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

Abstract

Genetic engineering of bacteria using the Vitreoscilla (bacterial) hemoglobin gene has been used to enhance bioremediation of several compounds which are models for, or are themselves, toxic chemicals which may contaminate soil and water. Initial experiments, done mostly in shake flasks, with Escherichia coli, Burkholderia sp. DNT and Pseudomonas aeruginosa demonstrated that expression of Vitreoscilla hemoglobin in heterologous hosts can enhance biodegradation of several aromatic compounds as well as an organophosphorus compound. These studies concentrated for the most part on enhancement of endogenous catabolic capabilities of the hosts; the presence of vgb/VHb enhanced both growth and biodegradation. The initial studies were followed by experiments in systems which more closely approximated conditions that would exist in field applications. These included soil columns, continuous flow reactors and membrane bioreactors. The latter work also enabled calculation of the effects of the presence of vgb/VHb on kinetic parameters such as growth rate, substrate and oxygen utilization rate, and degradation rate of pollutants, etc. Although not always the case, for the most part, and particularly in bioreactors, the advantages due to vgb/VHb were greater under conditions of limited aeration or hypoxic conditions.

Production of L‐DOPA and dopamine in recombinant bacteria bearing the Vitreoscilla hemoglobin gene

“…This difference was even more profound (up to 30-fold) in post-stationary phase (i.e., 24 h) cultures. These results are all in agreement with previous studies, showing a late-culture-phase dependence of VHb expression and thus its effects on cell growth, metabolism and products formation [30,44,51,76,79,91].…”

Combining co‐culturing of Paenibacillus strains and Vitreoscilla hemoglobin expression as a strategy to improve biodesulfurization

“…Growth promotion by heterologous expression of vgb has been demonstrated in various aerobic bacteria, and is likely due to enhanced delivery of oxygen to the respiratory chain; alternatively, VHb appears to be able to deliver oxygen to oxygenases (the first two steps in the 4S pathway involve addition of oxygen to DBT by dibenzothiophene monooxygenase), and in this way accelerate DBT metabolism (Stark et al . 2008; Stark et al . 2015).…”

Recent advances in understanding the structure, function, and biotechnological usefulness of the hemoglobin from the bacterium Vitreoscilla

“…Following these initial indications that engineering of a heterologous host with vgb could lead to enhanced growth and productivity, a large number of such applications followed (reviewed by Frey and Kallio 2003;Zhang et al 2007;Stark et al 2008). The hosts included both bacteria and eukaryotes, and increases were observed in a variety of parameters including production of cell mass, total protein, individual proteins, antibiotics, and fermentation products, as well as biodegradation of aromatic compounds.…”