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