Evaluation of growth, carbazole biodegradation and anthranilic acid production by Pseudomonas stutzeri

Abstract

-The proportion of nitrogenated compounds such as carbazole in heavy fractions of crude oil is higher in Brazil than in other parts of the world. The degradation of this compound by microorganisms has already been described for bacteria such as Pseudomonas stutzeri ATCC 31258. Assays were undertaken to assess the influence of different carbazole concentrations on cell growth, carbazole degradation and the formation of anthranilic acid (an intermediate in the carbazole degradation pathway). The results indicated that there was an accumulation of anthranilic acid in the medium with the higher concentration of substrate (10 g/L), which could be related to the inhibition of Pseudomonas stutzeri growth in an excess of carbazole. With 1 g/L of carbazole, growth was found to be ten times greater (0.37 g dry cell weight/L) and there was no accumulation of anthranilic acid (formation of around 7 mg/L), with complete carbazole degradation after three days.

Enhancement of Carbazole Denitrogenation Rate Using Magnetically DecoratedBacillus clausiiBS1

“…Inhibition of cell growth and denitrogenation activity by the by-products of CAR denitrogenation; ANA and CAT is known to be severe (Larentis et al, 2011), so this experiment was carried out to investigate the effect of different initial concentrations of ANA and CAT on the efficiency biodenitrogenation efficiency.…”

“…The denitrogenation activity of various microbial strains capable of denitrogenating CAR or its derivatives reported to be inhibited in the enzyme level by anthranilic acid and catechol, which consequently would inhibit cell growth and biodenitrogenation efficiencies (Larentis et al, 2011).…”

“…The growth and biodenitrogenation efficiencies of free cells were sharply decreased at higher initial concentrations of ANA and CAT (250 ppm), recording ≈ 7 I/Io, with CAR removal of ≈ 43% and final ANA and CAT concentrations of ≈ 283 and 280 ppm, respectively. Larentis et al (2011) reported that the growth of Pseudomonas stutzeri was 10 times lower after the accumulation of 140 ppm anthranilic acid. That proves the good tolerance of B. clausii BS1 to high concentrations of ANA and CAT.…”

“…CAR, the major nonbasic species, directly impacts the refining process in two ways: (a) it is converted during cracking into basic derivatives that can adsorb to the active sites of the cracking catalyst and (b) it is unexpectedly potent as a direct inhibitor of hydrodesulfurization, which is commonly included in the refining process in order to meet sulfur-content criteria. Finally, the presence of nitrogen compounds promotes the corrosion of refining equipment such as storage tanks and piping, which adds to the refining costs (Larentis et al, 2011). Nitrogen heteroaromatics can be eliminated from petroleum using high pressure and temperature hydroteating, but such process is expensive and hazardous.…”

“…These appear likely to cause less catalyst inhibition than their parent compound, and many polar intermediates could readily be extracted from petroleum streams into water, as nontoxic metabolites (Li et al, 2013). Many researches have focused on the isolation and identification of carbazole-biodenitrogenation (CAR-BDN) microorganisms, studying their BDN pathway as well as the genes and enzymes involved (Ouchiyama et al, 1993;Gai et al, 2007;Larentis et al, 2011;Singh et al, 2011), and rarely have focused on increase the rate of BDN, or development of immobilization method to increase the activity, stability, recovery, and reusability of the microorganisms.…”