Destruction of mixture of tri-hexa-chlorinated biphenyls by Rhodococcus genus strains

Destruction of polychlorinated biphenyls (PCBs) by strain-destructors Rhodococcus sp. B7a and Rhodococcus sp. G12a has been studied. It was shown that these strains destruct 78-95% of PCB mixture containing tri-hexa-chlorinated biphenyls. Rhodococcus destruct all components of the mixture of tri-, tetra-, penta-, and hexa-chlorinated biphenyls without accumulation of toxic chlorinated metabolites. The studied bacteria destruct PCB that are the most stable for oxidation, such as 2,5,2',5'-CB; 3,4,3',4'-CB; and 2,4,5,2',4',5'-CB. The most perspective strains are R. rubber P25, Rhodococcus sp. B7a and Rhodococcus sp. G12a whose metabolic potential can be used for biotechnological refinement of the environment from highly toxic pollutants.     

Specific biodegradation of polychlorinated biphenyls (PCBs) facilitated by plant terpenoids

The aim of this study was to examine how plant terpenoids, as natural growth substrates or inducers, would affect the biodegradation of PCB congeners. Various PCB degraders that could grow on biphenyl and several terpenoids were tested for their PCB degradation capabilities. Degradation activities of the PCB congeners, 4,4′-dichlorobiphenyl (4,4′-DCBp) and 2,2′-dichlorobiphenyl (2,2′-DCBp), were initially monitored through a resting cell assay technique that could detect their degradation products. The PCB degraders,Pseudomonas sp. P166 andRhodococcus sp. T104, were found to grow on both biphenyl and terpenoids ((S)-(−) limonene,p-cymene and α-terpinene) whereasArthrobacter sp. B1B could not grow on the terpenoids as a sole carbon source. The B1B strain grown on biphenyl exhibited good degradation activity for 4,4′-DCBp and 2,2′-DCBp, while the activity of strains P166 and T104 was about 25% that of the B1B strain, respectively. Concomitant GC analysis, however, demonstrated that strain T104, grown on (S)-(−) limonene,p-cymene and α-terpinene, could degrade 4,4′-DCBp up to 30%, equivalent to 50% of the biphenyl induction level. Moreover, strain T104 grown on (S)-(−) limonene, could also degrade 2,2′-DCBp up to 30%. This indicates that terpenoids, widely distributed in nature, could be utilized as both growth and/or inducer substrate(s) for PCB biodegradation in the environment.     

Biodegradation of seven polychlorinated biphenyls by a newly isolated aerobic bacterium (<Emphasis Type="Italic">Rhodococcus</Emphasis> sp. R04)

An aerobic bacterial strain, designated R04, belonging to the genus Rhodococcus has been isolated and characerized by 16S rDNA analysis. The capability of this strain to degrade seven different polychlorinated biphenyls (CBs), 500 ppm 3-CB, 3,4-CB, 4,4-CB, 2,4,6-CB, 2,4,5-CB, 2,3,4,5-CB and 3,4,3,4-CB in liquid medium, was evaluated. After 5 days of incubation, the concentration of chloride increased to 0.35 mM in cultures containing 3-CB and R04, whereas in cultures with 3,4-CB, 2,3,4,5-CB or 3,4,3,4-CB plus R04 the chloride content increased to 0.1 mM. However, non-stoichiometric amounts of chloride were produced in cultures with R04 and 4,4-CB, 2,4,6-CB and 2,4,5-CB. The spectrum of supernatants from R04 grown on seven PCBs had a UV-visible (UV-VIS) absorption at 200–500 nm, characteristic of biphenyl-derived cleavage products. Gas-chromatographic (GC) analysis showed that R04 was able to transform 100% of 3-CB and 3,4-CB after 1 day of incubation, and 95% of 4,4-CB, 2,4,6-CB, 2,4,5-CB, 2,3,4,5-CB and 3,4,3,4-CB after 5 days of incubation. The position of the chlorine substituents on the rings strongly influenced the degradation of polychlorinated biphenyls (PCBs) and their intermediate metabolites by Rhodococcus sp. R04. The degradation of PCBs was further evaluated by monitoring intermediate metabolites of PCBs.     

Characterization of multiple novel aerobic polychlorinated biphenyl (PCB)-utilizing bacterial strains indigenous to contaminated tropical African soils

Contaminated sites in Lagos, Nigeria were screened for the presence of chlorobiphenyl-degrading bacteria. The technique of continual enrichment on Askarel fluid yielded bacterial isolates able to utilize dichlorobiphenyls (diCBs) as growth substrates and six were selected for further studies. Phenotypic typing and 16S rDNA analysis classified these organisms as species of Enterobacter, Ralstonia and Pseudomonas. All the strains readily utilized a broad spectrum of xenobiotics as sole sources of carbon and energy. Growth was observed on all monochlorobiphenyls (CBs), 2,2′-, 2,3-, 2,4′-, 3,3′- and 3,5-diCB as well as di- and trichlorobenzenes Growth was also sustainable on Askarel electrical transformer fluid and Aroclor 1221. Time-course studies using 100 ppm of 2-, 3- or 4-CB resulted in rapid exponential increases in cell numbers and CB transformation to respective chlorobenzoates (CBAs) within 70 h. Significant amounts of chloride were recovered in culture media of cells incubated with 2-CB and 3-CB, suggesting susceptibilities of both 2- and 3-chlorophenyl rings to attack, while the 4-CB was stoichiometrically transformed to 4-CBA. Extensive degradation of most of the congeners in Aroclor 1221 was observed when isolates were cultivated with the mixture as a sole carbon source. Aroclor 1221 was depleted by a minimum of 51% and maximum of 71%. Substantial amounts of chloride eliminated from the mixture ranged between 15 and 43%. These results suggest that some contaminated soils in the tropics may contain exotic micro-organisms whose abilities and potentials are previously unknown. An understanding of these novel strains therefore, may help answer questions about the microbial degradation of polychlorinated biphenyls (PCBs) in natural systems and enhance the potential use of bioremediation as an effective tool for cleanup of PCB-contaminated soils.     

Fungal bioconversion of toxic polychlorinated biphenyls by white-rot fungus, Phlebia brevispora

Toxic coplanar polychlorinated biphenyls (Co-PCBs) were used as substrates for a degradation experiment with white-rot fungus, Phlebia brevispora TMIC33929, which is capable of degrading polychlorinated dibenzo-p-dioxins. Eleven PCB congener mixtures (7 mono-ortho- and 4 non-ortho-PCBs) were added to the cultures of P. brevispora and monitored by high resolution gas chromatography and mass spectrometry (HRGC/HRMS). Five PCB congeners, 3,3′,4,4′-tetrachlorobiphenyl, 2,3,3′,4,4′-pentachlorobiphenyl, 2,3′,4,4′,5-pentachlorobiphenyl, 3,3′,4,4′,5-pentachlorobiphenyl, and 2,3′,4,4′,5,5′-hexachlorobiphenyl were degraded by P. brevispora. To investigate the fungal metabolism of PCB, each Co-PCB was treated separately by P. brevispora and the metabolites were analyzed by gas chromatography and mass spectrometry (GC/MS) and identified on the basis of the GC/MS comparison with the authentic compound. Meta-methoxylated metabolite was detected from the culture containing each compound. Additionally, para-dechlorinated and -methoxylated metabolite was also detected from the culture with 2,3,3′,4,4′-pentachlorobiphenyl, 2,3′,4,4′,5-pentachlorobiphenyl, and 2,3′,4,4′,5,5′-hexachlorobiphenyl, which are mono-ortho-PCBs. In this paper, we identified the congener specific degradation of coplanar PCBs by P. brevispora, and clearly proved for the first time by identifying the metabolites that the white-rot fungus, P. brevispora, transformed recalcitrant coplanar PCBs.     

Degradation of chlorinated biphenyls and products of their bioconversion by <Emphasis Type="Italic">Rhodococcus</Emphasis> sp. B7a strain

Strain Rhodococcus sp. B7a isolated from artificially polluted soil destructs mono- and di-substituted ortho- and/or para-chlorinated biphenyls with utilization of chlorinated benzoic acids and shows high degradation activity as regards trichlorinated biphenyls. It is shown that p-hydroxybenzoic and protocatehoic acids are the products of p-chlorobenzoic acid catabolism.     

Characterization of IS1676 from Rhodococcus erythropolis SQ1

To develop a transposable element-based system for mutagenesis in Rhodococcus, we used the sacB gene from Bacillus subtilis to isolate a novel transposable element, IS1676, from R. erythropolis SQ1. This 1693 bp insertion sequence is bounded by imperfect (10 out of 13 bp) inverted repeats and it creates 4 bp direct repeats upon insertion. Comparison of multiple insertion sites reveals a preference for the sequence 5′-(C/T)TA(A/G)-3′ in the target site. IS1676 contains a single, large (1446 bp) open reading frame with coding potential for a protein of 482 amino acids. IS1676 may be similar to an ancestral transposable element that gave rise to repetitive sequences identified in clinical isolates of Mycobacteriumkansasii. Derivatives of IS1676 should be useful for analysis of Rhodococcus strains, for which few other genetic tools are currently available. Received: 1 April 1999 / Received revision: 6 July 1999 / Accepted: 1 August 1999     

Mineralization of PCBs by the genetically modified strain Cupriavidus necator JMS34 and its application for bioremediation of PCBs in soil

Polychlorobiphenyls (PCBs) are classified as “high-priority pollutants.” Diverse microorganisms are able to degrade PCBs. However, bacterial degradation of PCBs is generally incomplete, leading to the accumulation of chlorobenzoates (CBAs) as dead-end metabolites. To obtain a microorganism able to mineralize PCB congeners, the bph locus of Burkholderia xenovorans LB400, which encodes one of the most effective PCB degradation pathways, was incorporated into the genome of the CBA-degrading bacterium Cupriavidus necator JMP134-X3. The bph genes were transferred into strain JMP134-X3, using the mini-Tn5 transposon system and biparental mating. The genetically modified derivative, C. necator strain JMS34, had only one chromosomal insertion of bph locus, which was stable under nonselective conditions. This modified bacterium was able to grow on biphenyl, 3-CBA and 4-CBA, and degraded 3,5-CBA in the presence of m-toluate. The strain JMS34 mineralized 3-CB, 4-CB, 2,4′-CB, and 3,5-CB, without accumulation of CBAs. Bioaugmentation of PCB-polluted soils with C. necator strain JMS34 and with the native B. xenovorans LB400 was monitored. It is noteworthy that strain JMS34 degraded, in 1 week, 99% of 3-CB and 4-CB and approximately 80% of 2,4′-CB in nonsterile soil, as well as in sterile soil. Additionally, the bacterial count of strain JMS34 increased by almost two orders of magnitude in PCB-polluted nonsterile soil. In contrast, the presence of native microflora reduced the degradation of these PCBs by strain LB400 from 73% (sterile soil) to approximately 50% (nonsterile soil). This study contributes to the development of improved biocatalysts for remediation of PCB-contaminated environments.     

Isolation and characterization of a novel polychlorinated biphenyl-degrading bacterium, Paenibacillus sp. KBC101

The biphenyl-utilizing bacterial strain KBC101 has been newly isolated from soil. Biphenyl-grown cells of KBC101 efficiently degraded di- to nonachlorobiphenyls. The isolate was identified as Paenibacillus sp. with respect to its 16S rDNA sequence and fatty acid profiles, as well as various biological and physiological characteristics. In the case of highly chlorinated biphenyl (polychlorinated biphenyl; PCB) congeners, the degradation activities of this strain were superior to those of the previously reported strong PCB degrader, Rhodococcus sp. RHA1. Recalcitrant coplanar PCBs, such as 3,4,3,4-CB, were also efficiently degraded by strain KBC101 cells. This is the first report of a representative of the genus Paenibacillus capable of degrading PCBs. In addition to growth on biphenyl, strain KBC101 could grow on dibenzofuran, xanthene, benzophenone, anthrone, phenanthrene, naphthalene, fluorene, fluoranthene, and chrysene as sole sources of carbon and energy. Paenibacillus sp. strain KBC101 presented heterogeneous degradation profiles toward various aromatic compounds.     

Influence of chlorobenzoic acids on the growth and degradation potentials of PCB-degrading microorganisms

The biodegradation of polychlorinated biphenyls (PCBs) by diverse bacteria including those utilized in this study is often incomplete, a concomitant accumulation of chlorobenzoic acids (CBAs) are released as dead-end products. The build-up of these metabolites in the growth medium may result in feed-back inhibition and impede PCB biotransformation. In this investigation using GC-ECD and HPLC analyses, we confirmed that CBAs inhibit growth and PCB biodegradation potentials of five tropical bacteria namely, Pseudomonas aeruginosa SA-1, Enterobacter sp. SA-2, Ralstonia sp. SA-3, Ralstonia sp. SA-5 and Pseudomonas sp. SA-6. Among the four CBAs (2-CBA, 3-CBA, 4-CBA acids and 2,3-diCBA), 3-CBA was the strongest inhibitor followed by 4-CBA. Furthermore, we found that 3-CBA heavily inhibited growth of SA-3 and SA-6 on monochlorobiphenyls by 82–90% while elimination rate was inhibited by 71–88%. In the case of 2,3-diCBA, inhibition was generally less than 60%. However, effects of both acids were stronger in SA-3 than SA-6. We also found that 3-CBA and 2,3-diCBA completely inhibited carbon-chloride cleavage of 2-CB and 3-CB since cultivation in the absence of the acids resulted in recovery of 23–50% chloride in the culture fluids of organisms. These findings may therefore, have practical and ecological significance and are useful for improving the efficiency and the stability of some biological treatment processes.     

Dechlorination of polychlorinated biphenyl congeners by an anaerobic microbial consortium

  An anaerobic methanogenic microbial consortium, developed in a granular form, exhibited extensive dechlorination of defined polychlorinated biphenyl (PCB) congeners. A 2,3,4,5,6-pentachlorobiphenyl was dechlorinated to biphenyl via 2,3,4,6-tetrachlorobiphenyl, 2,4,6-trichlorobiphenyl, 2,4-dichlorobi-phenyl and 2-chlorobiphenyl (CB). Removal of chlorine atoms from all three positions of the biphenyl ring, i.e., ortho, meta and para, was observed during this reductive dechlorination process. Biphenyl was identified as one of the end-products of the reductive dechlorination by GC-MS. After 20 weeks, the concentrations of the dechlorination products 2,4,6-CB, 2,4-CB, 2-CB and biphenyl were 8.1, 41.2, 3.0 and 47.8 μM respectively, from an initial 105 μM 2,3,4,5,6-CB. The extent and pattern of the dechlorination were further confirmed by the dechlorination of lightly chlorinated congeners including 2-CB, 3-CB, 4-CB, 2,4-CB and 2,6-CB individually. This study indicates that the dechlorination of 2,3,4,5,6-CB to biphenyl is due to ortho, meta and para dechlorination by this anaerobic microbial consortium. Received: 30 April 1996 / Received revision: 26 July 1996 / Accepted: 5 August 1996     

磁性纳米颗粒介导分离技术筛选土壤中多氯联苯降解菌及其降解特性

【背景】磁性纳米颗粒介导分离(magnetic nanoparticle-mediated isolation, MMI)技术是近年来发展起来的一种无须底物标记就能从复杂菌群中分离活性功能微生物的方法,目前尚无研究报道该技术应用于难降解污染物3,3′,4,4′-四氯联苯(3,3′,4,4′-tetrachlorobiphenyl, PCB77)。【目的】从土壤中筛选PCB77活性降解菌并研究其污染物降解特性。【方法】利用磁性纳米颗粒(magnetic nanoparticles, MNPs)富集原位活性PCB77降解菌群,通过高通量测序分析细菌群落变化,经平板筛选得到PCB77降解菌,并研究其对多氯联苯和多溴联苯醚的降解特性。【结果】基于MMI技术获取的富集培养液能够高效地转化PCB77,与对照组相比底物降解效率从6%提升至79.3%,同时该富集培养液中细菌物种多样性显著降低,群落组成发生明显变化。从对照组和MMI处理组中分别筛选到PCB77降解菌红球菌CT2和类芽孢杆菌MT2,发现红球菌为对照组中唯一的优势物种,而MMI处理组的优势物种由红球菌和类芽孢杆菌共同组成。菌株MT2对PCB...     

Characterization of selected actinomycetes degrading polyaromatic hydrocarbons in liquid culture and spiked soil

Summary Five strains of the Rhodococcus and Gordonia genera were evaluated for their potential use in bioremediation of polycyclic aromatic hydrocarbons (PAH) with or without another substrate (co-substrate). Their ability to produce biosurfactants or to degrade phenanthrene when growing on glucose, hexadecane and rapeseed oil was tested in liquid medium at 30 °C. All strains showed biosurfactant activity. The highest reduction in surface tension was recorded in whole cultures of Rhodococcus sp. DSM 44126 (23.1%) and R. erythropolis DSM 1069 (21.1%) grown on hexadecane and Gordonia sp. APB (20.4%) and R. erythropolis TA57 (18.2%) grown on rapeseed oil. Cultures of Gordonia sp. APB and G. rubripertincta formed emulsions when grown on rapeseed oil. After 14 days of incubation, Rhodococcus sp. DSM 44126 degraded phenanthrene (initial concentration 100 μg ml⁻¹) as sole carbon source (79.4%) and in the presence of hexadecane (80.6%), rapeseed oil (96.8%) and glucose (below the limit of detection). The other strains degraded less than 20%, and then with a co-substrate only. Rhodococcus sp. DSM 44126 was selected and its performance evaluated in soil spiked with a mixture of PAH (200 mg kg⁻¹). The effect of the addition of 0, 0.1 and 1% rapeseed oil as co-substrate was also tested. Inoculation enhanced the degradation of phenanthrene (55.7% and 95.2% with 0.1% oil and without oil respectively) and of anthracene (29.2% with 0.1% oil). Approximately 96% of anthracene and 62% of benzo(a)pyrene disappeared from the soil (inoculated and control) after 14 days and anthraquinone was detected as a metabolite. Rhodococcus sp. DSM 44126 was identified as Rhodococcus wratislaviensis by 16S rRNA sequencing and was able to degrade anthracene as sole carbon source in liquid culture.     

Analysis of changes in congener selectivity during PCB degradation by Burkholderia sp. strain TSN101 with increasing concentrations of PCB and characterization of the bphBCD genes and gene products

We isolated and characterized a gram-negative bacterium, Burkholderia sp. strain TSN101, that can degrade polychlorinated biphenyls (PCBs) at concentrations as high as 150 μg Kaneclor 300/ml, a PCB mixture equivalent to Aroclor 1242. Growing cells of strain TSN101 degraded most of the tri- and tetrachlorobiphenyls in medium containing 25 μg Kaneclor 300/ml. Using PCB concentrations of 50–150 μg of Kaneclor 300/ml, the congener selectivity pattern was different and the pattern of chlorine substitution strongly affected degradation of some congeners. At 25 μg Kaneclor 300/ml, strain TSN101 degraded di- and trichlorinated congeners with chlorine substitutions at both the ortho and the para positions. At higher concentrations of Kaneclor 300, di- and trichlorobiphenyls with ortho substituents in both phenyl rings were not degraded well. Trichlorobiphenyls with para and meta substitutents were degraded equally well at all concentrations studied. The ability of strain TSN101 to degrade ortho and para-substituted congeners was confirmed using a defined PCB mixture with chlorine substituents at 2′- and 4′-positions. A 5-kb DNA fragment containing the bphBCD genes was cloned and sequenced. Comparison of the deduced amino acid sequences of these genes with related proteins indicated 99 and 98% sequence similarity to the BphB and BphD of Comamonas testosteroni strain B-356, respectively. The bphC gene product showed 74% sequence similarity to the BphC of Burkholderia cepacia strain LB400 and exhibited a narrow substrate specificity with strong affinity for 2,3-dihydroxybiphenyl. A bphC-disrupted mutant of Burkholderia sp. strain TSN101, constructed by gene replacement, lost the ability to utilize biphenyl, thus supporting the role of the cloned bph gene in biphenyl metabolism. Received: 18 February 1997 / Accepted: 19 August 1997     

Cometabolic degradation of polychlorinated biphenyls (PCBs) by axenic cultures of Ralstonia sp. strain SA-5 and Pseudomonas sp. strain SA-6 obtained from Nigerian contaminated soils

Substantial metabolism of 2,3,4,5-tetrachlorobiphenyl (2,3,4,5-tetraCB) and 2,3′,4′,5-tetraCB by axenic cultures of Ralstonia sp. SA-5 and Pseudomonas sp. SA-6 was observed in the presence of biphenyl supplementation, although, the strains were unable to utilize tetrachlorobiphenyls as growth substrate. The former was more amenable to aerobic degradation (∼70% degradation) than the latter (22–45% degradation). Recovery of 2,5-chlorobenzoic acid and chloride from 2,3′,4′,5-tetraCB assay is an indication of initial dioxygenase attack on the 3,4-dichlorophenyl ring. The PCB-degradative ability of both strains was also investigated by GC analysis of individual congeners in Aroclor 1242 (100 ppm) following 12-day incubation with washed benzoate-grown cells. Results revealed two different catabolic properties. Whereas strain SA-6 required biphenyl as inducer of the degradation activity, such induction was not required by strain SA-5. Nearly all the detectable congeners in the mixture were extensively degraded (% reduction in ECD area counts for individual congeners ranged from 50.0 to 100% and 14.2 to 100%, respectively, for SA-5 and SA-6). The two strains exhibited no noticeable specificity for congeners with varying numbers of chlorine substitution and positions. The degradative competence of these isolates most especially SA-5 makes them among the most versatile PCB-metabolizing organisms yet reported.     

Cyanobactericidal effect of <Emphasis Type="Italic">Rhodococcus</Emphasis> sp. isolated from eutrophic lake on <Emphasis Type="Italic">Microcystis</Emphasis> sp

A bacterium, which was observed in all cultivations of Microcystis sp., was isolated and designated as Rhodococcus sp. KWR2. The growth of bloom-forming cyanobacteria, including four strains of Microcystis aeruginosa and Anabaena variabilis, was suppressed by up to 75–88% by 2% (v/v) culture broth of KWR2 after 5 days. But KWR2 did not inhibit eukaryotic algae, Chlorella vulgaris and Scenedesmus sp. An extracellular algicidal substance produced by KWR2 showed a cyanobactericidal activity of 94% and was water-soluble with a molecular weight of lower than 8 kDa.     

Metabolism of 4,4′-dichlorobiphenyl by white-rot fungi Phanerochaete chrysosporium and Phanerochaete sp. MZ142

Degradation experiment of model polychlorinated biphenyl (PCB) compound 4,4′-dichlorobiphenyl (4,4′-DCB) and its metabolites by the white-rot fungus Phanerochaete chrysosporium and newly isolated 4,4′-DCB-degrading white-rot fungus strain MZ142 was carried out. Although P. chrysosporium showed higher degradation of 4,4′-DCB in low-nitrogen (LN) medium than that in potato dextrose broth (PDB) medium, Phanerochaete sp. MZ142 showed higher degradation of 4,4′-DCB under PDB medium condition than that in LN medium. The metabolic pathway of 4,4′-DCB was elucidated by the identification of metabolites upon addition of 4,4′-DCB and its metabolic intermediates. 4,4′-DCB was initially metabolized to 2-hydroxy-4,4′-DCB and 3-hydroxy-4,4′-DCB by Phanerochaete sp. MZ142. On the other hand, P. chrysosporium transformed 4,4′-DCB to 3-hydroxy-4,4′-DCB and 4-hydroxy-3,4′-DCB produced via a National Institutes of Health shift of 4-chlorine. 3-Hydroxy-4,4′-DCB was transformed to 3-methoxy-4,4′-DCB; 4-chlorobenzoic acid; 4-chlorobenzaldehyde; and 4-chlorobenzyl alcohol in the culture with Phanerochaete sp. MZ142 or P. chrysosporium. LN medium condition was needed to form 4-chlorobenzoic acid, 4-chlorobenzaldehyde, and 4-chlorobenzyl alcohol from 3-hydroxy-4,4′-DCB, indicating the involvement of secondary metabolism. 2-Hydroxy-4,4′-DCB was not methylated. In this paper, we proved for the first time by characterization of intermediate that hydroxylation of PCB was a key step in the PCB degradation process by white-rot fungi.     

Molecular biological characterization of biphenyl-degrading bacteria and identification of the biphenyl 2,3-Dioxygenase α-subunit genes

Bacterial isolates from soils contaminated with (chlorinated) aromatic compounds, which degraded biphenyl/chlorinated biphenyls (CB) and belonged to the genera Rhodococcus and Pseudomonas, were studied. Analysis of the 16S rRNA gene sequences was used to determine the phylogenetic position of the isolates. The Rhodococcus cells were found to contain plasmids of high molecular mass (220–680 kbp). PCR screening for the presence of the bphA1 gene, a marker indicating the possibility for induction of 2,3-dioxygenase (biphenyl/toluene dioxygenase subfamily), revealed the presence of the bphA1 genes with 99–100% similarity to the homologous genes of bacteria of the relevant species in all pseudomonad and most Rhodococcus isolates. A unique bphA1 gene, which had not been previously reported for the genus, was identified in Rhodococcus sp. G10. The absence of specific amplification of the bphA1 genes in some biphenyl-degrading bacteria (Rhodococcus sp. B7b, B106a, G12a, P2kr, P2(51), and P2m), as well as in an active biphenyl degrader Rhodococcus ruber P25, indicated the absence of the genes encoding the proteins of the biphenyl/toluene dioxygenase subfamily and participation of the enzymes other than this protein family in biphenyl/CB degradation.     

Biotransformation of soybean isoflavones by a marine <Emphasis Type="Italic">Streptomyces</Emphasis> sp. 060524 and cytotoxicity of the products

A marine Streptomyces sp. 060524 capable of hydrolyzing the glycosidic bond of isoflavone glycosides, was isolated by detecting its β-glucosidase activity. 5 isoflavone aglycones were isolated from culture filtrates in soybean meal glucose medium. They were identified as genistein (1), glycitein (2), daidzein (3), 3′,4′,5,7-tetrahydroxyisoflavone (4), and 3′,4′,7-trihydroxyisoflavone (5), based on UV, NMR and mass spectral analysis. The Streptomyces can selectively hydroxylate at the 3′-position in the daidzein and genistein to generate 3′-hydroxydaidzein and 3′-hydroxygenistein, respectively. The Strain biotransformed more than 90% of soybean isoflavone glycosides into their aglycones within 108 h. 3′-hydroxydaidzein and 3′-hydroxygenistein exhibited stronger cytotoxicity against K562 human chronic leukemia than daidzein and genistein.