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Fast and accurate laser tool monitors bacterial growth

Posted:  Thursday, March 31, 2016

Novel laser tool detects bacterial growth instantly! Such a tool may help reduce the wastage of foods that are past their expiry date and detect the contamination of invaluable medical resources. Researchers have developed a new, low-cost laser technique that enables fast, accurate, and non-invasive measurement of bacterial growth in packaged foods and blood samples.

The researchers from Zhejiang Normal University in China and Umeå University in Sweden published the study in the journal Applied Optics. They used an optical instrument known as tuneable diode laser absorption spectroscopy (TDLAS) to assess the growth of Staphylococcus aureus and Candida albicans. The sensitivity of TDLAS was enhanced by combining the rapid tuning technique with a method called wavelength modulation; the device was subsequently referred as WM-TDLAS.

TDLAS applies absorption spectrometry to measure the concentration of specific constituents within gaseous mixtures. The device works on the principle that when you shine a light on a sample, the different gases it contains will each absorb a particular wavelength. TDLAS indicates the amount of gas present from the reduction in the measured signal intensity.

The study indicated a high signal-to-noise-ratio data from organisms grown in limited spaces and exposed to inadequate amounts of nutrients in various samples. Jie Shao, an associate professor at the Institute of Information Optics at Zhejiang, explained, "By assessing the level of CO2 within a given closed compartment - bottle or bag - it's possible to assess the microbial growth."

The technology underlying TDLAS not only detects low concentration of gases but also evaluates other gaseous properties such as temperature, pressure, velocity, and mass flux. Future research may be directed towards applying this technology for detecting microbial growth in other settings.

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