Cells Of Kluyveromyces Fragilis Research Articles

The enzymatic hydrolysis and fermentation of pretreated wheat straw to ethanol

Autohydrolysis and ethanol-alkali pulping were used as pretreatment methods of wheat straw for its subsequent saccharification by Trichoderma reesei cellulase. The basic hydrolysis parameters, i.e., reaction time, pH, temperature, and enzyme and substrate concentration, were optimized to maximize sugar yields from ethanol-alkali modified straw. Thus, a 93% conversion of 2.5% straw material to sugar syrup containing 73% glucose was reached in 48 h using 40 filter paper units/g hydrolyzed substrate. The pretreated wheat straw was then fermented to ethanol at 43 degrees C in the simultaneous saccharification and fermentation (SSF) process using T. reesei cellulase and Kluyveromyces fragilis cells. From 10% (w/v) of chemically treated straw (dry matter), 2.4% (w/v) ethanol was obtained after 48 h. When the T. reesei cellulase system was supplemented with beta-glucosidase from Aspergillus niger, the ethanol yield in the SSF process increased to 3% (w/v) and the reaction time was shortened to 24 h.

The production of ethanol from lactose in a tubular reactor by immobilized cells of Kluyveromyces fragilis

An immobilized-cell tubular reactor for the continuous fermentation of lactose by Kluyveromyces fragilis was developed. Two types of supporting media were successfully tested; beechwood cubes and activated charcoal pellets. Ethanol productivity of 17.2 g/l/h was achieved from a 15% whey-lactose solution using K. fragilis immobilized on charcoal pellets, with a final ethanol concentration of 18 g/l. The use of two reactors in series demonstrated that it is possible to obtain up to 50 g/l of ethanol in the final product. No decrease in biological activity of the immobilized yeast cells occurred over a period of up to 31 days of continuous operation.

The use of immobilised cells of Kluyveromyces fragilis for the production of up-graded whey protein concentrates

The use of immobilised cells of Kluyveromyces fragilis for the production of up-graded whey protein concentrates

Hollow fibre bioreactor for ethanol production: Application to the conversion of lactose by Kluyveromyces fragilis

Kluyveromyces fragilis cells have been packed into the shell side of an industrial size hollow fibre module. The feed was pumped through the tube side under pressure. During continuous, single-pass operation with a synthetic lactose medium containing 50 g l −1 lactose, ethanol productivity was 30–60 g l −1 h −1 at dilution rates of 1–4 h −1. With 150 g l −1 lactose concentration, the productivity was 100–135 g l −1 h −1. Productivity was generally lower when cottage cheese whey permeate (45 g l −1 lactose) was used as the feed. Long-term stability of the hollow fibre bioreactor was good, provided adequate care was taken to bleed the gas generated and restrict cell concentration in the shell side.

Enzymatic Refining of Unconventional Protein for Nutritional Purposes

Studies were made on the possibilities of refining protein from the fodder yeast, Candida utilis, from Kluyveromyces fragilis cells and from the field bean by enzymatic means using pepsin and papain, followed by the reverse synthesis of proteins from hydrolysates as treated with alpha-chymotrypsin. The yield of refined protein was about 75%, as measured by amounts of nitrogen substances precipitated in 15% trichloroacetic acid. The refined yeast proteins contained no nucleic acids, while field bean protein was free of trypsin inhibitors. The refined proteins appeared to be neutral in respect of flavor substances.

Proteinkristalle und Tubuli-Bündel in Hefezellen: 1. Assemblierung und Desassemblierung

Protein crystals and bundles of tubules (tb) are induced inside of intact cells of Saccharomyces carlsbergensis and S. cerevisiae by incubation in hypertonic media both at room temperature and at 0 °C within a few minutes or by preparation of protoplasts. The induction is not possible in cells of Kluyveromyces fragilis and Rhodosporidium diabovatum. Formation of these structures depends on osmolality of the hypertonic media not on the kind of substances used. In cells previously cultured in medium containing glucose (5 %) instead of lactate (2 %) or ethanol (1 %) these structures can be induced only in few cases. Crystals and tb disappear within 1—4 hours provided that osmotic shock is followed by growth of cells or protoplasts.

Ergosterol is the only sterol in Kluyveromyces fragilis.

The sterol fraction has been extracted from cells of Kluyveromyces fragilis and analyzed by thin-layer chromatography, UV spectroscopy, gas-liquid chromatography and mass spectroscopy. Only ergosterol could be detected.