Fungal Oxidoreductases and Humification in Forest Soils. In: Shukla G, Varma A, editors. Soil Enzymology. Berlin: Springer Berlin Heidelberg; 2011. pp. 207-28. [DOI: 10.1007/978-3-642-14225-3_11]

Microbial Involvement in the Bioremediation of Total Petroleum Hydrocarbon Polluted Soils: Challenges and Perspectives

Nowadays, soil contamination by total petroleum hydrocarbons is still one of the most widespread forms of contamination. Intervention technologies are consolidated; however, full-scale interventions turn out to be not sustainable. Sustainability is essential not only in terms of costs, but also in terms of restoration of the soil resilience. Bioremediation has the possibility to fill the gap of sustainability with proper knowledge. Bioremediation should be optimized by the exploitation of the recent “omic” approaches to the study of hydrocarburoclastic microbiomes. To reach the goal, an extensive and deep knowledge in the study of bacterial and fungal degradative pathways, their interactions within microbiomes and of microbiomes with the soil matrix has to be gained. “Omic” approaches permits to study both the culturable and the unculturable soil microbial communities active in degradation processes, offering the instruments to identify the key organisms responsible for soil contaminant depletion and restoration of soil resilience. Tools for the investigation of both microbial communities, their degradation pathways and their interaction, will be discussed, describing the dedicated genomic and metagenomic approaches, as well as the interpretative tools of the deriving data, that are exploitable for both optimizing bio-based approaches for the treatment of total petroleum hydrocarbon contaminated soils and for the correct scaling up of the technologies at the industrial scale.

Tyrosinase and laccase-producing Bacillus aryabhattai TFG5 and its role in the polymerization of phenols

BACKGROUND

Tyrosinases and laccases are oxidoreductase enzymes that are used widely in the food, feed, textile, and biofuel industries. The rapidly growing industrial demand for bacterial oxido-reductases has encouraged research on this enzyme worldwide. These enzymes also play a key role in the formation of humic substances (HS) that are involved in controlling the biogeochemical carbon cycle, providing nutrients and bio-stimulants for plant growth, and interacting with inorganic and organic pollutants besides increasing carbon sequestration and mitigating greenhouse gas emission in the environment. The present study aimed to screen and characterize extracellular tyrosinase and laccase-producing soil bacteria that could be utilized in the polymerization of phenols.

RESULTS

Twenty isolates from different soil samples collected from forest ecosystems were characterized through ARDRA using restriction digestion with AluI, HpaII, and HaeIII restriction enzymes. The results of Hierarchical Cluster Analysis (HCA) revealed a 60 % similarity coefficient among 13 out of 20 isolates, of which, the isolate TFG5 exhibited only 10 % similarity when compared to all the other isolates. The isolate TFG5 exhibited both tyrosinase (1.34 U.mL- 1) and laccase (2.01 U.mL- 1) activity and was identified as Bacillus aryabhattai. The increased polymerization activity was observed when B. aryabhattai TFG5 was treated with phenols. The monomers such as catechol, p-Hydroxy benzoic acid, ferulic acid, and salicylic acid were polymerized efficiently, as evidenced by their FT-IR spectra depicting increased functional groups compared to the standard mushroom tyrosinase.

CONCLUSIONS

The polymerization ability of B. aryabhattai TFG5 could be applied to phenol-rich wastewater treatment for efficient precipitation of phenols. Furthermore, tyrosinases can be used for enhancing the synthesis of HS in soil.

A New Ciboria sp. for Soil Mycoremediation and the Bacterial Contribution to the Depletion of Total Petroleum Hydrocarbons

A Ciboria sp. strain (Phylum Ascomycota) was isolated from hydrocarbon-polluted soil of an abandoned oil refinery in Italy. The strain was able to utilize diesel oil as a sole carbon source for growth. Laboratory-scale experiments were designed to evaluate the use of this fungal strain for treatment of the polluted soil. The concentration of total petroleum hydrocarbons (TPH) in the soil was 8,538 mg/kg. Mesocosms containing the contaminated soil were inoculated with the fungal strain at 1 or 7%, on a fresh weight base ratio. After 90 days of incubation, the depletion of TPH contamination was of 78% with the 1% inoculant, and 99% with the 7% inoculant. 16S rDNA and ITS metabarcoding of the bacterial and fungal communities was performed in order to evaluate the potential synergism between fungi and bacteria in the bioremediation process. The functional metagenomic prediction indicated Arthrobacter, Dietzia, Brachybacerium, Brevibacterium, Gordonia, Leucobacter, Lysobacter, and Agrobacterium spp. as generalist saprophytes, essential for the onset of hydrocarbonoclastic specialist bacterial species, identified as Streptomyces, Nocardoides, Pseudonocardia, Solirubrobacter, Parvibaculum, Rhodanobacter, Luteiomonas, Planomicrobium, and Bacillus spp., involved in the TPH depletion. The fungal metabolism accelerated the onset of specialist over generalist bacteria. The capacity of the Ciboria sp. to deplete TPH in the soil in treatment was also ascertained.

Features of the chemical structure of different organic matter pools in Haplic Chernozem of the Streletskaya steppe: 13C MAS NMR study

The aim of the current research was to study structural features of four organic matter (OM) pools isolated by the modified method of granulo-densimetric fractionation from two Сhernozems. We purposed to relate these features to the OM allocation and the transformation processes. The pools included: 1) free light fraction located in an inter-aggregate space, 2) light fraction occluded inside the microaggregates, 3) OM bound with clay particles, and 4) OM bound with a residual heavy fraction left after light fractions and clay separation. Soils of contrasting land uses: steppe and long-term permanent bare fallow were selected to assess changes that occur in soil OM during the degradation. We used ¹³C CP/MAS NMR spectroscopy controlling the quantitativeness of spectra with the aid of ¹³C DP/MAS NMR. The obtained spectra of the studied fractions clearly differed in the proportion of main functional groups. The occluded OM is more aromatic compared to the free OM. The structural changes observed at transition from the free light fraction to the occluded one indicate an active decomposition of lignin and carbohydrates in the latter fraction. This provides in the occluded OM appropriate conditions for the formation of "young HA": high local concentration of substrates and spatial proximity of enzymes. At C-deficiency (bare fallow) the chemical structure of the occluded OM is very close to that of humic acids. The chemical structure of the clay bound OM reflects high content of products of microbial origin. OM of the residual heavy fraction differs from that of the clay: the proportions of main functional groups in it are more close to that of the free light fraction, but with higher carboxyl content. Heavy fractions also differ under acid treatment: the residue losses less carbon. The above-mentioned differences show that the division of heavy fractions into two components is reasonable. Various acid hydrolyzability indicates a predominance of strong chemical bonds in the occluded OM and the significant contribution of weak bonds in the clay OM, i.e., the occluded OM is highly condensed, in contrast, components of the clay OM are largely interconnected by hydrogen-, coordinate, hydrophobic and other relatively weak bonds. Soil degradation under extreme land use leads not only to OM scarcity, but also to its greater hydrolyzability, strong enrichment with aromatic fragments and depletion of carbohydrate and aliphatic fragments in all studied fractions. Degradation changes in the occluded OM are most pronounced. Our results demonstrate that the applied fractionation scheme coupled with quantitative ¹³C CP/MAS NMR spectroscopy is a very promising approach for evaluating processes of soil OM transformation and degradation.

Mycoremediation of Old and Intermediate Landfill Leachates with an Ascomycete Fungal Isolate, Lambertella sp

In the present study, an Ascomycete fungal strain, Lambertella sp., isolated from environmental polluted matrices, was tested for the capacity to reduce the contamination and the toxicity of intermediate and old landfill leachates. Batch tests in flasks, under co-metabolic conditions, were performed with two different old leachates, with suspended and immobilized Lambertella sp. biomass, resulting in a soluble chemical oxygen demand depletion of 70% and 45%, after 13 and 30 days, respectively. An intermediate landfill leachate was treated in lab-scale reactors operating in continuous conditions for three months, inoculated with immobilized Lambertella sp. biomass, in absence of co-substrates. The Lambertella sp. depleted the corresponding total organic carbon by 90.2%. The exploitability of the Lambertella sp. strain was evaluated also in terms of reduction of phyto-, cyto-, and mutagenicity of the different Landfill Leachates at the end of the myco-based treatment, resulting in an efficient depletion of leachate clastogenicity.