Isolation and immobilization of dextransucrase from leuconostoc mesenteroides cultures

The time course of dextransucrase production by immobilized cells of Leuconostoc mesenteroides DSMZ 20241 in calcium alginate beads, the concentration of alginate gel, the size of bead inoculum and the successive reuse of beads were studied. Isolation and partial purification of the crude dextransucrase were carried out by fractional precipitation with acetone or ammonium sulfate separately. The fraction obtained at 75% ammonium sulfate saturation was most active. Further purification was conducted by gel filtration on sephadex G-100 and the most active protein peak was rechromatographed on CM-sephadex C-50. Immobilization of the purified enzyme on various supports was carried out. The enzyme had a relatively low thermostability, but the immobilized enzyme was more resistant to different heat treatments than the free enzyme. Some ions as Zn+2 and lead partially inhibited the activities of different purified dextransucrase preparations, while other ions as Ca+2 and Fe+3 enhanced their activities

Optimization of different cultural conditions for m-cresol degradation by free and immobilized bacillus laterosporus cells

Optimization of the cultural conditions that facilitate the degradation of m-cresol by a locally isolated bacterial strain Bacillus laterosporus free and entrapped cells was attempted. Bacterial cells entrapped in 2% Ca-allginate beads were more active than free cells and showed a 20% higher rate of m-cresol degradation. Medium No. 1 was most favorable for m-cresol utilization. Supplementing the medium with yeast extract stimulated degradation especially at concentration 0.2 g/l. Optimum concentration of ammonium salts, phosphate salts and magnesium sulfate were 3 g/l and 1.5 g/l, respectively. Optimum concentration of trace elements was 4 ml/l and its omission reduced the rate of degradation. Initial pH of the medium that gave the highest rate of degradation was pH 7 and incubation temperature of 35C. Addition of some amino acids to the mineral medium did not improve degradation rate. The best alginate concentration was 2% and the optimum quantity of beads was 20 ml/ 100 ml medium. The rate of degradation increased by increasing the m- cresol concentration up to 500 mg/l, while higher concentrations [1 g/l] decreased the degradation ability of the entrapped cells

Degradation of meta-cresol in waste waters by entrapped bacillus laterosporus cells

Degradation of m-cresol in different waste water samples instead of the mineral medium was carried out. Meta-cresol degradation in nonsterile waste water was slower than in sterile. However, the entrapped Bacillus laterosporus cells proved to actively degrade m- cresol in all the tested water samples except in the case of two samples collected from El-Max region near Alexandria Harbor. The growth and rate of degradation in both free and entrapped cell cultures were affected by Pb and Hg salts at concentrations higher than 10 mg/l. The rate of degradation was reduced by 75% when 100 mg/l and salts of these metals were present in the medium. Also, the rate of degradation was reduced in presence of 5 mg/l of zinc or cadmium salts. It was noticed that entrapped cells did not show higher resistance than the free cells in presence of the tested heavy metals. The presence of 4-chlorophenol, 4-bromophenol or p- nitrophenol in the medium delayed the degradation time and the rate of degradation was much lower in presence of these substituted phenols together with m-cresol. However, the degradation activity was not completely lost

new approach for the utilization of didymosphearia sp in biocontrol of the black root rot disease of cotton

The gas chromatographic analysis showed the presence of 3-methyl phenol [3-MP] as a major metabolite produced by Didymosphearia sp, cells. Immobilized cell cultures gave the highest yields of 3-MP showing their Superiority over free cells. Presence of tyrosine or phenyl alanirne enhanced the production of 3-MP. Twenty per cent alginate bead concentration was found optimum for the production of the same metabolite. Radial growth of Thielaviopsis basicola was completely inhibited by the culture filtrate of 6-day old mobilized Didymosphaeria. The disease index of cotton seedlings decreased by 34% when the soil was amended with alginate beads entrapping Diymosphaeria cells

Oxidation of N-tetradecane by selected immobilized fungi

Penicillium frequentans, Gibberella fujikuroi and Mortierella isabellina spores were entraped in calcium alginate gel. A 4% glucose and 0.4% ammonium sulfate concentrations were most suitable for a good surface mycelial weft on the beads. The free cells were found to give better growth and higher oxidation of n-tetradecane than the immobilizedd cells of Penicillium frequentans. The utilization of smaller bead size in the entrapment of the same mold greatly activated the formation of oxidation products. A better oxidation was obtained on using an air-lift-reactor