2 but arthrospores and conidia contained a higher proportion of C_18:1.     

Inhibition of Topoisomerases by Fatty Acids

The inhibitory effects of various fatty acids on topoisomerases were examined, and their structure-activity relationships and mechanism of action were studied. Saturated fatty acids (C_6:0 to C_22:0) did not inhibit topoisomerase I, but cis-unsaturated fatty acids (C_16:1 to C_22:1) with one double bond showed strong inhibition of the enzyme. The inhibitory potency depended on the carbon chain length and the position of the double bond in the fatty acid molecule. The trans-isomer, methyl ester and hydroxyl derivative of oleic acid had no or little inhibitory effect on topoisomerases I and II. Among the compounds studied petroselinic acid and vaccenic acid (C_18:1) with a cis-double bond were the potent inhibitors. Petroselinic acid was a topoisomerase inhibitor of the cleavable complex-nonforming type and acted directly on the enzyme molecule in a noncompetitive manner without DNA intercalation.     

Hydrocarbons,phenols and sterols of the testa and pigment strand in the grain of Hordeum distichon

Material from the testa of decorticated barley grains contained hydrocarbons, esters, triglycerides, free sterols, 5-n-alkylresorcinols, and traces of free alcohols, carbonyl compounds, and various polar, acidic materials. The hydrocarbon fraction was mainly a series of n-alkanes, extending at least from C₁₁ to C₃₆, in which the C₂₉ and C₃₁ components were prominent. Two minor series of alkanes were also present. Sometimes a trace of an unsaturated hydrocarbon was detected. The ester fraction contained sterols and alkanols esterified by fatty acids, which differed in relative amounts from the fatty acids found in the triglycerides. The triglycerides were thought to have leached from within the grain. At least five free sterols were present, including sitosterol and campesterol. The 5-n-alkylresorcinols were at least twelve members of a homologous series, of which four, C₂₅, C₂₇, C₂₉, and C₃₁, made 98% of the total. Members of the series with even numbers of carbon atoms were also present. It is suggested that they are partly responsible for excluding microorganisms from the interior of the grain. The testa membrane, with the associated pigment strand, contained an estolide of fatty acids and various hydroxyacids, a polysaccharide component, and uncharacterized material.     

Determination of structure and composition of suberin from the roots of carrot, parsnip, rutabaga, turnip, red beet, and sweet potato by combined gas-liquid chromatography and mass spectrometry

Suberin from the roots of carrots (Daucus carota), parsnip (Pastinaca sativa), rutabaga (Brassica napobrassica), turnip (Brassica rapa), red beet (Beta vulgaris), and sweet potato (Ipomoea batatas) was isolated by a combination of chemical and enzymatic techniques. Finely powdered suberin was depolymerized with 14% BF₃ in methanol, and soluble monomers (20-50% of suberin) were fractionated into phenolic (<10%) and aliphatic (13-35%) fractions. The aliphatic fractions consisted mainly of ω-hydroxyacids (29-43%), dicarboxylic acids (16-27%), fatty acids (4-18%), and fatty alcohols (3-6%). Each fraction was subjected to combined gas-liquid chromatography and mass spectrometry. Among the fatty acids very long chain acids (>C₂₀) were the dominant components in all six plants. In the alcohol fraction C₁₈, C₂₀, C₂₂, and C₂₄ saturated primary alcohols were the major components. C₁₆ and C₁₈ dicarboxylic acids were the major dicarboxylic acids of the suberin of all six plants and in all cases octadec-9-ene-1, 18-dioic acid was the major component except in rutabaga where hexadecane-1, 16-dioic acid was the major dicarboxylic acid. The composition of the ω-hydroxyacid fraction was quite similar to that of the dicarboxylic acids; 18-hydroxy-octadec-9-enoic acid was the major component in all plants except rutabaga, where equal quantities of 16-hydroxyhexadecanoic acid and 18-hydroxyoctadec-9-enoic acid (42% each) were found. Compounds which would be derived from 18-hydroxyoctadec-9-enoic acid and octadec-9-ene-1, 18-dioic acid by epoxidation, and epoxidation followed by hydration of the epoxide, were also detected in most of the suberin samples. The monomer composition of the six plants showed general similarities but quite clear taxonomic differences.     

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.     

Separation of some mono-, di- and tri-unsaturated fatty acids containing 18 carbon atoms by high-performance liquid chromatography and photodiode array detection

Positional and geometric isomers of mono-, di- and tri-unsaturated fatty acids containing 18 carbon atoms were separated on commercially available reversed-phase columns in gradient systems composed of acetonitrile and water, utilizing photodiode array detection. The biological samples were hydrolyzed with 2 M NaOH for 35–40 min at 85–90°C. After cooling, the hydrolysates were acidified with 4 M HCl and the free fatty acids were extracted with dichloromethane. The organic solvent was removed in a gentle stream of argon. The fatty acids were determined after pre-column derivatization with dibromacetophenone in the presence of triethylamine. The reaction components were mixed and reacted for 2 h at 50°C. Separations of derivatized fatty acids were performed on two C₁₈ columns (Nova Pak C₁₈, 4 μm, 250×4.6 mm, Waters) by binary or ternate gradient programs and UV detection at 254 and 235 nm. The geometric and positional isomers of some unsaturated fatty acids were substantially retained on the C₁₈ columns and were distinct from some saturated fatty acids, endogenous substances in biological samples or background interference. Only slight separation of critical pairs of cis-9 C_18:1/cis-11 C_18:1 and cis-6 C_18:1/trans-11 C_18:1 was obtained. A ternate gradient program can be used for complete fractionation of a mixture of conjugated linoleic acid isomers (CLA) from cis-9, cis-12 and trans-9, trans-12 isomers of C_18:2. The CLA isomers in the effluent were monitored at 235 nm. The CLA isomers were differentiated from saturated and unsaturated fatty acids using a photodiode array detector. The utility of the method was demonstrated by evaluating the fatty acid composition of duodenal digesta, rapeseed and maize oils.     

Die Lipide von Endomycopsis vernalis bei verschiedener Stickstoff-Ernährung

1. Endomycopsis vernalis was cultivated on media with different N supply: series A 1%, series B 0,125% asparagine. Sonified cells were extracted and yielded 14.3% (A) and 65.3 (B) total lipids/non lipid dry matter respectively.
2. Neutral and complex lipids were separated by rubber membrane dialysis. There is no difference in the percentage of complex lipids of both series. The increase of lipids in cells grown on low N level is due to a higher content of neutral lipids.
3. Components of the neutral lipids, analysed by DC, were diglycerides, triglycerides, free and esterified ergosterol. Their percentage is influenced by the nutritional conditions. There is a significant increase of triglycerides and of sterol esters in the high lipid cells of series B.
4. Methyl esters of component fatty acids of glycerides and sterol esters were analyzed by GLC. Saturated acids C₁₄, C₁₅, C₁₆, C₁₇, C₁₈, monoenic acids C₁₆ and C₁₈, linoleic and linolenic acids were found to be present. Major acids were in all cases 18:1 (17–57%), 18:2 (18–50%) and 16:0 (10–18%). Linolenic acid is higher in di-and triglycerides of low lipid cells of series A than in high lipid cells of series B. Both qualitative and quantitative differences of fatty acids were found in sterol esters of series A and B respectively.
5. The major components of complex lipids, identified by DC and isolated by CC, in both series, were phosphatidyl choline (A:36.5, B:41.0%) and phosphatidyl ethanolamine (A:24.9, B:20.5%) in addition to small amounts of lysophosphatidyl choline, lysophosphatidyl ethanolamine, phosphatidyl serine, monophosphoinositide, diphosphatidyl glycerol and, possibly cerebroside like substances.
6. Methyl esters of the fatty acids of phosphatidyl choline and ethanolamine from both series were determined by GLC. In all samples 16:0, 18:0, 18:1, 18:2 and 18:3 acids were present besides of traces of 16:1 and 17:0. In contrast to neutral lipids the major acid of phospholipids is linoleic (53–58%), followed by oleic (8–24%) and linolenic acid (1–18%). The percentages of palmitic (4–8%) and stearic acids (tr.-1%) are small. Low lipid cells of series A differ from high lipid cells of series B by an increase of linolenic, and a decrease of linoleic acids, both in phosphatidyl choline and phosphatidyl ethanolamine.

     

Chemical composition of cornicle secretion of the brown citrus aphid Toxoptera citricida

Brown citrus aphid Toxoptera citricida Kirkadly is considered as an important pest of citrus because it vectors citrus tristeza closterovirus. Aphids secrete a fluid from their cornicles as a defensive mechanism against natural enemies. Earlier studies on cornicle secretions of aphids focus only on triglycerides and fatty acids. In the present study, three different methods are used to investigate the chemical composition of the cornicle fluid of T. citricida. Gas chromatography with flame ionization detection is used to detect and quantify the triglycerides after trimethylsilyl derivatization, and gas chromatography‐mass spectrometry (GC‐MS) is used to determine the fatty acid composition after derivatization with boron trifluoride–methanol. Other compounds are detected using GC‐MS after methoxyamine hydrochloride and N‐methyl‐N‐(trimethylsilyl)trifluoroacetamide derivatization. The major fatty acid in the cornicle secretion of T. citricida is palmitic acid. Oleic, stearic, myristic, myristoleic and sorbic acids are also detected, although in low amounts. Sorboyl, dipalmitoyl (C_6‐2, C₁₆, C₁₆) and disorboyl, stearoyl (C_6‐2, C_6‐2, C₁₈) are the main triglycerides detected in cornicle secretion. Trehalose is the most predominant sugar (558.2 mm ), followed by glucose (92.0 mm ) and inositol (48.8 mm ). Many amino acids, including proline, glycine, alanine and serine, are also detected. In addition, the cornicle secretion is rich in many organic acids, including malic, citric, succinic and lactic acid. Information obtained from the present study improves our understanding of the chemical composition of the cornicle secretion of the brown citrus aphid.     

Expression and Characterization of CYP52 Genes Involved in the Biosynthesis of Sophorolipid and Alkane Metabolism from Starmerella bombicola

Three cytochrome P450 monooxygenase CYP52 gene family members were isolated from the sophorolipid-producing yeast Starmerella bombicola (former Candida bombicola), namely, CYP52E3, CYP52M1, and CYP52N1, and their open reading frames were cloned into the pYES2 vector for expression in Saccharomyces cerevisiae. The functions of the recombinant proteins were analyzed with a variety of alkane and fatty acid substrates using microsome proteins or a whole-cell system. CYP52M1 was found to oxidize C₁₆ to C₂₀ fatty acids preferentially. It converted oleic acid (C_18:1) more efficiently than stearic acid (C_18:0) and linoleic acid (C_18:2) and much more effectively than α-linolenic acid (C_18:3). No products were detected when C₁₀ to C₁₂ fatty acids were used as the substrates. Moreover, CYP52M1 hydroxylated fatty acids at their ω- and ω-1 positions. CYP52N1 oxidized C₁₄ to C₂₀ saturated and unsaturated fatty acids and preferentially oxidized palmitic acid, oleic acid, and linoleic acid. It only catalyzed ω-hydroxylation of fatty acids. Minor ω-hydroxylation activity against myristic acid, palmitic acid, palmitoleic acid, and oleic acid was shown for CYP52E3. Furthermore, the three P450s were coassayed with glucosyltransferase UGTA1. UGTA1 glycosylated all hydroxyl fatty acids generated by CYP52E3, CYP52M1, and CYP52N1. The transformation efficiency of fatty acids into glucolipids by CYP52M1/UGTA1 was much higher than those by CYP52N1/UGTA1 and CYP52E3/UGTA1. Taken together, CYP52M1 is demonstrated to be involved in the biosynthesis of sophorolipid, whereas CYP52E3 and CYP52N1 might be involved in alkane metabolism in S. bombicola but downstream of the initial oxidation steps.     

Effects of insect cuticular fatty acids on in vitro growth and pathogenicity of the entomopathogenic fungus Conidiobolus coronatus

Eighteen fatty acids identified in the cuticle of three insect species representing differing susceptibilities to C. coronatus infection, were tested for effects on the in vitro growth and pathogenicity of the parasitic fungus. At all applied concentrations (0.1-0.0001% w/v) growth was inhibited by C_16:0, C_16:1, C_18:0, C_18:1, C_18:2, C_18:3, C_20:0 and C_20:1. At high concentrations spore germination was inhibited by C_7:0, C_8:0, C_9:0, C_10:0, C_12:0, C_18:2 and C_18:3 and hyphal growth was merely retarded by C_5:0, C_6:0, C_6:2, C_14:0, C_16:0, C_16:1, C_18:0, C_18:1, C_20:0 and C_20:1. The presence of C_15:0 at the 0.1% concentration stimulated growth of C. coronatus. Sporulation was inhibited by all concentrations of C_16:0 and C_18-20 fatty acids. Low concentrations of C_5:0, C_6:0, C_6:2 and C_7:0 enhanced sporulation. Fatty acids C_5-12 as well as C_18:3, C_20:0 and C_20:1 decreased the ability of fungal colonies to infect G. mellonella while C_16:1 elevated it thus suggesting that C_16:1 may stimulate production of enzymes involved in the host invasion. Toxicity of metabolites released into incubation medium decreased with varying degrees in the presence of C_6:0, C_6:2, C_7:0, C_9:0, C_12:0, C_16:1, C_18:2, C_18:3, C_20:0 and C_20:1; other fatty acids had no effect. Further work is needed to analyse the effects of exogenous fatty acids on the C. coronatus enzymes implicated in fungal pathogenicity as well as on the production of insecticidal metabolites.     

Leishmania species: fatty acid composition of promastigotes

The fatty acid composition of the total lipid fractions of five different Leishmania organisms grown on Eagle's medium was determined by gas chromatography. The major fatty acids identified in the total lipid fractions of L. donovani, L. tropica major, L. tropica minor, L. tropica (England strain), and L. enriettii were C_12:0, C_13:0, C_14:0, C_15:0, C_16:0, C_17:0, C_18:0, C_18:1, C_18:2, and C_18:3. The statistical differences among the fatty acid methyl esters of different Leishmania organisms are discussed.Gas chromatographic analysis of the fatty acid methyl esters of the total lipid fractions of the original Eagle's medium and the media after harvesting of various Leishmania species revealed the presence of C_18:3 fatty acid in the total lipid fraction of the medium of L. donovani and the complete absence of 18-carbon unsaturated fatty acids in the total lipid fraction of the medium of L. enriettii. The use of such differences in the differentiation of various Leishmania species is discussed.     

Grevillea robusta seed oil: A source of ω-5 monoenes

The fatty acids from Grevillea robusta seed oil triglycerides contain 22.5 % ω-5 monoenes ranging in chain length from C₁₄ to C₂₈. C₁₆ to C₂₆ saturates (18 %), C₁₈ to C₂₄ ω-9 monoenes (55 %), C₁₈ diene (2.3 %) and C₁₈ triene (0.7 %) make up the remainder of the acids.     

In vitro culture of coconut endosperm: callus induction and its fatty acids

Summary Successful induction of callus from coconut endosperm was achieved by using the tissue situated near the micropylar end of a young fruit. For initiation of callus, a high concentration of auxin (20 to 100 ppm) was added to the basal medium containing activated charcoal. Subcultured callus showed a 40-fold increase during culture of three months. Based on the analysis of fatty acid composition, the maturation of endosperm was characterized by an increase in short chain fatty acids (C₈, C₁₀, C₁₂, C₁₄)and a decrease in long chain fatty acids (C₁₆, C_{18: 1}, C_{18: 2}). In developing endosperms, proportion of short chain fatty acids was higher in lipids of the antipodal than those of other regions. In the final stage of maturation, around 82% of total fatty acids was short chain fatty acids, while the proportion of long chain fatty acids decreased up to 16%. The fatty acid composition of callus subcultured for six months was comparable to that of the immature endosperm. Lipids were accumulated in callus as globular bodies.     

Isolation and identification of cuticular compounds from the mediterranean flour moth,Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), their antibacterial activities and biological functions

Cuticular analysis of Ephestia kuehniella females by gas chromatography-mass spectrometry revealed the presence of four groups of chemical compounds including alkane, alcohol, aldehyde and fatty acid. The cuticular n-alkanes ranged from 12 to 18, 20, 23, 24 and 29 carbon atoms in the chain. The most abundant n-alkanes detected in the cuticular extracts were C₁₄ (14.98%) and C₁₈ (8.15%). Cuticular fatty acids included hexadecenoic acid, 9-octadecenoic acid and 9,12-octadecenoic acid. Two types of alcohol including, 2-methyl-Z,Z-3,13-octadecadienol and 9-methyl-Z-10-tetradecen-1-ol acetate, were found in the cuticular lipids of the females. Two aldehyde components, (E)-11-hexadecenal and 9,17-octadecadienal, were identified in the cuticular extract of E. kuehniella. Antibacterial activity of the cuticular compounds was tested against Bacillus subtilis, Bacillus thuringiensis and Escherichia coli. These compounds from the moths inhibited the growth of Gram-positive bacteria. The functional characteristics of the cuticular compounds operating as pheromones, species-associated compounds and host-resistant compounds to bacterial infection are discussed.     

Stearic acid methyl ester: A new extracellular metabolite of the obligate methylotrophic bacterium Methylophilus quaylei

Methyl esters of fatty acids, free fatty acids, and hydrocarbons were found in the culture liquid and in the cellular lipids of the obligate methylotrophic bacterium Methylophilus quaylei under optimal growth conditions and osmotic stress. The main extracellular hydrophobic metabolite was methyl stearate. Exogenous free fatty acids C₁₆–C₁₈ and their methyl esters stimulated the M. quaylei growth and survivability, as well as production of exopolysaccharide under osmotic and oxidative stress, playing the role of growth factors and adaptogens. The order of hydrophobic supplements according to the ability to stimulate bacterial growth is C_{18: 1} > C_{18: 0} > C_{16: 0} > methyl oleate > methyl stearate > no supplements > C_{14: 0} > C_{12: 0}. The mechanism underlying the protective action of fatty acids and their methyl esters is discussed.     

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