Search

To characterize whether environmental low temperature is involved in metabolic regulation, Channa punctata species of fish were exposed to cold (4~8°C) for 30 min, 1 hr and 2 hrs since they are much energetic and survive in the critical environment. The inorganic phosphate (Pi) in skeletal muscle was significantly increased after 1 hr in cold compared to control fish kept in ambient temperature, however, although lower, stimulatory response to cold for 2 hrs was also observed. In separate examinations, Na+-K+ ATPase activity in the extract of skeletal muscle was determined and enhanced significantly after 1 hr and 2 hrs. The results appear to indicate that the increased Pi in response to cold might be due to the higher activity of Na+-K+ ATPase. To clarify the regulatory mechanism of the enzyme, groups of fish were exposed to cold with 100 mM Na2HAsO4 for 1 hr and 2 hrs. The enhanced Na+-K+ ATPase activity was reduced significantly when treated with Na2HAsO4 compared to the control and also to the respective cold exposed fish. The experimental findings indicate that arsenic is involved in the regulation of cold induced Na+-K+ ATPase activity. The enhanced Na+-K+ ATPase activity in skeletal muscle of this species in cold and its inhibition by arsenic may play a critical role in environment.

Production of alkaline protease from B. licheniformis N-2 was studied in shake flask experiments in growth medium comprised of (g/l): glucose, 10; soybean meal, 10; K2HPO4, 5; MgSO4.7H2O, 0.5; NaCl, 0.5; CaCl2.2H2O, 0.5. Different process parameters, such as fermentation period, initial pH, incubation temperature, agitation speed, and size and age of inoculum, were optimized for the maximum yield of the alkaline protease. Maximum enzyme production (991.04 PU/ml) was obtained after 24 h of incubation at 37 °C in growth medium of pH 10. The optimum inoculum size and age were determined as 2.0% (v/v) and 24 h, respectively. Kinetics of growth and protease production by this microorganism were also analyzed at all optimum conditions. Biomass (Yx/s) and product yield (Yp/s) coefficients were determined as 0.375 g of cells/g of glucose and 99.3 PU/g of glucose, with a growth rate of (0.215 h-1) after 24 h of incubation. Thereafter, a continuous decrease in biomass and product yield was observed. The results indicate that enzyme production by B. licheniformis N-2 was entirely growth-associated and that a major portion of the enzyme was secreted in the post exponential phase.