Saturday, December 8, 2012

A new era in microbiology: back to Pasteur's times?

(first published April 25th 2010 by Juha V. Mentu)

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.

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 machines themselves.

Monday, December 3, 2012

Monitoring of microbial growth and sporulation

pH, temperature, nutrients and biocides are usually observed when the risks of microbial growth and sporulation inside paper machines should be estimated. Fourth important factor, time, will be often ignored, no matter it plays a most significant role in paper process microbiology. The simple figure above shows two important parameters which reveal the microbiological status of the white water in an anonymous paper machine (my personal data ca. 2006): Colony Count (CC, indicating the count of vegetative bacterial cells per ml) and Spore Count (SC, indicating the count of bacterial spores per ml). It is obvious that this very sample contains relatively high amounts of nutrients to secure the rapid growth of bacteria (the growth rates of bacteria, carried by white water, are usually much lower but bacterial densities, in opposite, on a very high, stabile levels). What is especially important in this case is the rapid increase of bacterial spores - producers of process biofilms after their outgrowth and risks for product hygiene in their original form - which seems to take place after ca. 0,5 days storage time. This event takes place practically always when the flow of white water, pulp and broke have been stopped during the delays of constant machine operation. The hygiene status of the total process would then be very important to know - how much spoiled water and broke can be supplied from towers to the process, are there risks to have biodeteriorated raw materials from the storage tanks, is there any need to use shock dosing of biocides in some sites etc. - but it cannot be done by using CC, SC or any other cultivation technique which give analytical results only after several days' incubation periods. Long analytical delays in colony count analyses also totally prevent the efficient application of HACCP hygiene control procedures into paper machine environment. - These are the facts which motivate me personally to continue planning rapid, ON LINE process hygiene methods.