Effects of Vitreoscilla hemoglobin on the 2,4-dinitrotoluene (2,4-DNT) dioxygenase activity of Burkholderia and on 2,4-DNT degradation in two-phase bioreactors

Abstract

Expression of vgb, encoding Vitreoscilla hemoglobin (VHb), in Burkholderia strain YV1 was previously shown to improve cell growth and enhance 2,4-dinitrotoluene (2,4-DNT) degradation compared with control strain DNT, especially under hypoxic conditions. In the work reported here, the ratio of 2,4-DNT degraded to oxygen uptake was approximately 5-fold larger for strain YV1 than for strain DNT. The addition of purified VHb to cytosolic fractions of strain DNT increased 2,4-DNT degradation 1.5-fold, compared with 1.1-fold for control bovine Hb, but increased the 2,4-DNT degradation 2.7-fold when added to partially purified 2,4-DNT dioxygenase, compared with 1.3-fold for bovine Hb. This suggests a direct transfer of oxygen from VHb to the oxygenase. In a bioreactor at high 2,4-DNT concentration (using 100 ml oleyl alcohol containing 2 g 2,4-DNT as the second phase) with 1.5 l culture, both strains could remove 0.8 g 2,4-DNT by 120 h; and, under the same conditions in a fed-batch reactor, the degradation increased to 1 g for strain YV1 but not for strain DNT.

Role of Hemoglobin in Improving Biodegradation of Aromatic Contaminants under Hypoxic Conditions

“…Burkholderia strain DNT is an aerobic bacterium known to degrade a wide range of both aliphatic and aromatic toxic organic chemicals such as trichloroethylene (TCE), trinitrotoluene (TNT) and 2,4-DNT [Haigler et al, 1996;Munakata-Marr et al, 1996;Spanggord et al, 1991;Suen and Spain, 1993;Suen Growth was in shake flasks, except in the case of the Lin et al [2003] experiments, which were run in two-phase bioreactors. Burkholderia is Burkholderia strain DNT.…”

“…Further studies with the Burkholderia system showed that the VHb-related enhancement occurs in a variety of media, and is relatively greater under hypoxic compared with higher aeration conditions [Nasr et al, 2001]. This work was followed by experiments demonstrating a direct stimulation by VHb of the first enzyme in the Burkholderia DNT catabolic pathway, perhaps due to direct delivery of oxygen from VHb to this oxygenase [Fish et al, 2001;Lee et al, 2004;Lin et al, 2003]. At the same time, the initial genetic engineering experiments, which had all been done using vgb carried on plasmid pSC160 [Liu et al, 1995], were extended to show that vgb could be stably integrated into the host chromosome and result in the same enhancement of aromatic compound degradation [Chung et al, 2001;Kim et al, 2005].…”

Expression of Vitreoscilla hemoglobin in Gordonia amarae enhances biosurfactant production

“…There is evidence that the beneficial effects in bacteria are the result of direct interaction of VHb with the terminal respiratory oxidase, delivering oxygen to it to enhance oxidative phosphorylation and thus the production of ATP [16,30,32]. In the case of bioremediation enhancement, a direct delivery of oxygen by VHb to oxygenases which degrade aromatics may occur [20,21].…”

Enhancement of Biodesulfurization in Two-Liquid Systems by Heterogeneous Expression of Vitreoscilla Hemoglobin

“…Similar results were previously observed in the degradation of 2,4-dinitrotoluene (2,4-DNT), which was catalyzed by dioxygenase in Burkholderia spp. (10). Moreover, the Dsz enzymes are soluble and found in the cytoplasm (5,9).…”