THERMAL STABILIZATION OF FOUR MICROBIAL β-GALACTOSIDASES BY HISTIDINE, CASEIN AMINO ACIDS AND CASEIN

Thermal stability of four microbial β-galactosidases was evaluated in the presence of casein, casein amino acids and histidine. The enzymes from Esch-erichia coli, Kluyveromyces marxianus and Streptococcus thermophilus were stabilized up to 60 fold by these additives, but there was little effect on the enzyme from Aspergillus oryzae. Stabilization by casein amino acids and histidine was largely lactose dependent. Casein amino acids were not as effective as casein for any enzyme. For the K. marxianus enzyme, histidine alone was as effective as casein and the stabilizing effect was proportional to the logarithm of the histidine concentration.     

THE AMINO ACIDS CONTENT OF SOME IRAQI DATES

SUMMARY –Amino acid content and nutritive value of three varieties of Iraqi dates was studied. Protein of the date was acid hydrolyzed for 24 hr and the amino acid content determined in a Phoenix automatic analyzer. The protein content on a fresh weight basis was 1.96% for Zahdi, 1.89% for Hillawi and 2.38% for Sayer. The following amino acids were present in these varieties: lysine, histidine, arginine, aspartic acid, threonine, glutamic acid, serine, prolin, glycine, alanine, cystine, valine, methionine, isoleucine, leucine, tyrosine and phenylalanine. Glutamic acid was present in highest concentration and Sayer variety contained more amino acids than Hillawi and Zahdi. Tryptophan and half-cystine may have been destroyed during acid hydrolysis.     

Incorporation of Histidine and β-Alanine into the Macromolecular Fraction of Beef Soup Stock During Heating

Beef soup stock solution was heated at 95 °C, and the macromolecular fractions were obtained by dialysis. Amino-acid analysis indicated that histidine and β-alanine increased. The existence of β-alanine suggests incorporation of carnosine into the macromolecular fraction during beef extract production. To confirm the incorporation of carnosine, the macromolecular fraction was digested and the β-alanine-containing fraction was purified. This resulted in a tripeptide that consisted of glutamic acid, histidine, and β-alanine which was isolated. It was resistant to an aminopeptidase and a carboxypeptidase and released glutamic acid and carnosine when treated with γ-glutamyltranspeptidase. These results suggest that a portion of carnisone was incorporated into the macromolecular fraction and formed γ-glutamyl-β-alanyl-histidine.     

DIETARY FATTY ACIDS AND AMINO ACIDS OF CAMELINA SATIVA SEED

Abstract Camelina sativa ( L. ) Crantz is an ancient oilseed crop. Camelina seed can be used as a food ingredient and raw material for the production of oil. The by-product from the production of oil by pressing (oil cakes) was traditionally used as fodder ingredient.
Camelina seed samples for analyses were collected from geographically remote localities in Europe and in Scandinavia (6° W - 25° E, 48 - 61° N). The seed was analyzed for the content of oil, fatty acids, total nitrogen and amino acids.
The mean content of oil in the seed was 43.3 ± 0.22%/DM. The predominating acid, α-linolenic (18:3 n-3), was 37.8 ± 0.17%; and others were oleic acid (18:1 n-6) 13.4 ± 0.13%; linoleic acid (18:2 n-6) 14.8 ± 0.12%; gondoic acid (20: 1 n-9) 15.4 ± 0.16% and erucic acid (22: 1 n-9) was 2.76 ± 0.07%/total FA.
Crude protein was 42.5 ± 0.46%/fat free DM. Considerable amounts of essential amino acids were present, such as arginine 8.15 ± 0.06%; glycine 5.44 ± 0.04%; isoleucine 3.96 ± 0.02%; leucine 6.63 ± 0.04%; lysine 4.95 ± 0.04%; phenylalanine 4.19 ± 0.04%; proline 5.09 ± 0.03%; threonine 4.25 ± 0.03% and valine 5.42 ± 0.04%. The methionine content was 1.72 ± 0.04% and cystine, 2.12 ± 0.05% (A.A. g/16 g N).     

UPTAKE OF AMINO ACIDS IN BOTTOM FERMENTATIONS

The net uptake of amino acids in full-scale brewery fermentations with a strain of Saccharomyces carlsbergensis at 8–9° C. has been followed by analysing amino acids in fermenting wort and beer. The amino acids are usually taken up very incompletely and their uptake follows a certain order, not very different from that observed by British authors using top yeast fermenting at 15° C. The order is not quite constant, however; particularly the uptake of arginine and of ammonia are subject to variations. The amino acids can be divided, according to their rate of absorption and degree of utilization, into three clear-cut groups. The results suggest that it is the system allowing entry of amino acids into the cell that is of prime importance and that this is not capable of regulating the uptake to the demand of amino acids as building blocks for yeast protein. The results are considered in the light of recent investigations on amino acid permeases of yeast, and the metabolic roles of the most rapidly absorbed amino acids, serine, asparagine, glutamine, and threonine, are discussed.     

ISOLATION AND SOME PROPERTIES OF THE THERMOSTABLE β-GALACTOSIDASE OF PYROCOCCUS WOESEI EXPRESSED IN ESCHERICHIA COLI

The enzyme with β-galactosidase activity from E. coli BL21(DE3) transformant containing the gene encoding enzyme from Pyrococcus woesei (DSM 3773) was isolated using cell extraction in 0.01 M phosphate buffer (pH 7.2), protein thermopredpitation at 85C, precipitation at acetone/extract ratio of 1:1 (v/v) and gel filtration on Sephadex G-200. The increase in the enzyme specific activity was determined using ONPG as substrate. The activity increased from 2.9 × 10³ U/mg protein to 37 × 10³ U/mg. Thermoprecipitation removed 78% of E. coli protein and retained 92% of the cell extract activity. The acetone precipitation and gel filtration applied in the next purification steps led to homogeneous enzyme with specific activity of 37,700 U/mg protein. The isolated enzyme had a half-life of 23 h and 9 h during incubation at 85C and 100C, respectively, in 0.1 M citrate-phosphate buffer (pH 5.4).     

WORT COMPOSITION AND BEER FLAVOUR. I. THE INFLUENCE OF SOME AMINO ACIDS ON THE FORMATION OF HIGHER ALIPHATIC ALCOHOLS AND ESTERS

Wort, to which was added various amounts of glucose solution containing either (NH₄)₂SO₄ or one of the amino acids alanine, leucine, isoleucine, valine or proline, was fermented, and in the resulting beers the concentrations of ethyl acetate, isoamyl acetate, n-propanol, isobutanol, and amyl alcohols were determined by gas chromatography. The nitrogen source had some effect on the formation of higher alcohols, in addition to the effect due to conversion of some of the amino acids to the corresponding alcohols via the Ehrlich pathway. Ethyl acetate formation was not significantly affected by the nitrogen source, and iso-amyl acetate formation increased when amyl alcohol formation increased.     

MOLECULAR CHARACTERIZATION OF THE β-CONGLUTIN OF LUPIN SEEDS

β‐conglutin from Lupinus campestris was extracted and purified by gel filtration chromatography. The protein with molecular mass around 190 kDa showed by SDS‐PAGE three major polypeptides of 53, 60 and 63 kDa and a minor polypeptide of 30 kDa. Isoelectric focusing of the native protein gave three isoforms with isoelectric points of 6.2, 6.3 and 6.4. Its sedimentation coefficient was 8.0S, with a hydrodynamic diameter of 110 Å and possessed antigenic determinants in common with 7S proteins from common bean and soybean.