ISOLASI DAN IDENTIFIKASI BAKTERI PENGHASIL PROTEASE YANG DISKRINING DARI TERASI

<em>Terasi</em><em> is a traditional fermented shrimp paste of Indonesia popularly used as an important ingredient in many Indonesian cuisines, and further screened for their protease-producing bacteria. A total of 117 bacterial isolates were retrieved from 4 terasi samples. When inoculatedusing skim milk agar, 71 isolates (~61%) produced distinct clear zones implying their proteolytic activity. A bacterial isolate namely Bacillus S2-3 wasselected for further study due to its widest clear zones when thebacterial cells and culture supernatant were used. This strain could grow up to 60^oC with a broad pH range of 5 – 9. The optimal growth condition was at pH 6 and 37^oC. The enzyme activity was also characterized using azocasein method. The optimal pH of bacterialenzymes was between 6 and 7 whereas the optimal temperature of BacillusS2-3 proteases was 22 – 24^oC. For thermostability, the S2-3 enzymes remained active up to 2h at 40 and 50^oC. The results ofbiochemical tests, BacillusS2-3 was identified as Bacillussubtilis, later explored it is potential for the purposes for food industry</em>

DEFECT PHYSICS AND INTRINSIC p-TYPE CONDUCTIVITY IN TOPOLOGICAL INSULATOR AuTlS2

Using first-principles calculations, we systematically investigate the defect physics in topological insulator AuTlS 2. An optimal growth condition is explicitly proposed to guide for the experimental synthesis. The stabilities of various native point defects under different growth conditions and different carrier environments are studied in detail. We show that the p-type conductivity is strongly preferred in AuTlS 2, and the band gap can be engineered by the control of intrinsic defects. Our results demonstrate that AuTlS 2 is an ideal p-type topological insulator which can be easily integrated with traditional semiconductor.

The Growth Of High-Quality MCT Films by MBE Using in Situ Ellipsometry

The ellipsometry and RHEED study of MCT grown on (112) CdTe and GaAs by MBE was carried out. The dependence of ellipsometric parameter on composition is evaluated. As shown we can measure the growth rate, the roughness changing, initial temperature and composition by ellipsometry in situ. We investigated the evolution of roughness of film surface. We observed the appearance of surface roughness at initial stage of MCT growth under various composition (XcdTe0÷0.4). The following growth in optimal growth condition (including constancy of substrate temperature) gives us the smoothing of the surface and supplies us the high-quality MCT films. It is found that under constant temperature of substrate heater we can not grow the thick, perfect film of MCT. The concentration, mobility and life time of carriers in MCT films were respectively: n=1.8*1014 ÷8.2*1015cm−3, μn=44000÷370000cm2 V−1 s−1, τ=40÷220ns;p=1.8*1015÷8.4*1015 cm−3, μp=215÷284 cm2V−1 s−1 τ=12÷20ns.