Complete Biodegradation Research Articles

Stabilisation of biodried municipal solid waste fine fraction in landfill bioreactor

The biodrying process of solid waste is a pre-treatment for the bio-stabilisation of the municipal solid waste. This study aims to investigate the fate of the municipal solid waste fine fraction (MSWFF) resulting from a biodrying treatment when disposed in landfills that are operated as bioreactors. Biodried MSWFF was apparently stable due to its low moisture content that slows down the microbial activity. The lab-scale anaerobic bioreactors demonstrated that a proper moisture content leads to a complete biodegradation of the organic matter contained in the biodried MSWFF. Using a pilot-scale landfill bioreactor (LBR), MSWFF stabilisation was achieved, suggesting that the leachate recirculation could be an effective approach to accomplish the anaerobic biodegradation and biostabilisation of biodried MSWFF after landfilling. The biostabilisation of the material resulting from the LBR treatment was confirmed using anaerobic and aerobic stability indices. All anaerobic and aerobic indices showed a stability increase of approximately 80% of the MSWFF after treatment in the LBR. The similar values of OD7 and BMP stability indices well agree with the relationship between the aerobic and anaerobic indices reported in literature.

Epoxy Coenzyme A Thioester Pathways for Degradation of Aromatic Compounds

Aromatic compounds (biogenic and anthropogenic) are abundant in the biosphere. Some of them are well-known environmental pollutants. Although the aromatic nucleus is relatively recalcitrant, microorganisms have developed various catabolic routes that enable complete biodegradation of aromatic compounds. The adopted degradation pathways depend on the availability of oxygen. Under oxic conditions, microorganisms utilize oxygen as a cosubstrate to activate and cleave the aromatic ring. In contrast, under anoxic conditions, the aromatic compounds are transformed to coenzyme A (CoA) thioesters followed by energy-consuming reduction of the ring. Eventually, the dearomatized ring is opened via a hydrolytic mechanism. Recently, novel catabolic pathways for the aerobic degradation of aromatic compounds were elucidated that differ significantly from the established catabolic routes. The new pathways were investigated in detail for the aerobic bacterial degradation of benzoate and phenylacetate. In both cases, the pathway is initiated by transforming the substrate to a CoA thioester and all the intermediates are bound by CoA. The subsequent reactions involve epoxidation of the aromatic ring followed by hydrolytic ring cleavage. Here we discuss the novel pathways, with a particular focus on their unique features and occurrence as well as ecological significance.

Captopril and its dimer captopril disulfide: Photodegradation, aerobic biodegradation and identification of transformation products by HPLC–UV and LC–ion trap-MSn

In some countries effluents from hospitals and households are directly emitted into open ditches without any further treatment and with very little dilution. Under such circumstances photo- and biodegradation in the environment can occur. However, these processes do not necessarily end up with the complete mineralization of a chemical. Therefore, the biodegradability of photoproduct(s) by environmental bacteria is of interest.Cardiovascular diseases are the number one cause of death globally. Captopril (CP) is used in this study as it is widely used in Egypt and stated as one of the essential drugs in Egypt for hypertension. Three tests from the OECD series were used for biodegradation testing: Closed Bottle test (CBT; OECD 301 D), Manometric Respirometry test (MRT; OECD 301 F) and the modified Zahn–Wellens test (ZWT; OECD 302 B). Photodegradation (150W medium-pressure Hg-lamp) of CP was studied. Also CBT was performed for captopril disulfide (CPDS) and samples received after 64min and 512min of photolysis.The primary elimination of CP and CPDS was monitored by LC–UV at 210nm and structures of photoproducts were assessed by LC–UV–MS/MS (ion trap). Analysis of photodegradation samples by LC–MS/MS revealed CP sulfonic acid as the major photodegradation product of CP. No biodegradation was observed for CP, CPDS and of the mixture resulting from photo-treatment after 64min in CBT. Partial biodegradation in the CBT and MRT was observed in samples taken after 512min photolysis and for CP itself in MRT. Complete biodegradation and mineralization of CP occurred in the ZWT.

PLGA-based nanoparticles: Effect of chitosan in the aggregate stabilization. A dielectric relaxation spectroscopy study

Chitosan-modified polylactic-co-glycolic acid (PLGA) nanoparticles with average diameter of 200nm in PBS buffer solution have been investigated by means of dielectric relaxation spectroscopy measurements in the frequency range (1MHz–2GHz) where interfacial polarizations occur. PLGA-based nanoparticles offer remarkable advantages in different biotechnological fields, such as their biocompatibility, easiness of administration and rather complete biodegradation. However, despite the use of these drug delivery systems is increasing, little is known about the basic process involved in the formation of complexes and in the subsequent release kinetics. In the present work, we have characterized the colloidal behavior of PLGA-based nanoparticles in the presence of oppositely charged chitosan polyelectrolyte by means of dynamic light scattering, electrophoretic mobility and radiowave dielectric relaxation measurements. In particular, we have emphasized how the presence of a coating layer at the nanoparticle surface could exert a marked slowing-down in the drug release. The consequence of this finding is briefly discussed at the light of some biological implications.

In situ TCE degradation mediated by complex dehalorespiring communities during biostimulation processes

SummaryThe bioremediation of chloroethene contaminants in groundwater polluted systems is still a serious environmental challenge. Many previous studies have shown that cooperation of several dechlorinators is crucial for complete dechlorination of trichloroethene to ethene. In the present study, we used an explorative functional DNA microarray (DechloArray) to examine the composition of specific functional genes in groundwater samples in which chloroethene bioremediation was enhanced by delivery of hydrogen‐releasing compounds. Our results demonstrate for the first time that complete biodegradation occurs through spatial and temporal variations of a wide diversity of dehalorespiring populations involving both Sulfurospirillum, Dehalobacter, Desulfitobacterium, Geobacter and Dehalococcoides genera. Sulfurospirillum appears to be the most active in the highly contaminated source zone, while Geobacter was only detected in the slightly contaminated downstream zone. The concomitant detection of both bvcA and vcrA genes suggests that at least two different Dehalococcoides species are probably responsible for the dechlorination of dichloroethenes and vinyl chloride to ethene. These species were not detected on sites where cis‐dichloroethene accumulation was observed. These results support the notion that monitoring dechlorinators by the presence of specific functional biomarkers using a powerful tool such as DechloArray will be useful for surveying the efficiency of bioremediation strategies.

Specific features of oil biodegradation in meadow-chestnut soils of the Stavropol region (model experiment)

Oil biodegradation in oil-contaminated meadow-chestnut soils under the impact of different biological preparations was studied in a model experiment. The soils differed from one another in the age of contamination and in the presence/absence of the stage of preliminary biological remediation. Background uncontaminated soils served as the control. To characterize oil degradation, the indices of basal respiration (BR) and dehydrogenase activity (DA) and data on oil concentrations in the soil were applied. It was shown that the most complete biodegradation of oil takes place in the soils with recent oil contamination in comparison with the soils contaminated with oil for 6.5 and 19.5 months. Maximum BR values were observed in the soils contaminated with oil for 19.5 months, whereas maximum DA values were observed in the soils contaminated with oil for 6.5 months. According to the multivariate analysis of variance, the major factors affecting the rate of oil biodegradation were the age of oil contamination, the biological preparation applied, and the presence (or absence) of the stage of preliminary biological remediation. These factors specified 18, 72, and 3% of the total variance of the residual oil content in the samples, respectively. The type of the applied biological preparations had the major effect on the BR and DA indices specifying 63 and 53% of their total variances, respectively. The results obtained in this study can be used as recommendations for remediation of oil-contaminated soils in the Stavropol region.

Comparison of nuclear magnetic resonance methods for the analysis of organic matter composition from soil density and particle fractions

Environmental contextThe association of specific organic matter (OM) compounds with clay mineral surfaces is believed to protect these compounds from degradation and thus result in long-term protection in soil. The molecular-level composition of soil OM associated with soil fractions was measured and compared using solid-state 13C nuclear magnetic resonance (NMR) and solution-state 1H NMR methods. Combining these methods allowed more detailed characterisation of OM associated with different soil fractions and will improve the understanding of OM dynamics in soil. AbstractOrganic matter (OM) associated with fine soil fractions is hypothesised to be protected from complete biodegradation by soil microbes. It is therefore important to understand the structure and stage of decomposition of OM associated with various soil fractions. Solid-state 13C nuclear magnetic resonance (NMR) spectroscopy has been used extensively to investigate the OM composition of soils and soil fractions. Solution-state 1H NMR spectroscopy has not been used as much but is an emerging tool for analysing soil OM because 1H NMR spectra are often better resolved and provide information that complements the structural information obtained from solid-state 13C NMR experiments. This study compares one-dimensional solution-state 1H NMR and solid-state 13C NMR methods for assessing the degradation and composition of OM in three different soils, and their light and clay-size fractions. The alkyl/O-alkyl degradation parameter was consistent across all NMR methods and showed that OM associated with clay-size fractions were at more advanced stages of degradation as compared to that in light density soil fractions. Solution-state 1H and diffusion edited (DE) 1H NMR results showed the presence of high concentrations of microbial-derived peptidoglycan and peptide side-chains in clay-sized fractions. Lignin was also identified in clay-sized fractions using solid-state 13C and solution-state 1H NMR techniques. The combination of solid-state 13C and solution-state 1H NMR methods provides a more detailed analysis of OM composition and thereby facilitates a better understanding of the fate and preservation of OM in soil.

Bioremediation of Dyestuff Compounds using Indigenous Microorganism in a Bioreactor

Dyes are synthesized in a reactor, filtered, dried, blended with other color additives to produce the final product. The liquid effluent resulting from the manufacture of colored dye contains toxic organic residues and inorganic compounds. The present treatment technology involves: neutralization, flocculation, coagulation-settling, carbon adsorption, detoxification of organics by oxidation and biological treatments. In spite of the present treatment, the discharge effluent contains the color residual toxic compounds. In the present research study the dye effluent discharged at the waste disposal site has been characterized for physico-chemical and microbial characterization. The microorganisms adapted at contaminated sites have been isolated and cultured to use as a biomass for bioremediation of identified toxic organic compounds present in dye effluent. GC-MS has identified -octadecene; 5-Eicosene, (E)-; Di (2-ethylhexyl) phthalate; 1-nonadecene; Butyl-2-ethylhexyl phthalate; 5-Chloro-1,3-benzodioxole; 2-Oxazolidinone, 3, -dimethyl-5- phthalate; 1-Phenyl-5-methylnona-1, 3, 4-triene; and 2,2-Dimethyl-N-(3-methylpenyl) propanamide dye compounds in discharge effluents. The bioremediation of dye stuff- discharged effluent was carried out in a laboratory bioreactor using indigenous microbial consortium under controlled environmental conditions. The biodegradation studied at an interval of every hour for a day and thereafter each day for a period of 21 days, till the complete biodegradation takes place. Biodegradation has been studied using GC-MS; the intermediate compounds were found to be biodegraded into pthalic acid – a non toxic compound. The indigenous microbial consortium developed was found effective and efficient to biodegrade dye compounds into environmental friendly compounds.

In vivo biodegradation of a new PVP-Hydrogel

The target applications of the hydrogel biomaterials are the “difficult wounds”, that is the wounds caused by burns, abrasions and ulcerations, by vascular or endocrine disorders (diabetes). This study describes the in vivo biodegradation process of a new biomaterial (PVP-Hydrogel), comparing it with a haemostatic biomaterial (Matemo) which had showed a complete biodegradation process in previous experiments. The new hydrogel consists of three biocompatible polymers: Polyvinyl pyrrolidone (PVP), Agar and Polyethylene glycol (PEG), at first mixed and then sterilized by gamma irradiation at 25 kGy. For the experimental protocol, the dorsal skin of a rat was incised creating two pouches in its subcutaneous tissue so as to introduce a specimen (1 cm2 of size) of Matemo on the left side, and of PVP-Hydrogel on the right side. The intervention was repeated on 6 different rats, while other 3 were used as controls. Of all treated animals, some were sacrificed after 45 days and some others after 90 days from the operation. Subsequently, the dorsal skin of each animal was inspected on both implant sides, taking skin and subcutaneous tissue fragments for histological studies. The microscopic analysis of the implant area fully confirmed the macroscopic analysis: the implanted PVP-Hydrogel still appeared in situ and almost intact, not at all biodegraded but anchored to the dermal layer and to the muscular fascia. At the end of the prefixed deadlines of the experiment, that is at the 45th and the 90th day post-implant, the biomaterial had kept intact without any sign of biodegradation, while on the left side the Matemo had been completely reabsorbed. The connective tissue, in which the hydrogel was enclosed, appeared like a thin capsule, proliferating and isolating the biomaterial with a minimum attraction of macrophages in the wall. Therefore, it is impossible to document a biodegradation process of the hydrogel in vivo, but on the contrary it is possible to confirm the very long persistence of the biomaterial in situ showing no sign at all of inflammation. The results of this in vivo study show that this new hydrogel could be used in humans for the applications listed above, because it just kept intact in the body for a very long time without causing adverse histological reactions.

Aerobic biodegradation of a mixture of sulfonated azo dyes by a bacterial consortium immobilized in a two‐stage sparged packed‐bed biofilm reactor

AbstractThe biodegradation of the sulfonated azo dyes, Acid Orange 7 (AO7) and Acid Red 88 (AR88), by a bacterial consortium isolated from water and soil samples obtained from sites receiving discharges from textile industries, was evaluated. For a better removal of azo dyes and their biodegradation byproducts, an aerobically operated two‐stage rectangular packed‐bed biofilm reactor (2S‐RPBR) was constructed. Because the consortium's metabolic activity is affected by oxygen, the effect of the interstitial air flow rate QGI on 2S‐RPBR's zonal values of the oxygen mass transfer coefficient kLa was estimated. In the operational conditions probed in the bioreactor, the kLa values varied from 3 to 60 h−1, which roughly correspond to volumetric oxygen transfer rates, dcL/dt, ranging from 20 to 375 mg O2 L−1h−1. Complete biodegradation of azo dyes was attained at loading rates BV,AZ up to 40 mg L−1d−1. At higher BV,AZ values (80 mg L−1 d−1), dye decolorization and biodegradation of the intermediaries 4‐amino‐naphthalenesulphonic acid (4‐ANS) and 1‐amino‐2‐naphthol (1‐A2N) was almost complete. However, a diminution in COD and TOC removal efficiencies was observed in correspondence to the 4‐aminobenzenesulfonic acid (4‐ABS) accumulation in the bioreactor. Although the oxygen transport rate improved the azo dye mineralization, the results suggest that the removal efficiency of azo dyes was affected by biofilm detachment at relatively high QGI and BV,AZ values. After 225 days of continuous operation of the 2S‐RFBR, eight bacterial strains were isolated from the biofilm attached to the porous support. The identified genera were: Arthrobacter, Variovorax, Agrococcus, Sphingomonas, Sphingopyxis, Methylobacterium, Mesorhizobium, and Microbacterium.

Carbon footprint of bioplastics using biocarbon content analysis and life-cycle assessment

Abstract

Controlling degradation rate of poly(lactic acid) for its biomedical applications

Poly(lactic acid) (PLA) is widely used in many different biomedical applications due to its biocompatibility, complete biodegradability, and non-toxic degradation products. However, PLA may be limited in particularly long degradation, which is not always desirable in many biomedical applications. In this short review, we summarized some of the most recent studies on controlling the degradation rate of PLA, employing copolymerization, blending, additives and irradiation. This review discussed the pros and cons of those methods considering their applications to bioabsorbable fixation or drug delivery devices. We also suggested the design parameters for PLA treatment for its wide applicability to biomedical fields.

Aerobic biodegradation of nonylphenol ethoxylates in shaking-flask test

Nonylphenol ethoxylates (NPEOs), which are widely used for industrial and domestic purposes, exert adverse effects on wildlife after being used and discharged into the environment. However, their ultimate biodegradability and biodegradation pathway remains unclear. In this study, the aerobic degradability of nonylphenol ethoxylates (NPEOs) by the acclimated microorganisms in active sludge was examined using shaking-flask tests. The degradation of benzene rings in NPEOs was determined using UV spectroscopy and high performance liquid chromatography (HPLC). Results showed that more than 80% of benzene rings were removed after 8-10 days of degradation, and the majority of NPEOs were also removed after 9 days of degradation, indicating NPEOs and the benzene rings could be ultimately degraded by microorganisms in acclimated active sludge. Electrospray ionization-mass spectroscopy (ESI-MS) analysis of biodegradation intermediates indicate that stepwise omega, beta-oxidation of EO chains or fission of EO chains, and further omega, beta-oxidation of alkyl-chain for short-EO-chain NPEOs constitute the main pathway in the early stage, and complete biodegradation occur when the benzene rings in these molecules are opened in the later stage. Normal 0 21 false false false ES-CL X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabla normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

Bioaugmentation of a rotating biological contactor for degradation of 2-fluorophenol

The performance of a laboratory scale rotating biological contactor (RBC) towards shock loadings of 2-fluorophenol (2-FP) was investigated. During a period of ca. 2months organic shock loadings of 25mgL−1 of 2-FP were applied to the RBC. As no biodegradation of 2-FP was observed, bioaugmentation of the RBC with a 2-FP degrading strain was carried out and, along ca. 6months, organic shock loadings within a range of 25–200mgL−1 of 2-FP were applied. Complete biodegradation of 50mgL−1 of 2-FP was observed during operation of the reactor. The RBC showed to be robust towards starvation periods, as after ca. 1month of non-supply of the target compound, the reactor resumed 2-FP degradation. The inoculated strain was retained within the biofilm in the disks, as the 2-FP degrading strain was recovered from the biofilm by the end of the experiment, thus bioaugmentation was successfully achieved.

Pharmacological Characterization of Chemically Synthesized Monomeric phi29 pRNA Nanoparticles for Systemic Delivery

Previous studies have shown that the packaging RNA (pRNA) of bacteriophage phi29 DNA packaging motor folds into a compact structure, constituting a RNA nanoparticle that can be modularized with functional groups as a nanodelivery system. pRNA nanoparticles can also be self-assembled by the bipartite approach without altering folding property. The present study demonstrated that 2'-F-modified pRNA nanoparticles were readily manufactured through this scalable bipartite strategy, featuring total chemical synthesis and permitting diverse functional modularizations. The RNA nanoparticles were chemically and metabolically stable and demonstrated a favorable pharmacokinetic (PK) profile in mice (half-life (T(1/2)): 5-10 hours, clearance (Cl): <0.13 l/kg/hour, volume of distribution (V(d)): 1.2 l/kg). It did not induce an interferon (IFN) response nor did it induce cytokine production in mice. Repeat intravenous administrations in mice up to 30 mg/kg did not result in any toxicity. Fluorescent folate-pRNA nanoparticles efficiently and specifically bound and internalized to folate receptor (FR)-bearing cancer cells in vitro. It also specifically and dose-dependently targeted to FR(+) xenograft tumor in mice with minimal accumulation in normal tissues. This first comprehensive pharmacological study suggests that the pRNA nanoparticle had all the preferred pharmacological features to serve as an efficient nanodelivery platform for broad medical applications.

Effect of nitrogen limitation on enrichment of activated sludge for PHA production

Polyhydroxyalkanoates (PHA) are good candidates to plastics because of their material properties similar to conventional plastics and complete biodegradability. The use of activated sludge can be a cheaper alternative to pure cultures for PHA production. In this study, effect of nitrogen limitation during acclimatization period of biomass on production of polyhydroxyalkanoate was investigated. Activated sludge was selected in two sequencing batch reactors operated with and without nitrogen limitation. Batch tests were performed to examine polymer productions of activated sludges acclimatized to different nitrogen regimes. Responses of biomass to different organic loading rates, organic acids, and carbon to nitrogen (C/N) ratios were studied by determining specific polymer storage rate, polymer storage yield, and sludge polymer content of biomasses. Results obtained from batch experiments showed that concentrations of polymer accumulated by two different sludges increased directly with initial substrate concentration. Observed highest polymer yields for the biomasses enriched with and without nitrogen deficiency were 0.69 g COD PHA g(-1) COD S and 0.51 g COD PHA g(-1) COD S, and corresponding polymer contents of biomasses were 43.3% (g COD PHA g(-1) COD X) and 38.3% (g COD PHA g(-1) COD X), respectively. Polymer yields for both biomasses decreased with substrate shift however, biomass enriched with nitrogen deficiency adapted well to acetate-propionate mixture. The results presented in this study showed that polymer storage ability of biomass was improved more under dynamic conditions with nitrogen deficiency when compared to that without nitrogen deficiency. Limiting ammonia availability during batch experiments also caused higher polymer production by suppressing growth, as well as during enrichment of biomass.

Natural-Fiber-Reinforced Composite Treated with Polyamines Used as a Support for the Biodegradation and Adsorption of Toluene

The effect of the addition of two different polyamines into a foamed polymeric matrix with embedded natural fiber, to synthesize biocomposites, was studied during the degradation of toluene in batch experiments. The synthesized biocomposites were able to adsorb and facilitate the degradation of toluene by micro-organisms attached in the biocomposite matrix, at a high extent (80%), in a very short period of time (1 day). The adsorption and biodegradation processes were simultaneous. The molecular weight of polyamine had a slight effect on toluene adsorption, with the lower-molecular-weight polyamine being more favorable for the adsorption process. However, the biocomposites, with polyamines, were not able to carry out the complete biodegradation of toluene during the term of experiment (26 days). The absence of polyamine in the biocomposite had a dramatic effect on adsorption and biodegradation of toluene, improving both processes and showing a CO2 production that is 730% higher than biocomposites synthesized with polyamine, because of a toxic and/or barrier effect of polyamine. This biocomposite, synthesized without polyamine, was able to carry out the complete biodegradation during the first 5 days, and it had adequate cyclic performance.

Enhanced biodegradation of 2‐chloronitro‐benzene using a coupled zero‐valent iron column and sequencing batch reactor system

AbstractBACKGROUND: This study focused on the effectiveness of the zero‐valent iron (ZVI) pre‐treatment for enhancing the biodegradability of 2‐chloronitrobenzene (2‐ClNB), and further to evaluate the performance and mechanism of a coupled ZVI column–sequencing batch reactor (SBR) system treating 2‐ClNB contained wastewater.RESULTS: 2‐ClNB was readily transformed into 2‐chloroaniline (2‐ClAn) with the efficiency over 99.9% by ZVI column, and its biodegradability was significantly enhanced via ZVI pretreatment. The transformed effluent was subsequently fed into the SBR followed by 2‐ClAn loading of 3.4–117.2 g m−3 d−1 and COD loading around 1000 g m−3 d−1. A 2‐ClAn removal efficiency over 99.9% and COD removal efficiency of 82.0–98.1% were obtained. Moreover, 91.9 ± 0.1% TOC removal efficiency and 107.1 ± 6.0% chloride recovery efficiency during one cycle confirmed the complete biodegradation of 2‐ClAn in the coupled system. 16S rDNA PCR‐DGGE analysis suggested that ZVI pretreatment enhanced the diversity of the microbial community and promoted enrichment of the functional microorganisms degrading 2‐ClAn in the following SBR.CONCLUSION: ZVI pretreatment significantly enhanced the biodegradability of 2‐ClNB, and the coupled ZVI–SBR system demonstrated excellent performance when treating wastewater containing 2‐ClNB. Copyright © 2011 Society of Chemical Industry

Effect of surfactants, dispersion and temperature on solubility and biodegradation of phenanthrene in aqueous media

In the present study surfactant addition with the help of either a mechanical dispersion or a thermal treatment was applied in order to increase the solubility and the bioavailability of phenanthrene in aqueous media, and therefore to promote its biodegradation. Among four tested surfactants (Tween 80, Brij 30, sodium dodecyl sulphate and rhamnolipids), Brij 30 (0.5 g L −1) showed the best results allowing us to attain about 20 mg L −1 of soluble phenanthrene. An additional thermal treatment at 60 °C for 24 h, 200 rpm permitted to increase the solubility of phenanthrene in the presence of Brij 30 (0.5 g L −1) to about 30 mg L −1. Higher dispersions of phenanthrene particles as well as the reduction of their size were obtained using Ultra-Turrax and French press. The biodegradation of phenanthrene by Pseudomonas putida was then investigated. The reduction of size of phenanthrene particles by mechanical dispersion did not influence its biodegradation, suggesting that P. putida consumed only soluble phenanthrene. The addition of Brij 30 (0.5 g L −1) permitted to obtain more phenanthrene metabolized. The use of Brij 30 coupled with a transitory heating of phenanthrene-containing medium at 60 °C led to an even more complete biodegradation. This might be a promising way to enhance biodegradation of PAHs.

Degradation of dimethyl-sulfoxide-containing wastewater using airlift bioreactor by polyvinyl-alcohol-immobilized cell beads

Airlift bioreactor containing polyvinyl-alcohol-immobilized cell beads was investigated for its capability of biodegradation of dimethyl sulfoxide (DMSO) in term of sludge characteristics including the strategy of acclimation with sucrose and the protection of microorganism from poisoning of DMSO by PVA cell beads. Media condition with sucrose at 50 mg L −1 was beneficial to the biodegradation of DMSO in the fresh PVA entrapped-sludge, but became insignificant in the acclimated one as for tolerance of DMSO toxicity. The removal efficiency of DMSO had the highest rate at 1.42-kg DMSO per kilogram of suspended solid per day after series acclimation batches in the oxygen-enriched airlift bioreactor treated with the 1187.4 mg L −1 of DMSO. Microbial consortium was required for the complete biodegradation of DMSO without any dimethyl sulfide produced. Pseudomonas sp. W1, excreting extracellular monooxygenase identified by indole, was isolated to be one of the most effective DMSO-degrading microorganism in our airlift bioreactor.