**6. Acknowledgment**

This chapter is based on several research performed at VTT and other research institutes and universities.

#### **7. References**


be between 2 and 2.5 times higher than that in Helsinki. In North Scandinavia it would be between 0.5 and 0.25, which will point out, the effect if climate on risk of decay development in outdoor structure varied vide within Europe. These coefficients can be used as one step to evaluate the effect of macroclimate conditions on service life of cladding and decking. Another way to evaluate the macroclimate conditions is presented by Thelandersson et al (2011) using Meteonorm climate data. By calculating the daily dose and accumulating the dose for one year a measure of the risk of decay is obtained. This is made for several sites, and the result in terms of dosedays can be compared between the different sites. To be able to compare different sites, the dose was transferred to a relative dose by dividing it by the dose for the "base-station" Helsinki. Due to the variation of climate across Europe, relative doses between 0.6 (northern Scandinavia) and 2.1 (Atlantic coast in Southern Europe) were

There are several factors involved with the bio-deterioration of materials and buildings, and mathematic modelling that may help us to understand the complicated interaction of many factors. The presented numerical mould growth and decay development models are based on experimental results from several research projects. It is suitable for post-processing temperature and humidity data from any numerical simulation of hygrothermal conditions in building constructions. However, it must be kept in mind when performing the assessment that there is a great uncertainty coupled to this kind of analysis: the variation of the material sensitivities is high, estimation of a product sensitivity class is difficult without testing, the surface treatments may enhance or reduce growth potential, different mould species have different requirements for growth and the evaluation of the actual conditions in the critical material layers may include uncertainties. The best way to use the predicted mould growth and decay development as an assessment tool is to compare different solutions with each others: The solution with the lowest risk for the mould growth or decay

development would most probably also have least other moisture related problems

This chapter is based on several research performed at VTT and other research institutes

Adan, O.C.G. 1994. On the fungal defacement of interior finishes. Eindhoven University of

Ayerst, G. 1969. The effects of moisture and temperature on growth and spore germination

Clarke, J.A. Johnstone, C.M. Kelly, N.J. Mclean, R.C. Anderson, J.A., Rowan N.J. and Smith,

Grant, C., Hunter, C.A., Flannigan, B. and Bravery, A.F. 1989. The moisture requirements of moulds isolated from domestic dwellings. Internat. Biodet. 25:259-284.

J.E. 1998. A technique for prediction of the conditions leading to mould growth in

Technology. Thesis. Eindhoven, pp. 83-185.

in some fungi. J. Stored Prod. Res. 5:127-141.

buildings. Building and Environment 34 pp 515-521.

obtained.

**5. Conclusion** 

**6. Acknowledgment** 

and universities.

**7. References** 


**26** 

**The Release of** 

*Technical University of Lodz* 

Marek Solecki

*Poland* 

**Compounds from Microbial Cells** 

Compounds present in the microbial cells are of great commercial value. Their separation requires disintegration of cell walls and cytoplasmic membranes. The disintegration of microorganisms on an industrial scale is carried out, among the others, in bead mills (Chisti & Moo-Young, 1986; Geciowa et al., 2002; Hatti-Kaul & Mattiasson, 2003). A bead mill is a container filled with beads that are set in circular motion by a rotating stirrer. Microorganisms dispersed in the liquid are disrupted due to the impact of beads. The mechanism of cell destruction is a result of combined action of normal and tangential forces. There are three basic types of this mechanism: collisions of beads, grinding and rolling performed by the beads. Disintegration is a very complex process. In this process, cell walls of microorganisms are disrupted, intracellular compounds are released and dissolved in the continuous phase, cell walls are subjected to microgrinding, the released macromolecular compounds are cut and the released enzymes interact. Rheological properties of the

Currie et al. (1974) described disintegration kinetics of microorganisms in the bead mill. The authors developed a linear model by comparing experimental data with results obtained during the disintegration process carried out in a high-pressure homogenizer (Hetherington et al., 1971). A logical model based on the analogy to the theory of gas kinetics was proposed by Melendres et al. (1998). They presumed that microorganisms could be destroyed due to collisions of dispersed beads of the packing. A phenomenological model based on the flow of suspension between two volumes was developed by Heim & Solecki (1998). The authors assumed that cells were disrupted while moving from a safe volume to the one in which no living microorganisms could exist. Basing on the sequence of events: cell disruption – the release of intracellular compounds, Melendres et al. (1993) developed a nonlinear model of the release of selected intracellular enzymes. Heim et al. (2007) described nonlinearity of the kinetics caused by changes in the disintegration conditions which was a result of the process run. Nonlinearity of the disintegration process resulting from subsequent decline of the biggest fractions of yeast cells was observed by Solecki (2009). Earlier, Whitworth (1974) described nonlinearity of cell disintegration kinetics in a suspension containing microorganisms (*Candida lipolytica*) which belonged to the same species and occurred in two morphological forms. The recently developed theory of random transformations of dispersed matter makes it possible to include in the description the fundamental phenomena observed during the process (Solecki, 2011). The aim of the study was to

**1. Introduction** 

suspension and its continuous phase are changed.

