Trends in environmental microbiology with references from paper industry microbiology

The history of microbiology contains several eras with different targets. I will refer them in this way (based on my over 30 years experience as microbiologist and teacher of microbiology and biochemistry):

In the beginning, cultivation and observation of microorganisms was the main target. Doctors like Pasteur and Koch were very innovative and developed intelligent culture medias and vessels to perform very delicate experiments. The everlasting fight against pathogenic microbes was the primary target but Louis Pasteur started to help eg. wine producers to solve their quality problems, caused by microbes.

The combination of microbiology and biochemistry on the second era was very satisfying by solving questions concerning the huge amount of anabolic and catabolic processes included in microbial growth. More and more were also learned in the area of microbial ecology. Questions like "who? what? when? where? how? why?" were partially solved (ref. MADSEN,E.L. 2008. Environmental Microbiology. From Genomes to biochemistry. Blackwell Publishing).

"Third era" can be described by the novel methods to identify bacteria. Biochemical test kits (API etc.) were replaced by Fatty Acide Methylated Ester method (FAME) by Hewlett-Packard on 80's. After it, molecular biology methods, based on ribosomal RNA and DNA, helped to construct the development lines of microorganisms.

Today is the time of new era. We know the "family trees" of bacteria but we should now continue with environmental microbiology and microbial ecology to solve questions like "How, why, by whom and in which conditions will the raw materials of paper industry be biodeteriorated?", "How can we prevent these processes by setting the process conditions unsuitable for those biochemical processes?", "Can we prevent the growth of biofilms and slimes in an ecological way?", "How to prevent selectively the growth of toxin producers like Bacillus cereus in paper and board processes?", how to fight against Legionella in paper industry?".

Names are not the most important thing. Most important is, how the bacteria act in different ecological niches of a paper machine. This work has to be done by using simulations of paper processes which is possible by wet end simulators of research units (as an example: VTT in Jyväskylä, Finland) and laboratory/field instruments (like biofilm detectors in the processes or PMEU incubators by Samplion Ltd.).

The role of PMEU is getting more and more important because this method helps to detect microbial growth of different types (biofilms included) in a very short period of time as well as to test simultaneously the effects of alternative biocides in small-scale tests whose growth parameters match with the growth conditions in the real processes.

We are - and we shall - turn back to the era of Pasteur & Koch: the names are already known, and we shall now investigate, what the contaminating microbes are doing in the industrial processes and how to prevent losses of raw material, machine stops and poor quality of the products by simulating growth processes in small-scale tests, performed in the laboratory or in the field, by the machies themselves.

"Top Three" microbiological problems of paper machines

Certain types of microbiological problems in paper mills seem to be acute all the time. Looking back to last months, this may be "Top Three" among them:

* Microbiological spoilage of raw materials. This is an everlasting hazard for mineral and starch slurries, and the reasons are very easy to understand: both raw materials mentioned may contain high densities of bacteria (mainly aerobic sporeformers and actinobacteria), slurries containing starch are very nutritive growth media for different microbial species and the very challenging biocidic treatments of slurries (especially mineral ones), when inaccurate, can lead to the total spoilage of them.

* Growth of biofilm and production of slime. This problem seems to be connected to poor washing and boil-out programs which leave rests of biofilm inside the machine and give growth time for it because too long running periods. The chose of ineffective biocide and/or its insufficient dosing can also stimulate the activity of these trouble-makers.

* Microbial growth in the broke system. Especially big machines with large broke towers suffer of this problem. If the basic biocide program is insufficient and the retention times inside the towers are too long, aerobic population tend to increase the number of its cells to the level of 10 000 000 cfu/g or even higher. Consumption of oxygen by respirating bacteria leads to anaerobic conditions, redox potential will be dropped and the growth conditions for both fermentative and anaerobic bacteria turns to be excellent. Drop of pH, slime and spore formation, smells and odours - even the production of H2S and H2 - will be found in such situations.

There are some measures to prevent these hazards. Growth period of microbial population shall be kept as short as possible, the control of waterborne and bioflim bacteria shall be as rapid and frequent as possible and the bioside programs, intended in killing of raw material, process water and biofilm bacteria shall be evaluated more frequently.

A realistic and accurate way to control both process water and biofilm growth, as well as to evaluate biocide programs, is now available. The Finnish company SAMPLION Ltd is manufacturing and selling "Portable Microbiological Enrichment Unit", a "mini-fermentor" for 10 simultaneous tests in controlled conditions, to detect the failures of biocide programs in only hours (watesr) or days (biofilms). Some results of PMEU's paper industry applications will be published in next Spring - coming back to refer them later.

Some wrong ideas about the overdosing of biocides will also rise up frequently among publicity. Basically it is not a question of only the cubic meters of biocides consumed, however, The chose of most effective biocides for different areas of processes towards different problems, the dosing of these compounds, their type of action and some other factors play a major role when building an effective biocide program for paper machine. Overdosing of biocides is a problem only in cases, when the program does not work, and leads to the loss of money and the rise of biocide concentration in paper machine effluents.