Search

A method was developed to produce pure maize starch from maize flour using a protease processing step, and additional salt washing and sulphite steeping steps. A range of commercial protease enzymes were evaluated for this purpose. The laboratory scale procedure that was developed, using one protease in particular (Promod P25P, thermolysin), produced relatively pure starch (

D(−)-Lactic acid was produced by Lactobacillus delbrueckii DSM 20072 (ATCC 9649) (LD), L(+)-lactic acid by Lactobacillus casei subsp. rhamnosus DSM 20021 (ATCC 7469) (LC) and by Lactobacillus salivarius subsp. salivarius DSM 20492 (ATCC 11742) (LS) on MRS medium and glucose substrate homofermentatively in batch cultures. LS exhibited the highest specific growth rate (μ = 1·41 h−1) and the highest specific productivity (π = 5·45 h−1). Acetate and citrate stimulated its growth. Substrate inhibition occurred at 30 g litre−1 glucose for LD, 26 g litre−1 glucose fo LC, and no inhibition was observed up to 100 g litre−1 glucose for LS. 60 g litre−1 lactate solution at pH 6 caused only slight product inhibition of LS. The product was extracted by four different amine carriers (Amberlite LA2, Hoe F2562, Hostarex A327 and Alamin 366) in the presence of modifiers (long-chain alcohols, alkylphosphates and acidic organic compounds) in kerosene and butylacetate, and a phosphinoxide (Cyanex 923). When using Hostarex A327 in oleylic alcohol or Cyanex 923 (phosphinoxide carrier) in kerosene or in oleylic alcohol, no modifier was necessary. The extent of lactic acid extraction was evaluated and the separation of lactic acid from citric and acetic acids was investigated. The re-extraction of the free acid under different conditions was not very successful. A maximum lactic acid yield of 72% was obtained. Except for kerosene and oleyl alcohol, the biocompatibility of the other chemicals was unsatisfactory. Their application for in situ extraction cannot be recommended. Recovery of the free lactic acid by electrodialysis and bipolar membrane is very promising. In situ recovery is possible.

Methylation analysis, enzymic digestion, n.m.r. spectroscopy, and Smith degradation showed that the major extracellular polysaccharide, isolated from cultures of the fungus Glomerella cingulata, was a (1----3)-beta-D-glucan with side chains of 1-4 (1----3)-linked beta-D-glucose residues attached to position 6. A (1----6)-beta-D-glucan was produced by the fungus in small proportions. Treatment of the (1----3,1----6)-beta-D-glucan (890,315) with greater than 0.05M NaOH at greater than 150 degrees, or Me2SO-H2O with a concentration of dimethyl sulfoxide of greater than 80%, irreversibly destroyed the highly ordered structure responsible for the high viscosity of aqueous solutions. The strong shift of the lambda max of aqueous solutions of Congo Red by the degraded glucan, the fact that the mol. wt. of the original glucan was approximately 4 times higher than that of the degraded polymer, and the suppression of the n.m.r. signals for C-3 indicated that the original glucan had a highly ordered structure, probably built up from single helices.

The unnatural keto-sugar L-ribulose, presently more readily available, is an interesting “chiral pool” product. Some key-intermediates for its transformation are described.

Hexamethylentetramin-[Hexa]-Proben verschiedener Herkunft — Hexa DAB 7 (Fa. Merck), Hexa pro anal. (Fa. Merck), Hexa (Eigenpraparat), Hexa (unbekannter Herkunft) — wurden mit GC- und GC/MS-Analyse auf die Gegenwart fluchtiger organischer Verbindungen untersucht. Formaldehyd, Aceton, Methylamin, Trimethylamin-N-oxid und Chloroform konnten gaschromatographisch nachgewiesen und teilweise durch GC/MS-Analyse abgesichert werden. Sekundare und tertiare aliphatische Amine waren in keiner der Hexa-Proben zugegen.

Thirteen N-(1-deoxy- d -fructos-1-yl)-N-nitroso- l -amino acids were prepared, in 83–95% yield, by nitrosation of the corresponding “fructose-amino acids” with sodium nitrite in water-hydrochloric acid, at pH 3. The 1H-n.m.r. spectra were complicated by the presence of different sugar-ring forms (α,β-furanoses and-pyranoses). In addition, signal doubling for all proton resonances were observed for the E/Z isomer N-nitroso compounds. Signals of β- d -pyranoses unequivocally can be assigned as >50% in solution equilibrium. In D2O, some compounds showed a slow H-D-exchange for H-1a and H-1b. Ring conformation for all E/Z isomer β-pyranoses was 2C5( d ). The 13C-n.m.r.-spectra exhibited resonances of all four ring-forms, with signal doubling for E/Z isomers, all of which could be assigned. Signals of open chain-forms were not present. For the β- d -pyranose forms, changes of chemical shifts, caused by N-nitrosation, were calculated by comparison with the educts (Δδ values) and separately discussed for E- and Z-isomers. The separation by reversed-phase, ion-pairing, l.c., and the pKa values of the nitroso derivatives are reported, as well as the e.i.-mass spectra of their per(trimethylsilyl) derivatives.

Analysis of N-nitroso compounds. II. Separation and quantitative determination of N-nitroso-N-alkylureas and N-nitroso-N-alkylurethans by high-speed high-pressure liquid chromatography . Physical data, elementary analysis data and IR, UV, NMR and mass spectra have been determined for N-nitroso-N-alkylureas and N-nitroso-N-alkylurethans. The fragmentation patterns in the mass spectrometer induced by electron impact are discussed. A fast separation is described of model mixtures of alkyl homologous N-nitroso-N-alkylureas and N-nitroso-N-alkylurethans by reversed-phase liquid—liquid distribution in a liquid chromatograph. Detection is carried out by UV absorption at 254 nm. Calibration curves for the quantitative determination of separated N-nitroso-N-alkylureas are given. The lowest detection limit for N-nitroso-N-methylurea was 10 ng.

Analysis of N-nitroso compounds. V. Trace analysis of N-nitrosoamino acids: Gas chromatography and spectroscopy of N-nitrosoamino acid methyl esters N-Nitrosoamino acids (N-NO-sarcosine, N-NO- l -proline, N-NO-4-OH- l -proline and N-NO- d,l -piperidine-2-carboxylic acid) were reacted with methanol-H+ or diazomethane to the corresponding methyl esters in preparative and analytical scale. N-NO-4-OH- l -proline methyl ester was reacted with N-methyl-N-trimethylsilyl-trifluoroacetamide to give N-NO-4-O-trimethylsilyl- l -proline methyl ester in quantitative yield. The N-nitrosoamino acid methyl esters were characterized by physical (b.p., m.p., RF values) and spectral data (infrared, mass spectrometry, 1H nuclear magnetic resonance (NMR), 13C NMR). The fragmentations of N-NO-sarcosine methyl ester, N-NO- l -proline methyl ester and N-NO- d,l -piperidine-2-carboxylic acid methyl ester induced by electron impact in the mass spectrometer, were studied by high-resolution measurements, metastabile ions, DADI-technique and defocusing method. The ratios of E- and Z-isomers of N-nitrosoamino acid methyl esters in solution are determined by 1H NMR spectroscopy. The resonances of the methyl ester protons appear as two singlets. This is explained by interaction of the N-NO-groups with the methyl ester protons via cyclic arrangements in equilibria of E- and Z-isomers and confirmed by the 1H NMR spectrum of N-NO-sarcosine-trideuteromethyl ester. The N-nitrosoamino acids are quantitatively converted to the corresponding N-nitrosoamino acid methyl esters by reacting with diazomethane. These derivatives of N-nitroso-amino acids (including N-NO-4-O-trimethylsilyl- l -proline methyl ester) can be separated by gas-liquid chromatography on OV-17 as stationary phase. This derivatization procedure allows separation and quantitative determination of N-nitrosoamino acids by gas-liquid chromatography and confirmation by gas-liquid chromatographic-mass spectrometric analysis in nanogram amounts.

2,2-Dimethyl-1,3-dioxolane-4-carboxylic acid derived chiral building blocks were prepared from substituted α,β-unsaturated acids with high enantiomeric purities by enzymatic hydrolysis of their n.butyl esters.

Drei Modell-Gemisched-Glucose/dl-Alanin,d-Glucose/l-Lysin undd-Glucose/l-Glutaminsaure wurden unter Zugabe von Natriumnitrit unter Maillard-Bedingungen gebraunt. Die Zugabe von Natriumnitrit erfolgte vor und nach der Braunung. Im letzteren Fall schlos sich eine kurze Nachbraunung an. Die Reaktionsbedingungen — pH-Wert und Braunungstemperaturen — wurden variiert. Die Analyse der alkalibestandigen wasserdampffluchtigen Maillard-Produkte erfolgte durch GC und GC/MS-Analyse. Bei den identifizierten Produkten handelt es sich um alkylierte Pyrazine, Furan- und Pyridin-Derivate. Nitrosopiperidin wurde aus dem Braunungsansatzd-Glucose/l-Lysin (Nitritzugabe nach der Braunung) massenspektrometrisch nachgewiesen. Die Anderung des pH-Wertes um eine Einheit, sowie die Anderung der Braunungstemperatur innerhalb des Temperaturbereiches 100–150° C haben auf die qualitative Zusammensetzung der fluchtigen Maillard-Produkte eines betrachteten Modell-Gemisches keinen Einflus. Ein geringer Unterschied wird hinsichtlich der quantitativen Zusammensetzung beobachtet.

High-resolution, 1 H- (360 and 400 MHz) and 13 C-n.m.r. (90.52 and 100.57 MHz) spectra of the mutarotated N -(1-deoxy- d -fructos-1-yl)- l -amino acids (“fructose-amino acids”) 1–14 in D 2 O are reported. The 1 H spectra allow unambiguous assignment of the signals of the major constituents (β-pyranose forms). Signals of the other forms are not well resolved and therefore not interpreted. The 13 C spectra of 1–14 show ∼64% of β-pyranose, ∼15% of α-furanose, ∼15% of β-furanose, and ∼6% of α-pyranose forms. For N -(1-deoxy- d -fructos-1-yl)- l -alanine ( 2 ), 2% of the keto form is present. In solution in D 2 O, H-1 of the fructose moieties undergoes a slow H/D-exchange, which is strongly accelerated at more-basic pH values. Compound 2 is stable over the pH range 0.7–11.9, as revealed by 13 C-n.m.r. spectroscopy. The 13 C-shift changes caused by protonation/deprotonation are given. There is no significant change in the ratios of the various forms with change in pH.

Benzyl esters of saturated normal and some branched fatty acids (C 1 -C 12 ) and of saturated and unsaturated even-numbered long chain fatty acids (C 14 -C 20 ) were prepared by reaction with phenyldiazomethane. Mass spectra of the individual esters were recorded. A mixture of all the prepared saturated esters was separated on an SE-30 column and identified in the μg range by a combination of gas chromatography and mass spectrometry. Separation of saturated and unsaturated long chain fatty acid benzyl esters was achieved on an EGSS-X column at 210°. A general fragmentation scheme for this class of substances is proposed and the formation of the main fragments is discussed.