Protease production by thermophilic Bacillus sp strain SMIA-2 cultivated in liquid cultures containing trisodium citrate reached a maximum in 9h, with levels of 1.93U/mg protein. The microorganism utilized several carbon sources for the production of protease. Starch was the best substrate, followed by trisodium citrate, citric acid and sucrose. Among the various organic and inorganic nitrogen sources, ammonium nitrate was found to be the best. Studies on the protease characterization revealed that the optimum temperature of this enzyme was 60ºC. The enzyme was stable for 2h at 30ºC, while at 40ºC and 80ºC, 14% and 84% of the original activities were lost, respectively. The optimum pH of the enzyme was found to be 8.0. After incubation of crude enzyme solution for 24h at pH 5.5, 8.0 and 9.0, a decrease of about 51%, 18% and 66% of its original activity was observed respectively. A stronger inhibitory effect was observed in the presence of K + , Hg 2+ and Cu 2+ . Hg + resulted in the complete loss of activity at 1mM concentrations. Activity was stimulated by Mn 2+ and Ca +2 , indicating that these ions had a functional role in the molecular structure of the enzyme.

No abstract

Studies on the α-amylase production were carried out with a bacterial strain isolated from a soil sample. The cells were cultivated in a mineral medium containing soluble starch as sole carbon source. The addition of calcium (10 mM) or peptone (1%) and yeast extract (0.5%) to the mineral medium shortened the lag period and improved the growth and α-amylase synthesis. The addition of glucose to the culture diminished greatly the synthesis of α-amylase, demonstrating that a classical glucose effect is operative in this organism. The optimum temperature and initial medium pH for amylase synthesis by the organism were 50°C and 7.0 respectively. The optimal pH and temperature for activity were 6.0 and 50°C respectively. The enzyme extract retained 100% activity when incubated for one hour at 90°C and 40% at 60°C for 24 h. The addition of glucose to the culture diminished greatly the synthesis of α-amylase.

α-amylase (1,4-α-D-glucan glucanohydrolase, EC 3.2.1.1) production by thermophilic Bacillus sp strain SMIA-2 cultivated in liquid media containing soluble starch reached a maximum at 48h, with levels of 57U/ mL. Studies on the α-amylase characterization revealed that the optimum temperature for activity was 70ºC. The enzyme was stable for 2h at 50ºC, while at 60ºC, 70ºC and 90ºC, 4%, 13% and 38% of the original activities were lost, respectively. The optimum pH of the enzyme was 7.5. After incubation of crude enzyme solution for 24h at pH 7.5, a decrease of about 5% of its original activity was observed. The enzyme was strongly inhibited by Co 2+ , Cu 2+ and Ba 2+ , but less affected by Ca 2+ , Mg 2+ , Ni 2+ , Sr 2+ and Mn 2+. The enzyme in 1M and 5M NaCl solutions the enzyme retained 70% and 47% of the original activity after 24h of incubation at 4ºC, respectively.

α-Amylase production by thermophilic Bacillus sp strain SMIA-2 cultivated in liquid cultures containing soluble starch as a carbon source and supplemented with 0.05% whey protein and 0.2% peptone reached a maximum activity at 32 h, with levels of 37 U/mL. Studies on the amylase characterization revealed that the optimum temperature of this enzyme was 90ºC. The enzyme was stable for 1 h at temperatures ranging from 40-50ºC while at 90ºC, 66% of its maximum activity was lost. However, in the presence of 5 mM CaCl2, the enzyme was stable at 90ºC for 30 min and retained about 58% residual activity after 1 h. The optimum pH of the enzyme was found to be 8.5. After incubation of enzyme for 2 h at pH 9.5 and 11.0 was observed a decrease of about 6.3% and 16.5% of its original activity. At pH 6.0 the enzyme lost about 36% of its original activity. . In the presence of 2.0 M NaCl, 63% of amylase activity was retained after 2 h incubation at 45ºC. The amylase exhibited more than 70% activity when incubated for 1 h at 50ºC with sodium dodecyl sulphate. However, very little residual activity was obtained with sodium hypochlorite and with hydrogen peroxide the enzyme was completely inhibited. The compatibility of Bacillus sp SMIA-2 amylase with certain commercial detergents was shown to be good as the enzyme retained 86%, 85% and 75% of its activity after 20 min incubation at 50ºC in the presence of the detergent brands Omo ® , Campeiro ® and Tide ® , respectively.