Biodegradation of bisphenol-A in river sediment.

This research investigated the aerobic and anaerobic degradation of bisphenol-A (BPA) in river sediment. With the addition of 250 µg g⁻¹ BPA, the percentages of BPA remaining in sediment from sites A, B, and C were 21.9 %, 3.5 % and 12.5 %, respectively, after 5 days of incubation under aerobic conditions; degradation was not significant after 140 days of incubation under anaerobic conditions. The aerobic degradation of BPA was enhanced by adding yeast extract (5 mg L⁻¹), sodium chloride (1 %), cellulose (0.96 mg L⁻¹), brij 30 (55 µM), brij 35 (91 µM), rhamnolipid (130 mg L⁻¹), or surfactin (43 mg L⁻¹), with rhamnolipid yielding higher BPA degradation than the other additives. 2,4-bis (1,1-dimethyl ethyl) phenol, an intermediate product resulting from the aerobic degradation of BPA was accumulated in sediments. Of the bacterial strains isolated from the sediment, strains J1, J2, J3, and J4 expressed the best aerobic degrading ability. The highest BPA degradation rate was found in the sediment by the addition of strains J1, J2, J3, and J4 combined, whereas the sediment without the addition of the 4 strains had the lowest biodegradation rate. This research offers feasible methods for the removal of BPA in river sediment for bioremediation.

Biodegradation of phthalate esters in polluted soil by using organic amendment.

This study investigated the biodegradation of the phthalate esters (PAEs) di-n-butyl phthalate (DBP) and di-(2-ethyl hexyl) phthalate (DEHP) in sludge and sludge-amended soil. DBP (100 mg kg(-1)) and DEHP (100 mg kg(-1)) were added to sewage sludge, which was subsequently added to soil. The results showed that sewage sludge can degrade PAEs and the addition of sewage sludge to soil enhanced PAE degradation. Sludge samples were separated into fractions with various particle size ranges, which spanned 0.1-0.45 µm to 500-2000 µm. The sludge fractions with smaller particle sizes demonstrated higher PAE degradation rates. However, when the different sludge fractions were added to soil, particle size had no significant effect on the rate of PAE degradation. The results from this study showed that microbial strains F4 (Rhodococcus sp.) and F8 (Microbacterium sp.) were constantly dominant in the mixtures of soil and sludge.

Biodegradation of tetrachlorobisphenol-A in river sediment and the microbial community changes.

This study investigated the aerobic degradation of tetrachlorobisphenol-A (TCBPA) in sediment samples collected at three sites along Erren River in southern Taiwan. TCBPA biodegradation rate constants (k(1)) and half-lives (t(1/2)) ranged from 0.03 to 0.06 day(-1) and 11.6 to 23.1 days, respectively. The biodegradation of TCBPA was enhanced by the addition of cellulose, yeast extract, sodium chloride, brij 30, brij 35, surfactin, and rhamnolipid. Of the micro-organism strains isolated from the sediment, we found that strains L1 and L5 (identified as Bacillus megaterium and Pseudomonas putida) expressed the best biodegrading ability. The inoculation of sediment with the TCBPA-degrading bacteria could enhance the efficiency of degradation.

Biodegradation of phenanthrene and pyrene in compost-amended soil.

This study investigated the biodegradation of the polycyclic aromatic hydrocarbons (PAHs) phenanthrene and pyrene in compost and compost-amended soil. The degradation rates of the two PAHs were phenanthrene>pyrene. The degradation of PAH was enhanced when the two PAHs were present simultaneously in the soil. The addition of either of the two types of compost (straw and animal manure) individually enhanced PAH degradation. Compost samples were separated into fractions with various particle size ranges, which spanned 2-50 microm, 50-105 microm, 105-500 microm, and 500-2000 microm. We observed that the compost fractions with smaller particle sizes demonstrated higher PAH degradation rates. However, when the different compost fractions were added to soil, compost particle size had no significant effect on the rate of PAH degradation. Of the micro-organisms isolated from the soil-compost mixtures, strains S1, S2, and S8, which were identified as Arthrobacter nicotianae, Pseudomonas fluorescens, and Bordetella Petrii, respectively, demonstrated the best degradation ability.

Biodegradation of phenanthrene and pyrene from mangrove sediment in subtropical Taiwan.

This study investigated the effects of various factors on the biodegradation of the polycyclic aromatic hydrocarbons (PAHs) phenanthrene and pyrene, and characterized the structure of the microbial community in mangrove sediment from subtropical Taiwan. The degradation of PAH was enhanced by the addition of brij 30, tween 80, yeast extract, hydrogen peroxide, sodium chloride or cellulose. However, PAH degradation was inhibited by the addition of humic acid, di-(2-ethylhexyl), phthalate (DEHP) or nonylphenol. Our results also showed that the addition of various substrates changed the microbial community in mangrove sediment. The strains MS2 (Dyella ginsengisoli) and MS4 (Bacillus pumilus) were the constantly dominant bacteria under various treatments in the mangrove sediment.

Anaerobic degradation of nonylphenol in soil.

This study investigated the effects of various factors on the anaerobic degradation of nonylphenol (NP) in soil. The results show that the optimal pH for NP degradation was 7.0 and that the degradation rate was enhanced when the temperature was increased. The addition of compost enhanced NP degradation. The individual addition of the electron donors lactate, acetate, and pyruvate inhibited NP degradation. The high-to-low order of NP degradation rates under three anaerobic conditions was sulfate-reducing conditions > methanogenic conditions > nitrate-reducing conditions. The results show that sulfate-reducing bacteria, methanogen, and eubacteria are involved in the anaerobic degradation of NP, with sulfate-reducing bacteria being a major component of the soil. Of the anaerobic strains isolated from the soil samples, strain AT3 expressed the best ability to biodegrade NP.

Anaerobic degradation of five polycyclic aromatic hydrocarbons from river sediment in Taiwan.

This study investigated the anaerobic degradation of five polycyclic aromatic hydrocarbons (PAHs) from Erren River sediment in southern Taiwan. The degradation rates of PAH were in the order: acenaphthene > fluorene > phenanthrene > anthracene > pyrene. The degradation rate was enhanced when the five compounds were present simultaneously in river sediment. Comparison of the PAH degradation rates under three reducing conditions showed the following order: sulfate-reducing conditions > methanogenic conditions > nitrate-reducing conditions. The addition of electron donors (acetate, lactate and pyruvate) enhanced PAH degradation under methanogenic and sulfate-reducing conditions. However, the addition of acetate, lactate or pyruvate inhibited PAH degradation under nitrate-reducing conditions. The addition of heavy metals, nonylphenol and phthalate esters (PAEs) inhibited PAH degradation. Our results show that sulfate-reducing bacteria, methanogen and eubacteria are involved in the degradation of PAH; sulfate-reducing bacteria constitute a major microbial component in PAH degradation. Of the microorganism strains isolated from the sediment samples, we found that strain ER9 expressed the greatest biodegrading ability.