G. Moulin

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.

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.

Optimization of the wheat puroindoline-a production in Pichia pastoris.

Aims: A recombinant puroindoline‐a (rPIN‐a) was produced using the methylotrophic yeast Pichia pastoris.

Influence of culture conditions on the biosynthesis of Schwanniomyces castellii phytase

SummaryThe 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.

Development of high-cell-density fermentation for heterologous interleukin 1\ production in Kluyveromyces lactis controlled by the PH05 promoter

The use of a phosphate organic form taken up by Kluyveromyces lactis removes repression of the PHO5 promoter and releases heterologous interleukin 1\ synthesis while providing sufficient phosphate for growth. The oxidative metabolism of high-cell-density fed-batch and chemostat cultures was thus maintained under derepressed protein synthesis conditions. Interleukin 1\ production was then growth-associated, an unusual mode of protein synthesis regulation under the control of the PHO5 promoter.

Isolation and characterization of a mutant of Schwanniomyces castellii with altered respiration

We have tried to isolate respiratory deficient mutants of the amylolytic yeast Schwanniomyces castellii CBS 2863 after mutagenesis with acriflavine. One of the mutants called DR 12 has been studied in more detail. Pasteur effect present in the wild-type is lost in the mutant, on the contrast an obvious Crabtree effect was observed: fermentation was almost as active in aerobiosis as in anaerobiosis. Moreover, the rate of anaerobic fermentation of the mutant was almost twice that of the wild type. This mutant was cytrochrome b-deficient while the amount of the other cytochromes was larger than in the wild-type. Moreover, the level of these remaining cytochromes in the mutant was higher on non-repressive medium than on glucose medium. However, the fact that the mutant DR 12 retained a cyanide-sensitive respiration and that it was able to grow on ethanol as a non-fermentable substrate is noteworthy.

Influence of culture conditions on the cell yield and amylases biosynthesis in continuous culture by Schwanniomyces castellii

Schwanniomyces castellii excreted α-amylase and amyloglucosidase into the medium in the presence of starch. The biosynthesis and the rate of excretion were influenced by dissolved oxygen (specially for α-amylase), pH of the culture and dilution rate. The cell yield observed (0.59) remained constant up to D=0.35h-1 with starch as substrate. But in the case of growth on glucose, the yield observed was equal to 0.62 up to a dilution rate of D=0.18 h-1. Beyond this value Y x/s decreased and ethanol was produced. The onset of fermentation dependend partly on the nature of the substrate and not only on the environment in particular on the quantity of dissolved oxygen present.

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.

Study of carbon dioxide release from Feta cheese

Abstract 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.