Effects of culture conditions on enhancement of 2,4-dinitrotoluene degradation by Burkholderia engineered with the Vitreoscilla hemoglobin gene

Growth and degradation of 2,4-dinitrotoluene (2,4-DNT) were compared in liquid cultures in shake flasks for Burkholderia sp. strain DNT and strain DNT engineered to produce Vitreoscilla (bacterial) hemoglobin (strain YV1). Parameters varied included aeration rate, initial 2,4-DNT concentration (50 and 200 ppm), and concentration and type of cosubstrate (yeast extract, succinate, casamino acids, and tryptic soy broth). 2,4-DNT degradation increased with increasing cosubstrate concentration and was greater for strain YV1 than strain DNT under most conditions tested; the greatest advantages of YV1 (up to 3.5-fold) occurred under limited aeration. A third strain (YV1m), derived from YV1 by repeated growth on 2,4-DNT-containing medium, demonstrated increased 2,4-DNT degradation (up to 1.3-fold compared to YV1) at 200 ppm 2,4-DNT. The growth profiles of the three strains with respect to each other were in general similar to those of the degradation patterns of 2,4-DNT.