Low cost and renewable H2S-biofilter inoculated with Trichoderma harzianum.

The use of biogas to produce hydrogen is currently gaining more attention. One of the drawbacks for the valorization of biogas is the presence of H2S, a hazardous molecule that can cause damage in the metallic internal structures of industries. In this study, the H2S-removal performance of a fungi-based biofilter was investigated. First, an H2S-resistant fungal species was isolated from an industrial digestate and identified as Trichoderma harzianum. The capacity of this microorganism to metabolize H2S in a mineral medium was confirmed. Then, a bioreactor was constructed and put in place to monitor the elimination of gaseous H2S. A mix of cardboard, perlite, woodchips, and wood pellets was used as filling. Microbial development and the outlet gas composition were monitored during a 60-day experimental process during which H2S was completely removed. 97% of the introduced sulphur was detected in the used filling material (fungal species + packing material) by elemental analysis. 24% of the detected sulphur was identified by ion-exchange chromatography as SO42-. Elemental analysis, gas chromatography, and ion-exchange chromatography were used to determine the bioreactor sulphur balance. Metagenomic analysis underlined that H2S elimination was due to the presence of Trichoderma harzianum with a H2S-specific bacterial consortium.

Investigations of benzo[a]pyrene encapsulation and Fenton degradation by starch nanoparticles.

Starch nanoparticles were produced by dialysis method from octenyl succinic anhydre (OSA) and 1,4-butane sultone (BS). The properties of the self-assembled nanoparticles were characterized by NMR spectroscopy (DOSY), fluorescence spectroscopy and dynamic light scattering (DLS). In order to investigate the formation of hydrophobic microdomains, the Nile Red dye was used as a fluorescent probe to evaluate the critical aggregation concentration (CAC) of modified starch in aqueous solution. The results show that the entrapment of the molecular guest was effective and only restricted by the solubility limit of the starch. Then, the modified starch was applied to solubilize benzo[a]pyrene (BaP) in view of degradation by Fenton process. Finally, it has been shown that 95% of BaP was degraded when it was encapsulated in OSA-BS-starch nanoparticles.

Lipid metabolism and benzo[a]pyrene degradation by Fusarium solani: an unexplored potential.

In a search for indigenous soil saprotrophic fungi for bioremediation purposes, Fusarium solani, a saprotrophic fungus belonging to the phylum Ascomycota, was isolated from a fossil carbon contaminated soil. The effect of the carbon source, glucose or olive oil, was investigated in vitro on the biomass produced by F. solani and on the degradation of benzo[a]pyrene (BaP) in mineral medium. After only 12 days of incubation, BaP degradation by F. solani was higher (37.4%) with olive oil used as the carbon source than the one obtained with glucose (4.2%). Catalase activity increased in the presence of olive oil (3.4 µkat mg-1 protein) in comparison with glucose (2.1 µkat mg-1 protein). When olive oil was used as the carbon source, BaP degradation increased up to 76.0% in the presence of a specific catalase inhibitor, 3-Amino-1,2,4-triazole (2 mM). This metabolic engineering strategy based both on the use of olive oil as carbon source (cultivation strategy) and on the blocking of the catalase activity could be an innovative and promising approach for fungal biodegradation of BaP and consequently for bioremediation of soil contaminated with polycyclic aromatic hydrocarbons.

Synthesis of modified potato starches for aqueous solubilization of benzo[a]pyrene.

For soil rehabilitation, the surfactant-enhanced remediation has emerged as a promising technology. For this purpose, starch derivatives were difunctionalized by 1,4-butane sultone (BS) and 2-octen-1-ylsuccinic anhydride (OSA). Eight distinct products were obtained under different synthesis conditions. The chemical structural characteristics were investigated by (1)H NMR spectroscopy. The compounds were evaluated for their apparent aqueous solubility and their ability to increase the solubility of a hydrophobic pollutant such as benzo[a]pyrene (BaP), used as a polycyclic aromatic hydrocarbon model. In comparison with native starch, the best obtained compound increased starch apparent aqueous solubility by a factor of 10 (up to 3.50g/L) and also stimulated 77-fold BaP aqueous solubilization (up to 232.97µg/L) underlining its very high surfactant property. In this study, the right balance between hydrophobic character (octenyl succinate group (OS) grafted) of starch derivatives and starch apparent aqueous solubility (BS grafted) was highlighted.

Energy-dependent uptake of benzo[a]pyrene and its cytoskeleton-dependent intracellular transport by the telluric fungus Fusarium solani.

In screening indigenous soil filamentous fungi for polycyclic aromatic hydrocarbons (PAHs) degradation, an isolate of the Fusarium solani was found to incorporate benzo[a]pyrene (BaP) into fungal hyphae before degradation and mineralization. The mechanisms involved in BaP uptake and intracellular transport remain unresolved. To address this, the incorporation of two PAHs, BaP, and phenanthrene (PHE) were studied in this fungus. The fungus incorporated more BaP into cells than PHE, despite the 400-fold higher aqueous solubility of PHE compared with BaP, indicating that PAH incorporation is not based on a simple diffusion mechanism. To identify the mechanism of BaP incorporation and transport, microscopic studies were undertaken with the fluorescence probes Congo Red, BODIPY®493/503, and FM®4-64, targeting different cell compartments respectively fungal cell walls, lipids, and endocytosis. The metabolic inhibitor sodium azide at 100 mM totally blocked BaP incorporation into fungal cells indicating an energy-requirement for PAH uptake into the mycelium. Cytochalasins also inhibited BaP uptake by the fungus and probably its intracellular transport into fungal hyphae. The perfect co-localization of BaP and BODIPY reveals that lipid bodies constitute the intracellular storage sites of BaP in F. solani. Our results demonstrate an energy-dependent uptake of BaP and its cytoskeleton-dependent intracellular transport by F. solani.

Synthesis of alkylated potato starch derivatives and their potential in the aqueous solubilization of benzo[a]pyrene.

For the development of renewable bioproducts able to solubilize organic persistent pollutant such as benzo[a]pyrene (BaP), modified potato starch was synthesized by alkylation. The addition of alkyl chains was performed with three different alkylation agents: epoxyalkane, alkenyl succinic anhydride and 1,4-butane sultone. Twelve alkylated starches were obtained with different molar substitutions (MS) and various alkyl chain lengths (to three carbons up to sixteen). The chemical structural characteristics were investigated by methods of (1)H NMR and FTIR. In comparison with the native starch, the ether modified starches showed in general an enhancement of their aqueous solubility whereas the ester modified starches stimulated the BaP aqueous solubilization. Indeed, the compounds P6 and P12, which increased 40-fold the BaP aqueous concentration, present high surfactant properties.

Exploring micromycetes biodiversity for screening benzo[a]pyrene degrading potential.

Twenty-five strains of filamentous fungi, encompassing 14 different species and belonging mainly to Ascomycetes, were tested for their ability to degrade benzo[a]pyrene (BaP) in mineral liquid medium. The most performing isolates for BaP degradation (200 mg l(-1)) in mineral medium were Cladosporium sphaerospermum with 29 % BaP degradation, i.e., 82.8 µg BaP degraded per day (day(-1)), Paecilomyces lilacinus with 20.5 % BaP degradation, i.e., 58.5 µg BaP day(-1), and Verticillium insectorum with 22.3 % BaP degradation, i.e., 64.3 µg BaP day(-1), after only 7 days of incubation. Four variables, e.g., biomass growth on hexadecane and glucose, BaP solubilization, activities of extracellular- and mycelium-associated peroxidase, and polyethylene glycol degradation, were also studied as selective criteria presumed to be involved in BaP degradation. Among these variables, the tests based on polyethylene glycol degradation and on fungal growth on hexadecane and glucose seemed to be the both pertinent criteria for setting apart isolates competent in BaP degradation, suggesting the occurrence of different mechanisms presumed to be involved in pollutant degradation among the studied micromycetes.

Fenton degradation assisted by cyclodextrins of a high molecular weight polycyclic aromatic hydrocarbon benzo[a]pyrene.

This paper investigates the effect of native beta-cyclodextrin (beta-CD) and its CD derivatives, such as hydroxypropyl-beta-cyclodextrin (HPBCD) and randomly methylated-beta-cyclodextrin (RAMEB), on the solubilization of a high molecular weight polycyclic aromatic hydrocarbon benzo[a]pyrene (BaP) and on its degradation by Fenton's reaction. The results show that BaP apparent solubility was significantly increased in the presence of cyclodextrin (CD) in the following order: beta-CD

Benzo[a]pyrene degradation using simultaneously combined chemical oxidation, biotreatment with Fusarium solani and cyclodextrins.

The interest of simultaneously combining chemical (Fenton's reaction) and biological treatments for the degradation of a high molecular weight polycyclic aromatic hydrocarbon benzo[a]pyrene (BaP) has been studied in laboratory tests. An optimal concentration of 1.5x10(-3) M H(2)O(2) as Fenton's reagent was firstly determined as being compatible with the growth of Fusarium solani, the Deuteromycete fungus used in the biodegradation process. For the enhancement of BaP solubilisation, cyclodextrins were also used in the performed tests. The best degradation performance was achieved through the use of 5x10(-3) M hydroxypropyl-beta-cyclodextrin (HPBCD) in comparison with randomly methylated-beta-cyclodextrin (RAMEB). When Fenton's treatment was combined with biodegradation, a beneficial effect on BaP degradation (25%) was obtained in comparison with biodegradation alone (8%) or with chemical oxidation alone (16%) in the presence of HPBCD for 12 days of incubation.

Preliminary evidence of the role of hydrogen peroxide in the degradation of benzo[a]pyrene by a non-white rot fungus Fusarium solani.

In order to study the enzymatic mechanisms involved in the successive steps of BaP degradation by a Deuteromycete fungus Fusarium solani, we developed an indirect approach by using inhibitors of enzymes. We used either specific inhibitors of peroxidases (i.e. salicylhydroxamic acid) and of cytochrome P-450 (i.e. piperonyl butoxyde) or inhibitors of both enzymes (i.e. potassium cyanide). Surprisingly, no expected decrease of BaP degradation was observed with most inhibitors tested. On the contrary, more BaP was degraded. Only butylated hydroxytoluene, which acts as a free radical scavenger, inhibited BaP degradation. The inhibition of these enzymes, which use H(2)O(2) as a cosubstrate, might have resulted in an increase of hydrogen peroxide availability in the fungal cultures. This enhancement could induce formation of reactive oxygen species (ROS) which might be the agents that initiate benzo[a]pyrene oxidation. This study proposed a hypothetic alternative metabolic pathway involved in PAH metabolism by Fusarium solani.

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) by Cladosporium sphaerospermum isolated from an aged PAH contaminated soil.

The ability of a Deuteromycete fungus, Cladosporium sphaerospermum, previously isolated from soil of an aged gas manufacturing plant, to degrade polycyclic aromatic hydrocarbons was investigated. This strain was able to degrade PAHs in non-sterile soils (average 23%), including high molecular weight PAHs, after 4 weeks of incubation. In a microcosm experiment, PAH depletion was clearly correlated to fungal establishment. In liquid culture, this strain degraded rapidly benzo(a)pyrene during its early exponential phase of growth (18% after 4 days of incubation). Among extracellular ligninolytic enzyme activities tested, only laccase activity was detected in liquid culture in the absence or in presence of benzo(a)pyrene. C. sphaerospermum might be a potential candidate for an effective bioremediation of aged PAH-contaminated soils.