Some effects of diazinon on the microflora of submerged soils
SummaryThe application of diazinon, an organophosphorus insecticide, at the rate of 2 kg and 20 kg active ingredient per hectare to submerged Maahas clay significantly stimulated the actinomycete population. A distinct zone of brown pigmentation formed in that part of the profile commonly referred to as the oxidized layer. A profuse growth of actinomycetes developed from the soil samples of this pigmented zone when streaked onto the nutrient agar. A visible increase in algal populations was noted in the standing water of the diazinon-treated soil.
Bacterial, Azotobacter, Actinomycetes, and Fungal Population in Soil after Diazinon, Imidacloprid, and Lindane Treatments in Groundnut (Arachis hypogaea L.) Fields
Bacterial, azotobacter, actinomycetes, and fungal populations were determined in groundnut (Arachis hypogaea L.) fields between July and November for three consecutive years (1997–1999) after insecticide treatments. Diazinon was applied for both seed and soil treatments. However, imidacloprid and lindane were used for seed treatments. An average half-life (t 1/2) of diazinon in seed- and soil-treated fields was found to be 29.32 and 34.87 days, respectively. Its residues were found for 60 days in both cases. In diazinon seed treatment, an increase in azotobacter, fungi, and actinomycetes populations was observed in samples from the 15th and 30th days, and this trend continued until crop harvest. However, the bacterial population had not been affected by this treatment. The diazinon soil treatment had indicated some significant adverse effects on fungi and actinomycetes population, which recovered after 30 days. The population of bacteria and azotobacter increased significantly in this treatment. The residues of imidacloprid and lindane were found for 90 and 120 days with an average half-life of 40.9 and 53.3 days, respectively. Imidacloprid had no significant effect on fungi and actinomycetes populations up to 15 days, and between 15 to 60 days some adverse effects were indicated. However, some significant increases in bacterial and azotobacter population were observed. Lindane had no effect on bacterial and fungal population. However, its adverse effects were observed in actinomycetes and azotobacter populations between 30 to 60 days.
l-Phenylalanine dehydrogenase from Brevibacterium sp. for production of l-phenylalanine by reductive amination of phenylpyruvate
SummaryFor production of l-phenylalanine the reductive amination of phenylpyruvate, catalyzed by phenylalanine-dehydrogenase was examined. To reach high levels and a sufficient stability of the inducible intracellular enzyme, growth conditions of Brevibacterium sp. are optimized. For continuous production of l-phenylalanine in an enzyme membrane reactor, the kinetic parameters of the partially purified enzyme are determined.In continuous production a space time yield of 37.4 g l-Phe l-1 d-1 can be reached.By means of the measured kinetic parameters and simultaneous calculation of the mass balances of all reaction components the behaviour of the reactor can be simulated. For certain conditions the multi-enzyme-system shows multiple steady-states.