RESUMEN
The mutual impact of low-quality lignite and high-density polyethylene (HDPE) during open system pyrolysis was investigated, aiming to improve utilization of lignite with simultaneous treatment of HDPE waste. Pyrolysis of lignite, HDPE, and their mixture (mass ratio, 1:1) was performed at temperatures 400, 450, 500, 550, and 600 °C. Initial substrates and pyrolysis products were characterized by thermogravimetric analysis (TGA), gas chromatography-mass spectrometry (GC-MS), specific carbon isotope analysis of individual hydrocarbons (δ13C), Rock-Eval pyrolysis, and elemental analysis. The positive synergetic effect during co-pyrolysis of lignite/HDPE mixture was observed at temperatures ≥450 °C, with the greatest being at 500 °C. The highest yield of liquid co-pyrolysis products with a similar composition to that of crude oils is also noticed at 500 °C. The yields of liquid and gaseous products and quality of pyrolytic products obtained by co-pyrolysis of lignite/HDPE mixture are notably improved compared with pyrolysis of lignite alone. On the other hand, data obtained from pyrolysis of HDPE alone indicate that it cannot be concurrent to well-developed catalytic thermal processes for polymer recycling. However, concerning the huge amount of produced HDPE, at least part of this plastic material can be reused for advanced thermal treatment of lignite, particularly in countries where this low-rank coal represents the main source of energy.
RESUMEN
Pseudomonas aeruginosa san ai, an alkaliphilic, metallotolerant bacterium, degraded individual selected petroleum compounds, i.e., n-alkanes (n-hexadecane, n-nonadecane) and polycyclic aromatic hydrocarbons (fluorene, phenanthrene, pyrene) with efficiency of 80%, 98%, 96%, 50% and 41%, respectively, at initial concentrations of 20 mg L-1 and in seven days. P. aeruginosa san ai showed a high biodegradative capacity on complex hydrocarbon mixtures, the aliphatic and aromatic fractions from crude oil. The efficiency of P. aeruginosa san ai degradation of crude oil fractions in seven days reached stage 3-4 of the oil biodegradation scale, which ranges from 0 (no biodegradation) to 10 (maximum biodegradation). Identified metabolites concomitant with genomic and enzymatic data indicated the terminal oxidation pathway for the n-alkane degradation, and the salicylate and phthalate pathways for fluorene biodegradation. Polyextremophilic P. aeruginosa san ai, as a biosurfactant producer with multidegradative capacity for hydrocarbons, can be used in an improved strategy for environmental bioremediation of hydrocarbon-contaminated sites, including extreme habitats characterized by low or elevated temperatures, acidic or alkaline pH or high concentrations of heavy metals.
RESUMEN
The Pseudomonas aeruginosa san ai strain was investigated for its capability to degrade the 2,6-di-tert-butylphenol (2,6-DTBP) plastic additive, a hazardous and toxic substance for aquatic life. This investigation was performed under different parameter values: 2,6-DTBP concentration, inoculum size, pH, and temperature. The GC-MS study showed that P. aeruginosa efficiently degraded 2,6-DTBP in the pH range of 5-8 at higher temperatures. Under exposure to 2,6-DTBP concentrations of 2, 10, and 100 mg L-1, the strain degraded by 100, 100, and 85%, respectively, for 7 days. Crude enzyme preparation from the biomass of P. aeruginosa san ai showed higher efficiency in 2,6-DTBP removal than that shown by whole microbial cells. Gene encoding for the enzymes involved in the degradation of aromatic compounds in P. aeruginosa san ai was identified. To complement the genomic data, a comparative proteomic study of P. aeruginosa san ai grown on 2,6-DTBP or sunflower oil was conducted by means of nanoLC-MS/MS. The presence of aromatic substances resulted in the upregulation of aromatic ring cleavage enzymes, whose activity was confirmed by enzymatic tests; therefore, it could be concluded that 2,6-DTBP might be degraded by ortho-ring cleavage. A comparative proteomics study of P. aeruginosa san ai indicated that the core molecular responses to aromatic substances can be summarized as the upregulation of proteins responsible for amino acid metabolism with emphasized glutamate metabolism and energy production with upregulated enzymes of glyoxylate bypass. P. aeruginosa san ai has a high capacity to efficiently degrade aromatic compounds, and therefore its whole cells or enzymes could be used in the treatment of contaminated areas.