| Abstract: | Summary Although pineapple plants have been found to produce proteases ex vitro, most of the biotechnological investigations of this crop have been focused on propagation. The procedure involving the use of temporary immersion bioreactors is one of the most outstanding because of its high multiplication rate. We previously recorded specific protease activity in the culture medium during the pre-elongation step of this protocol. Therefore, we decided to modify the culture medium composition of this phase looking for an increase in protease excretion. Four independent experiments were performed to evaluate the effects of different levels of sucrose (0–350.4 mM), inorganic salts [0–200% Murashige and Skoog (MS) salt strength], inositol (0–2.20 mM), and thiamine (0–1.2μM). The following indicators were recorded: shoot fresh mass per bioreactor; and protein concentration, proteolytic activity, and specific protease activity in culture media. Specific protease activity, the most important indicator recorded, was highest with 262.8 mM sucrose, 100% MS salt strength, 0.3 μM thiamine and no inositol. Results shown here demonstrate that conditions adequate for propagation purposes (87.6 mM sucrose, 100% MS salt strength, 0.55 mM inositol, 0.3 μM thiamine) are not always adequate for protease excretion. |
