Mauri Mäkelä

Effect of temperature on retention time reproducibility and on the use of programmable fluorescence detection of fifteen polycyclic aromatic hydrocarbons

Abstract The effect of temperature on the retention of 15 polycyclic aromatic hydrocarbons (PAHs), included in the US Environmental Protection Agency method 610, on polymeric octadecylsilyl (ODS) high-performance liquid chromatography phases is described. Indeno[1,2,3-cd]pyrene, dibenz[a,h],anthracene and benzo[ghi]perylene are especially prone to change their retention on polymeric ODS phases with temperature. Using temperature control, (ΔT ⩽ 0.1°C) we have reached good retention time reproducibility: R.S.D. better than 0.07% (n = 10) for all the 15 PAHs. In practice this means that the retention time of indeno[1,2,3-cd]pyrene varies within 2 s. For the multiple-wavelength shift fluorescence detection retention time reproducibility is an absolute prerequisite.

Enhanced conversion of starch to cyclodextrins in ethanolic solutions by Bacillus circulans var alkalophilus cyclomaltodextrin glucanotransferase

Improved formation of cyclodextrins (CDs) from starch in ethanolic solutions byBacillus circulans var alkalophilus cyclomaltodextrin glucanotransferase was studied. The β- and γ-CD yields increased and α-CD yield gradually decreased as the ethanol concentration was raised. The ethanol concentration required for maximal CD yield depended essentially on starch concentration. The ethanols effect was pronounced at high starch concentrations. For example, with 30% (w/v) starch, the CD yield was 2.4-fold (146.5 g/L) in the presence of 15% (v/v) ethanol. The effect of dimethylsulfoxide on the formation of CDs was similar to that of ethanol. The disintegration of β- and γ-CDs were narrowly interdependent on the formation of a α-CD and malto-sugars. The amount of reducing sugars decreased from a dextrose equivalent value of roughly 7.5 to 4.5 in the presence of ethanol at starch concentrations 1-30% (w/v). The effect of ethanol on starchy materials from various sources was similar. It was concluded that ethanol retards the decomposition of β-CD by a general mechanism involving a decreased activity of water.

Spectrophotometric measurement of hydroxylamine and its O-alkyl derivatives

An easy spectrophotometric method was developed to quantify compounds having an ONH2 (amino-oxy) function (e.g., hydroxylamine, canaline, O-aminoserine, and amino-oxy acetic acid). Stoichiometric reactions occur, in practice, between the amino-oxy compounds and the aldehydic group of pyridoxal 5′-phosphate in aqueous solution. When the reaction had reached equilibrium the concomitant decrease in absorption at 405 nm was used as the measure of the amino-oxy functions. Thus it is possible to determine amino-oxy compounds at about the same concentration as pyridoxal 5′-phosphate can be measured spectrophotometrically. The present method was applied to follow the enzymic hydrolysis of canavanine to canaline. Based on the measured apparent kinetic constants, a specific way to determine hydroxylamine among its O-alkylethers was advised, as well.

Proton and Carbon Inventory during the Growth of an Alkaliphilic Bacillus Indicates That Protons are Independent from Acid Anions

Abstract Sugar catabolism and pH-dynamics in culture medium of an alkaliphilic bacterium, Bacillus circulans var. alkalophilus were studied. The moles of carbon in 1% glucose (55 mmol/ l ) media were recovered almost quantitatively in acetic acid (65–75 mmol/ l ), formic acid (40–45 mmol/ l ) and CO 2 (90–100 mmol/ l ). The moles of acids needed to achieve the minimum pH of the medium during bacterial growth approximately corresponded to the moles of produced acids. However, the timing of the pH minimum did not match with the appearance of the acids, but the required amount of acids were detected several hours later in the medium. During active growth, the concentration of dissolved oxygen remained zero at all reasonable aeration levels in a fermentor. It was concluded that sugars are not metabolized through the tricarboxylic acid cycle, but the reduction potential generated from dehydrogenation of sugars is the driving force for the growth followed by the very effective transfer of hydrogen atoms/protons onto molecular oxygen/oxygen anion. The eventual rise of the pH shall result from re-equilibration of the redox state, and not from consumption of acids or generation of basic compounds as suggested previously.

Cyclodextrins: Production, properties and applications in food chemistry

Abstract Cyclodextrins have diverse, important applications in food industry. These applications are based on the ability of cyclodextrins to form molecular complexes with small—molecular compounds. Cyclodextrins are harmless in oral administration and advantageous effects by cyclodextrins are achieved by simple mixing of small amounts of them to the material being stabilized. Development of convenient and cost‐effective processes for production of cyclodextrins are undergoing and there are promises in the near future for obtaining cyclodextrins which are realistic in price to be used in foods. While cyclodextrins have been used for more than ten years in Japan as natural additives in foods, the legislation for their approval in foods is still under development in Europe and USA.

Isolation and Purification of Gamma-Cyclodextrin by Affinity Chromatography

An affinity chromatographic process for purification of gamma-cyclodextrin (CD) was developed. It was based on a specific inclusion complex formation between 1,8-naphthylic acid anhydride coupled to aminated Biogel P-6. This gel completely separated gamma-CD from other CDs and from acyclic dextrins. The capacity of one liter of the gel was more than 20 g gamma-CD per one run.

Acid-base chemistry of vitamin B6 compounds in methanol

The enzymatic reactions involving pyridoxal 5′-phosphate (PLP) can be simulated in solutions; thus, this system forms a favorable model for understanding the requirements of the enzymatic catalysis. We have studied in methanol protonic equilibria of the imines formed between PLP or salicylaldehyde (SA) and various amino acids, using UV and NMR spectroscopy. A glass electrode and an operationalpH* scale were used to control acidity. The first protonation of the phosphate of PLP imines can be detected by UV spectroscopy withpK* at 10.8, proved by [31P]-NMR. The second protonation of phosphate (pK* at 4.8) is accompanied by increased hydrolysis of the imines. The imines of aspartate deviate from the imines of nondicarboxylic amino acids indicating that the β-carboxyl of aspartate is internally hydrogen-bonded. PLP-2-aminobutanol Schiff base does not show with [1H]-NMR atpH* 7 separate peaks for ketoenamine-enolimine tautomers even at -90°C, SA-phenylalanine shows an unidentified absorption at 350–380 nm. This was tentatively assigned a trans structure.

Cultural Characteristics of an Cyclomaltodextrin Glucano-Transferase-Producing Alkalophilic Bacillus Sp.

Time course of the growth of cyclomaltodextrin glucanotransferase (CGTase)-producing Bacillus circulans var. alkalophilus was studied in detail in a standard shaking-flask cultivation. The growth curve was biphasic and during the first phase of it the pH sharply dropped by 1.3–1.5 units. Most of the total carbohydrates disappeared distinctly prior to the bulk growth and simultaneously a transient peak of reducing sugars with saccharifying and liquefying amylolytic activities were found but only traces of CGTase. During the active cell growth the pH recovered by about 0.5 units and till the stationary phase around 65% of CGTase was excreted into the medium. The CGTase activity increased by about 20% in the stationary phase and the rest of CGTase released slowly during the death phase.