Degradation of morpholine by Mycobacterium sp. isolated from contaminated wastewater collected from Egypt

Abstract

The biodegradation of morpholine has attracted much interest because morpholine causes environmental pollution. Ten species belonging to nine genera were tested for their abilities to degrade morpholine in mineral salts medium containing morpholine (1 g/l). Mycobacterium sp. isolated from polluted water sample collected from Abu Za”baal lakes, effectively utilized morpholine as carbon, nitrogen and energy source. The tested Mycobacterium was able to grow in high concentrations of morpholine but the rapidly increase in pH of the growth medium and accumulation of ammonia inhibited bacterial growth and complete mineralization of morpholine. The molar conversion ratio of morpholine to ammonia was 1:0.89. Growing of the selected bacterium in liquid medium with 1 g/l morpholine at 37°C and pH 6.5, enhanced morpholine degradation. Addition of metyrapone to the growth medium inhibited morpholine degradation. Immobilization of Mycobacterium cells in sodium alginate increased morpholine degradation compared with free cells. At high concentrations of morpholine (4 to 6 g/l), there was a decrease in both cell viability and respiration of Mycobacterium but no genotoxicity was found.

Key words: Morpholine, Mycobacterium, biodegradation, pollution, ammonia, cytochrome P450, metyrapone, immobilization.