Many techniques used in criminalistics, medical diagnostics, in phylogenetic studies and in organisms identification and differentiation are based on polymerase chain reaction (PCR). The choice of routine method to be applied routinely in a particular laboratory, is not easy and necessitate the knowledge and understanding of some one. In this paper, to facilitate the choice of the routine method for microorganism identification and differentiation, the detailed description of following methods is presented: RAPD (Randomly Amplified Polymorphic DNA), PCR-RFLP (PCR-Restriction Fragments Length Polymorphism), RISA (Ribosomal Intergenic Spacer Analysis), AFLP (Amplified Fragment Length Polymorphism), Multiplex PCR and Real-time PCR. The methods were compared by the most useful characteristics such as: application field, analysis repeatability, difficulty degree, analysis duration, automation possibility and cost.

The influence of temperature and type of packaging material on the saccharolytic activity of freeze-dried yeast Saccharomyces cerevisiae during storage was investigated. Yeast’s after mixing with maltodextrin (8%, used as a protective substance), were frozen at -30°C and dried at 40°C /0.63 mbar for 20 h. Dried samples were stored at -18, 4 and 25°C in high (PETmet/PE, PET/AL/PE) and low (PET/PE, OPP) barrier bags. It was found that in order to remain at least 80% of the saccharolytic activity of dried yeast’s after 12 weeks, compared to the activity after drying, it is necessary to store them at 4°C in the bags with a high barrier against oxygen and water (PETmet/PE) or at -18°C in any package. To ensure the maintenance of over 90% of the activity is necessary to use the high-barrier packaging (PETmet/PE or PET/AL/PE) and storage temperature -18°C.

Lipolytic activity of seven yeast strains: Candida famata MI1a, C. intermedia BI2a, C. kefyr PII1b, C. sphaerica FII7a, Geotrichum penicillatum EII6a, Saccharomyces kluyveri BII3a and Yarrowia lipolytica PII6a was investigated. These strains representing yeast species occurring in mould cheese Rokpol are potential cheese co-starters. The extra and intracellular lipolytic activity of the yeast was analyzed against tributyrine and p-nitrophenyl derivatives of fatty acids. Also their ability to hydrolyze bovine milk fat was assayed. It was shown that generally activity of extracellular yeast lipases were higher than of intracellular enzymes. The most lipolytic were strains Y. lipolytica PII6a and C. sphaerica FII7a, which preferentially hydrolyzed butyrate p-nitrophenyl derivative and release the highest amounts of oleic acid from milk fat.