Real -Time microbial testing, Promex Micro-respirometer 4200

Prom is a major manufacturer and supplier of biocides with more than 45 years experience in serving the chemical and coatings industry. Our broad ranges of Promex biocides are of the most efficient and highest qualities which meet all regulatory compliances and it is our mission to ensure that customers receive maximum product satisfaction and local support across the world. We work closely with customers both scientifically and commercially to gain the best results, tailoring our technical services to meet customer needs, and providing full microbiological support for our biocide customers. It is with this in mind that Prom launched a unique micro-respirometer technology, the PROMEX™ 4200 Micro-Respirometer, to measure microbial contamination along side its extensive range of eco-friendly biocides as a commitment to customer services.

The PROMEX 4200 Micro-Respirometer

Figure 1: The PROMEX™ 4200 Micro-Respirometer

Microbial contamination of aqueous solutions, such as paint, can compromise the performance, functionality and the general aesthetics of a product and thus cause product spoilage and greatly increase production costs. Levels of contamination are commonly monitored using dip-slides, which are time-consuming and unreliable, or by Total Viable Counts which are time-consuming and expensive. With these methods the incubation period required to produce a result can be several days, which in a production environment is far from ideal and it’s common to safeguard by dosing liberally with biocides. Equipment is now available that allows assessment of microbial contamination in minutes rather than days.

The PROMEX™ 4200 Micro-Respirometer can quantitatively measure total aerobic microbial contamination in aqueous solutions. The detection levels are as low as 102cfu with results obtained within 30 minutes; this can establish the need for biocide dosing and, if necessary, optimize the biocide required.

Respirometry is a well established technique but the application of a novel and patented configuration in the PROMEX™ 4200 Micro-Respirometer has enabled detection limits to be dramatically reduced. The PROMEX™ 4200 is based upon technology developed in a collaborative project carried out with the Institute of Biotechnology, University of Cambridge.

The instrument monitors by means of a pressure sensor, at a controlled constant temperature, where a test and reference sample are placed in enclosed chambers. Within the chambers oxygen is taken up by any viable aerobic organisms in the sample and an equal volume of carbon dioxide (CO2) is released. The CO2 gas which is a product of respiration by aerobic microorganisms present in a sample is absorbed by granules which are located directly above the surface of the solutions. As the CO2 gas is absorbed, a net loss in pressure results as oxygen is consumed by the microorganisms. The difference in pressure between the two chambers is monitored in real time, at a rate of once per second, and the resulting slope can be analysed (see Figure 2). The magnitude of the difference in pressure (slope) can then be related to the number of viable organisms present in the sample (see Figure 3).

Real-time assessment with the PROMEX™ 4200 Micro-Respirometer allows quantification of aerobic microbial contamination and optimisation of biocide protocols; significantly reducing costs, improving product quality and streamlining QC procedures.

The PROMEX 4200 Micro-respirometer:?

Rapid: A result can be obtained in minutes, with a sample size of < 2ml. Sensitive: Detection limits of down to less than 103 cfu are readily achieved. Outperforms dip-slides and TVC’s

Simple: Alternative modes of operation allow for sophisticated research or routine quality control.

Cost Effective: Cost per test compares favourably with dip-slides, and significantly lower than TVC’s. Can optimise the use of Biocides.

Data analysis of the slope produced by the aerobic respiration of microorganisms

Figure 2: Data analysis of the slope produced by the aerobic respiration of microorganisms in a test sample. Analysis of the slope can enable a direct comparison to the number of viable organisms present in the sample.

Comparative data analysis of a serially diluted contaminated paint sample by Total Viable Counts (TVCs)

Figure 3: Comparative data analysis of a serially diluted contaminated paint sample by Total Viable Counts (TVCs) and the Promex™ 4200. This indicates a net loss in pressure resulting from oxygen consumption by the microorganisms monitored in real time at a rate of once per second (SD; N=3). As the paint is diluted the net loss of pressure decreases due to less microorganism being present.

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