Providing a sound habitat for man in space.

Microbiological growth on materials in an indoor environment contributes to the well known "sick building syndrome". The inhabitants' health and well-being is affected by injurious vapours and odours given off to the air. This is particularly pronounced in new and better tightened houses with unconventional building materials and wider employment of air conditioning. The European Space Agency has recognized the problems to be expected in a totally closed and self-supported long-term habitat and has induced work on the selection of materials, resistant to microbiological growth, and on other microbial contamination control measures. Requirements and procedures are being established as a basis for the microbiological cleanliness of the manned space environment and for the avoidance of microbiological growth on materials and equipment. Methods are being developed, suitable for testing and predicting the resistivity to microbiological growth of materials to be used in long-term space habitats.

The role of microorganisms in the formation of pitch deposits in pulp and paper mills.

The cause of pitch deposit formation seems still not fully understood. The work reported here demonstrates that microorganisms effect the agglomeration of emulgated resin droplets and the formation of sticky precipitates. Pitch deposits from mills consist mainly of ethanol-soluble resins. It is also the ethanol-soluble fraction of wood resins which forms stable emulsions and which is easily agglomerated by microorganisms. Pitch deposits, collected from various pulp and paper mills, were all found to contain large amounts of microorganisms. Sterile resin emulsions prepared from pitch deposits remained stable over long periods. After inoculation with microorganisms the emulsions were destabilized and the resins completely precipitated as sticky lumps. Various bacteria and fungi are capable of agglomerating the resins, but species isolated from water, pulp and slime in paper mills were usually most effective. Resins from fresh wood were precipitated at a faster rate than aged resins. Problems of pitch formation can be considerably reduced when microbial growth is kept under control in the production system. To be effective, the control measures, e.g. slimicides, must be applied at the right place and time, and in the correct concentrations. This presupposes a thorough knowledge of the plant's microbiological condition which can only be obtained by microbiological examination. Practical cases of the appropriate application of biocides in pulp and paper mill systems are discussed.