Enzyme synthesis was found to be repressed by rapidly metabolizable nitrogen sources such as amino acids or ammonium ion concentrations in the medium 22, 24. However, one report indicated no repression in the fibrinolytic protease activity with the use of ammonium salts 43. An increase in fibrinolytic protease production by the addition of ammonium sulphate was also observed by Amrita Raja and Nancy Khess 43. Similarly, sodium nitrate was found to be stimulatory for fibrinolytic protease production 43. Substitution of silver nitrate in the basal medium with sodium nitrate increased enzyme production even more 71.
pH and temperature: The important characteristic of most microorganisms is their strong dependence on the extracellular pH for cell growth and enzyme production. The culture pH also strongly affects many enzymatic processes and transport of various components across the cell membrane 87. The optimum pH 5-8 reported for maximum fibrinolytic protease production by Bacillus subtilis, β-hemolytic 71, 73, 79, Oidiodendron flavum 82, Schizophyllum commune 83, 84, Pseudomonas aeruginosa 43, Bacillus lichniformis B4 44, Rhizomucor miehei 78, Ganoderma lucidum VK 12 85, Escherichia coli 86, Candida guilliermondii 66, Bacillus cereus GD55 77. In view of a close relationship between fibrinolytic protease synthesis and the utilization of nitrogenous compounds, pH variations during fermentation may indicate kinetic information about the fibrinolytic protease production, such as the start and end of the fibrinolytic protease production period.
Nitrogen is essential for protein and chlorophyll synthesis, however too much nitrogen promotes excessive vigour, delayed maturity and can lead to soft, poorly coloured fruit with storage issues. It is well documented in many crops, including apples, about the positive interaction between nitrogen and potassium.
Potassium ions act as a carrier for nitrate from root to leaf, where proteins are synthesised and photosynthates are metabolised. So with adequate potassium input balancing out the nitrogen input, nitrogen is much more efficiently metabolised to useful components such as amino acids and proteins and so yield potential is optimised and quality maximised. Potassium could be viewed somewhat as an antidote to excessive nitrogen levels.