Biodegradation of PAHs by fungi in contaminated-soil containing cadmium and nickel ions

Abstract

The study investigated the degradation of the polycyclic aromatic hydrocarbons (PAH) benzo(a)anthracene, benzo(a) fluoranthene, benzo(a) pyrene, chrysene and phenanthrene in a soil that was sterilized and inoculated with the nonligninolytic fungi, Fusarium flocciferum and Trichoderma spp. and the ligninolytic fungi, Trametes versicolor and Pleurotus ostreatus in the presence of cadmium (Cd) and nickel (Ni) during a ten week incubation period. The soil pH was initially 5.3 and after amendment increased to 7.0. The fungi degraded the tested PAHs between 21 and 93% by the end of the tenth week. The fungi degraded the less-soluble PAHs containing five or six aromatic rings more slowly than those containing fewer aromatic rings. Although the presence of cadmium and nickel in the soil affected the activity of the enzymes produced by the fungi, no significant decrease in PAH degradation was found in the contaminated soil containing 50 or 100 mg kg -1 of Cd and Ni. However, at 300 and 500 mg kg -1 , degradation of the PAHs by the fungi was impaired and the severity of the impairments increased with the increase in the concentrations of Cd and Ni. This was probably due to the lack of the activities of some enzymes such as Mn-dependent peroxidase, which could have resulted from the poor colonization of the fungi at these concentrations.

Bioaugmentation of Native Fungi, an Efficient Strategy for the Bioremediation of an Aged Industrially Polluted Soil With Heavy Hydrocarbons

“…The detailed PAHs biodegradation efficiencies in B and BS were respectively: 36.12 and 8.17% for benzo(b,k)fluoranthene; 42.27 and 11.73% for benzo(a)pyrene, and 28.27 and 5.88% for benzo(g,h,i)perylene. This result is rather coincident with the criterion that correlates the increase in recalcitrance of PAHs with the molecular weight and number of aromatic rings, as described previously (Atagana, 2009;Serrano Silva et al, 2009), though such conclusions have been contested by other authors (Tiehm et al, 1997;Rafin et al, 2000;Wu et al, 2008;Hesham et al, 2016;Fayeulle et al, 2019). The efficient removal of benzo(a)pyrene could be explained by the relatively high initial concentration of this PAH, which could generate concentration gradients that enhanced its mass transfer rate toward microorganisms, as described previously by Li et al (2007).…”

“…Chemical analysis showed a total nitrogen and phosphorous content of 300 mg-N kg −1 and 6 mg-P kg −1 , respectively, a moisture of 12% (w/w), and a water holding capacity 34% (w/w). Elemental analysis yielded a molar ratio C(carbon):H(hydrogen):N(nitrogen):S(sulfur) of 13:3:0.2:0.6, which indicated that the C:N ratio was slightly above the recommended values (25:1:1 to 38:1:1), according to Atagana (2009) and Alexander (1999), for the fungal PAHs bioremediation under an optimum water and oxygen content. The comparative elemental analysis of a pristine soil sample taken near the polluted site under study indicated that the carbon content in the later was increased from 2% up to 13% (Supplementary Table 1).…”

Effect of Nickel as Stress Factor on Phenol Biodegradation by Stenotrophomonas maltophilia KB2

“…Nickel is one of the elements necessary for the growth of microorganisms and plays essential roles in various microbial cellular processes when incorporated into nickel-dependent enzymes (acetyl CoA decarbonylase/synthase, urease, methylenediurease, Ni-Fe hydrogenase, carbon monoxide dehydrogenase, methyl coenzyme reductase) [18]. In excessive amounts, it becomes toxic to microorganisms, which in turn leads to inhibition of the bacteria growth and decomposition of organic compounds [19,20]. Four mechanisms of nickel toxicity are distinguished: (a) Ni replaces the essential metal of metalloproteins, (b) Ni binds to catalytic residues of non-metalloenzymes, (c) Ni binds outside the catalytic site of an enzyme to inhibit allosterically, (d) Ni indirectly causes oxidative stress [18,21,22].…”

“…In the case of other hydrocarbons, the presence of Ni 2+ ions caused: acceleration of the toluene degradation by P1 and P19 strains [33] and inhibition of the crude oil or phenanthrene biodegradation [20,[34][35][36][37]. The bacteria: Pseudomonas aeruginosa CA207Ni, Burkholderia cepacia AL96Co and Corynebacterium kutscheri FL108Hg grew in hydrocarbon media amended with nickel and cobalt (at 5.0 mM) without any changes due to metal toxicity.…”

“…The shift between Proteobacteria and Actinobacteria was beneficial to the removal of the organic pollutant [39]. Significant factors determining the course of microbial transformation are metal concentration and molecular weight of the compound, which could be due to their physical and chemical properties, which are a function of the number of rings in their structure [20,40].…”