Solid-state cultures of Fusarium oxysporum transform aromatic components of olive-mill dry residue and reduce its phytotoxicity

The present study mainly investigated the ability of solid-state cultures of the non-pathogenic Fusarium oxysporum strain BAFC 738 to transform aromatic components to reduce the phytotoxicity in olive-mill dry residue (DOR), the waste from the two-phase manufacturing process. Lignin, hemicellulose, fats and water-soluble extractives contents of DOR colonized by the fungus for 20 weeks were reduced by 16%, 25%, 71% and 13%, respectively, while the cellulose content increased by 25%. In addition, the ethyl acetate-extractable phenolic fraction of the waste was reduced by 65%. However, mass-balance ultra-Wltration and size-exclusion chromatography experiments suggested that the apparent removal of that fraction, mainly including 2-(3,4-dihydroxyphenyl)ethyl alcohol and 2-(4-hydroxyphenyl) ethyl alcohol, was due to polymerization. Mn-peroxidase and Mn-independent peroxidase activities were found in F. oxysporum solid-state cultures, while laccase and aryl alcohol oxidase activities were not detected. Tests performed with seedlings of tomato (Lycopersicum esculentum L.), soybean (Glycine maximum Merr.), and alfalfa (Medicago sativa L.) grown on soils containing 6% (w/w) of bioconverted DOR (kg soil)¡1 showed that the waste’s phytotoxicity was removed by 20 weeks-old fungal cultures. By contrast, the same material exhibited a high residual toxicity towards lettuce (Lactuca sativa L.).L'articolo é disponibile sul sito dell'editore: http://www.sciencedirect.co

Degradation of tetracyclines and sulfonamides by stevensite- and biochar-immobilized laccase systems and impact on residual antibiotic activity

BACKGROUND: Stevensite and biochar were investigated to covalently immobilize laccase from Myceliophthora thermophila (MtL) and Pleurotus eryngii (PeL) through the sequential application of aminopropyltriethoxysilane and glutaraldehyde. The immobilized preparations were tested to remove three tetracyclines and six sulfonamides at 0.1 mmol L−1 of each antibiotic. Degradation experiments were conducted both in the absence and in the presence (0.2 mmol L−1) of ABTS, 1-hydroxybenzotriazol (HBT), syringaldehyde or violuric acid. The residual antibiotic activity was tested towards five bacterial species and a bacterial consortium from wastewater. RESULTS: Higher values of activity yields (74% and 70.3%) and catalytic capabilities (1426 and 1405 IU g−1) were obtained with PeL on stevensite and biochar than with MtL. Stevensite enabled higher reusability and storage stability than biochar. Best removals of tetracyclines and sulfonamides were obtained with immobilized-laccase systems coupled to ABTS or syringaldehyde. Immobilized-laccase/ABTS systems removed 100% of tetracyclines while only chlortetracycline was completely removed in the presence of syringaldehyde. With ABTS, the most effectively removed sulfonamides were sulfathiazole and sulfadiazine (up to 100% and 54%), while syringaldehyde best supported the removal of sulfanilamide, sulfamethazine and sulfamethoxazole (up to 42%, 45% and 46%, respectively). In some cases, an effective antibiotics removal led to either low or no residual antibiotic activity. CONCLUSION: MtL and PeL were immobilized successfully on biochar and stevensite. The addition of either ABTS or syringaldehyde enhanced significant removals, up to 100%, of tetracyclines and sulfonamides by the immobilized laccase systems. Noteworthy, biochar-immobilized laccases/ABTS led to complete suppression of the antibiotic activity of tetracyclines. © 2018 Society of Chemical Industry

Implications of polluted soil biostimulation and bioaugmentation with spent mushroom substrate (Agaricus bisporus) on the microbial community and polycyclic aromatic hydrocarbons biodegradation

Different applications of spent Agaricus bisporus substrate (SAS), a widespread agro-industrial waste, were investigated with respect to the remediation of a historically polluted soil with Polycyclic Aromatic Hydrocarbons (PAH). In one treatment, the waste was sterilized (SSAS) prior to its application in order to assess its ability to biostimulate, as an organic amendment, the resident soil microbiota and ensuing contaminant degradation. For the other treatments, two bioaugmentation approaches were investigated; the first involved the use of the waste itself and thus implied the application of A. bisporus and the inherent microbiota of the waste. In the second treatment, SAS was sterilized and inoculated again with the fungus to assess its ability to act as a fungal carrier. All these treatments were compared with natural attenuation in terms of their impact on soil heterotrophic and PAH-degrading bacteria, fungal growth, biodiversity of soil microbiota and ability to affect PAH bioavailability and ensuing degradation and detoxification. Results clearly showed that historically PAH contaminated soil was not amenable to natural attenuation. Conversely, the addition of sterilized spent A. bisporus substrate to the soil stimulated resident soil bacteria with ensuing high removals of 3-ring PAH. Both augmentation treatments were more effective in removing highly condensed PAH, some of which known to possess a significant carcinogenic activity. Regardless of the mode of application, the present results strongly support the adequacy of SAS for environmental remediation purposes and open the way to an attractive recycling option of this wasteThis work was financially supported by the Ministry of Science and Innovation of Spain (Project CTM2009-13140-C02-02

Bioaugmentation of a historically contaminated soil by polychlorinated biphenyls with Lentinus tigrinus

Background: Several species belonging to the ecological group of white-rot basidiomycetes are able to bring about the remediation of matrices contaminated by a large variety of anthropic organic pollutants. Among them, polychlorobiphenyls (PCBs) are characterized by a high recalcitrance due to both their low bioavailability and the inability of natural microbial communities to degrade them at significant rates and extents. Objective of this study was to assess the impact of a maize stalk-immobilized Lentinus tigrinus CBS 577.79 inoculant combined with soybean oil (SO), as a possible PCB-mobilizing agent, on the bioremediation and resident microbiota of an actual Aroclor 1260 historically contaminated soil under unsaturated solid-phase conditions. Results: Best overall PCB depletions (33.6 ± 0.3%) and dechlorination (23.2 ± 1.3%) were found after 60 d incubation in the absence of SO where, however, the fungus appeared to exert adverse effects on both the growth of biphenyl- and chlorobenzoate-degrading bacteria and the abundance of genes coding for both biphenyl dioxygenase (bph) and catechol-2,3-dioxygenase. A significant (P < 0.001) linear inverse relationship between depletion yields and degree of chlorination was observed in both augmented and control microcosms in the absence of SO; conversely, this negative correlation was not evident in SO-amended microcosms where the additive inhibited the biodegradation of low chlorinated congeners. The presence of SO, in fact, resulted in lower abundances of both biphenyl-degrading bacteria and bph. Conclusions: The PCB depletion extents obtained in the presence of L. tigrinus are by far higher than those reported in other remediation studies conducted under unsaturated solid phase conditions on actual site soils historically contaminated by Aroclor 1260. These results suggest that the bioaugmentation strategy with the maize stalk-immobilized mycelium of this species might be promising in the reclamation of PCB-contaminated soils. The addition of SO to matrices contaminated by technical PCB mixtures, such as Aroclor 1242 and Delor 103 and characterized by a large preponderance of low chlorinated congeners, might not be advisable

Immobilized inocula of white-rot fungi accelerate both detoxification and organic matter transformation in two-phase dry olive-mill residue

The potential use for agronomic purposes of dry olive-mill residue (DOR), solid waste from the olive oil two-phase extraction process, might be impaired by its phytotoxicity. Although fungal treatments can detoxify DOR, long times are required for these processes. The objective of this study was to assess whether the addition of immobilized fungal inocula to DOR might improve colonization rates, thus reducing the time necessary for its detoxification and bioconversion. Inocula of Panus tigrinus CBS 577.79 and Phlebia sp. DABAC 9 immobilized on either chopped maize stalks or polyurethane sponge (PS) led to higher removals of both phenols and phytotoxicity from DOR than free inocula after 4 weeks of incubation. Best dephenolization (85%) was with PS-immobilized Phlebia sp., the use of which reduced germinability inhibition of Lepidium sativum and Lactuca sativa by 80 and 71.4%, respectively. Regardless of the type of inoculant, a low degree of humification was obtained

Effect of mobilizing agents on mycoremediation and impact on the indigenous microbiota

BACKGROUND: Mobilizing agents (MAs) have been suggested to improve the fungal degradation of polycyclic aromatic hydrocarbons (PAHs) in soil. Three different MAs (Tween 20, Tween 80 and soybean oil) were investigated for their ability to stimulate contaminant degradation by either Phlebia sp. DABAC 9 or Allescheriella sp. DABAC1 in a soil spiked with amixture of PAHs. RESULTS: Phlebia sp. and Allescheriella sp. markedly differed in their growth capabilities under non-sterile conditions and withoutMAs (3.0 versus 0.1 μg ergosterol g−1 soil, respectively). However, soybean oil led to a 35-fold increase of Allescheriella sp. growth. Contaminant degradations by Phlebia sp. DABAC 9 and Allescheriella sp. DABAC 1 were best supported by soybean oil and Tween 20, respectively. Enumeration of cultivable bacteria and denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S rRNA showed that microbial density and biodiversity were positively affected by the mycoremediation especially with Allescheriella sp., the use of which led to an evident detoxification. CONCLUSIONS: Allescheriella sp. DABAC 1 appears to be a promising strain in the remediation of PAH-contaminated soils. The different response of the two fungi to MAs addition confirms the stringent need for a preliminary lab-scale assessment of fungus/MA combinations prior to application.L'articolo è disponibile sul sito dell'editore: http://www.onlinelibrary.wiley.co

Ligninolytic enzymes production by Dichostereum sordulentum cultures in the presence of Eucalyptus bark as a natural laccase stimulator

A strain of a fungal species, i.e., Dichostereum sordulentum, not yet isolated from either Uruguay or decayed Eucalyptus spp. wood, was investigated for its ability of producing extracellular ligninolytic enzymes. To this aim, the strain was grown on a N-rich liquid medium added with either bark or wood Eucalyptus dunnii sawdust. The former additive was more effective than the latter instimulating laccase leading to a production of 4.78 IU mL-1 which was further enhanced by the concomitant presence of 80 ppm CuSO4 (6.56 IU mL-1). The two order of magnitude higher proanthocyanidin content in bark than in wood suggests that this fraction might be responsible for the higher stimulatory effect of the former on laccase production