Hypersaline Lake Urmia: a potential hotspot for microbial genomic variation

Lake Urmia located in Iran is a hypersaline environment with a salinity of about 27% (w/v). Metagenomic analyses of water samples collected from six locations in the lake exhibited a microbial community dominated by representatives of the family Haloferacaceae (69.8%), mainly those affiliated to only two genera, Haloquadratum (59.3%) and Halonotius (9.1%). Similar to other hypersaline lakes, the bacterial community was dominated by Salinibacter ruber (23.3%). Genomic variation analysis by inspecting single nucleotide variations (SNVs) and insertions/deletions (INDELs) exhibited a high level of SNVs and insertions, most likely through transformation for abundant taxa in the Lake Urmia community. We suggest that the extreme conditions of Lake Urmia and specifically its high ionic concentrations could potentially increase the SNVs and insertions, which can consequently hamper the assembly and genome reconstruction from metagenomic reads of Lake Urmia

Colonization and Biodegradation of Photo-Oxidized Low-Density Polyethylene (LDPE) by New Strains of 'Aspergillus' sp. and 'Lysinibacillus' sp.

The primary objective of this study was the isolation of low-density polyethylene (LDPE)-degrading microorganisms. Soil samples were obtained from an aged municipal landfill in Tehran, Iran, and enrichment culture procedures were performed using LDPE films and powder. Screening steps were conducted using linear paraffin, liquid ethylene oligomer, and LDPE powder as the sole source of carbon. Two landfill-source isolates, identified as 'Lysinibacillus xylanilyticus' XDB9 (T) strain S7-10F and 'Aspergillus niger' strain F1-16S, were selected as super strains. Photo-oxidation (25 days under ultraviolet [UV] irradiation) was used as a pretreatment of the LDPE samples without pro-oxidant additives. The PE biodegradation process was performed for 56 days in a liquid mineral medium using UV-irradiated pure LDPE films without pro-oxidant additives in the presence of the bacterial isolate, the fungal isolate, and the mixture of the two isolates. The process was monitored by measuring the fungal biomass, the bacterial growth, and the pH of the medium. During the process, the fungal biomass and the bacterial growth increased, and the pH of the medium decreased, which suggests the utilization of the preoxidized PE by the selected isolates as the sole source of carbon. Carbonyl and double bond indices exhibited the highest amount of decrement and increment, respectively, in the presence of the fungal isolate, and the lowest indices were obtained from the treatment of a mixture of both fungal and bacterial isolates. Fourier transform infrared (FT-IR), x-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses showed that the selected isolates modified and colonized preoxidized pure LDPE films without pro-oxidant additives

Biodegradation of low-density polyethylene (LDPE) by mixed culture of Lysinibacillus xylanilyticus and Aspergillus niger in soil.

In this study, two strains of Aspergillus sp. and Lysinibacillus sp. with remarkable abilities to degrade low-density polyethylene (LDPE) were isolated from landfill soils in Tehran using enrichment culture and screening procedures. The biodegradation process was performed for 126 days in soil using UV- and non-UV-irradiated pure LDPE films without pro-oxidant additives in the presence and absence of mixed cultures of selected microorganisms. The process was monitored by measuring the microbial population, the biomass carbon, pH and respiration in the soil, and the mechanical properties of the films. The carbon dioxide measurements in the soil showed that the biodegradation in the un-inoculated treatments were slow and were about 7.6% and 8.6% of the mineralisation measured for the non-UV-irradiated and UV-irradiated LDPE, respectively, after 126 days. In contrast, in the presence of the selected microorganisms, biodegradation was much more efficient and the percentages of biodegradation were 29.5% and 15.8% for the UV-irradiated and non-UV-irradiated films, respectively. The percentage decrease in the carbonyl index was higher for the UV-irradiated LDPE when the biodegradation was performed in soil inoculated with the selected microorganisms. The percentage elongation of the films decreased during the biodegradation process. The Fourier transform infra-red (FT-IR), x-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to determine structural, morphological and surface changes on polyethylene. These analyses showed that the selected microorganisms could modify and colonise both types of polyethylene. This study also confirmed the ability of these isolates to utilise virgin polyethylene without pro-oxidant additives and oxidation pretreatment, as the carbon source

Effect of polyethylene wax/soy protein-based dispersion barrier coating on the physical, mechanical, and barrier characteristics of paperboards

Application of barrier dispersion coatings on paperboards, which must have proper moisture and grease resistance for food applications, has always been an interesting subject for the packaging industry. In this study, paperboards were coated with a novel dispersion barrier coating prepared through mixing soy protein isolate (SPI) and polyethylene wax (PE-wax). Different characterization methods were used to study the effects of coating and its composition on the physical, mechanical, and barrier characteristics of paperboards. The results indicated that the incorporation of PE-wax into the coating formulation caused significant reduction of the viscosity of coating slurries. It had no effect on the coating weight of the samples but increased the thickness of the coated paperboards as compared with those coated with SPI only. The increase of the wax content led to a reduction of 5-16% in the tensile strength values in comparison with the uncoated paperboards. Barrier characteristics, i.e., water vapor permeability (WVP), surface wettability, and water resistance, improved by adding PE-wax. In addition, it was found that there was a critical level for the addition of PE-wax, 50% of SPI, as no oil migration was detected when the paperboards coated with SPI coatings contained less than 50% PE-wax.Peer reviewe

Carbonyl and double bond indices values determined using FTIR from LDPE films before and after 126 days incubation in soil in various treatments.

<p><i>CI</i> carbonyl index, <i>DBI</i> double bond index, (Δ%) difference between carbonyl and double bond indices of films before and after 126 days of biodegradation (shown as a percentage). (SP: Soil + non-UV-irradiated PE; SUP: Soil + UV-irradiated PE; SMP: Soil + Selected Microorganisms + non-UV-irradiated PE; SMUP: Soil + Selected Microorganisms + UV-irradiated PE).</p

XRD spectra of non-UV and UV-irradiated pure LDPE films before and after incubation in soil with different treatments.

<p>(A) XRD spectra of non-UV-irradiated pure LDPE films without pro-oxidant additives before and after 126 days of incubation in soil with different treatments: (a) blank (no UV irradiation, no incubation); (b) non-UV-irradiated LDPE after incubation in soil in the absence of the selected microorganisms (SP treatment); (c) non-UV-irradiated LDPE after incubation in soil in the presence of the selected microorganisms (SMP treatment). (B) XRD spectra of UV-irradiated pure LDPE films without pro-oxidant additives before and after 126 days of incubation in soil with different treatments: (a) blank (after 25 days' UV irradiation, no incubation); (b) UV-irradiated LDPE after incubation in soil in the absence of the selected microorganisms (SUP treatment); (c) UV-irradiated LDPE after incubation in soil in the presence of the selected microorganisms (SMUP treatment).</p

FT-IR spectra of non-UV-irradiated pure LDPE films before and after incubation in soil in various treatments.

<p>(A) FT-IR spectra of non-UV-irradiated pure LDPE films without pro-oxidant additives before and after 126 days of incubation in soil in the presence and absence of the selected microorganisms from 500–4000 cm-1. (B) The changes in the bands between 500 and 2,000 cm-1 of the FT-IR spectra of non-UV-irradiated pure LDPE films without pro-oxidant additives before and after 126 days of incubation in soil with different treatments: (a) blank (no UV irradiation, no incubation); (b) non-UV-irradiated LDPE after incubation in soil in the absence of the selected microorganisms (SP treatment); (c) non-UV-irradiated LDPE after incubation in soil in the presence of the selected microorganisms (SMP treatment).</p

FT-IR spectra of UV-irradiated pure LDPE films before and after incubation in soil in various treatments.

<p>(A) FT-IR spectra of UV-irradiated pure LDPE films without pro-oxidant additives before and after 126 days of incubation in soil in the presence and absence of the selected microorganisms from 500–4000 cm-1. (B) The changes in the bands between 500 and 2,000 cm-1 of the FT-IR spectra of UV-irradiated pure LDPE films without pro-oxidant additives before and after 126 days of incubation in soil with different treatments: (a) blank (after 25 days' UV irradiation, no incubation); (b) UV-irradiated LDPE after incubation in soil in the absence of the selected microorganisms (SUP treatment); (c) UV-irradiated LDPE after incubation in soil in the presence of the selected microorganisms (SMUP treatment).</p

pH changes in inoculated, un-inoculated and blank soil samples for UV- and non-UV-irradiated pure LDPE films.

<p>Each data point represents the average of three replicates ± SD. (S: Soil; SM: Soil + Selected Microorganisms; SMP: Soil + Selected Microorganisms + non-UV-irradiated PE; SMUP: Soil+ Selected Microorganisms + UV-irradiated PE; SP: Soil + non-UV-irradiated PE; SUP: Soil + UV-irradiated PE).</p

Mineralisation profile of UV- and non-UV-irradiated pure LDPE films incubated in the soil with various treatments for 126 days.

<p>Each data point represents the average of three replicates ± SD. (SP: Soil + non-UV-irradiated PE; SUP: Soil + UV-irradiated PE; SMP: Soil+ Selected Microorganisms + non-UV-irradiated PE; SMUP: Soil+ Selected Microorganisms + UV-irradiated PE).</p