P. Galzy

Purification and properties of the phytase from Schwanniomyces castellii

Abstract 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.

Fatty acid and carotenoid composition ofRhodotorula strains

Lipid content and composition of fatty acids with 6–25 carbon atoms were studied on strains of the 13 pink or red yeast species belonging to the genusRhodotorula. The total amount of lipid represented an average of 13% of the dry weight. The neutral and polar lipid fractions were analyzed separately. For all the strains studied, the major fatty acids in both fractions were oleic, linoleic and palmitic acids, which formed 80% of the total number of fatty acids. A notable amount of arachidonic acid, a precursor of eicosanoid hormones, was found inR. acheniorum, R. aurantiaca andR. bacarum. Depending on the strain, 1–10 carotenoid pigments were detected; β-carotene was always the major carotenoid present.

Purification and properties of the β-glucosidase of a yeast capable of fermenting cellobiose to ethanol: Dekkera intermedia van der walt

SummaryThe intracellular enzyme β-glucosidase of Dekkera intermedia was partially purified by ion-exchange chromatography and gel filtration. The molecular weight of this enzyme was 310,000; its optimum pH was 5.0 and optimum temperature was 55°C. This enzyme was active against different β-glucosides and was inhibited by p-chloromercurybenzoate, gluconolactone, and glucose. A “glucosyltransferase” activity appeared in the presence of ethanol. The biosynthesis of this enzyme was constitutive but repressed by glucose.

UTILIZATION OF PHYTATE BY SOME YEASTS.

SummaryOf 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.

Production of Food and Fodder Yeasts

A decade or so ago, there was considerable interest in developing single cell protein production from raw materials. Many factors have influenced the development of fodder yeast technology, notably the biochemistry and physiology of the yeast. It is shown that those considerations have led to the choice of a continuous fermentation technology.

Enzymatic fatty esters synthesis in aqueous medium with lipase from Candida parapsilosis (Ashford) Langeron and Talice

SummaryThe synthesis of fatty esters in aqueous medium by alcohoiysis catalysed by lipase from Candida parapsilosis (EC.3.1.1.3) is described. The transesterification of rapeseed oil with methanol leads to an equilibrium state after eight hours, with a yield (methyl esters formed/ total fatty acids initially present in the acylglycerols) of at least 53% (73, 45, 65% of the linolenic, linolek and oleic acids respectively). Yield was already about 42% after four hours of catalysis. This transesterification was permitted by methanol inhibition of hydrolysis of the esters.

Natural nitriles and their metabolism.

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.RésuméCe travail passe en revue les nombreux composés nitrillques qui ont été isolés du royaume des plantes et animaux. Deux types de molécules à potentiel toxique sont largement répandus, notamment les glycosides cyanogènes et les cyanolipides. De nombreux autres nitriles aromatiques et alystatiques sont synthétisés dans une moindre mesure. Diverses études sur la synthèse et la dégradation de ces composés cyanogenes sont également passés en revue afin de mettre en évidence lemploi putalli des différents microorganismes pour la detoxification de denrées et matières alimentalres.

Ester synthesis in aqueous media in the presence of various lipases

SummaryThe ability of seven lipase preparations to catalyse methyl ester synthesis in aqueous media was compared and the synthesis reaction (esterification or alcoholysis) determined. Three behaviours were observed: three enzymes catalysed ester synthesis by esterification of free fatty acids and one enzyme catalysed alcoholysis but the other three lipases did not catalyse a net ester synthesis under the conditions tested. The three groups also differed by the influence of methanol on the hydrolysis reaction. The first group was not significantly inhibited up to the highest methanol concentration tested (5 M). Hydrolysis in the presence of the enzyme of the second group was increasingly inhibited with increasing methanol concentrations. In the presence of the third group, hydrolysis was 40 to 50% inhibited for all the concentrations tested (0.2–5 M).

Purification and properties of the lipase fromCandida deformans (zach) langeron and guerra

Palm oil being solid at room temperature could be converted into a fluid oil by substitution of about 40–50% of its palmitic acid. This could be achieved by a fermentation process or using yeast lipase.Candida deformans CBS 2071 seemed suitable for this purpose: therefore, its lipase was isolated and studied. This enzyme was purified by acetone precipitation followed by chromatographies on Sephadex C 50 and Sephadex G 150. The purification factor achieved was ×70, and the protein and activity yields were 0.25% and 18%, respectively. The homogeneity of the purified enzyme was verified by polyacrylamide gel electrophoresis. The enzyme molecular weight was estimated at 207,000. Its activity is optimal between 40 C and 50 C and its optimum pH is 7.0. This enzyme is thermo-resistant and loses only 14% and 18% of its activity, respectively, when heated to 45 C and 55 C for 30 min. Its activation energy was 2.75 kcal.mole−1 and its inactivation energy was around 21 kcal.mole−1. This enzyme is activated by Ca++, Mg++ and Co++ and inhibited by Cu++, Zn++, and p-chloromercuribenzoate (pCMB) and EDTA.The synthesis of this lipase is induced by lipid substrates in the culture medium and inhibited by glucose. This enzyme attacks primarily the 1- (or 3-) position of all triglycerides tested. Hydrolysis was preferential for triglycerides containing short chain fatty acids. The triglycerides with monounsaturated monoacids were more quickly hydrolyzed, than those with saturated monoacids. The presence of two and especially three double bonds in the fatty acid chain seemed to slow down the rate of hydrolysis.

Fatty hydroxamic acid biosynthesis in aqueous medium in the presence of the lipase-acyltransferase from Candida parapsilosis

The lipase-acyltransferase from Candida parapsilosis has been shown to catalyze fatty hydroxamic acid biosynthesis in a biphasic lipid/aqueous medium. The substrates of the reaction were an acyl donor (fatty acid or fatty acid methyl ester) and hydroxylamine. The transfer of acyl groups from a donor ester to hydroxylamine (aminolysis) was catalyzed preferentially to the reaction of free fatty acids. The highest synthesis activity was obtained in the presence of 1 M hydroxylamine at 45 degrees C and pH 6. This work confirmed the originality of the enzyme from Candida parapsilosis, which acts more like an acyltransferase than an hydrolase. This feature makes it an enzyme of choice for the direct bioconversion of oils in aqueous medium.