Immobilization of alkaliphilic Bacillus sp. cells for xylanase production using batch and continuous culture.

Agar-immobilized alkaliphilic Bacillus sp. AR-009 cells were used for xylanase production using batch and continuous culture. In a batch culture, maximum enzyme production was observed after 48 h and remained high up to 72 h. In repeated batch cultivation, immobilized cells produced an appreciable level of xylanase activity in seven consecutive batches without any significant decline in productivity. For continuous xylanase production, immobilized cells were packed in a jacketed glass column and sterile medium was continuously pumped. A stable continuous production of xylanase was observed over a period of 1 mo. The volumetric productivity of the continuous culture was 17-fold higher than the batch culture using free cells.

Production of raw-starch digesting amyloglucosidase by Aspergillussp GP-21 in solid state fermentation.

Aspergillus sp GP-21 produced a raw-starch digesting amyloglucosidase which showed optimum activity at 65 degrees C and pH 5.0-5.5. At 50 degrees C the enzyme converted about 40% of raw corn starch to glucose within 48 h. Enzyme production was studied in solid state fermentation using wheat bran. Productivity was affected by the level of moisture, incubation temperature and the presence or absence of supplements. Maximum enzyme production was observed at a moisture level of 75% and at 30 degrees C. Enzyme production was stimulated by supplementing wheat bran with 0.25% proteose peptone, 1% trace mineral solution, 0.01% CaCl2 and 0.01% MgSO4.

Purification and properties of two thermostable alkaline xylanases from an alkaliphilic bacillus sp

Two xylanases, designated XylA and XylB, were purified from the culture supernatant of the alkaliphilic Bacillus sp. strain AR-009. The molecular masses of the two enzymes were estimated to be 23 kDa (XylA) and 48 kDa (XylB) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The optimum pHs for activity were 9 for XylA and 9 to 10 for XylB. The temperature optima for the activity of XylA were 60 degreesC at pH 9 and 70 degreesC at pH 8. XylB was optimally active at 75 degreesC at pH 9 and 70 degreesC at pH 8. Both enzymes were stable in a broad pH range and showed good stability when incubated at 60 and 65 degreesC in pH 8 and 9 buffers.

Changes in the antigenic profile of Leishmania parasites following shifts in temperature.

We have examined by immunoblotting the antigen profiles of Leishmania parasites which have undergone upward shifts in ambient temperature during culture. Parasites in the promastigote insect vector stage were grown to stationary growth phase at 25 degrees C, and then further cultured at the 37 degrees C temperature experienced in the mammalian host. Changes in the immunoblot profiles of the parasites occurred within one day of culture at mammalian ambient temperature. Serum antibodies from patients with active Leishmania infections showed reactivity with antigenic determinants of greater than Mr 38,000 that were expressed by parasites at 37 degrees C, and which were not comparably observed on immunoblots of 25 degrees C cultured organisms. The promastigotes of Leishmania species which cause either cutaneous or visceral leishmaniasis express differing forms of the 37 degrees C induced high molecular weight determinants, however, these molecules express cross-reactive epitopes. Previous studies have suggested that temperature may play a role in the differentiation process between the insect and host life cycle stages of Leishmania. Our results suggest that the antigenic profile of Leishmania parasites may also be affected by the expression of products from temperature sensitive biosynthetic pathways.