Improvement of isoamyl acetate productivity in sake yeast by isolating mutants resistant to econazole

Sake yeast strains were improved so as to produce larger amounts of isoamyl acetate than the parental strain by isolating econazole-resistant mutants. Econazole, an imidazole antimycotic, directly interacts with unsaturated fatty acids in the yeast cell membrane, where it also inhibits the synthesis of ergosterol and decreases the ratio of unsaturated to saturated fatty acids. In contrast, alcohol acetyltransferase (AATase), which catalyzes the synthesis of isoamyl acetate, is inhibited by unsaturated fatty acids. Fifty econazole-resistant mutants were isolated from a sake yeast, Kyokai no. 701, several of which produced approximately 1.4 to 2.4 times more isoamyl acetate and an almost equal amount of isoamyl alcohol compared with the parental strain. The AATase activities of the mutants in koji extract were 1.2 to 1.4 times higher, and the unsaturated to saturated fatty acid ratios were lower, than in the parental strain.     

Evaluation of Milk Quality in Delivering Sterilized Milk with Soft Tank Transportation System

ABSTRACT:  A new transportation system is proposed recently to improve the defects of liquid transportation by tank trucks. This method is called "soft tank transportation system"; a driver installs a sac-like container (soft tank), which is made from a tarpaulin with high-pressure resistant-waterproof zippers, in a general cargo vehicle. To evaluate the quality of sterilized milk by using the soft tank transportation system, ground and marine transportation for a long distance which took about 36 h from the shipper's loading to the receiver's unloading in a high-temperature summer season (average outside temperature was 33.4 °C) were carried out. Although the difference of milk temperature before and after the delivery varied from −0.7 to +1.4 °C, there was no difference in milk quality (fat, nonfat solids, total dissolved solids, and pH) and no coliform bacteria were detected. It can be evaluated that sterilized milk was carried in keeping good conditions by soft tank transportation system.     

Water/Oil Emulsions Prepared by the Membrane Emulsification Method and Their Stability

We developed and tested a simple method to measure dispersed droplet size of W/O emulsions. Then, using a microporous glass membrane treated with oil phase, we produced a W/O emulsion with high water content (40% w/w) at a high emulsification rate by the membrane emulsification method, and assessed its stability. In comparison with emulsions by the stirring methods, variations in dispersed droplet size and viscosity of emulsions by membrane method were small and the emulsions were more stable. Droplet size was not related to the stability of the W/O emulsion prepared by membrane emulsification.     

Effect of an additionally introduced degQ gene on di-d-fructofuranosyl 2,6′:2′,6 anhydride (DFA IV) production by recombinant Bacillus subtilis in a single culture production system

Di-d-fructofuranosyl 2,6′:2′,6 anhydride (DFA IV) was produced directly from sucrose using a single culture of recombinant Bacillus subtilis 168 carrying the levan fructotransferase (lft) gene. In this study, three plasmids carrying the degQ36 gene, which is a degQ allele of B. subtilis (degQ36) with a degQ36 mutation on its promoter, were constructed to overproduce intact DegQ in B. subtilis 168. The transformant B. subtilis/pHT-D36 (with the degQ36 gene) consumed sucrose and produced levan at a higher rate than B. subtilis/pHT43 (without the degQ36 gene). The transformant B. subtilis/pLFT-GD36, carrying the lft and degQ36 genes, also consumed sucrose at a higher rate and produced more DFA IV than B. subtilis/pLFT-G, carrying the lft but without the degQ36 gene. B. subtilis/pLFT-GD36 produced 43.5 g/l of DFA IV and consumed 240 g/l of sucrose (96% of added sucrose) by 72 h of cultivation, whereas B. subtilis/pLFT-G produced 23.4 g/l of DFA IV with 76.9 g/l of sucrose still remaining in the system. Sucrose-inducible expression vectors were also constructed, which made it possible to produce DFA IV without IPTG induction. Using these vectors, sucrose consumption rates were enhanced and DFA IV production was increased upon introduction of the degQ36 gene. From these results, it can be concluded that the additionally introduced regulatory gene, degQ, was able to stimulate sucrose conversion to levan, and therefore increased DFA IV production in this system.     

Paper-based diagnostic devices for evaluating the quality of human sperm

Male infertility, which amounts to half of all infertility cases, is a serious problem worldwide. The percentage of fertility-related patients in sub-Saharan African countries is higher than that for the developed countries. In low-resource countries, examination of sperm characteristics for male infertility cannot be undertaken because of poor clinical access. To evaluate male fertility in assisted reproductive medicine laboratories, the numbers of motile human sperm, the degree of sperm motility, and sperm morphology have been commonly analyzed using a microscope. It is challenging to monitor the health status of human sperm in resource-limited or remote settings for two primary reasons: (1) high capital cost (equipment for currently accepted procedural standard), and (2) complexity of the currently accepted procedural standard used to simultaneously measure human sperm concentration and motility by skillful embryologists. Determining the health status of human sperm in order to evaluate fertilization capacity using various types of low-cost, easy-to-use, and rapid devices (or systems) is a longstanding but interesting biotechnologically relevant issue in various scientific communities such as male reproduction. Furthering such efforts will inherently influence birth rate in both developed and developing nations. We have demonstrated an inexpensive but robust and easy-to-handle device for monitoring the health status of human sperm made by patterning a piece of paper and measuring the activity of a specific enzyme—a simple and elegant solution. After applying semen to the hydrophilic center circle of our patterned paper, a thiazine assay can be used to suggest sperm concentration in semen, and a tetrazolium-based colorimetric assay (MTT assay) data can be used to help estimate the percentage of motile human sperm (sperm motility) in semen based on the character that motile human sperm moved in and on the paper. Using this paper-based device, we can evaluate fertility levels without consulting doctors and use our assay to compare results with World Health Organization (WHO) reference values for sperm concentration (>2×10⁷) and motility (>50 %). The duration and cost of one entire test are 30 min and 0.1 USD, respectively. We believe that this paper-based assay system would be useful for fertility checks based on WHO references, without need of a microscope, at home. Using this assay method, males in developed or developing countries who are reluctant or unable to consult assisted reproductive technologies clinics can self-analyze their sperm characteristics. We further note that our approach adheres to WHO regulations, especially in regard to in vitro diagnostic device performance with an associated diagnostic algorithm to enhance diagnostic accuracy (compared with just one diagnostic output), and we wish to emphasize that our research could significantly advance a broad range of diagnostic developments including paper-based diagnostic devices, in vitro diagnostic devices, and diagnosis of other diseases in various divisions of translational medicine. These results, we believe, will be of interest to a wide scientific audience working in materials science (biomaterials), chemistry (analytical and clinical), lab-on-a-chip technologies (the development of diagnostic tools), reproductive medicine, bioengineering, and translational medicine.     

Visibility of disjoint polygons

Consider a collection of disjoint polygons in the plane containing a total ofn edges. We show how to build, inO(n ²) time and space, a data structure from which inO(n) time we can compute the visibility polygon of a given point with respect to the polygon collection. As an application of this structure, the visibility graph of the given polygons can be constructed inO(n ²) time and space. This implies that the shortest path that connects two points in the plane and avoids the polygons in our collection can be computed inO(n ²) time, improving earlierO(n ² logn) results.     

Composition Regulation by Flow Copolymerization of Methyl Methacrylate and Glycidyl Methacrylate with Free Radical Method

It is important to match the feeding ratio of comonomers to the composition ratio in the resulting copolymers as closely as possible in industrial production, where the goal is often to produce more a homogeneous composition in copolymers. In this study, a flow copolymerization system with a conventionally initiated free radical method, together with randomly selected polymerization conditions is investigated. It is succeeded in achieving a closer match between the composition ratio and feeding ratio than previously reported in the copolymerization of styrene with methyl methacrylate and of glycidyl methacrylate with methyl methacrylate, which will widen the range of applications, by precisely controlling the mixing and heating in a flow polymerization apparatus. This is confirmed by the fact that the estimated values of reactivity ratios, r₁ and r₂, which are used in the reaction kinetics of copolymerization, are close to 1.