Keratinase, Caseinolitic, Cellulase and β-Mananase Activities of Bacteria Isolated from the Black Sea

Abstract

For a long time, the main interest in the marine environment, considered extreme, was the isolation and identification of natural products with biological properties, and for that, numerous organisms and chemical structures have been studied. Thus, marine bacteria isolated from various substrates, such as sediments, seawater, and mangrove detritus, are producers of enzymes with different activities, i.e., amylase, cellulase, alginate lyase, chitinase, glucosidase, inulinase, keratinase, ligninase, xylanase, and others. Nowadays, researchers are also focusing on the enzymes produced in the marine environment that can present special properties. Therefore, the aim of this study was to investigate the ability of marine strains of microorganisms to exhibit cellulase, β-mannanase, keratinase, and caseinolytic activities. Methods. Enzymatic activities were studied in the culture liquid supernatant. To determine β-mannanase and cellulase activities, guar gum galactomannan and Na-carboxymethylcellulose respectively were used as substrates. Casein and crushed defatted feathers served as substrates for the determination of proteolytic activity. Results. Growing 10 cultures of microorganisms on a nutrient medium containing chicken feathers as the sole source of carbon and nitrogen (nutrient medium 1) did not give positive results. When using medium 2, active growth was observed in four of the studied strains (51, 52, 54, 247) in the supernatant of culture liquid (CLS), the activity of which both to keratin (6.0—16.0 U/mL) and casein (0.025—0.33 U/mL) was found. In the CLS of only six of the 10 studied cultures (7, 20, 51, 52, 50, 247), cellulase and β-mannanase activities were observed. The highest cellulase activity was found in culture 20 (1.8 U/mL). The activity of culture 7 was somewhat lower (1.0 U/mL). An insignificant activity was noted in cultures 54 (0.06 U/mL), 56, and 50 (0.05 U/mL). Trace levels of activity were observed in culture 247. Conclusions. Strains 7, 20, 247, and 51, for the first time isolated from the Black Sea, are promising for further studies as producers of cellulase, β-mannanase, keratinase, and caseinolytic enzymes.