In the present study, methylated silk sericin (MeSS) was prepared and a bead-type drug delivery carrier was formulated for the potent treatment of Helicobacter pylori infection. Sericin was reacted with methanol in the presence of hydrochloric acid as a catalyst under mild conditions to form an ester bond between the carboxyl group of sericin and the hydroxyl group of methanol. The methylation of silk sericin was confirmed by Fourier transform infrared spectroscopy (FTIR) and point of zero charge (pH_pzc) studies. The formulated MeSS beads swelled more under acidic conditions, which is below the pH_pzc of the MeSS. The release behavior of the model drug from the MeSS beads in the medium was extremely pH-sensitive. These results suggest that the formulated MeSS beads have the potential to be an effective antimicrobial agent carrier for the treatment of H. pylori infection.

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We examined 8,640 bp of the Samia cynthia ricini (Scr) fibroin gene together with the 5’ and 3’ flanking sequences and deduced the Scr-fibroin amino acid sequence. A large region of the Scr-fibroin amino acid sequence consists of repetitive arrays, which include a common polyalanine block and one of four variable nonpolyalanine blocks. These four types of nonpolyalanine blocks were rich in glycine (Gly) residues, differing from saturniid fibroins in which at least one type of nonpolyalanine block is Gly poor. The presence of abundant Gly residues increases the GC content of the Scr-fibroin gene. However, preferential use of GGA and GGU isocodons for Gly decreases the GC content. The amino acid sequences of C-terminal regions among saturniid fibroins were conserved, but were considerably diversified from non-saturniid fibroins. Three conserved Cys residues in the C-terminal region, which are conserved in Antheraea pernyi and A. yamamai fibroins, contribute to S-S bond formation between the fibroin homodimers, although another three cysteine residues conserved between C-terminal regions of Bombyx mori and Galleria mellonella fibroin heavy chain contribute to formation of disulfide bonds between fibroin heavy chain (fhc) and fibroin light chain (flc).

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Bacillus thuringiensis (Ishiwata, 1901; Berliner, 1915) produces parasporal inclusions prior to spore formation; these inclusions are insecticidal. Therefore, B. thuringiensis is used as a microbial pesticide. B. thuringiensis has been detected conventionally in the natural environment, such as in the soil and on plant surfaces as well as in farms and natural fields. To date, the detection rate of B. thuringiensis (the BT index) with standard methods is very low. In this study, we developed a highly efficient detection method to isolate B. thuringiensis from urban environments. In our experiments, The urban environment used was defined as the campus of the College of Bioresource Sciences at Nihon University. The urban samplings were composed of a mixed microbe layer including B. thuringiensis. The BT index was consistently >50% in this study. Our results suggested that the urban environment we examined is a reservoir of many varieties of B. thuringiensis.

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An entomogenous fungus, Cordyceps militaris, grows on larvae and pupae of the silkworm, Bombyx mori. To overcome problems in the establishment of fungal infection caused by advancing pupal-adult development, we tested the effects of carbon dioxide (CO₂) anesthesia. Pupae inoculated with C. militaris were held in CO₂ anesthesia for 2 days. Almost all pupae exposed to CO₂ were infected with C. militaris, but the rate of infection of chilled or untreated pupae decreased with increasing stage of pupal-adult development at inoculation. The results indicate that exposure of silkworm pupae to CO₂ enhances infection rate. This treatment will support the mass production of C. militaris for pharmacological uses.

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