Abstract: An arrangement for controlling the rotational speed of an output rotational part of a fluid friction coupling is provided. A fan for cooling components of a motor vehicle is coupled with a driving rotational part by way of a shearing fluid whose effective fluid quantity determines the transferrable torque. The arrangement contains an adjusting unit (which can be electrically driven in a timed manner) for the variable adjustment of the effective shearing fluid quantity and contains a temperature controller stage to which the temperature of at least one medium whose temperature can be influenced by the output rotational speed is fed. The invention, the temperature controller stage is followed by a rotational speed controller stage to which, on the input side, the output signal of the temperature controller stage is fed as the dessired rotational output speed as well as the rotational driving speed and which, via of its output signal, drives the shearing fluid quantity adjusting unit of the coupling.

Abstract: Stable microbial enzyme with alcohol dehydrogenase activity having an activity maximum at ca. 50.degree. C., process for its isolation and its use for the enantioselective reduction/oxidation of organic keto compounds/hydroxy compounds wherein, depending on the type of the starting compounds R- or S-hydroxy compounds are obtained. In particular an alcohol dehydrogenase obtainable from Lactobacillus brevis has proven to be suitable.

Abstract: Known fluid friction clutches, which are electromagnetically controlled from either an engine side or a driving side, require very strong and space-consuming coils in order to produce magnetic forces which are sufficient to control valve levers which, on the side of the clutch away from the coil, open or close a connection opening between a storage chamber and a working chamber. To address this problem, the magnet coil is placed as close as possible to the clutch housing and, by way of inserted flux guiding rings, achieve a magnetic shunt of the lines of magnetic flux such that the coil does not have to be overdimensioned. The flux guiding rings extend to just in front of an armature of the valve lever and, with small radial air gaps, to the housing of the coil. The rings can otherwise be arranged opposite the rotatable shaft made of a magnetic material. Such clutches are appropriate for use as fan clutches of vehicle engines.

Abstract: The invention is directed to obtaining phenylalanine-dehydrogenase containing microorganisms by a special selection process comprising obtaining microorganisms, especially strains of Rhodococcus and the phenylalanine-dehydrogenase obtained in them. With the help of this enzyme there are obtained L-.alpha.-aminoacids from the corresponding ketocarboxylic acids by reductive amination.

Abstract: To increase the idling rotational speed of a fluid friction coupling, the static pressure in the reservoir space is increased by a differential pressure valve which opens toward the reservoir chamber at a defined differential pressure between the working chamber and the reservoir chamber. The fluid friction coupling includes a driving element; a driven-end coupling housing including a reservoir chamber and a working chamber; a partition for separating the reservoir chamber from the working chamber; a return passage arranged in the coupling housing between the working chamber and the reservoir chamber; and a differential pressure valve arranged within or in the region of the return passage.

Abstract: The aspartame content in aqueous solutions is determined by enzymatic cleavage of aspartame to aspartic acid and phenylalanine methyl ester by means of a peptidase, followed by a detection reaction cocatalyzed by adenine dinucleotide. The phenylalanine is, after elimination of the ester group by means of chymotrypsin, converted by phenylalanine dehydrogenase in the presence of NAD.sup.+ into phenylpyruvate, and the aspartame concentration is measured via the NADH or NH.sub.3 formation which occurs as a consequence. Alternatively, the aspartic acid is converted by a cell extract which acts on aspartic acid in the presence of NADP.sup.+, and the resultant NADPH or NH.sub.3 is used to determine aspartame concentration. These enzymatic reactions preferably are carried out in consecutive enzyme columns with carrier-immobilized enzymes by the FIA technique. The proportion of hydrolysis products can be measured by analyzing another sample omitting the peptidase reaction.

Abstract: The selective determination of .alpha.-ketoisocaproate in samples of body fluids, especially in serum, is achieved, without previous separation, directly in the fluid and in the presence of NADH, by means of a KIC-specific D-.alpha.-hydroxy-isocaproic dehydrogenase that originates specifically from strains of Lactobacillus casei producing this enzyme, in particular strains of Lactobacillus casei subspecies pseudoplantarum or casei. The KIC determination is used, in particular, for diagnosing maple syrup urine disease. Expedient for this purpose are analytical kits which have a divisible stock of D-.alpha.-hydroxyisocaproic dehydrogenase from Lactobacillus casei, in particular from the Lactobacillus casei (DSM 20008).

Abstract: A phenylethanol dehydrogenase capable of catalyzing the reduction of acetophenone to R(+)-phenylethanol in the presence of NADPH was isolated from Lactobacilli such as Lactobacillus kefir. The dehydrogenase is also capable of catalyzing the reduction of aromatic, alicyclic and aliphatic ketones selected from the group consisting of p-bromoacetophenone, methylcyclohexanone, acetone, methyl hexyl ketone, 4-phenyl-2-butanone, 1-phenyl-1,2-propanedione, ethyl pentyl ketone, pinacolone, propiophenone and p-chloroacetophenone. The dehydrogenase is rapidly inactivated by EDTA, but conventional inhibitors, chelators and SH-protecting reagents have only a slight effect on activity. The enzyme has a K.sub.M of 6.times.10.sup.-4 M for acetophenone. The dehydrogenase is capable of catalyzing the enzymatic reduction of carbonyl compounds to form optically active hydroxy compounds in the presence of NADPH.

Abstract: A process for the enzymatic preparation of acetoin, particularly (+)-acetoin, employs a diacetyl reductase which can be obtained from a yeast or Lactobacillus strain.

Abstract: The invention relates to a method for resolving carbamate racemates of amino acids or norephedrine by enzmatic resolution.

Abstract: A microbiologically produced .alpha.-acetylamino cinnamic acid acylase and a method for its production from Brevibacterium species NCIB 12246 or NCIB 12247. The new enzyme can be used as constituent of a coupled enzyme system for enzymatic conversions which run via the intermediary stage .alpha.-imino-.beta.-phenylpropionic acid or phenylpyruvic acid.

Abstract: The subject matter of the invention is a new D(-)-mandelate-dehydrogenase and obtaining it from Lactobacillus curvatus DSM 20019 (obtainable from the German Collection of Microorganisms). The new enzyme can be used for the enzymatic conversion of D(-)-mandelic acid and various other D-2-hydroxycarboxylic acids into the corresponding 2-ketocarboxylic acids or from benzoyl formate and various other 2-ketocarboxylic acids conversion to the corresponding D-2-hydroxycarboxylic acids.

Abstract: A fluid friction clutch is disclosed which has a working chamber formed by an output component in which a driving disk that is connected with an input component can rotate. For the adjustment of the degree of clutching, the working chamber can be filled by fluid supplied from a reservoir chamber developed as a pressure chamber and connected with the working chamber via a fluid connection, such as a pipe, a borehole, or similar means. This fluid connection is developed in such a way that, by means of admitting compressed air to the reservoir chamber, fluid can be delivered in a controlled manner from said reservoir chamber into the working chamber. A fluid friction clutch of this type has not movable mechanical valve parts, which is particularly advantageous when the compressed air is admitted to the reservoir chamber in surges, which would result in a rapid wear in the case of the known embodiments.

Abstract: The enzyme D-2-hydroxy-4-methylpentanoic acid dehydrogenase has been prepared by culturing readily available Lactobacillus or Leuconostoc, microorganisms, such as Lactobacillus casei ssp. pseudoplantarum and Leuconostoc mesenteroides. The microbiologically produced enzyme has special characteristics and is capable of converting D-2-hydroxycarboxylic acids, such as D-2-hydroxy-4-methylpentanoic acid to the corresponding 2-ketocarboxylic acid and is capable of enzymatically converting 2-ketocarboxylic acids, such as 2-keto-4-methylpentanoic acid and 2-ketobutyric acid to the corresponding D-2-hydroxycarboxylic acid.

Abstract: The invention is directed to a microbiologically produced L-phenylalanine-dehydrogenase and a process for its recovery from Brevibacterium species DSM 2448. The new enzyme can be used for the enzymatic conversion of phenyl pyruvic acid, p-hydroxyphenyl pyruvic aid, indolyl pyruvic acid or 2-keto-4-(methylmercapto)-butyric acid into the corresponding L-.alpha.-aminocarboxylic acids.

Abstract: The purpose of the invention is the new enzyme L-2-hydroxy-4-methylpentanoic acid-dehydrogenase and its recovery from Lactobacillus confuses. The new enzyme can be used to enzymatically change L-2-hydroxy-4-methylpentanoic acid and various other L-2-hydroxy-carboxylic acids into the corresponding 2-ketocarboxylic acids or 2-keto-4-methylpentanoic acid and various other 2-ketocarboxylic acids into the corresponding L-2-hydroxycarboxylic acids.

Abstract: A fluid friction clutch comprising a rotatable assembly comprising a clutch housing member and a clutch cover member defining a working chamber therein, the working chamber being connected with a working fluid reservoir, valve lever means in said reservoir for controlling the admission of working fluid from the reservoir to the working chamber where it serves to transfer torque between a rotatable disc disposed in the working chamber and said rotatable assembly, means for actuating the valve lever means comprising a pressure chamber formed from a pressure chamber housing and a flexible membrane carrying a pressure plate which directly engages the valve lever means, the pressure chamber housing and membrane being joined to the rotatable assembly to rotate therewith, and means for introducing a pressure medium such as compressed air into said pressure chamber to actuate the valve lever means and control the admission of working fluid from the reservoir into the working chamber, said pressure medium introducing

Abstract: A fluid friction clutch, especially for driving the cooling fan of an internal combustion engine. The rotating clutch housing has a separating wall defining a fluid reservoir chamber and a drive chamber and the separating wall has a passage which is opened and closed by a valve. The valve is actuated by an electromagnet disposed substantially coaxially with the clutch. A permanent magnet is attached to the valve assembly coaxially with the electromagnet and of opposite polarity to the magnetic field polarity which occurs when the electromagnet is energized. Upon energization, the opposing magnetic fields repel the two magnets and cause the valve to close, thereby disengaging the clutch. When the electromagnetic is deenergized, a spring reopens the valve and permits full engagement of the clutch.