A research group from Tyumen State University and the Tyumen Scientific Center of the Siberian Branch of the Russian Academy of Sciences evaluated the effect of temperature on the growth and enzymatic activity of bacteria of the genus Bacillus isolated from frozen sediments.
A research group from Tyumen State University and the Tyumen Scientific Center of the Siberian Branch of the Russian Academy of Sciences under the leadership of Academician of the Russian Academy of Sciences Vladimir Melnikov evaluated the effect of temperature on the growth and enzymatic activity of bacteria of the genus Bacillus isolated from frozen sediments.
Human interest in bacteria is not least associated with their synthesis of enzymes - proteins that accelerate chemical reactions. Thus, proteases are responsible for the breakdown of complex proteins, lipases - fats, and pectinases - complex carbohydrates.
Despite the widespread use of bacterial enzymes in food, textile, pharmaceutical and other fields, their use has significant drawbacks. For example, unwanted chemical reactions, the number of which increases with increasing temperature.
Not so long ago, scientists drew attention to bacteria that can exist in extreme conditions. These include psychrotrophic bacteria living at low temperatures. Psychrotrophs can solve the disadvantages associated with obtaining bacterial enzymes. The only problem is that their biology and potential for use are poorly understood.
The research team isolated nine strains of the bacterium of the genus Bacillus from the frozen sediments of Western Siberia: B. megaterium, B. cereus, B. simplex, and B. subtilis.
Scientists have compared the adaptation and growth of crops at temperatures of 5 ° C, 22 ° C and 45 ° C. It turned out that at a temperature of 22 ° C, cultures grow at the fastest rate. Cultivation at 5 ° C significantly slows down the growth of bacteria, but allows you to achieve the highest cell density. At a high temperature of 45 ° C, the culture of bacteria grows so rapidly that it does not have time to achieve comparable indicators.
At the next stage of the study, the authors evaluated the effect of these temperatures on the enzymatic activity: catalase, dehydrogenase, lipase, amylase and protease.
Catalase activity for most bacteria was maximal at 5 ° C and decreased with increasing temperature. A similar picture was observed in the case of another enzyme, dehydrogenase: the maximum activity at 5 ° C, 22 ° C, and 45 ° C was 0.165 mg / (ml day), 0.112 mg / (ml day), and 0.005 mg / (ml ⋅day), respectively.
The best indicators of lipase activity were found at temperatures of 5 ° C and 22 ° C. It is noted that B. cereus strains were characterized by high lipase activity at 5 ° C, and B. megaterium and B. subtilis strains at 22 ° C. In the case of α-amylase activity, only B. cereus strains had high values at 5 ° C and 22 ° C.
Among other strains, only B. megaterium 629 showed high amylase activity at 5 ° C. It should be noted that the high activity of proteases in the studied cultures was less rare. At 22 ° C, it was observed in three strains at once: B. megaterium 206, Bacillus sp. 3M and B. subtilis 948P. At a temperature of 5 ° C, the highest protease activity was demonstrated by two strains - B. cereus and B. simplex 948P-1.
As a result of research, it was found that temperatures of five and 22 ° C are optimal for the growth of bacterial strains of the genus Bacillus. This pattern also applies to enzyme activity, which decreases as the temperature rises to 45 ° C. According to the authors, active synthesis of enzymes is a universal mechanism of life at low temperatures.
The authors emphasize that this work expands the understanding not only of the limits of tolerance for growth and enzymatic activity of microbiota from permafrost to the effect of the temperature factor, but also of its application in applied biotechnological research.