Thursday, February 28, 2008

Microscopy as a control tool in paper industry.

A microscope, intended for microbiology, can be very effective tool in the microbiological control of paper machines. There are some technical differences between paper analysis and microbiological analysis microscopes, mainly in their optical features (depth of field as an inverse factor to distinction of small details etc.) but, in most cases, a middle-price, modern paper analysis microscope can be modified for microbiological examinations.

Some illumination methods - not so familiar on other areas of microscopy - are especially beneficial for paper industry microbiology analyses. Dark Field illumination (with special condensor) can help to find tiny (< 1 micrometer) microorganisms, Phase Contrast illumination (needs certain types of condensors and objectives) is excellent when checking living, non-stained preparates and UV Epifluorescence Microscopy opens new chances to differentiate living and non-living microscale objects.

Assaying microbial activities in paper machine processes.

To evaluate the potential of microbial growth in paper industry processes, traditional colony count analyses do not fulfil all needs.

Colony count analyses (cfu/ml or cfu/g) are well-known methods to detect certain microbes or microbial groups. The are valuable when specified troublemakers shall be detected.

Total effects of microbial growth cannot be seen by using only cfu methods because
* they do not show the activities of microbes, only their counts
* they are performed in artificial environment (nutrient media), not in the original samples

Rapid incubation of process samples is needed to show potential hazard, caused by process population. Biocide testing is also better to do in original samples from beginning to the end.

The most promising method to perform these kind of "mini-fermentations" today is PMEU incubation (Portable Microbiological Enrichment Unit; FINNOFLAG Oy; Kuopio, FINLAND) which gives results of microbial activities and effects of biocides in hours (compared with days when cfu methods are applied). No protecting, stimulating, inhibiting or other selecting effects of nutrient media are also totally excluded in process sample incubations.

One of the main ideas of microbiology is: Both the counts and activities of microbes shall be taken into account. Populations with relatively high colony counts can have slow metabolic activity - and in opposite.

As a summary: microbial activity, not the count of colonies, causes problems in paper industry processes.

Monday, February 25, 2008

Mineral pigments and fillers as a hazard to the paper production hygiene?

"Microbial contaminants will decrease the quality of pigments and fillers in paper and board industry. Microbe-caused spoilage of these raw materials as well as indirect deteriorative effects of these spoiled additives on the machine housekeeping, production and hygienic properties of paper products are well-known problems at the mills." (MENTU, J. et al. 1997. Microbiological Control of Pigments and Fillers in Paper Industry. In: Transactions of the 11th Fundamental Research Symposium in held at Cambridge: September 1997. PIRA International, Surrey,UK).

If we start to examine the routes of microbes into the paper manufacturing processes, mineral pigments and fillers have a role as one of the most important agents to contaminate the paper and board production processes.

This is caused by the characteristic features of these additives: they are (excl. Precipitated Calsium Carbonate) all originated from rocks and contain high counts of soil microbes: spore-forming and other bacteria as well as fungi. Depending of the further treatments of the raw minerals, the quality of minerals will get better or worser. A wide variation of colony counts can be detected in mineral slurries, ranging from 0 to over 10 000 000 cfu/ml!

Biocidic treatment of minerals is a challenging tasks for several reasons. Bacterial spores (very common form of bacteria in minerals) tolerate traditional biocides better than vegetative bacteria; minerals have microbe-covering effects; long transportation and storing periods give extended growth time for microbes etc.

Paper machines need minerals day and night. This everlasting input of mineral-borne bacteria acts as a significant contamination route. Control methods to detect spoiled lots and CCP's of the "coating kitchens" should work very fast and give early warnings in emergence situations as well as documentation of the overall quality of different brands of minerals.

How to build up this kind of reliable mb control for mineral pigments and fillers?

Some new alternatives of traditional, long-lasting and labourious colony count analyses really exists today.