A thermophilic Bacillus stearothermophilus F1 that produced an extremely thermostable alkaline protease was isolated from decomposed oil palm branches. The isolated protease was purified to homogeneity by heat treatment, ultrafiltration and gel filtration chromatography with a 128-fold increase in specific activity and 75% recovery. The protease, which is a serine-type enzyme, has a relative molecular mass of 33 500 by sodium dodecyl sulphatepolyacrylamide gel electrophoresis but only 20 000 by gel-filtration chromatography. The enzyme was optimally active at pH 9.0 and was stable for 24 h at 70° C and in the pH range from 8.0 to 10.0. It was capable of hydrolysing many soluble and insoluble protein substrates but no esterase activity was detected. The enzyme activity was markedly inhibited by Co2+ and Hg2+, whereas Mg2+, Fe2+, Cu2+, Zn2+ and Sr2+ had little or no inhibitory effect. However, Mn2+ strongly activated the protease activity. The protease exhibited a high degree of thermostability [t 1/2 (85° C) = 4 h, (90° C) = 25 min]. The stability at higher temperatures (85° C and above) was shown to be dependent on the presence of Ca2+.

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ABSTRACT:The graft copolymerization of methyl acrylate onto sago starch was carried out by a free radical initiating process. The free radicals were produced by the chemical initiation method in which ceric ammonium nitrate was used as an initiator. It was found that the percentages of grafting, grafting efficiency, and rate of grafting were all dependent on the concentration of ceric ammonium nitrate (CAN), methyl acrylate (MA), sago starch (AGU), mineral acid (H 2 SO 4 ), and reaction temperature and period. The variables affecting the graft copolymerization were thoroughly examined. The optimum yield of grafting was obtained when the concentration of CAN, MA, AGU, and H 2 SO 4 were used at 8.77 ϫ 10 Ϫ3 , 0.803, 0.135, and 0.175 mol L Ϫ1 , respectively. The optimum reaction temperature and period were 50°C and 60 min, respectively. The rate of graft polymerization was explored on the basis of experimental results and reaction mechanism. The evidence of grafted copolymers was investigated by using FTIR spectroscopy, TG, and DSC analysis.

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