The accumulation of microplastics in the world oceans is one of the main global problems of the modern world. The Black Sea is the main source of seafood for people from several countries, including Bulgaria. The pollution of the Black sea is a result of various factors, especially anthropogenic. The aim of this study was to determine the presence and accumulation of microplastics in the Black Sea mussel Mytilus galloprovincialis L., 1819, harvested from different locations along the northern Bulgarian Black Sea coast. Within each microplastic morphological group, three size classes were recognized: 100-200 μm, 25-100 μm, and ≤ 25 μm. Microplastics were found in the soft tissues of all studied specimens but in a different ratio of pellets, fibers and fragments. Generally, the pellets were the most often registered particles, followed by irregularly-shaped fragments, whereas fibers were less numerous. The dominant part of the isolated plastics are made of polyethylene (PE), and polyethylene terephthalate (PET). Our results pointed out serious pollution with plastic particles in the Bulgarian Black Sea aquatory, which in the future may seriously affect the health of the mussel population and also human health.

An exopolysaccharide (EPS) was isolated from Lactobacillus plantarum Ts and purified by size exclusion chromatography train. L. plantarum showed the highest production (9.4 ± 0.8 g/l) of EPS. Furthermore, L. plantarum was cultured in medium with volume of 5 L and the EPS was extracted by ethanol precipitation. By HPLS analysis demonstrated, that the EPS has two fractions - polymer and olygomer. The molecular mass of the EPS from both fractions is respectively 8.3x104 Da for the greater pic and 5.0x102 Da. Fourier transform infrared spectroscopy analysis showed the presence of hydroxyl and carboxyl groups and glycosidic linkages. TLC analysis indicated that the EPS was a heteropolymer composed of fructose, and sucrose as monomeric constituent units. The strain L. plantarum and pathogenic E. coli 3398, St. aureus 745, B. subtilis 6633, S. typhimurium 3591, L. monocytogenes 863 and E. aerogenes 3691 were tested for their growth utilizing the EPS from L. plantarum as the sole carbon source for its possible use as a prebiotic. L. plantarum exhibited growth in the EPS supplied medium compared with sucrose as carbon source, whereas the pathogenic strains did not grow in the EPS-supplied medium. In vitro evaluations showed that, like other reported polysaccharides, this EPS displayed significant prebiotics properties.

This paper presents a study on the microbial status of different fish species and their habitats in the Bulgarian Black Sea area. The samples were collected in the period of January 2021 until March 2021. The fish species we used in this study were Black Sea turbot (Scophthalmus maximus), round goby (Neogobius melanostomus), shore rockling (Gaidropsarus mediterraneus) and European anchovy (Engraulis encrasicolus). The BIOLOG system was used for microbiological determination. From the different fish species, different species of microorganisms were isolated (using selective nutrient media). From the torbut, we isolated species Enterococcus villorum with 24 × 103 cells in 1 ml, Moraxella nonliquefaciens with 70 × 103 cells in 1 ml and Pseudomonas synxantha with 123 × 103 cells. Pseudomonas putida was isolated from the round goby with 20 × 103 cells in 1 ml. The species Streptococcus entericus with 123 × 103 cells in 1 ml was isolated from the shore rockling. Pseudomonas fulva with 60 × 103 cells in 1 ml was isolated from the European anchovy. A total of 223 × 103 cells in 1 ml of Pseudomonas agarici were isolated from Trachinus draco. Pseudomonas tolaasii with 145 × 103 cells in 1 ml were isolated from Merlangius merlangus. A different species of bacteria of the genus Pseudomonas was found for each of the investigated species of Black Sea fish. Apparently, the species Pseudomonas is characteristic of marine Teleostei and is important for the life and metabolism of these vertebrates. These microorganisms probably are resident species and developed not as result of pollution or environmental change.