Biocide screening methods

Why to do toxicity testing Not all products work equally well in all systems. Some work well as inhibitors, others as killers. Toxicity testing gives a list of products to consider when designing a program. 

First rule out biocides that are not compatible with the machine parameters e.g. temperature, pH, redox potential, source of contamination, impact on paper quality (smell, brightness), agreement (food packaging, cigarette paper). 

Then run toxicity and killing tests to determine the MIC (Minimum Inhibition Concentration) and identify the 

These evaluations can be done using toxicity tests based on reductase test ( Minitox ) or ATP measurement ( Tracide ) and plating methods as Petri dishes. 

Toxicity measurement this is a rapid test for biocide product selection, using resazurin. 

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Bag kill study classic biocide screening method for additives... 

Radioactive methods are not routinely used by field personnel. However, they have been particularly useful in a number of applications including biocide screening programs, identification of nutrient sources, and assessment of key metabolic processes in various corrosion situations [9]. 

Biocide tests against planktonics were similar to methods described by Bragg et al. for persistent biocide screening. A mixed culture from the selected field brine was grown in reduced Tryp-Soy broth (TSB) (Table 5) and was inoculated (5 mL) into 200-mL aliquots of polymer injection fluid (PIF) (Table 5) containing biocides. After 3 weeks, the system was challenged with another 5-mL inoculum to test biocidal persistence. Controls without biocides were also prepared. Subcultures were made into reduced TSB at times indicated later to determine biocide effectiveness. 

Vastly different methods are available for cultivation of biofilms. Basically, these can be described as either batch-mode or continuous mode methods. In batch studies, growth substrata in the form of coupons or glass slides are placed in e.g. Petri-dishes or other holders filled with medium. Under the action of undefined shear forces, investigations in so-called beaker reactors are conducted. A further test system which operates in batch mode and continues to become prominent is the miniaturized test system comprising microtitre plates, in which 96 wells enable the simulation of various experimental conditions simultaneously under static conditions (Geneveaux et al., 1996 O Toole et al., 1999). In general, biocide tests in batch systems are simpler to run, have shorter durations, and are very simple to carry out. Therefore, they are well-suited for initial comparisons or screenings of different biocides, or different concentrations and contact times of a particular biocide. 

Introduction. To operate a successful microbial control program, it is essential to use standard field methods for evaluating microbial populations, screening and selecting biocides that will be effective in controlling microbial populations in the paper system. This section outlines, in detail, field microbiological methods used to monitor bacterial populations and to measure their response to biological control measures. 

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