초록
Precipitation of insoluble complexes between alpha-amylase from Aspergillus oryzae and polyacrylic acid was studied by us in a previous work as a strategy of protein concentration and purification. Here we studied the effect of these polyelectrolytes on the stability of the enzyme at the pH of higher interaction (3.00), as well as the stability of the precipitates formed after applied the above methodology. The polymers showed a stabilizing effect on the activity of alpha-amylase at pH 3.00, given the kinetic constants achieved when adjusting the experimental data to a process of first order inactivation: 2.20e<SUP>-2</SUP>+/-2e<SUP>-3</SUP> for alpha-amylase alone, 7.7e<SUP>-3</SUP>+/-3e<SUP>-4</SUP> and 8.2e<SUP>-3</SUP>+/-2e<SUP>-4</SUP> for polyacrylic acid 240,000 and 100,000, respectively. Also, this stabilizing effect is intensified when complexes are in the solid precipitated form before redissolve, given the lower kinetic constants of inactivation obtained: 1.7e<SUP>-3</SUP>+/-2e<SUP>-4</SUP> and 2.6e<SUP>-3</SUP>+/-2e<SUP>-4</SUP> for polyacrylic acid 240,000 and 100,000, respectively. In a subsequent step, a strain of A. oryzae was used as enzymatic source. In order to stimulate alpha-amylase production and secretion by the microorganism, we used a minimum culture medium with wheat processing residues as substrate. This has economic and environmental benefits, because of the recycling of agricultural wastes. This culture showed a maximum productivity at the fourth day of incubation. When the technique of concentration and purification of alpha-amylase was implemented from this culture we obtained purification factors around two and recoveries around 70%. These results demonstrate that this methodology is suitable for the concentration and purification of alpha-amylase from A. oryzae. Besides, it is inexpensive since it uses agricultural materials without commercial value.