Contribuição ao estudo das condições de fermentação para produção de L-asparaginase por Erwinia aroidease
AUTOR(ES)
Luis Antonio Minim
DATA DE PUBLICAÇÃO
1991
RESUMO
Cell growth and enzyme formation were studied in batch fermentation for the purpose of obtaining L-asparaginase from Erwinia aroideae. Initially, the influence of some nutrients on the L-asparaginase production and cell growth, on synthetic medium in Erlenmeyrs flasks were investigated. The optimum lactose concentration was 1% when the enzyme and cell mass reached 0.102UI/ml and 1.45 g/l, respectively. Above this limit the production of enzyme was inhibited and the cell mass remained constant. The addition of asparagine into the medium enhanced L- asparaginase production. Cell mass and L-asparaginase activity reached 1.64 g/l and 0.17 UI/ml, respectively, with a 0.4% asparagine concentration. Above this limit, the increase in the cell mass and L-aspaginase activity was reduced. There was no inhibition up to 1.6% of asparagine concentration. Using diluted powdered cheese whey, as a nutrient suply, the production of cell mass and enzyme was insignificant when the whey lactose Concentration was 1%. The optimum whey lactose concentration was 3%, obtaining a maximum L-asparaginase activity of 0.11 UI/ml. Supplementing the diluted powdered cheese whey (2.73%) with 0.3% of triptone and 0.5% of asparagine, the production of cell mass and L-asparaginase had a great enhancement, achieving 0.542 UI/ml of L-asparaginase activity and 4.52 g/l of cell mass, greater than the production when yeast extract was used. Pilot plant fermentation experiments were made in a 16 liters fermenter; powdered cheese whey was used diluted (2.73%), complemented with 0.3% of triptone and 0.5% of asparagine, as a fermentative medium. Optimum temperatures for L-asparaginase and cell mass production were 24.5°C and 28°C, respectively. Maximum L-asparaginase Activity (2.02 UI/ml) was obtained at 24.5°C, 500 rpm of agitation and 7.5 l/min of aeration; the cell mass concentration was 5.88 g/l. When the temperature was increased from 24.5°C to 28°C the enzymatic activity decreased 39%. Activation energy of cell growth was 8034 cal/mol. The pH controlled process, compared with the process without control, did not give satisfactory results. Increase of oxigen incorporation into the medium enhanced the production of L-asparaginase and cell mass.
