Friday, November 4, 2011
New Microbiological Methods for P&P Industry
It seems that new methods for P&P microbiology are needed.
After discussions in PulPaper Congress in Helsinki, June 2010, it is obvious that traditional colony count methods cannot tell the truth about process problems.
These methods, originally developed for clinical microbiology, seem to have too high nutrient content. They cannot, therefore, select the "troublemakers" from the process samples. Bacteria like Gram-negative rods and Bacillus sp. are overestimated in these analyses but eg. filamentous bacteria cannot grow on common, commercial agar media.
Identification of bacteria can be important in some cases. Food poisoning species from the genuses Bacillus, Staphylococcus and Clostridia and hygiene indicators like coliforms, E.coli and Enterococci should be found in raw material control in the production of high hygiene products (LPB, other food-grade cartonboards and papers as well as tissue-type products). If not covered by other bacteria, they can be found with CC analyses. PCR also gives a good way to distinct them among other bacteria.
These methods cannot reveal some severe problems, however. Biofilm formation and comparative biocide testing are two types of investigations which cannot be performed with agar cultivations or molecular biology methods. They should be done either in machine trials or simulations. PMEU methods seem to be the best alternatives for rapid evaluation of biofilm formation and biocide testing today because they exclude all artefacts, caused by artificial growth medium (in colony counts) or too high selection of microorganisms (in PCR). CC's and PCR can be adopted to certain tests but when the subject of the study is to see, what happens in the real paper processes, simulation methods like PMEU shall be chosen.