The source and content of vitamin B12 in the tempehs.

Vitamin B12 contents were determined on 10 commercial tempeh samples purchased from various markets in Jakarta, Indonesia. A relatively high vitamin B12 content was found, i.e., 19 ng/g (ranges from 1.8 to 41.4 ng/g). As soybeans contain no vitamin B12, the amount of vitamin in the tempeh must therefore be derived from the other sources during the fermentation process. The tempeh prepared in the laboratory by inoculation of the commercial starter into the sterile soybean contained a much higher amount of vitamin B12, 127 ng/g (ranges from 122 to 136 ng/g). Pure mold and a single species of bacteria were isolated from the starter and commercial tempehs. Pure mold did not produce vitamin B12 in the sterile broth, soybean and medium used for vitamin B12 production. Only the isolated bacteria, identified as K. pneumoniae, could produce vitamin B12 in those substrates. The presence of mold did not significantly enhance or inhibit the vitamin B12 production by K. pneumoniae. It was, therefore, concluded that K. pneumoniae, the bacteria contaminated during the process of tempeh production, was responsible for the vitamin B12 production.

Superoxide dismutase and catalase activities of cultured erythrocytes infected with Plasmodium falciparum.

It has already shown that catalase activity is significantly decreased in red cells of patients with P. falciparum. The mechanism suggested was by this enzyme inactivation through increased H2O2 generated during malarial infection. The present study was performed to verify this hypothesis. Catalase activities of red cells with high or low parasitemia in patients with P. falciparum were found to be lower than those of normal red cells. However, P. falciparum-infected red cells cultured for one week showed similar SOD and catalase levels to normal red cells. There was also no significant difference in the catalase levels between the parasitized and non-parasitized red cells. The difference in catalase activity of infected red cells before and after culture could be explained in terms of the activation of mononuclear cells and macrophages in vivo. During the sojourn of the parasitized red cells in close proximity to the macrophages of the spleen, they might trigger oxidative bursts resulting in increased H2O2. In order to protect themselves from oxidant damage, the catalase in the infected red cells could be inactivated by H2O2 resulting in the reduction of this enzyme.