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| Focusing on the antibacterial activities of plants in search for measures to prevent poisoning; what are the safe methods of controlling microorganisms? |
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Research activities undertaken by the food hygiene laboratory led by Professor Nakano are focused on the development of microbial control methods using natural agents. Clostridium botulinum, Salmonella, Escherichia coli O157 and other food poisoning bacteria are the key research targets in his laboratory. The researchers aim to control such bacteria through antibacterial activities that reduce the occurrence, growth and propagation of bacteria.
“There are two types of antibacterial activities. One is ‘bacteriostasis,’ which means reducing the propagation of bacteria. The other is ‘sterilization,’ which means killing and eliminating all bacteria. In our laboratory, we promote research in both these areas.” |
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According to Professor Nakano, trends in the background of such research activities include consumers’ preferences for good taste, delicious food, health, and convenience. He adds, “To exemplify some emerging risks, when people do not want to use many preservatives, pathogenic bacteria that had been controlled by such preservatives may start to propagate actively. Similarly, when vacuum packaging is used to enhance convenience, anaerobic bacteria may proliferate in such packs.” In fact, low-salt pickles, for example, provide favorable conditions for microbes.
Under these circumstances, Professor Nakano focuses on plants to reduce the propagation of food poisoning bacteria. Plants contain various kinds of antibacterial agents to protect themselves from diseases. Tea catechins and the volatile components of wasabi (Japanese horseradish) are some examples, and have already been applied to products. Professor Nakano’s laboratory is focused on seasonings, herbs, and herbal medicines, and is promoting research toward the possible application of their antibacterial effect to food preservation. |
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| A rare laboratory that handles Clostridium botulinum, and that possesses advanced hurdle technology |
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Professor Nakano’s research is remarkable in its rarity and innovation.
First, research activities involving Clostridium botulinum are only rarely undertaken. This is because revised laws require the stringent handling of this bacterium. Even food companies are not allowed to use it. “We recognize our responsibility and mission when we handle this bacterium,” says Professor Nakano. For preservation experiments conducted to set expiry dates for food products, food companies are obliged to use indicator bacteria that have properties similar to those of Clostridium botulinum. Nakano’s laboratory also uses these indicator bacteria for experiments, and provides them to food companies.
Second, his laboratory also possesses innovative “hurdle technology.” Experiments have indicated that, when several “hurdles” (i.e., microbial control factors) set at a low level are combined, the combined effect eventually becomes non-clearable. “Hurdle technology” aims to control microorganisms with low hurdles based on the above. This is always kept in mind and emphasized in Nakano’s laboratory, which is an extremely rare lab that leads many other researchers to engage in experiments using the combination of several factors.
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| It was during his doctoral course that Professor Nakano first encountered Clostridium botulinum. In those days, the first cases of infant botulism were occurring in Japan, and his experience in tackling that disease sparked the beginning of his career. The professor remarks, “Clostridium botulinum is a type of spore-forming bacterium, which forms and scatters ‘spores,’ which are similar to seeds in plants. Spores do not die under normal heating conditions. They also proliferate without air, because Clostridium botulinum is anaerobic bacterium. Infant botulism is caused by honey that has been contaminated by the spores of Clostridium botulinum in the natural environment. Unlike food poisoning, spores simply pass through adult intestines, but rarely dwell there and only produce toxins in the intestines of infants under one year old who have immature intestinal flora. Measures have been established to avoid the feeding of honey to infants.” His then mentor told him that very few people were researching Clostridium botulinum from the perspective of food hygiene, and therefore strongly urged him to select it as his life-long research theme. This led to Professor Nakano’s present career. |
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According to the professor, “research on food poisoning often starts with cases that have actually occurred, examining why they have occurred.” One of the well-known cases of food poisoning in Japan was the case caused by Escherichia coli O157 in lightly pickled Chinese cabbage in a nursing home for the elderly in Sapporo.
In this case, food poisoning was caused by the inadequate sterilization of vegetables. Only about 99% of the bacteria in vegetables can be eliminated, even by using solution with a concentration 100 times higher than that in test tubes. There are no applicable legal standards either. The convenience store industry has formulated guidelines, and it is urgently required to establish effective sterilization methods, which is also a future research theme of ours. |
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| Everything is aimed at contributing to society; Professor Nakano’s expectations for future researchers |
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The final goal of his research is to “create a world where food safety is guaranteed.” In other words, food safety is not guaranteed at present. Although people eat to stay healthy, they are often exposed to the health risks through their eating habits. To put an end to such an unacceptable situation, Professor Nakano believes there are three possible means.
First, researchers should make achievements in their research. Professor Nakano states, “Rather than clarifying mechanisms, they need to find methods and data that can be usefully applied to business practice, and provide them to food companies.”
Second, as many human resources as possible who have acquired a comprehensive understanding of food hygiene through education should be sent out into society.
The third need is to re-educate people who work in actual business. In each aspect, Professor Nakano believes that it is essential to disseminate the findings of specialists throughout business practice.
The professor also sends the following message to prospective young researchers.
“Louis Pasteur, regarded as the founder of microbiology, once said, ‘Fortune smiles upon the prepared.’ Unless we continuously improve our ‘prepared mind,’ we might overlook a great discovery passing through during an experiment. To enhance our prepared mind, we need to study a broad range of disciplines, and engage in discussions with people outside our specialty, rather than limiting ourselves to our assigned research themes. Furthermore, many questions become difficult to ask at my age, but young students are free to ask all kinds of questions. Their teachers would definitely give them reasonable answers. Do not hesitate to ask questions whenever you have the opportunity, and keep enhancing your ‘prepared mind.’” |
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| Hiroyuki Nakano |
| Professor, Laboratory of Food Microbiology and Hygiene
December 1, 1982 – October 15, 1992 Research Associate, School of Applied Biological Science, Hiroshima University
October 16, 1992 – March 31, 2002 Associate Professor, School of Applied Biological Science, Hiroshima University
April 1, 2002 – present Professor, School of Applied Biological Science, Hiroshima University
Posted on Feb 24, 2017 |
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