Estudo comparativo da produção, purificação e caracterização das B - amilases de Bacillus megaterium e Bacillus polymyxa

AUTOR(ES)
DATA DE PUBLICAÇÃO

1979

RESUMO

Of 851 micro-organisms (fungi and bacteria) obtained from various sources (soil, water, vegetables) two strains of β-amylase producing bacteria were isolated, employing potato agar and nutrient agar as culture media. These strains were identified as Bacillus megaterium and Bacillus polymyxa. The β -amylase.production of these bacteria was studied at different temperatures to determine the best temperature range of fermentation. The range for Bacillus megaterium was between 26°-29°C and for Bacillus polymyxa between 34°-36°C. The effect of various carbohydrate and nitrogen sources and their concentrations was also studied. The best culture medium for the β -amylase production by Bacillus megaterium was: 0,5% starch, 1% soybean flour, 1% of yeast extract and in the case of Bacillus polymyxa: 2% starch, 1% casein, 1% of yeast extract. The method used for assessing the production of β -amylase in relation to pH and cellular mass, was rotatory shake and mini-fermentation at the temperature of 28°C for Bacillus megaterium and 35°C for Bacillus polymyxa, during 60 hours. After centrifugation the supernatant of the culture was used as the S-amylase source and purified as follows: pre¬cipitation was effected with 80% solution of (NH4)2S04; the precipitate was dialised and fractioned using DEAE-cellulose and CM-cellulose columns. A comparative characterization of the activity of the β -amylases obtained, showed following resu1ts: best conditions for Bacillus megaterium were pH 6.5 and a temperature of 40°-45°, the enzyme being stab1e in the range of pH 5.0-7.5 and inactiv¬ated above 55°C. The km was 0.52mg/ml, Vmax 1.02~mol/min/mg, and the percentage of starch hydro1ysis was 61.3. For Bacillus polymyxa the optimum pH and temperature were 7.0 and 450C, respectively, the enzyme being stab1e in the range between pH 4.0 and 9.0, and inactivated above 60°C. The km was 1.92mg/ml, Vmax 1.04μmo1/min/mg and the degree of starch hydrolysis was 68.8%.

ASSUNTO(S)

microorganismos quimica microbiologica

ACESSO AO ARTIGO

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