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The 1H chemical shifts, 1H-1H coupling constants, 13C chemical shifts, and some 1H-13C and 13C-19F coupling constants have been determined for seven 3-substituted-9-chloroacridines and for the corresponding 3-substituted-9-aminoacridines. The effects produced by the substituent in position 3 on the 1H and 13C chemical shifts are discussed using two empirical models, those of Smith and Proulx (F, R, Q*) and Reynolds (σF, σR0, I, O, M).

Hydroxamic acids (HA), with the general formula R–CO–NHOH, are chelating agents which may be used in a number of interesting applications, such as medicine and waste water treatment. In this paper, we describe the enzymatic synthesis of HA with various chain lengths (from C2 to C18), using three microbial enzymes. For short- and middle-chain HA synthesis, using amidases from Rhodococcus sp. R312, the optimal working pH was found to be pH 7 or 8, depending on the amide substrate used. Different Michaelis–Menten constants were also determined. For fatty HA synthesis, using lipase from Candida parapsilosis, the optimal working conditions were determined to be pH 6, 1 M hydroxylamine and 40°C. Because of the favorable bioconversion yields achieved, the enzymatic synthesis of HA with the appropriate biocatalysts appears to be an interesting alternative to chemical synthesis.

International audience; The lactic acid bacterium,Lactobacillus casei, produces an intracellular β-glucosidase when grown on Man-Rogosa-Sharpe (MRS) medium with cellobiose as carbon source. The β-glucosidase activity is produced intracellulary, and no extracellulary activity was detected. The enzyme was purified by ion-exchange chromatography and gel filtration. The molecular mass of the purified intracellular β-glucosidase as estimated by gel filtration was 480 kDa, consisting of six probably identical subunits. The enzyme exhibited optimum activity at 35°C and pH 6.3 with citrate-phosphate buffer. The enzyme was active against soluble glycosides with (1→4)-β configuration and from Lineweaver Burk plots, Km value of 16 mmol/L was found for β-pNPG. The β-glucosidase was competitively inhibited by glucose, and no glycosyl transferase activity was observed in the presence of ethanol.

Chelating properties of hydroxamic acids with iron(III) were used for the quantitative determination of several monohydroxamic acids. Maximum absorption was obtained at a wavelength of ca. 500 nm for all iron(III)/monohydroxamic acid complexes tested. Determination of the molar extinction coefficient (ϵ M ) for each complex simplified the monohydroxamic acid assay since a mean ϵ M value could be determined for each family of iron(III)/monohydroxamic acid complexes. These results confirmed the influence of the NH 2 group in the coordination of α-, β-, and γ-aminohydroxamic acids with iron(III). Finally, this study showed the high sensitivity of the spectrophometric hydroxamic acid assay, with a minimum required concentration of 2.5 × 10 −5 to 5.0 × 10 −5 mol l −1 as a function of the monohydroxamic acid concerned. The method was validated under biological conditions for Spectrophotometric quantification of an enzyme-catalyzed acyl transfer reaction resulting in hydroxamic acid production.

Candida molischiana 35M5N β -glucosidase was immobilized to Duolite A-568 resin with high immobilization efficiency (86%). The immobilized β -glucosidase was used to improve the aromatic quality of Muscat wine with two types of reactor. After the enzymatic treatment, gas chromatography/mass spectrometry (GC-MS) analysis indicated a significant increase in flavor compounds: nerol, geraniol, linalool, γ -terpinene, 2-phenylethanol and benzyl alcohol. The comparison of the two reactors showed that with the same amount of immobilized β -glucosidase, the hydrolysis was complete (100%) after 6 h 15 min of treatment with the fluidized bed reactor. With the packed bed reactor, similar results (90%) were obtained after 16 h 40 min of treatment. The immobilized β -glucosidase was found to be very stable during the two treatments. The system described is an example of the use of a biocatalyst for the flavor enrichment of beverages that could be employed in industry.

Glucose metabolism in a Crabtree-negative yeast, Schwanniomyces castellii, and a cytochrome b-deficient mutant of this strain was investigated in chemostat culture. The wild-type and mutant strains exhibited the same behavior. Oxidative metabolism was observed when the substrate uptake rate (qS) was low. Fermentative metabolites were excreted when the qS value was higher than 0.40 g.g-1.h-1, indicating the occurrence of a respirofermentative metabolism; however, the respiratory quotient (RQ) remained near 1. When fermentation occurred, the cytochrome pathway was repressed but not the salicylhydroxamic acid (SHAM)-sensitive pathway. The presence of an alternative SHAM-sensitive respiratory pathway and the presence of phosphorylation site I in all metabolic conditions explained the RQ value of 1 and accounted for high biomass yields in oxidative metabolism conditions (0.62 g.g-1 for the wild-type strain and 0.31 g.g-1 for the cytochrome b-deficient mutant strain).

Y. GUEGUEN, P. CHEMARDIN, P. LABROT, A. ARNAUD AND P. GALZY. 1997.The lactic acid bacterium, Leuconostoc mesenteroides, when grown on an arbutin-containing medium, was found to produce an intracellular b-glucosidase. The enzyme was purified by chromatofocusing, ion-exchange chromatography and gel filtration. The molecular mass of the purified intracellular b-glucosidase, as estimated by gel filtration, was 360 kDa. The tetrameric structure of the b-glucosidase was determined following treatment of the purified enzyme with dodecyl sulphate (SDS). The intracellular bglucosidase exhibited optimum catalytic activity at 50°C and pH 6 with citrate‐phosphate buffer, and 5·5 with phosphate buffer. The enzyme was active against glycosides with (1:4)-b ,( 1 :4)-a and (1:6)-a linkage configuration. From Lineweaver‐Burk plots, Km values of 0·07 mmol l 1 and 3·7 mmol 1 1 were found for p-nitrophenyl-bD-glucopyranoside and linamarin, respectively. The b-glucosidase was competitively inhibited by glucose and by D-gluconic acid‐lactone and a glucosyl transferase activity was observed in the presence of ethanol. The b-glucosidase of Leuconostoc mesenteroides, with cyanogenic activity, could be of potential interest in cassava detoxification, by hydrolysing the cyanogenic glucosides present in cassava pulp.

The 1,3-regiospecific lipase from Candida deformanscatalysed the esterification of oleic acid and propanediol in biphasic aqueous/lipid medium without organic solvent. The highest conversion of oleic acid into 1,2-propanediol ester was 74% in 24 h with 6.25 mol/l 1,2-propanediol and 0.08 mol/l oleic acid, and produced 100% monoester. The esterification of 1,3-propanediol converted up to 98% of oleic acid into esters in 24 h (with 7.5 mol/l 1,3-propanediol and 0.08 mol/l oleic acid) and formed 35-90% monoester depending on 1,3-propanediol initial concentration (2.5-10 mol/l).

The specific activity of the microsomal delta 12-desaturase system, which transforms oleic acid into linoleic acid, was about 16 pmol/min/mg protein. However, most of the total activity was nonsedimentable even after a 200000 x g centrifugation for 100 min. The study of various physicochemical parameters showed that this enzymatic complex, functioning optimally between pH 7 and 8, had low thermal stability. Ca2+ which may cause an aggregation of the microsomes, and Hg2+ completely inhibited the activity, whereas Mg2+, Mn2+, and Zn2+ were activators. The delta 12-desaturase system was relatively specific toward oleic acid, though isomers of this fatty acid also had an action, either as substrates or as competitive inhibitors, on the activity of the system. The study of the effect of the exogenous oleoyl-CoA and elaidoyl-CoA on the specific activity of the delta 12-desaturase system showed a preference toward oleoyl-CoA.

An infrared technique was adapted for measuring gas exchanges in loaves and slices of Feta cheese as a model system. The main factors affecting the solubility and the production of CO 2 in feta, the cheese model system, were described in a short theoretical part. An application of the above method gave the following results: average rates of CO 2 release with cheese loaves in air were approximately 35 ± 8.5 and 36 ± 5 μmol h −1 kg −1 at 4 and 10 °C respectively. The rates increased considerably with slices of feta cheese. Yeast growth and CO 2 production increased when cold storage was not maintained, while anaerobic conditions limited CO 2 release.

Candida molischiana 35M5N β-glucosidase was immobilized to Duolite A-568 resin. Higher immobilization efficiency (86%) was achieved with citrate−phosphate buffer (0.1 M) at pH 4. The study of the immobilized β-glucosidase demonstrated that the physicochemical properties were similar to those of the free enzyme. Free and immobilized β-glucosidase were used to treat muscat wine and apricot fruit juice. GC−MS analysis indicated a significant increase in the flavor compounds nerol, geraniol, linalool, 2-phenylethanol, and benzyl alcohol in the muscat wine and linalool, α- and γ-terpinene, α-terpineol, 2-phenylethanol, and α-pinene in the apricot fruit juice. The immobilized β-glucosidase was found to be very stable under fruit juice or wine conditions and could be used repeatedly for several hydrolyses of bound aroma. The efficiency of this experimental catalyst was successfully tested with several fruit juices and wines containing various amounts of precursors. Keywords: Wines; fruit juices; aroma precursors...

The filamentous fungus Botrytis cinerea, grown on a cellobiose medium, was found to produce three intracellular β-glucosidases (GluI, II, and III). These enzymes were visualized by activity staining after separation by native polyacrylamide gel electrophoresis. GluI, which represents 95.5% of the total β-glucosidase activity, was purified to homogeneity by ion-exchange chromatography and gel filtration. The molecular mass of the purified intracellular β-glucosidase estimated by gel filtration was 350 kDa. The tetrameric structure of the β-glucosidase was determined following treatment of the purified enzyme with dodecyl sulphate. The intracellular β-glucosidase exhibited optimum catalytic activity at 50°C and pH 7 with citrate-phosphate buffer and 6.5 with phosphate buffer. The enzyme was active against glycosides with (1 → 4)-β, (1 → 2)-β, and (1 → 4)-α linkage configuration. The β-glucosidase was competitively inhibited by glucose and by d -gluconic-acid-lactone, and a glucosyl transferase activity was observed in the presence of ethanol.

The purified lipase from Candida deformans was shown to catalyse ester production in aqueous media by esterification of free fatty acids but not by alcoholysis. As the enzyme also catalysed ester hydrolysis, the influence of various physico-chemical factors on ester hydrolysis and synthesis was studied and compared. Substrate specificities were also studied. Both activities had the same pH and temperature optima, and did not require a metal cofactor. Tyrosine appeared to be one of the amino acids of the enzyme required by both catalytic activities, whereas serine-reactive reagents inhibited synthesis only. The highest synthesis and hydrolysis activities were obtained with mono-, di- and tri-unsaturated fatty acids containing a [cis] delta-9 unsaturation and 16 to 18 carbon atoms. Only esters of primary alcohols were hydrolysed and synthesised. For alcohols ranging from methanol to butanol, synthesis activity increased with the length of the alcohol whereas hydrolysis activity of the corresponding esters decreased. The presence of alcohol inhibited hydrolysis. An optimum concentration was found for each primary alcohol at which ester synthesis was maximum and hydrolysis was low.

An alcohol dehydrogenase HUADHII was purified 43.2-fold from Hanseniaspora uvarum K 5 . The enzyme was trimeric with subunits of mol. wt 42 kDa. The N-terminal amino acid sequence of HUADHII has between 45 and 75% identity with part of the sequence of isoenzymes related to group I from Saccharomyces cerevisiae and Kluyveromyces lactis. C2-C4 alcohols and aldehydes were the preferred substrates. The presence of an 'α' double bond increased the enzyme activity both for alcohols and aldehydes. It was significantly inhibited by metal-binding agents and thiol reagents. Kinetic studies suggested that HUADHII catalyses the oxidation of ethanol by a random sequential mechanism. It appears that HUADHII, a cytoplasmic fermentative enzyme, is structurally and functionally similar to members of the group I alcohol dehydrogenases.

C. LAMBRECHTS, J. ESCUDERO AND P. GALZY. 1995. The esterases of Brevibacterium sp. R312 were found to have an intracellular location. Electrophoresis of lysed cell supernatant fluids revealed seven bands of esterase activity in the presence of α-naphthyl acetate. Eight esterases were separated by anion exchange chromatography. The three main esterases (esterase 4b, 2 and 4a) of Brevibacterium sp. R312 were purified. The molar masses, the pH optima, the temperature optima and heat stabilities were determined. Esterase 2 differed from the two others in sensitivity to inhibitors. Esterase 4b differed from esterases 2 and 4a in its substrate specificity. This enzyme hydrolyses aliphatic and nitrophenyl esters. The spectrum of activity of the two other esterases is narrower. They hydrolysed only naphthyl esters and, in the case of esterase 2, tributyrate and ethyl butyrate.

Esterase activity of Brevihacterium linens 62 and Brevibacterium sp. R312 was detected. Each strain had esterase activities that hydrolyzed p-nitrophenyl acetate and α-naphthyl acetate. Biosynthesis and optimum pH and temperature of the two esterase activities showed that the latter were caused by different esterases. The influence of the culture medium and the growth substrate on biosynthesis of the esterase systems were studied. Hydrolysis of methylthioacetate and phenethyl acetate by cell extracts of the two strains was done. No enzymatic ester synthesis reaction was observed. However, transfer reactions by cell extracts of the two strains were done.

The enzymatic synthesis of dodecyl. β- d -glucopyrano-side was studied by using the β-glucosidase from Candida molischiana 35M5N in the examination of transglucosylation and hydrolysis reversion reactions. On account of cost considerations, the condensation reaction was optimized. The effects of the extraction solvent, the initial 1-dodecanol and glucose concentrations, the temperature and the incubation time were studied. The optimal conditions for the enzymatic synthesis of dodecyl. β- d -glucopyranoside by the condensation reaction were: 90% (v/v) 1-dodecanol initial concentration; glucose concentration (50 m m ), temperature 40°C and reaction time 20 h.

We have isolated a gene (bgln) encoding β-glucosidase (βGlu) from a cosmid library of the yeast, Candida molischiana 35M5N. The nucleotide sequence of bgln and its flanking regions was determined. This gene was found to be composed of 2289 bp and 763 amino acid (aa) residues encoding an 83.3-kDa protein. The aa sequence shared eleven putative N -glycosylation sites. Homology comparisons showed that this enzyme can be considered as a new member of the family-3 glycosyl hydrolases. Multiple alignment experiments revealed four conserved regions on aa sequences from βGlu of this family.

The lipid composition, particularly the fatty acid composition (6–25 carbon atoms), of one strain of each species of Lipomyces and Waltomyces was determined; the influence of the culture temperature on the lipid composition was also studied. The neutral lipid fraction, essentially composed of intracellular triacylglycerols, and the polar fraction, composed of membrane phospholipids, were analyzed separately. For all strains and in the two fractions, the major fatty acids were oleic, linoleic, palmitic, palmitoleic, stearic, and α-linolenic acids, which formed 85% of the total fatty acids. Small amounts of γ-linolenic, dihomo-γ-linolenic, and arachidonic acids were present, which indicated the presence of Δ12, Δ15, Δ6, and Δ5 desaturases. Waltomyces lipofer and Lipomyces tetrasporus were the two species richest in lipids and fatty acids. In the genus Lipomyces and in Waltomyces, maintenance of membrane fluidity at low temperature required an increase in unsaturated fatty acids and the accumulation of short-chain fatty acids, especially in the polar lipid fraction; in the case of Lipomyces anomalus, the synthesis of branched fatty acids may be a third way to maintain membrane fluidity.Key words: Lipomyces, Waltomyces, lipid composition, fatty acids.

Five different Micrococcus spp. were isolated from the surface of Roquefort cheese: M. roseus, M. sedentarius, M. lylae, M. luteus and M. varians. During culture on synthetic medium these bacteria produced acetic acid as the main volatile fatty acid and propanol as the main alcohol. On a complex medium these isolates synthesized additional volatile fatty acids. Studies were made of the effect of pH, of water activity adjusted with sodium chloride or sorbitol, and of temperature on growth rates. All five isolates were inhibited at a pH lower than 5.5 and grew at temperatures from 4 o to 44 o C; they were halotolerant and multiplied at NaCl concentrations up to 20%, corresponding to a water activity of 0.884

After verification that the phase from Schwanniomyces castellii was able to hydrolyze the phytic acid in soft wheat bran and in glandless cotton flour, the ability of the strain to develop in a medium containing one of these two substances as sole phosphate source was tested. Growth was satisfactory in both cases, and 90-95% of phytic acid was hydrolyzed

Candida cacaoi has two different β-glucosidases. The present paper reports the study and purification of the exocellular β-glucosidase. This enzyme was purified by ion exchange chromatography and by gel filtration. Its molecular weight was estimated at 440 kDa. The oligomeric structure was determined following treatment of the purified enzyme with dodecyl sulphate (SDS). The structure is composed of four identical subunits of 110 ± 10 kDa. Its optimal temperature is 55°C, and the optimum pH is 4. The enzyme is active against all the glucosides with the following configuration: β(1-2), β(1-3), β(1-4), β(1-6), α(1-4) and α(1-6). These results could justify the utilization of the enzyme in the liberation of terpenols from terpenyl glucosides. This enzyme is constitutive and repressed by glucose.

A newCandida parapsilosis lipase was isolated and studied. This enzyme was purified by hydrophobic chromatography on a phenyl-sepharose CL4B column followed by gel permeation on a Sephacryl S300 HR column. It was a 160 kg·mol−1 molecular-weight oligomeric enzyme. Optimal activity was obtained at 45°C and pH 6.5. The lipase activity toward various acylglycerols and esters was studied. The hydrolysis rate was greater for secondary acylesters than for primary acylesters. This lipase showed a high specificity for long-chain fatty acids and particularly for polyunsaturated fatty acids. This enzyme was able to catalyze the synthesis of various oleoylesters in aqueous medium.

The influence of several factors on the biosynthesis of Schwanniomyces costellii phytase was studied in continuous culture. The level of phytase production increased with pH and dilution rate. It decreased when the phytic acid or phosphate content increased.

The nitrile hydratase from the mutant strain of Brevibacterium sp. ACV2 was purified and compared to that from the wild type R312. Its molecular weight was estimated at 80000. This enzyme is composed of 2 sub-units with 26000 and 27500 molecular weights. The nitrile hydratase of the mutant strain is different from that of the wild type by its pHi, optimum activity pH, and its rates of hydrolysis of cyanovaleramide and cyanovaleric acid which were 30 and 15 folds greater.

Chemical synthesis of N-epsilon-acyllysines on an industrial scale corresponds to new requirements in the surfactant field; only one chemical synthesis process is currently known for this type of molecule. A number of organic synthesis conducted in the laboratory so far have not made it possible to consider industrial development. However, biotechnologically, it has been shown that this molecule is easily accessible using a commercially available fixed lipase. Synthesis is caried out by causing a triglyceride to react with the lysine either with or without a solvent. The latter method gives the best results at the current stage of research. Given the availability of at least one fixed lipase on the market today, and the possibility of directly applying the reaction using oils, this reaction could be scaled up rapidly for industrial development. (Resume d'auteur)

The 1H chemical shifts, 1H-1H coupling constants, 13C chemical shifts, and some 1H-13C and 13C-19F coupling constants have been determined for seven 3-substituted-9-chloroacridines and for the corresponding 3-substituted-9-aminoacridines. The effects produced by the substituent in position 3 on the 1H and 13C chemical shifts are discussed using two empirical models, those of Smith and Proulx (F, R, Q*) and Reynolds (σF, σR0, I, O, M).

International audience; Promoter sequences recognized by Escherichia coli RNA polymerase were isolated from Brevibacterium sp. R312, a coryneform strain producing nitrile hydratase and amidase. Ten Escherichia coli clones containing promoter sequences were selected for their ability to grow with chloramphenicol concentrations of up to 1500 micrograms/ml. The strength of these promoter sequences was determined. We carried out a preliminary study of the strongest promoter having a chloramphenicol acetyl-transferase/beta-lactamase activities ratio of 18.4.

The production and excretion of benzyl alcohol oxidase (BAO) by Botrytis cinerea was increased by shaking and by increasing the temperature to 28°. Various grape components, used as a carbon supply, inhibited (glucose, pectin, tartaric and malic acids) or promoted (galactose) extracellular and mycelial BAO formation. Compounds added to the medium, with galactose as a carbon supply, inhibited (caffeic and gallic acids) or promoted (arginine, nicotinic acid) synthesis of this enzyme. Molarity and pH played a role in release of the mycelial BAO which seemed to be a cell-wall enzyme. These results suggest a possible role of this enzyme in the host-parasite relationship.

Wild-type and cytochrome-deficient strains of Schwanniomyces castellii were cultivated aerobically on citrate, and the effects of respiratory inhibitors on respiration, ATP levels and energy charge were measured. The obtained results demonstrate that every respiratory pathway of Schwanniomyces castellii involves phosphorylation site I, and suggest that the functioning of this site allows the alternative pathways to produce ATP.

Détermination des paramètres optimaux de la croissance en continu et en discontinu de Candida rugosa sur de l'huile de palme dont le point de fusion est abaissée par de l'ammoniaque. Etude des conditions de culture et en particulier de l'effet de l'oxygène dissout

Phytase from Schwanniomyces castellii was purified by anion exchange and gel filtration chromatography. The enzyme has a molecular weight of 490,000 with a glycosylation rate around 31%. The structure of the deglycosylated protein is tetrameric, with one large subunit (MW 125,000) and three identical small subunits (MW 70,000). The enzyme exhibits an uncommon preference for high temperature, with optimum activity at 77°C and thermostability up to 74°C. The optimum pH is 4.4. Phytate is completely dephosphorylated by the phytase and the K m is 38 μM.

Of 21 yeast strains screened for ability to hydrolyse phytic acid salts, nine strains grew on sodium phytate as sole source of inorganic phosphate. Of the five most interesting strains for their growth parameters tested and for their phytase activity in batch-culture,Schwanniomyces castellii CBS 2863 had the highest phytase activity in presence of 5 g phytate I−1.

A benzyl alcohol oxidase (BAO) was purified to homogeneity from Botrytis cinerea. The enzyme was found to have a molecular mass of 214 kD with a trimeric structure, and optimal pH and temperature of 5.0 and 30°C, respectively. The enzyme activity was not sensitive to metal ions or to metal ion chelators, while thiol blocking reagents strongly inhibited BAO activity. Sulfur dioxide irreversibly inhibited the enzyme activity and the inhibitory effect of ethanol was weak and reversible. Benzyl alcohol was the most effective alcohol substrate for BAO. Para or meta monosubstituted benzyl alcohol with methyl or methoxy groups were good substrates. BAO also oxidized cinnamyl alcohol, furfuryl alcohol, and some terpenic alcohols· with an alkenyl group near the reactive carbinol. Secondary alcohol, methanol and phenol were not substrates. Product inhibition studies suggested that benzaldehyde and benzyl alcohol were bound at different places to the active site. O2 was the only electron acceptor identified and Botr...

Hydrolysis and transport of maltose into Schwanniomyces castellii was studied under aerobic and anaerobic conditions. Amylase and glucosidase were not synthetized in presence of maltose in anaerobic conditions. Maltose permease was synthesized in anaerobiosis and its functioning is not inhibited. Glucose strongly repressed induction. The half-saturation constant for uptake of maltose was 0.06 mM. The rate of uptake of maltose was decreased by 2,4-dinitrophenol, antimycin or sodium azide. The significance of these results in relation to the Kluyver effect is discussed.

Acrylamide production from acrylonitrile has been carried out in a specially designed fluidized bed reactor using immobilized cells of Brevibacterium sp. A4. The cells were entrapped in modified barium alginate beads. The optimum conditions with regard to catalyst stability were determined as: pH, 7.5; temperature, 5 °C; maximum acrylamide concentration, 60 g l −1 . There was no diffusional limitation due to the gel. On line determinations of the kinetic constants were performed. A high value of the maximum hydration rate was found but, the Michaelis-Menten constant for acrylonitrile, K m , and the inhibition constant for acrylamide, K i , appeared to be higher than the values obtained for free enzyme. The volumetric productivity of the reactor varied with both the substrate concentration and the feed rate.

A rapid and effective method is described for electroporation of Brevibacterium sp. R312, a coryneform strain producing nitrile hydratase and amidase. The transformation efficiency of the method is 108 transformants per μg of plasmid under optimal conditions. Parameters optimised included field strength (11.8 kV cm−1), pulse length (2.4 ms), plasmid DNA concentration (0.25 μg ml−1 and cell density (1010 cells ml−1). Surprisingly, the transformation efficiency did not vary with the growth stage, in contrast to results in the literature. A shuttle vector was constructed containing several unique cloning sites down-stream of the SP6 RNA polymerase promoter.

Several steps to obtain a good malolactic bioconversion in wine and a new process are presented. These include the optimisation of the biocatalyst production, the purification and properties of malolactic enzymes from Lactobacillus sp. 89 and Leuconostoc oenos ATCC 23278, and the development of a bioconversion process together wih some applications to wine. The use of selected strains and processes could allow the control of malolactic transformation in all wines in spie of the presence of inhibiors such as sulphur dioxide.

A yeast strain isolated in the laboratory was studied and classified as a Candida molischiana. The β-glucosidase of this yeast strain was then purified. Its molecular weight, estimated by gel filtration, was 100,000. The enzyme consisted of only one subunit, identified after treatment with sodium dodecyl sulfate. Maximum activity was obtained at 55°C and pH 4 but the enzyme still possessed activity at pH 2.5. Active against different glucosides with β(1–2), β(1–3), β(1–4), β(1–6), and α(1–4) configurations it presented an α(1–6)-arabinofuranosidase activity. The enzyme was competitively inhibited by glucose (Ki 9.5 mm). A glucosyltransferase activity appeared in the presence of ethanol. The enzyme was constitutive but its synthesis was repressed by glucose.

A virus-like particle (VLP) of 42 nm diameter was isolated from the lipolytic microorganism Geotrichum candidum. The VLP contains a linear double-stranded RNA molecule of 1.70 μm in length. Proteins of VLP were studied by polyacryl amide gel electrophoresis.

2. ed. chap. 5 Mention d'édition : 2. ed.

Chemical synthesis of N-e-acyllysines on an industrial scale corresponds to new requirements in the surfactant field; only one chemical synthesis process is currently known for this type of molecule. A number of organic synthesis conducted in the laboratory so far have not made it possible to consider industrial development. However, biotechnologically, it has been shown that this molecule is easily accessible using a commercially available fixed lipase. Synthesis is carried out by causing a triglyceride to react with the lysine either with or without a solvent. The latter method gives the best results at the current stage of research. Given the availability of at least one fixed lipase on the market today, and the possibility of directly applying the reaction using oils, this reaction could be scaled up rapidly for industrial development.

Biotechnological synthesis of a new class of amphiphilic molecules—fatty hydroxamic acids—was carried out using the lipase ofMucor miehei by reacting hydroxyl amine with the fatty acids in their free or methyl ester form. Concurrently with enzymatic synthesis, chemical synthesis of hydroxamic fatty acids has also been developed by adapting methods that already existed for water-soluble acids. Different parameters were studied to determine the optimum operating conditions: temperature, molar ratio of reagents, quantity of biocatalyst and length of reaction. A general method, whatever the type of fatty acids used, is described.

The present work reviews the numerous nitrile compounds that have been isolated from plants and animals. Two kinds of potentially toxic molecules are widespread, namely the cyanogenic glycosides and cyanollpids. Many other aromatic and allphatic nitriles are synthesized to a lesser extent. Different studies on the synthesis and degradation of these cyanogenic compounds are also reviewed to emphasize the potential use of different microorganisms for the detoxification of food and foodstuff.

We have isolated and studied cytochromic-deficient mutants of the amylolytic yeast Schwanniomyces castellii in order to study the possible contribution of cytochromes to alternative pathways. Three mutants were found, lacking cytochrome b, a + a3, or b and a + a3. All strains presented two alternative pathways, which were induced in the wild strain when cytochromic respiration was suppressed by growth in the presence of inhibitors, or without copper. If cytochromic respiration was absent, the Yxs yields in aerobiosis were higher than in anaerobiosis. This shows that the alternative pathways play a part in energy conservation. Cytochrome a + a3 did not appear to be directly involved in the alternative pathways.

Twenty one yeast strains were tested for their β-glucosidase activity. Only four produced significant quantities of β-glucosidase but none of them was able to secrete it. These four strains were tested under fermentative conditions and none of them was able to ferment cellobiose anaerobically.

Optimum culture conditions of Brevibacterium sp. A4 for production of nitrile hydratase were determined by two mathematical methods: the Hadamard method and graphic analysis of response areas. A minimal medium was optimized and the basic roles of Fe2+ and Mg2+ were clearly shown. The influence of physico-chemical factors (pH, temperature and light conditions) on the culture and on nitrile hydratase were also studied. Various results permit the production of Brevibacterium sp. A4 cells with low protease and high nitrile hydratase contents.