)egatlov(i4 esluPthgeh0.5 µm0.2 µmFrom Rion, Takashi Minakami of the Development Depart-ment, Particle Counter Division, joined the research project team.“I studied electrical engineering in college,” says Minakami. “All my friends who studied in the mechanical and control engi-neering department dreamed of making a Mobile Suit Gundam of their own. Of course, I also shared the same aspiration for space.”Belonging to the Gundam generation, Minakami was natu-rally excited to work on a project involving space. Another proj-ect member from Rion was Kazuma Sekimoto, who took part in the research and development of the microbial particle counter.In 2021, Soichi Noguchi, a veteran astronaut staying on the Kibo Japanese Experiment Module for the third time, collected water for testing. The water sample placed in a bag was trans-ported to Earth by the Dragon supply ship which landed off the Florida Peninsula. After being sent from NASA to JAXA, the sample was measured immediately using a microbial particle counter at the Rion headquarters in Kokubunji, Tokyo. The counter displayed the number of microbial particles in the actual potable water.His first impression upon seeing the results, Professor Yamazaki recalls, was that it was pretty much as he had expect-ed—he had also measured the water sample at the same time using a fluorescence microscope.“The results of the count were around what I’d obtained with my microscope, so for me, the results confirmed the high accu-racy of the particle counter.” It should be noted that even the potable water we drink every day can sometimes be contaminated with microbes. The presence of microbes doesn’t automatically mean the water will be harmful. Governments around the world have set their own standards regarding the types and number of microbes permis-sible in potable water. What matters for the safety management of potable water is accurately assessing how many microbes are present in the water. For this purpose, the accuracy of microbial particle counters has proven to be effective.Because the culture method takes too much time to produce results, it isn’t practical to apply this on the space station. But, as Professor Yamazaki points out, measurements with fluorescence microscopes are also difficult.“Astronauts are accomplished people. But they aren’t all trained to be life science specialists,” says Professor Yamazaki.To begin with, the act of dropping a droplet of water onto a slide and observing it under a microscope is extremely difficult in microgravity environments on the ISS, or on the moon, where gravity is 1/6 of that on Earth. How about the Rion measuring instrument? Would it be possible to bring it aboard the space station? This was Minakami’s answer:“When I was first asked, ‘Can Rion’s instrument be used in space?’—I said it should be possible.”The particle counter doesn’t require handling water droplets. Instead, it uses a pressurized tube to feed the water sample to the interior of the instrument. Most such instruments tend to be very delicate and vulnerable to impact. But Rion’s counters have been designed to be carried around and used in the field. They’re built to withstand impact and vibration. But there was one major reason it couldn’t be used on the space station: the Mercury lamps not permitted on the ISSJobs related to space that inspiredthe Gundam generationFluorescencesignalScattered lightsignalTime© NASA TVTsukuba Space CenterIdentified as microbial particlesThreshold for fluorescence presence judgmentIdentified as non-microbial particles© JAXA/NASA© JAXAThe Dragon supply ship lands off the coast of the Florida peninsula. The samples are transported from NASA to JAXA.The samples then arrive at the Rion headquarters in Kokubunji, Tokyo, where they’re measured.Microbial particle counterA microbial particle counter enables automated real-time measurement of microbial particles present in liquids. It can identify microbial particles, decom-pose dissolved organic matter (carbon), and significantly reduce the fluorescence of the solvent (background noise) by irradiating the liquid with deep UV light, thus enabling the measurement of all microbial particles in the liquid.The samples collected on the ISS are transported to Earth by the Dragon supply ship.From the ISS to Rion: Route taken by potable water samples (performed three times: in January 2021, January 2022, and January 2023)The monitoring process begins with an astronaut collecting samples from the water dispenser on the ISS.Takashi MinakamiParticle Counter Development Depart-ment, Particle Counter Division. Joined Rion in 1997. He serves as the leader on the Rion side of the Micro Monitor Project, and promotes various projects as a member of the development team for microbial particle counters. He is an active member of an academic society in the pharmaceutical industry.
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