S.B. Prusiner proposed that the infectious agent of scraple, the prion, is PrPSc, a modified form of the normal host protein PrPC. Prn-p0/0 mice devoid of PrPC showed normal development and behavior. When inoculated with mouse scrapie prions, they remained free of scrapie symptoms for at least 13 months while wild-type controls all died within 6 months. Surprisingly, heterozygous Prn-p0/+ mice also showed enhanced resistance to scrapie. After introduction of Syrian hamster PrP transgenes, Prn-p0/0 mice became highly susceptible to hamster but not to mouse prions. These experiments show that PrPC, possibly at close to normal levels, is required for the usual susceptibility to scrapie and that lack of homology between incoming prions and the host's PrP genes retards disease.

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The fungus commonly used in tempeh production, Rhizopus oligosporus (DSMZ 1964), was grown in rice flour suspension and two intracellular phytases (RO1 and RO2) were isolated from the fungus, purified to near homogeneity in a five-step process and characterized. Enzyme recoveries after purification were 1.3% (RO1) and 1.6% (RO2) in relation to the phytase activity in the crude extract. Their estimated molecular mass was 45.0 Ϯ 5.0 kDa. The purified proteins belong to the acid phytases and they both exhibit two distinct pH optima at 3.0 and 4.5 for RO1 and 3.0 and 5.0 for RO2. Optimal temperature for the degradation of sodium phytate was determined to be 60C for RO1 and 55C for RO2. Kinetic parameters for the hydrolysis of sodium phytate were K m = 1.6 mM (RO1) and 0.13 mM (RO2) and V max = 0.044 U for RO1 and 0.155 U for RO2. The phytases from R. oligosporus exhibit a broad affinity for various phosphorylated compounds. PRACTICAL APPLICATIONSThis work reports the isolation, purification and characterization of two intracellular phytases from the tempeh fungus Rhizopus oligosporus. Interest 4 Corresponding in these enzymes has been stimulated by the fact that phytase supplements increase the availability of phosphorus in pig and poultry feed, and thereby reduce environmental pollution due to excess phosphate excretion in areas where there is intensive livestock production. One of the purified phytase fractions RO2 showed promising enzymatic properties such as low K m for phytate. This could be exploited for further biotechnological applications especially in the feed industry.

This study evaluates the quality of chilled squid Loligo vulgaris by non-destructive measurements of bioelectrical impedance from the first post-mortem day under controlled conditions. Squid samples were stored at 4.5 °C and 55% of relative humidity for 11 days. Impedance magnitude (|Z|) and phase (φ) at 200 frequencies (100Hz to 100MHz) were measured using an Agilent 4294A Precision Impedance Analyzer with needle-type multi-electrode array on days 1, 2, 3, 4, 5, 8, 9, 10, and 11 of storage. The changes in color, sensory properties, total volatile nitrogen, pH, and water holding capacity were also determined. The obtained results indicated that the samples could be classified into five to six distinctive groups by measuring the electrical parameters at frequencies close to 5MHz. In general, φ is less dependent on temperature and measurement setup than |Z|, while records at 5MHz correlate well with the days of storage (R2 = 0.968). The data imply that it is only possible to estimate the length of storage for the samples with measurements of phase angle, which can be useful for the development of new analytical instruments. Biosensors have a practical industrial application, as it is demonstrated that bioelectrical impedance data correlates well with the days of chilled storage.