Page 53 - FoodFocusThailand No.212 NOVEMBER 2023

STRONG QC & QA

MALDI-TOF technology consists of two main - Cost-effective: MALDI-TOF is a microbial identification
processes. The first process is Matrix-Assisted Laser technology with a low cost per sample. The average cost of its
Desorption/Ionization (MALDI), which involves analysis is lower than DNA sequencing, although less technically
mixing the sample with a specific matrix to produce challenging.
crystals. After the crystals are activated with laser light - Convenient and Simple: MALDI-TOF method does
of a specific wavelength, the sample in the matrix is not require complicated sample preparation step. Colonies of
ionized. In the second process, ions are accelerated interest can be selected directly from petri dishes for analysis,
by an electric field and transferred into a vacuum tube. allowing for faster identification and classification of
Ions are transported and separated at different speeds microorganisms.
in this process and before colliding with the detector Microbial identification is an important testing method for
in order to determine the mass of a given ion. This classifying and identifying genus or species of microorganisms,
process is known as Time of Flight (ToF) as it involves and the data obtained can be used to analyze the source of
separating substances in a vacuum tube at a speed contamination. Conventional bacterial identification relies
proportional to the mass of the ions. on the physical characteristics and biochemical tests of the
MALDI-TOF is a microbial identification technology microorganisms. These standard methods take 24 to 48
used to detect peptide chains made up of amino acid hours following the culture, while the MALDI-TOF method
sequences. Given that the mass of the peptide chains takes only 6 to 15 minutes and yields results that are
in different proteins varies, a mass spectrum obtained equally accurate to those of es standard methods to test and
from the MALDI-TOF test can differentiate the mass provide accurate results as accurate as standard methods. This
of identified proteins, focusing on microorganism MALDI-TOF test is affordable and reasonable and can be used
ribosomal proteins, which are conserved within in various applications.
bacterial species. This leads to faster and more
accurate microbial identification. Therefore, it can be
applied for various purposes, such as medical
diagnosis of pathogens, identification of bacteria in the More Information Service Info C007
production of biopharmaceuticals, and determination
of normal flora in the environment.
The MALDI-TOF technique is quite convenient and
simple. The sample can be prepared by growing
bacteria or other microorganisms directly on the culture
medium. In order to maximize accuracy, samples can
also be prepared by extracting bacterial proteins. The
bacteria can be collected, mixed in a matrix, and placed
onto a metal plate if they contain impurities or are
enclosed in a thick capsule. The metal plate is then
placed in the MALDI-TOF instrument for analysis. The
mass spectrum of the sample is produced for
comparison with the reference bacterial mass spectra
in the database after the sample is laser-ionized and
the ions produced are transported using an electric
field in the Time-of-Flight process. There are basically
no undiscovered microbes at the moment because of
how big and comprehensive the database is. This
technique can identify microorganisms at the species
level.

Advantages of MALDI-TOF in microbial
identification
- Fast and Efficient: MALDI-TOF is suitable for
applications in busy laboratories that need to swiftly
identify microbes as it can analyze samples in only a
few minutes. This is because MALDI-TOF technology
can accurately classify the mass of ribosomal protein,
and the results can be compared to those from
international databases. This is due to the fact that
MALDI-TOF technology can accurately classify the
mass of ribosomal protein and compare the results
with international databases. As a result, it can
accurately identify the species of microorganism.

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