Anaerobic Digestion of the Organic Fraction of Municipal Solid Waste in Plug-Flow Reactors: Focus on Bacterial Community Metabolic Pathways

The aim of this study is to investigate the performance of a pilot-scale plug-flow reactor (PFR) as a biorefinery system to recover chemicals (i.e., volatile fatty acids (VFAs)), and biogas during the dry thermophilic anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW). The effects of the hydraulic retention time (HRT) on both outputs were studied, reducing the parameter from 22 to 16 days. In addition, VFA variation along the PFR was also evaluated to identify a section for a further valorization of VFA-rich digestate stream. A particular focus was dedicated for characterizing the community responsible for the production of VFAs during hydrolysis and acidogenesis. The VFA concentration reached 4421.8 mg/L in a section located before the end of the PFR when the HRT was set to 16 days. Meanwhile, biogas production achieved 145 NLbiogas/d, increasing 2.7 times when compared to the lowest HRT tested. Defluviitoga sp. was the most abundant bacterial genus, contributing to 72.7% of the overall bacterial population. The genus is responsible for the hydrolysis of complex polysaccharides at the inlet and outlet sections since a bimodal distribution of the genus was found. The central zone of the reactor was distinctly characterized by protein degradation, following the same trend of propionate production

PCB in the environment: bio-based processes for soil decontamination and management of waste from the industrial production of Pleurotus ostreatus

Polychlorinated biphenyls (PCBs) are hazardous soil contaminants for which a bio-based technology for their recovery is essential. The objective of this study was to validate the exploitation of spent mushroom substrate (SMS), a low or null cost organic waste derived from the industrial production of P. ostreatus, as bulking agent in a dynamic biopile pilot plant. The SMS shows potential oxidative capacity towards recalcitrant compounds. The aim was consistent with the design of a process of oxidation of highly chlorinated PCBs, which is independent from their reductive dehalogenation. Feasibility was verified at a mesocosm scale and validated at pilot scale in a dynamic biopile pilot plant treating ten tons of a historically contaminated soil (9.28 ± 0.08 mg PCB/kg soil dry weight). Mixing of the SMS with the soil was required for the depletion of the contaminants. At the pilot scale, after eight months of incubation, 94.1% depletion was recorded. A positive correlation between Actinobacteria and Firmicutes active metabolism, soil laccase activity and PCB removal was observed. The SMS was found to be exploitable as a versatile low cost organic substrate capable of activating processes for the oxidation of highly chlorinated PCBs. Moreover, its exploitation as bulking agent in biopiles is a valuable management strategy for the re-utilisation of an organic waste deriving from the industrial cultivation of edible mushrooms

A new Thioalkalivibrio sp. strain isolated from petroleum-contaminated brackish estuary sediments: A new candidate for bio-based application for sulfide oxidation in halo-alkaline conditions

A new halo-alkaline sulfur-oxidising bacterial strain was isolated from brackish estuary sediments contaminated by total petroleum hydrocarbon. The isolate was classified as a new strain of Thioalkalivibrio sulfidiphilus sp., showing a higher capability of adaptation to pH and a higher optimal sodium concentration for growth, when compared to Thioalkalivibrio sulfidiphilus sp. HL-EbGr7, type strain of the species. The strain was capable to grow in saline concentrations up to 1.5 M Na+ and pH up to 10. The genome of the new isolate was sequenced and annotated. The comparison with the genome of Thioalkalivibrio sulfidiphilus sp. HL-EbGr7 showed a duplication of an operon encoding for a putative primary sodium extruding pump and the presence of a sodium/proton antiporter with optimal efficiency at halo-alkaline conditions. The new strain was able to oxidize sulfide at halo-alkaline conditions at the rate of 1 mmol/mg-N/h, suitable for industrial applications dedicated to the recovery of alkaline scrubber for H2S emission absorption and abatement

Degradation of BTEX mixture by a new Pseudomonas putida strain: role of the quorum sensing in the modulation of the upper BTEX oxidative pathway

A new Pseudomonas putida strain (AQ8) was isolated from a decommissioned oil refinery’s soil in Italy and characterized for its ability to degrade BTEX. The draft genome of the new strain was sequenced and annotated for genes that encode enzymes putatively involved in BTEX degradation and quorum sensing. The strain was transformed with a plasmid expressing lactonase, which cleaves the autoinducer quorum sensing signal molecule, the acyl-homoserine lactone, to obtain a quorum sensing minus strain. P. putida AQ8 depleted the 40% on average of all the components of the initial BTEX concentration in 36 h. The quorum sensing minus strain, in the same time interval, depleted only the 10% of the initial BTEX concentration. The role of quorum sensing in regulating the expression of the annotated benzene/toluene dioxygenase gene (benzA) and biphenyl/toluene/benzene dioxygenase (bphA) genes, which are involved in BTEX degradation, was studied by quantitative RT-real-time quantitative (q)PCR analysis. The qPCR data showed decreased levels of expression of the benzA and bphA genes in the quorum sensing minus strain. Our results showed, for the first time, quorum sensing modulation of the level of transcription of dioxygenase genes in the upper BTEX oxidation pathway

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