Hydrogen peroxide degradation by immobilized cells of alkaliphilic Bacillus halodurans

Whole cells of Bacillus halodurans LBK 261 were used as a source of catalase for degradation of hydrogen peroxide. The organism, B. halodurans grown at 55 degrees C and pH 10, yielded a maximum catalase activity of 275U g(-1) (wet wt.) cells. The catalase in the whole cells was active over a broad range of pH with a maximum at pH8-9. The enzyme was optimally active at 55 degrees C, but had low stability above 40 degrees C. The whole cell biocatalyst exhibited a K m of 6.6mM for H2O2 and V max of 707mM H2O2 min(-1) g(-1) wet wt. cells, and showed saturation kinetics at 50mM H2O2 . The cells were entrapped in calcium alginate and used for H2O2 degradation at pH 9 in batch and continuous mode. In the batch process, the immobilized preparation containing 1.5g (wet wt.) cells could be recycled at least four times for complete degradation of the peroxide in 50mL solution at 25 degrees C. An excess of immobilized biocatalyst could be used in a continuous stirred tank reactor for an average of 9 days at temperatures upto 55 degrees C, and in a packed bed reactor (PBR) for 5days before the beads started to deform.