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The scientific interest for the search of natural means of microbial inhibitors has not faded for several years. A search of natural antibiotics, so-called bacteriocins which are produced by lactic acid bacteria (LAB), gains a huge attention of the scientists in the last century, in order to reduce the usage of synthetic food additives. Pure bacteriocins with wide spectra of antibacterial activity are promising among the natural biopreservatives. The usage of bacteriocin(s) producing LAB as starter culture for the fermentation of some food products, in order to increase their shelf-life, when synthetic preservatives are not allowable, is also possible. There are a lot of studies focusing on the isolation of new bacteriocins from traditional fermented food, dairy products and other foods or sometimes even from unusual non-food matrices. Bacteriocins producing bacteria have been isolated from different sources with the different antibacterial activity against food-borne microorganisms. This review covers the classification of bacteriocins, diversity of sources of bacteriocin(s) producing LAB, antibacterial spectra of isolated bacteriocins and analytical methods for the bacteriocin purification and analysis within the last 15 years.

Introduction Vaccinium sp. is a widespread genus of dwarf-shrubs growing in the southern areas of taiga forests to the north areas of tundra forests. The well-known berries of these shrubs, such as cranberry, blueberry, bilberry, and lingonberry, are popular all over the world due to their high source of vitamins, phenolic compounds, organic acids, and minerals (Vendrame et al., 2016). Arbutin, hydroquinone, pyroside, salidroside, benzoic acid, vanillic acid, and p-hydroxybenzoic acids are the main phenolic compounds detected in V. vitis-idaea L. (Saario et al., 2002). Chlorogenic acid is the main acid in V. myrtillus L. leaves (Liu et al., 2014; Bujor et al., 2016). In bilberry fruit, high amounts of anthocyanins and hydroxycinnamic acid derivatives, as well as low amounts of flavonols, proanthocyanidins, and coumaroyliridoids, have been identified (Mikulic-Petkovsek et al., 2015). The berries of V. myrtillus and V. vitis-idaea are the most popular part of these plant among consumers and scientists, as a research object, due to their high antioxidant potential (Chu et al., 2011; Blumberg et al., 2013; Vendrame et al., 2016). Moreover, the leaves of these bushes are rich in antioxidants and other biologically active compounds that exhibit a wide spectra of biological activities (Vyas et al., 2013; Liu et al., 2014; Ferlemi and Lamari, 2016). Both V. myrtillus and V. vitis-idaea are forest plants, therefore the growth and production (berries or leaves) of these shrubs might be dependent on forest ecosystem sustainability. Phenolic compounds are important, not only due to their positive effect on human health, but because they are also important for the survival of plant, since they act as defensive agents against solar UV light, bacterial infections, and herbivores (Haukioja, 2005). Plant phenolics are one of the most widespread groups of secondary metabolites, and

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Determination of natural preservatives using electrophoretic or chromatographic techniques in fermented milk products is a complex task due to the following reasons: (i) the concentrations of the analytes can be below the detection limits, (ii) complex matrix and comigrating/coeluting compounds in the sample can interfere with the analytes of the interest, (iii) low recovery of the analytes, and (iv) the necessity of complex sample preparation. The aim of this study was to apply capillary zone electrophoresis coupled with contactless conductivity detection for the separation and determination of nisin in fermented milk products. In this work, separation and determination of natural preservative-nisin in fermented milk products is described. Optimized conditions using capillary zone electrophoresis coupled with capacitance-to-digital technology based contactless conductivity detector and data conditioning, which filter the noise of the electropherogram adaptively to the peak migration time, allowed precise, accurate, sensitive (limit of quantification: 0.02 μg/mL), and most importantly requiring very minute sample preparation, determination of nisin. Sample preparation includes following steps: (i) extraction/dilution and (ii) centrifugation. This method was applied for the determination of nisin in real samples, i.e. fermented milk products. The values of different nisin forms were ranging from 0.056 ± 0.003 μg/mL to 9.307 ± 0.437 μg/g.