Harald Röper

Comparison of the Production of Lactic Acid by Three Different Lactobacilli and its Recovery by Extraction and Electrodialysis

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.

N.m.r. spectroscopy of N-(1-deoxy-d-fructos-1-yl)-l-amino acids (“fructose-amino acids”)

Abstract 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.

Gas chromatography-mass spectrometry of C1-C20 fatty acid benzyl esters

Abstract 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.

The synthesis of optically active derivatives of erythritol

Abstract The acetonides 2 and 4, obtained from erythritol, are excellent substrates for SAM II lipase. The resulting homochiral mono-esters 3 and 5 are suitable chiral building blocks.

Enzymatic enantioselective hydrolysis of 2,2-dimethyl-1,3-dioxolane-4-carboxylic esters

Abstract 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.

D-Isomannide in synthesis: asymmetric Diels-Alder reactions with novel homochiral bis-imine Cu2+-catalysts

Abstract The synthesis of a set of novel homochiral bis-imine ligands 4 derived from d -isomannide 6 , and their application in the Cu 2+ -catalyzed asymmetric Diels–Alder reaction of cyclopentadiene and N - tert -crotonoyloxazolidinone 1 is reported.

Structural investigations of glucans from cultures of Glomerella cingulata Spaulding & von Schrenck

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.

L-ribulose - a novel chiral pool compound

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

An Efficient Preparation of Silylated Derivatives of L-Erythrulose 3,4-O-Acetals

Abstract An efficient and reproducible procedure for the preparation of 1-O-silylated derivatives of several 3,4-O-acetals of erythrulose from the parent sugar is described.

Analytik von N-nitroso-verbindungen : 2. Mitt. Trennung und quantitative bestimmung von homologen N-nitroso-N-alkylharnstoffen und N-nitroso-N-alkylurethanen durch schnelle hochdruckflüssigkeitschromatographie

Abstract 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.