■ Introduction to Research〓 Research Area : Animal Applied Microbiology

Studies on protein metabolism of lactic acid bacteria
Lactic acid bacteria (LAB) are known as fastidious microorganisms that require a wide variety ofexogenous free amino acids or peptides as nitrogen sources for growth. Most of Food stuffs suchas milk generally contain proteins but very low amount of free amino acids and peptides. Therefore, LAB first hydrolyze the proteins to get nutritious oligopeptides using their own cell-envelope
proteinases (CEP). The oligopeptides released are subsequently taken up by the LAB cells via
specific transport systems for further degradation into shorter peptides and free amino acids
using various intracellular peptidases. The CEP, transporters and peptidases are species- or
strain-specific, and their functional and enzymatic differences are an important factor to produce
the diversity on taste, flavor and health-promoting effect of fermented food products. In our laboratory, we are studying the protein metabolism of LAB; particularly focusing on characterizationof CEP and function of the oligopeptides released by CEP on fermented foods.

Studies on antimicrobial substances produced bylactic acid bacteria〓 Assoc. Prof.
ARAKAWA Kensuke

Lactic acid bacteria (LAB) are known as safe producers of antimicrobial substances such aslactic acid and bacteriocins. Bacteriocins, ribosomally biosynthesized antibacterial peptides,
have strong activity with a very small quantity and are easily degraded by digestive enzymes in
the animal gut. Food-derived antimicrobial peptides are also produced by LAB. Food proteinssuch as milk caseins are good origins of functional peptides, including with antimicrobial activity, released by hydrolysis using cell-envelope proteinases (CEP) of LAB. These antimicrobial
peptides are expected to be used as a safe natural preservative (biopreservative) for foods andfeeds. In our laboratory, we isolated some LAB strains with bacteriocin productivity and high
CEP activity for production of food-derived antimicrobial peptides, and characterized the bacteriocins and the food-derived antimicrobial peptides for application to foods and feeds.

〓 Research Area : Assisted Reproductive Medicine

The meiotic abnormalities in mouse and humanoocytes and their mechanisms
During the maturation process of human oocytes, numerous genes are responsible for meiosis. Recent studies
have begun to reveal that defects in some interrelated genes are the cause of female infertility. We aim to perform functional analyses of the process of oogenesis, during the first and second meiosis using oocytes frommutant mice, which present with a mutation, leading to genetically developed abnormalities on chromosomal
crossing-over during meiosis. In this way, we hope to contribute to the existing body of therapeutic strategies and preventive measures which can be taken against human infertility.
As ten to twenty percent of cases of infertility are considered
to be idiopathic, we also aim to perform a comprehensive
analysis of meiotic DNA mutations and thereby elucidate thecauses of infertility derived from those mutations.

The elucidation of the mechanism of dysmorphic phenotypes in humanoocytes and preventive measures against those dysmorphisms〓 Assoc. Prof.
OTSUKI Junko

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The dysmorphic phenotypes to be found in human oocytes are unlike any other species, with the exception of chimpanzee oocytes. Among these dysmorphisms, we have been focusing on two phenotypes:
smooth endoplasmic reticulum clusters (sERCs) and refractile/lipofuscin bodies. We have found that theincidence of mitotic and meiotic cleavage failure during the second polar
body extrusion is significantly higher in oocytes with sERCs than that inoocytes without sERCs. Regarding the refractile body (RB), we have reported that it presents with autofluorescence. Viewed by means of transmitted electron microscopy, the refractile bodies display the conventional
morphology of lipofuscin inclusions and consist of a mixture of lipids anddense granule materials. We aim to elucidate the mechanisms of thesedysmorphic phenotypes in human oocytes and work towards preventive
measures against them.