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Optical Engineering

Real-time optical monitoring of microbial growth using optimal combination of light-emitting diodes
Author(s): Ken-ichi Kobayashi; Takeshi Yamada; Akira Hiraishi; Shigeki Nakauchi
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Paper Abstract

We developed a real-time optical monitoring system consisting of a monochrome complementary metal-oxide semiconductor (CMOS) camera and two light-emitting diodes (LEDs) with a constant temperature incubator for the rapid detection of microbial growth on solid media. As a target organism, we used Alicyclobacillus acidocaldarius, which is an acidophilic thermophilic endospore-forming bacterium able to survive in pasteurization processes and grow in acidic drink products such as apple juice. This bacterium was cultured on agar medium with a redox dye applied to improve detection sensitivity. On the basis of spectroscopic properties of the colony, medium, and LEDs, an optimal combination of two LED illuminations was selected to maximize the contrast between the colony and medium areas. We measured A. acidocaldarius and Escherichia coli at two different dilution levels using these two LEDs. From the results of time-course changes in the number of detected pixels in the detection images, a similar growth rate was estimated amongst the same species of microbes, regardless of the dilution level. This system has the ability to detect a colony of approximately 26 μm in diameter in a detection image, and it can be interpreted that the size corresponds to less than 20 μm diameter in visual inspection.

Paper Details

Date Published: 3 December 2012
PDF: 8 pages
Opt. Eng. 51(12) 123201 doi: 10.1117/1.OE.51.12.123201
Published in: Optical Engineering Volume 51, Issue 12
Show Author Affiliations
Ken-ichi Kobayashi, Toyohashi Univ. of Technology (Japan)
Takeshi Yamada, Toyohashi Univ. of Technology (Japan)
Akira Hiraishi, Toyohashi Univ. of Technology (Japan)
Shigeki Nakauchi, Toyohashi Univ. of Technology (Japan)

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