Exploring community dynamics: Cultivable and uncultivable for the microbial-mediated bioremediation of oil-based paints polluted soil from aqueous media by Plackett-Burman statistically designed conditions.

Oil-based paint seriously threatens biodiversity due to its complex composition and biocide toxicity. Therefore, it alters the microbial diversity abundance and in modern approaches like metagenomic, a powerful tool to get insight into pollutants effect on soil microbial community abundance. Thus, present study aimed at "exploring community dynamics: cultivable and uncultivable for the microbial-mediated bioremediation of oil-based paints polluted soil from aqueous media by Plackett-Burman statistical designed conditions". The total DNA from oil-based paints polluted soil was extracted by PowerSoil DNA Isolation Kit. The 16S rDNA genes were amplified using universal primers and PCR amplicons were sequenced for analysis of metagenomes to determine the bacterial microbiome abundance. A total 133,140 sequence reads, 2857 Operational Taxonomic Units (OTUs) of 16S rRNA genes, and 30 bacterial phyla were retrieved from all the oil-based paints polluted samples (C, R498, B698 and G492) with the significant increase in Firmicutes (18.90 %, 52.39 %, 49.75 %, 44.36 %) and Actinobacteria (26.66 %, 28.93 %, 28.17 %, 14.68 %) whereas a decrease in Proteobacteria (19.53 %, 6.32 %, 9.37 %, 16.21 %), Chloroflexi (16.93 %, 8.71 %, 9.78 %, 18.17 %), and Bacteroidetes (8.96 %, 0.36 %, 0.41 %, 0.11 %) was recorded respectively. Additionally, the 100 % removal of oil-based paints (R498, B698 and G492) was achieved by the cultivable microbial consortia in laboratory settings. On the other hand for the R498 single cultivable pure isolates exhibited biodegradation potential as "PDB20, 91 %", "PDB14, 81 %", and "PDB16, 87 %" while for the blue B698, "PDB4, 86 %", "PDB20, 89 %", "PDB5, and PDB2, 80%". Moreover, in case of G492, maximum % removal was achieved with "PDB20, 93 %", "PDB5, 90 %", "PDB6, 90 %", "PDB16, 88 %", "PDB2, and PDB4, 89%". Conclusively, in comparison to R498 and B698, maximum percent removal was displayed by G492 and this might be attributed due to difference in pigment. Cultivable consortia and individual pure isolates demonstrated >80 % contribution in the % removal of oil-based paints.

Enhanced Oil Recovery by Potential Biosurfactant-Producing Halo-thermotolerant Bacteria Using Soil Washing and Sand-Packed Glass Column Techniques.

Biosurfactants offer numerous advantages over the chemical surfactants, especially in energy and environment-related applications. Microbial enhanced oil recovery (MEOR) is a technique to recover oil from reservoirs by using microbes and their metabolites. In present study, total sixteen morphologically distinct bacterial strains isolated from different salty areas of the district Khairpur Mir's, Pakistan, were investigated for their MEOR potential. Screening assays for thermotolerance and halotolerance declared 7 out of 16 (43.75%) bacterial isolates as thermotolerant (capable of growing in the temperature range 60-70 °C) and halotolerant (tolerating NaCl concentrations up to 17%, w/v). Moreover, five of them were screened as biosurfactant producers. Among, the lowest surface tension reduction was achieved with biosurfactants produced by the strains KJ2MO (27.8 mN/m) and KJ2SK (29.3 mN/m). The biosurfactant activity was found stable at temperature (100-121 °C, 1 h) and pH (4-10). Moreover, maximum oil recovery was obtained with biosurfactant of bacterial strain KJ2MO (54.7%, 51.25%) followed by KJ2SK (44.7%, 40.5%), KJ1WB (37%, 35.5%) and KJ2MD (37.8%, 31.9%) by using either techniques, i.e., soil washing and sand-packed column, respectively. Moreover, the potent species were identified as Pseudomonas pseudoalcaligenes KJ1WB, Bacillus aerius KJ2MD, Bacillus licheniformis KJ2SK, and Bacillus subtilis KJ2MO using 16S rRNA ribo-typing. The investigated species were found to be promising biosurfactants producers having potential for enhanced oil recovery and could be used in other environmental applications like bioremediation.

Correction to: Ecotoxicological assessment of oil-based paint using three-dimensional multi-species bio-testing model: pre- and post-bioremediation analysis.

The original publication of this paper contains a mistake.

Ecotoxicological assessment of oil-based paint using three-dimensional multi-species bio-testing model: pre- and post-bioremediation analysis.

The present study validates the oil-based paint bioremediation potential of Bacillus subtilis NAP1 for ecotoxicological assessment using a three-dimensional multi-species bio-testing model. The model included bioassays to determine phytotoxic effect, cytotoxic effect, and antimicrobial effect of oil-based paint. Additionally, the antioxidant activity of pre- and post-bioremediation samples was also detected to confirm its detoxification. Although, the pre-bioremediation samples of oil-based paint displayed significant toxicity against all the life forms. However, post-bioremediation, the cytotoxic effect against Artemia salina revealed substantial detoxification of oil-based paint with LD50 of 121 µl ml-1 (without glucose) and > 400 µl ml-1 (with glucose). Similarly, the reduction in toxicity against Raphanus raphanistrum seeds germination (%FG = 98 to 100%) was also evident of successful detoxification under experimental conditions. Moreover, the toxicity against test bacterial strains and fungal strains was completely removed after bioremediation. In addition, the post-bioremediation samples showed reduced antioxidant activities (% scavenging = 23.5 ± 0.35 and 28.9 ± 2.7) without and with glucose, respectively. Convincingly, the present multi-species bio-testing model in addition to antioxidant studies could be suggested as a validation tool for bioremediation experiments, especially for middle and low-income countries. Graphical abstract ᅟ.