Robert Ratomahenina

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.

A study of the influence of the growth media on the fatty acid composition in Candida lipolytica Diddens and Lodder

Candida lipolytica YB 423-12 is able to incorporate fatty acid from the culture medium when lipids are used as carbon substrate. The composition of cell lipids is largely dependent on that of the culture medium. An important Δ 9 desaturase activity acts on incorporated palmitic and stearic acids; and Δ 11-eicosenoic and erucic acids are shortened to oleic acid.

Purification and properties of the lipases from Rhodotorula pilimanae Hedrick and Burke

SummaryThe Rhodotorula pilimanae CBS 5804 strain secretes into the culture medium two lipases: their pH optima are 4 and 7. The two lipases were purified by precipitation with acetone followed by chromatography on SP-Sephadex C50 and Sephadex G200. The purification factors achieved in comparison with the supernatant culture were x74 for lipase I and x90 for lipase II. The molecular weights were estimated at 172,800 and 21,400 for lipase I and lipase II, respectively. Their activities are optimal between 45°C and 55°C. The activation energies were 5.9 kcal·mole-1 for lipase I and 12.4 kcal·mole-1 for lipase II. The inactivation energies were about 21.9 and 17.7 kcal·mole-1 for lipase I and lipase II, respectively. The enzymes are slightly inhibited by Cu2+, Co2+, Hg2+, Mn2+, N-acetylacetone, acetic acid and sodium lauryl sulphate. EDTA did not affect their enzymatic activity. These two lipases are secreted in the culture media in the absence of inducer; their biosynthesis is not inhibited by glucose. These lipases hydrolyse primarily the 1-(or 3-)position of all triglycerides tested.

Peculiar properties of lipase fromCandida parapsilosis (Ashford) langeron and talice

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.

Study of the growth of yeasts from feta cheese

The effects of various physicochemical parameters on the growth of three yeast strains were investigated, including: pH, sodium chloride content, water activity in the medium and temperature. All strains were unaffected by pH changes. Growth was optimal at pH 5.5, while these yeasts were able to develop within the pH 2.5-8 range. Suitable growth was obtained at temperatures of 4 degrees C-44 degrees C and the optimal temperature for growth was 32 degrees C for all three strains. Modelling of this latter parameter is described. Growth of microorganisms was considerably modified by increased NaCl or decreased water activity in the medium.

Study of physicochemical factors limiting the growth ofKluyveromyces marxianus

SummaryThe effects of various physicochemical parameters on the growth of twoKluyveromyces marxianus strains were investigated, including: pH values, sodium chloride, water activity in the medium and temperature. Both yeast strains were unaffected by pH changes. Optimal pH for growth was found to be 4 with both strains, but they were able to develop within the pH 3–8 range. Suitable growth was obtained at temperatures of 4–44°C and the optimal temperature for growth was 36°C for both strains. Modelling of this latter parameter is described. Growth of both microorganisms was considerably modified by increased NaCl or decreased water activity in the medium.

Isolation and characterization of a RNA-virus like particle from Candida curvata

Summary— A virus‐like particle (VLP) of 35 nm diameter has been isolated from the lipolytic yeast Candida curvata. The VLP contains a linear, double stranded RNA molecule of 1.55 μm in length.

A Study of Cyanide-Insensitive Respiration in the Genus Dekkera and Brettanomyces

Dekkera intermedia and Brettanomyces custersii were shown to have a respiratory pathway resistant to cyanide, antimycin A, and azide. This respiration remained sensitive to salicylhydroxamic acid (SHAM). The “cyanide‐resistant” respiration was induced mainly at the end of the growth phase and could reach 50% of total respiratory capacity.

Production of food yeasts from the solid fraction of palm oil

SummaryGrowth parameters of different species of yeast on ammonium soaps have been determined. All tested strains are able to use the solid part of palm oil, transformed into ammonium soaps. Growth parameters are acceptable for industrial use and it is possible to produce single cell protein from this substrate.

Biosynthesis regulation of the β-glucosidase produced by a yeast strain transformed by genetic engineering

The biosynthesis of the β-glucosidase enzyme was studied in a transformed yeast obtained by cloning in Saccharomyces cerevisiae the structural gene coding for β-glucosidase in Kluyveromyces fragilis. The enzyme biosynthesis was found to be non-adaptative, and repressed by glucose. These features are similar to those observed in K. fragilis. β-Glucosidase activity in the transformed yeast was much higher than in K. fragilis. We attempted to ferment cellobiose with the transformed yeast: practically no cellobiose was consumed, growth and ethanol production were negligible. Warburg experiments showed that cellobiose fermentation did not occur when the respiratory chain was not functioning.