Laura Raaska

Methodologies for the characterization of microbes in industrial environments: a review

Abstract. There is growing interest in research and development to develop novel tools to study, detect, and characterize microbes and their communities in industrial environments. However, knowledge about their validity in practical industrial use is still scarce. This review describes the advantages and limitations of traditional and molecular methods used for biofilm and/or planktonic cell studies, especially those performed with Listeria monocytogenes, Bacillus cereus, and/or Clostridium perfringens. In addition, the review addresses the importance of isolating the microorganisms from the industrial environment and the possibilities and future prospects for exploiting the described methods in the industrial environment.

Trapping the food safety performance of a small or medium-sized food company using a risk-based model. The HYGRAM® system

The requirements of implementing Hazard Analysis and Critical Control Points (HACCP) principles in food production are increasing. A practical risk quantification model, HYGRAM, was developed for small and medium-sized enterprises to meet this challenge. The model makes the user familiar with the HACCP principles by software-assisted guidance through the procedure, connecting special microbiological hazards, good hygiene practice, and other prerequisite programs to HACCP. HYGRAM is a tool to analyze and quantify risks of different processes, and to compare them. It is developed to relieve enterprises with limited resources in confirming the food safety of their production.

Desulfovibrionales-related bacteria in a paper mill environment as detected with molecular techniques and culture

The aim of the present study was to evaluate the suitability of a nested PCR-DGGE (denaturing gradient gel electrophoresis) method for the detection of Desulfovibrionales-related sulfate-reducing bacteria (SRB) from paper mill samples. The samples were also analyzed with culturing. SRB cause/enhance industrial problems, namely creation of foul-smelling gases (hydrogen sulfide) and biological corrosion, and so far there has not been a simple method to study these bacteria in paper mill laboratories. In our study, culturing was able to detect Desulfovibrionales-related bacteria from two different white waters, two different brokes, pulp, clay, and slime. Out of the isolated Desulfovibrionales, 23 enrichment cultures were further characterized with Desulfovibrionales-selective PCR-DGGE. An identical Desulfovibrio species sequence was found from paper machine I (broke I, slime, and pulp) and from paper machine II (broke II and white water II), suggesting an in-house contamination with the same strain. Desulfovibrionales-selective PCR-DGGE was also performed from DNA templates extracted directly from the paper mill samples. The DGGE profiles derived from the samples without prior enrichment were more diverse and the sequenced amplicons proved to belong to the Desulfovibrionales order. Moreover, molecular techniques were able to detect Desulfovibrionales-related bacteria from calcium carbonate samples whereas culture did not. Altogether, the nested PCR-DGGE method used in this study was suitable for the detection of Desulfovibrionales-related SRB directly from different paper mill samples and it could be used for the rapid identification of SRB-contaminated industrial sites and, when combined with sequencing, for tracing of the contamination routes.

Antagonistic activity of Staphylococcus siderophores and chemical biocides against Bacillus subtilis in a paper-machine environment

The antagonistic potential of nonpathogenic Staphylococcus strains against Bacillus subtilis wild and type strains were studied under conditions simulating a paper- and board-machine environment. The antimicrobial activity was measured by growth inhibition in an automated turbidimeter. The antagonistic potential was compared with that of generally used chemical biocides in a paper- and board-machine environment. The siderophore-containing extracts of Staphylococcus strains significantly inhibited vegetative growth of B. subtilis and delayed the germination of spores both in synthetic and in white-water media. The mill strains were more resistant than type strain against Staphylococcus siderophores and against chemical biocides. The Staphylococcus siderophore-containing extracts did not interfere with the bacteriostatic effect of chemical biocides, but no synergy was detected. The results indicate the potential for application of Staphylococcus siderophore-containing extracts as biocontrol agents in paper- and boardmachine environment.

Biogenic thiosulfate and oxalate in paper machine deposits connected to corrosion of stainless steels

Abstract Pick-up felts and deposits in wet end splash areas and in storage tanks of paper machines contained large amounts of thiosulfate (80– 16 000 mg kg −1 , wet weight) and oxalate (20– 2300 mg kg −1 , wet weight). These anions were absent ( mg l −1 ) in process water and found in raw materials only in low concentrations (5– 10 mg kg −1 , wet weight). Similar and larger amounts of thiosulfate, sulfite and oxalate were generated de novo from sulfate and sheets of chemical pulp in a splash area simulator fed with artificial paper machine white water in the laboratory. Stainless steel UNS S30400 coupons placed in the simulator developed significant corrosion pits within 4 weeks. Pitting was most extensive under or vicinal to patches where large amount of thiosulfate and oxalate accumulated in the pulp sheet. Pitting of UNS S31600 occurred only vicinal to the pulp sheet. The pitted steel surfaces accumulated large amounts of silicon containing material. The biogenic conversion of sulfate into compounds of lower oxidation states occurred more extensively on stainless steel UNS S30400 than on UNS S31600.

Ultrasonic Imaging – Nondestructive Methods to Detect Sterility of Aseptic Packages

This article is reproduced from the previous edition, volume 3, pp. 2195–2201,