α-L-Rhamnosidase Activity of Antarctic Strain of Pseudomonas mandelii U1

Abstract

In recent years, cold-adapted enzymes are increasingly used in industrial processes such as the food, textile and beverage industries. Moreover, cold-active enzymes are usually thermolabile and can be inactivated with little heat. This is especially important in reactions where it is necessary to inactivate an enzyme after it has completed its function, while maintaining conditions that allow other enzymes involved in the reaction to function. Among these enzymes, glycosidases play an important role, which are used in medical technological processes, the food industry, biotechnology for the purification and processing of raw materials, as well as in many other areas of human activity. Therefore, the aim of this work was to study the ability of the psychrotolerant bacterium Pseudomonas mandelii U1 to produce glycosidases, in particular a-L-rhamnosidases, and also to investigate their physicochemical properties and substrate specificity. Methods. Glycosidase activities were determined by Romero and Davis methods, protein – by Lowry method. Results. The study of enzymatic activities in the dynamics of growth indicates that already on the third day of cultivation in the supernatant of the culture liquid of P. mandelii U1 α-L-rhamnosidase activity (0.09 U/mg protein) was noted. On the fifth day of cultivation, in addition to α-L-rhamnosidase (0.09 U/mg protein), β-D-glucosidase (0.09 U/mg protein) and α-D-glucosidase (0.09 U/mg protein) activities were identified. On the seventh and ninth days of cultivation, the spectrum of glycosidase activities was wider, except for α-L-rhamnosidase (0.2 and 0.16 U/mg protein, respectively), β-D-glucosidase (0.02 and 0.05 U/mg protein, respectively) and α-D-glucosidase (0.04 and 0.08 U/mg of protein, respectively), α-D-mannosidase (0.025 and 0.025 U/mg protein, respectively), α-D-fucosidase (0.025 and 0.05 U/mg protein, respectively), N-acetyl-β-D-glucosaminidase (0.025 and 0.025 U/mg protein, respectively) and N-acetyl-β-D-galactosaminidase (0.025 and 0.025 U/mg protein, respectively). Since among the studied glycosidase activities, α-L-rhamnosidase was the highest, subsequent studies were aimed at investigating its properties. It was shown that P. mandelii U1 α-L-rhamnosidase has the pH optimum of action at 5.0, and the temperature optimum − at 4°C. Conclusions. The temperature optimum of P. mandelii U1 α-L-rhamnosidase preparation isolated from moss in Antarctica, Galindez Island, is 4°C, the optimum pH is 5.0, the enzyme is able to hydrolyze as synthetic substrates p-nitrophenyl-α-L-rhamnopyranoside, p-nitrophenyl-β-D-glucopyranoside, p-nitrophenyl-α-D-glucopyranoside, p-nitrophenyl-α-D-mannopyranoside, and natural substrates − naringin, neohesperidin and rutin, which suggests the possibility of its use in the future in food technologies, in particular in food processing and waste degradation at low temperatures.