Rheological Studies of Wheat Flour Dough

Dynamic rigidity G′, dynamic viscosity η′ and the relaxation spectrum L(t) of dough under periodic shear stress have been obtained. At first, G′ and η′ decreased rapidly with rest time, but maintained a constant value after 60 minutes. Values of both G′ and η′ decreased, and L(t) became flat with the decrease in water absorption and with the temperature. G′ increased slightly with the increase in salt content, but η′ decreased in a low frequency range.     

Single-laboratory validation for the determination of caffeic acid and seven caffeoylquinic acids in sweet potato leaves

A single-laboratory validation study was conducted on an HPLC method for the detection and quantification of caffeic acid (CA) and seven species of caffeoylquinic acids (CQAs) in lyophilized sweet potato leaves. The procedure for extraction of the analytes from the matrix and the HPLC conditions for the efficient separation of CA and CQAs were optimized. In the proposed method, a relative response factor to one of the CQAs (5-CQA) was used to quantify the others. The method performed well in terms of precision when carried out on five different days and demonstrated Horwitz ratio (HorRat) scores ranging from 0.5 to 1.0 for all analytes, which were well within the limits of performance acceptability. Accuracy testing at three levels showed an overall recovery of 94% when duplicated on five different days. Moreover, a stability study revealed that all analytes in both standard solution and sample extract were stable for 28?days.     

Studies on the “Salvage” Synthesis of Ribonucleosides and Their 5′-Phosphates by Microorganisms

Studies on the “salvage” synthesis of ribonucleosides and their 5′-phosphates from nucleic acid bases by microorganisms were undertaken. After screening test of less than one hundred strains of type culture, it was found that inosine was produced from hypoxanthine by Arthrobacter ureafaciens, A. simplex, Flavobacterium aquatile and F. suaveolens.

In certain conditions, inosine was further oxidized and hydrolyzed into xanthosine, uric acid and etc.

As for the conditions of cultivation and reaction, the components of the medium and pH of the culture medium were important factors.

Using the standard method, the yield of inosine from hypoxanthine by F. suaveolens reached more than 60%, and the conversion was stoichiometric and any other by-products were not detected.

Inosine, xanthosine, guanosine and uridine were produced from adenine, xanthine, guanine and uracil, respectively, by F. suaveolens.     

Utilization of Bacterial Xanthine Oxidase for Inorganic Phosphorus Determination

Two host-specific phytotoxic metabolites, AK-toxin I and II, were isolated from a culture broth of Alternaria alternata Japanese pear pathotype, the fungus causing black spot disease of susceptible Japanese pear cultivars. From chemical, spectral and X-ray crystallographic data, AK-toxin I was characterized as 8-(2′S, 3′S)-2′-acetylamino-3′-methyl-3′-phenyl-propionyloxy]-(8R,9S)-9,10-epoxy-9-methyl-deca-(2E,4Z,6E)-trienoic acid. The structure of AK-toxin II was also assigned to be 3′-demethyl derivative of AK-toxin I by comparing the spectral data with those of AK-toxin I.     

Induction of Mutants from the Tartrate Producing Bacterium,Gluconobacter suboxydans and their Properties

The purpose of the present investigation is to obtain the superior mutants from the tartrate producing strain, Gluconobacter suboxydans 2026Y2 previously isolated from nature. Some mutant strains obtained by treatment with N-methyl-N′-nitro-N-nitrosoguanidine were found to accumulate L(+) tartaric acid in culture broth with much higher yield than in the case of the wild strain.

The high tartrate productivity of the mutants was followed by the low accumulation of 2-ketogluconic acid. The mutants having high assimilability of 5-ketogluconate showed high tartrate productivity.

The culture conditions for tartaric acid production by a mutant, Gl. suboxydans N-3874, were investigated. As a result, the amount of tartaric acid accumulated in culture broth reached to a level of 14.6g/liter in the medium containing 5% glucose and 0.3% corn steep liquor.     

Studies on l-Glutamic Acid Fermentation by Microbacterium ammoniaphilum

The present investigation is concerned with the effects of biotin and glucose on glutamic acid fermenation by Microbacterium ammoniaphilum. Both optimal amounts of biotin necessary for maximum growth and maximum accumulation of glutamic acid were determined under the conditoin of various concentration of glucose. As the glucose concentratin was increased, the amounts of biotin required for maximum growth also increased proportionally to the glucose concentrations. The optimal amounts of biotin for maximum accumulation of glutamic acid were smaller than those for maximum growth of cells at any glucose concentration. It is suggested that the process of glutamic acid accumulation is inevitably associated with the process of cell multiplication by both experiments of successive culture of cells grown under the dose of biotin sufficient and deficient for maximum growth.     

The Effect of Gamma-Irradiation on the Sucrose Content in Sweet Potato Roots and Potato Tubers

The sucrose content in both potato tubers and sweet potato roots was considerably increased by gamma-irradiation. The maximum increase was achieved by an irradiation dose of 3 to 4 kGy for potatoes and 0.8 to 2 kGy for sweet potatoes. Cooling treatment (15°C, 2 weeks) for sweet potato roots also enhanced the sucrose content (almost 2 times) but was not additive to the irradiation treatment; the maximum sucrose content in irradiated sweet potato roots was in the range of 7 to 12% irrespective of the cooling treatment, depending on the variety of sweet potatoes. Irradiation made the sucrose content in the roots 2 to 4 times higher.     

Glutathione Oxidase from Bovine Skim Milk Membranes: Its Copurification with γ-Glutamyltransferase

Two hundred thirteen cytochrome P450 (P450) genes were collected from bacteria and expressed based on an Escherichia coli expression system to test their hydroxylation ability to testosterone. Twenty-four P450s stereoselectively monohydroxylated testosterone at the 2α-, 2β-, 6β-, 7β-, 11β-, 12β-, 15β-, 16α-, and 17-positions (17-hydroxylation yields 17-ketoproduct). The hydroxylation site usage of the P450s is not the same as that of human P450s, while the 2α-, 2β-, 6β-, 11β-, 15β-, 16α-, and 17-hydroxylation are reactions common to both human and bacterial P450s. Most of the testosterone hydroxylation catalyzed by bacterial P450s is on the β face.     

Choline Dehydrogenase of Pseudomonas aeruginosa A-16

The promotive effect of biotin (200~500 µg/liter) on l-lysine formation was investigated in Brevibacterium lactofermentum. This effect was observed only when glucose or pyruvate was used as sole carbon source, and accompanied with the specific incorporation of ¹⁸CO₂ into γ-CH₂ group of l-lysine. Brev. lactofermentum AJ 3445 (AEC^r) could grow on pyruvate medium supplemented with biotin at more than 200 µg/liter, while the same growth was observed with the addition of TCA cycle members or glutamate to pyruvate medium.

Phosphoenolpyruvate (PEP) carboxylase deficient mutant derived from AJ 3445 could not grow on glucose as sole carbon source, but on glucose plus 200 µg/liter of biotin. AJ 3445 grown on lactate medium containing 500 µg/liter of biotin and KHCO₃ contained the biotin-dependent pyruvate carboxylase.

These data suggest that this promotive effect of excess biotin on l-lysine formation may be brought about through the activation of pyruvate carboxylase by biotin.     

Purification and Properties of Proteases from a Marine-psychrophilic Bacterium

Protease which was found in the culture fluid of Pseudomonas sp. No. 548 was fractionated into four components with protease activity by a two step chromatography using DEAE-cellulose. Each protease was further purified by gel filtration on Sephadex G-100 and/or G-75. The protease of Ia was obtained in crystalline form and was shown to be homogeneous by analysis with electrophoresis, while the other three enzymes were also highly purified. The enzymatic properties of the proteases were investigated. All of the four enzymes were inactivated by ethylene diamine tetraacetate. Proteases Ia, Ib, and IIb were inactivated by diisopropylfluorophosphate. The optimum activity of protease Ia was shown to be at pH 10.0, and that of the other enzymes were at pH 7.0 to 8.0. The proteases of Ia, Ib, and IIb were stabilized by calcium ion. The effect of temperature, pH, and metal ions on the activity of the enzyme were also investigated.