Monitoring of acrylamide concentrations in potato chips in Japan between 2006 and 2010.

Acrylamide levels in commercially available potato chips in Japan were monitored between August 2006 and June 2010 using the xanthydrol derivative gas chromatography-mass spectrometry (GC-MS) method. Seasonal and annual changes in acrylamide concentrations were determined. Nationwide bimonthly sampling of potato chips was carried out using a four-level design, and seasonal variations were detected in which the minimum acrylamide concentration was observed in August, and the maximum between February and June. Seasonal variations became less apparent after August 2008 as a result of annual effects and/or mitigation measures taken by the potato chip producers. Sampling uncertainties were separated into time-to-time, city-to-city, and lot-to-lot variation, and the largest variation was shown to be lot-to-lot including bag-to-bag.

Phylogenetic analysis of Bacillus subtilis strains applicable to natto (fermented soybean) production.

Spore-forming Bacillus strains that produce extracellular poly-γ-glutamic acid were screened for their application to natto (fermented soybean food) fermentation. Among the 424 strains, including Bacillus subtilis and B. amyloliquefaciens, which we isolated from rice straw, 59 were capable of fermenting natto. Biotin auxotrophism was tightly linked to natto fermentation. A multilocus nucleotide sequence of six genes (rpoB, purH, gyrA, groEL, polC, and 16S rRNA) was used for phylogenetic analysis, and amplified fragment length polymorphism (AFLP) analysis was also conducted on the natto-fermenting strains. The ability to ferment natto was inferred from the two principal components of the AFLP banding pattern, and natto-fermenting strains formed a tight cluster within the B. subtilis subsp. subtilis group.

The use of summary statistics for sample size allocation for food composition surveys and an application to the potato group.

To give a quantitative guide to sample size allocation for developing sampling designs for a food composition survey, we discuss sampling strategies that consider the importance of each food; namely, consumption or production, variability of composition, and the restrictions within the available resources for sample collection and analysis are considered., Here we consider two strategies: 'proportional' and 'Neyman' are discussed. Both of these incorporate consumed quantity of foods, and we review some available statistics for allocation issues. The Neyman optimal strategy allocates less sample size for starch than proportional, because the former incorporates variability in the composition. Those strategies improved accuracy in dietary nutrient intake more than equal sample size allocation. Those strategies will be useful as we often face sample size allocation problems, wherein we decide whether to sample 'five white potatoes and five taros or nine white and one taros'. Allocating sufficient sample size for important foodstuffs is essential in assuring data quality. Nevertheless, the food composition table should be as comprehensive as possible.

Sampling variability and uncertainty in total diet studies.

Here, the uncertainty budget for a total diet study (TDS) was clarified by separating the total measurement uncertainty into the uncertainty arising from the compositional heterogeneity of food items between cities (referred to as inter-city variance), the heterogeneity of food items within cities (intra-city variance), and the chemical analysis of the food samples (analytical variance) at one study design. TDS samples were collected from 14 cities in Japan. Duplicate samples collected in each city were prepared from food items purchased from different shops, and the cadmium concentrations were measured individually to obtain the intra-city variance. These results were used to show the importance of sampling design in TDSs, by evaluating a sampling method known as a multi-stage design, in which multiple samples are collected from several cities. Such schemes have been applied to TDSs, but the uncertainty involved has not been assessed. An intra-city correlation was observed between the cadmium concentrations in samples from the same city, demonstrating that the effective sample size was not simply the number of cities and shops sampled. The TDS results showed a high intra-city variance, which was greater than the inter-city variance for all of the food groups studied, and particularly for the bean and potato groups. By combining the sampling and analytical uncertainties obtained, the sampling uncertainty across different primary sampling unit sizes and secondary sampling unit sizes was obtained. As suggested by the analysis of potatoes and beans, grouping food samples from different shops in the same city can improve the representativeness of the results.

A novel transformation system using a bleomycin resistance marker with chemosensitizers for Aspergillus oryzae.

Aspergillus oryzae is resistant to many kinds of antibiotics, which hampers their use to select transformants. In fact, the fungus is resistant to over 200microg/ml of bleomycin (Bm). By enhancing the susceptibility of A. oryzae to Bm using Triton X-100 as a detergent and an ATP-binding cassette (ABC) pump inhibitor, chlorpromazine, to the growing medium, we established a novel transformation system by Bm selection for A. oryzae. In a medium containing these reagents, A. oryzae showed little growth even in the presence of 30microg Bm/ml. Based on these findings, we constructed a Bm-resistance expression cassette (BmR), in which blmB encoding Bm N-acetyltransferase from Bm-producing Streptomyces verticillus was expressed under the control of a fungal promoter. We obtained a gene knockout mutant efficiently by Bm selection, i.e., the chromosomal ligD coding region was successfully replaced by BmR using ligD disruption cassette consisted of ligD flanking sequence and BmR through homologous recombination.