Performance evaluation of rhamnolipid biosurfactant produced by Pseudomonas aeruginosa and its effect on marine oil-spill remediation.

This study aimed to reveal that the effect of biosurfactant on the dispersion and degradation of crude oil. Whole genome analysis showed that Pseudomonas aeruginosa GB-3 contained abundant genes involved in biosurfactant synthesis and metabolic processes and had the potential to degrade oil. The biosurfactant produced by strain GB-3 was screened by various methods. The results showed that the surface tension reduction activity was 28.6 mN·m-1 and emulsification stability was exhibited at different pH, salinity and temperature. The biosurfactant was identified as rhamnolipid by LC-MS and FTIR. The fermentation conditions of strain GB-3 were optimized by response surface methodology, finally the optimal system (carbon source: glucose, nitrogen source: ammonium sulfate, C/N ratio:16:1, pH: 7, temperature: 30-35 °C) was determined. Compared with the initial fermentation, the yield of biosurfactant increased by 4.4 times after optimization. In addition, rhamnolipid biosurfactant as a dispersant could make the dispersion of crude oil reach 38% within seven days, which enhanced the bioavailability of crude oil. As a biostimulant, it could also improve the activity of indigenous microorganism and increase the degradation rate of crude oil by 10-15%. This study suggested that rhamnolipid biosurfactant had application prospect in bioremediation of marine oil-spill.

Characteristic microbiome and synergistic mechanism by engineering agent MAB-1 to evaluate oil-contaminated soil biodegradation in different layer soil.

Bioremediation is a sustainable and pollution-free technology for crude oil-contaminated soil. However, most studies are limited to the remediation of shallow crude oil-contaminated soil, while ignoring the deeper soil. Here, a high-efficiency composite microbial agent MAB-1 was provided containing Bacillus (naphthalene and pyrene), Acinetobacter (cyclohexane), and Microbacterium (xylene) to be synergism degradation of crude oil components combined with other treatments. According to the crude oil degradation rate, the up-layer (63.64%), middle-layer (50.84%), and underlying-layer (54.21%) crude oil-contaminated soil are suitable for bioaugmentation (BA), biostimulation (BS), and biostimulation+bioventing (BS+BV), respectively. Combined with GC-MS and carbon number distribution analysis, under the optimal biotreatment, the degradation rates of 2-ring and 3-ring PAHs in layers soil were about 70% and 45%, respectively, and the medium and long-chain alkanes were reduced during the remediation. More importantly, the relative abundance of bacteria associated with crude oil degradation increased in each layer after the optimal treatment, such as Microbacterium (2.10-14%), Bacillus (2.56-12.1%), and Acinetobacter (0.95-12.15%) in the up-layer soil; Rhodococcus (1.5-6.9%) in the middle-layer soil; and Pseudomonas (3-5.4%) and Rhodococcus (1.3-13.2%) in the underlying-layer soil. Our evaluation results demonstrated that crude oil removal can be accelerated by adopting appropriate bioremediation approach for different depths of soil, providing a new perspective for the remediation of actual crude oil-contaminated sites.

Application of bacterial agent YH for remediation of pyrene-heavy metal co-pollution system: Efficiency, mechanism, and microbial response.

The combination of organic and heavy metal pollutants can be effectively and sustainably remediated using bioremediation, which is acknowledged as an environmentally friendly and economical approach. In this study, bacterial agent YH was used as the research object to explore its potential and mechanism for bioremediation of pyrene-heavy metal co-contaminated system. Under the optimal conditions (pH 7.0, temperature 35°C), it was observed that pyrene (PYR), Pb(II), and Cu(II) were effectively eliminated in liquid medium, with removal rates of 43.46%, 97.73% and 81.60%, respectively. The microscopic characterization (SEM/TEM-EDS, XPS, XRD and FTIR) results showed that Pb(II) and Cu(II) were eliminated by extracellular adsorption and intracellular accumulation of YH. Furthermore, the presence of resistance gene clusters (cop, pco, cus and pbr) plays an important role in the detoxification of Pb(II) and Cu(II) by strains YH. The degradation rate of PYR reached 72.51% in composite contaminated soil, which was 4.33 times that of the control group, suggesting that YH promoted the dissipation of pyrene. Simultaneously, the content of Cu, Pb and Cr in the form of F4 (residual state) increased by 25.17%, 6.34% and 36.88%, respectively, indicating a decrease in the bioavailability of heavy metals. Furthermore, YH reorganized the microbial community structure and enriched the abundance of hydrocarbon degradation pathways and enzyme-related functions. This study would provide an effective microbial agent and new insights for the remediation of soil and water contaminated with organic pollutants and heavy metals.

Enhanced crude oil degradation by remodeling of crude oil-contaminated soil microbial community structure using sodium alginate/graphene oxide/Bacillus C5 immobilized pellets.

Bioaugmentation (BA) of oil-contaminated soil by immobilized microorganisms is considered to be a promising technology. However, available high-efficiency microbial agents remain very limited. Therefore, we prepared a SA/GO/C5 immobilized gel pellets by embedding the highly efficient crude oil degrading bacteria Bacillus C5 in the SA/GO composite material. The optimum preparation conditions of SA/GO/C5 immobilized gel pellets were: SA 3.0%, GO 25.0 µg/mL, embedding amount of C5 6%, water bath temperature of 50°C, CaCl2 solution concentration 3% and cross-linking time 20 h. BA experiments were carried out on crude oil contaminated soil to explore the removal effect of SA/GO/C5 immobilized pellets. The results showed that the SA/GO/C5 pellets exhibited excellent mechanical strength and specific surface area, which facilitated the attachment and growth of the Bacillus C5. Compared with free bacteria C5, the addition of SA/GO/C5 significantly promoted the removal of crude oil in soil, reaching 64.92% after 30 d, which was 2.1 times the removal rate of C5. The addition of SA/GO/C5 promoted the abundance of soil exogenous Bacillus C5 and indigenous crude oil degrading bacteria Alcanivorax and Marinobacter. In addition, the enrichment of hydrocarbon degradation-related functional abundance was predicted by PICRUSt2 in the SA/GO/C5 treatment group. This study demonstrated that SA/GO/C5 is an effective method for remediating crude oil-contaminated soil, providing a basis and option for immobilized microorganisms bioaugmentation to remediate organic contaminated soil.

Reconstruction of microbiome and functionality accelerated crude oil biodegradation of 2,4-DCP-oil-contaminated soil systems using composite microbial agent B-Cl.

Biodegradation is one of the safest and most economical methods for the elimination of toxic chlorophenols and crude oil from the environment. In this study, aerobic degradation of the aforementioned compounds by composite microbial agent B-Cl, which consisted of Bacillus B1 and B2 in a 3:2 ratio, was analyzed. The biodegradation mechanism of B-Cl was assessed based on whole genome sequencing, Fourier transform infrared spectroscopy and gas chromatographic analyses. B-Cl was most effective at reducing Cl- concentrations (65.17%) and crude oil biodegradation (59.18%) at 7 d, which was when the content of alkanes ≤ C30 showed the greatest decrease. Furthermore, adding B-Cl solution to soil significantly decreased the 2,4-DCP and oil content to below the detection limit and by 80.68%, respectively, and reconstructed of the soil microbial into a system containing more CPs-degrading (exaA, frmA, L-2-HAD, dehH, ALDH, catABE), aromatic compounds-degrading (pcaGH, catAE, benA-xylX, paaHF) and alkane- and fatty acid-degrading (alkB, atoB, fadANJ) microorganisms. Moreover, the presence of 2,4-DCP was the main hinder of the observed effects. This study demonstrates the importance of adding B-Cl solution to determine the interplay of CPs with microbes and accelerating oil degradation, which can be used for in-situ bioremediation of CPs and oil-contaminated soil.

A novel dehydrocoenzyme activator combined with a composite microbial agent TY for enhanced bioremediation of crude oil-contaminated soil.

Bioaugmentation (BA) and biostimulation (BS) synergistic remediation is an effective remediation strategy for oil-contaminated soil. In this study, the optimal combination system of composite microbial agent TY (Achromobacter: Pseudomona = 2:1) and dehydrocoenzyme activator (NaNO3 (7.0 g/L), (NH4)2HPO4 (1.0 g/L), riboflavin (6.0 mg/L)) was screened. Under the best combination system, the degradation rate of crude oil in oil-contaminated soil reached 79.44% after 60 d, which was 1.74 times and 1.23 times higher than that of compound microbial agent TY treatment and dehydrogenase activator treatment, respectively. In addition, a highly efficient combination system was found to target the degradation of oil C10-C28 fractions by gas chromatography (GC). The increased abundance of dehydrogenase coenzymes such as flavin nucleotides (FAD and FMN), coenzyme I (NAD+, Co I) and coenzyme II (NADP+, Co II) as well as dioxygenases and monooxygenases promote the degradation of crude oil. Furthermore, the dominant genera at the genus level in soil were analyzed by high-throughput sequencing, which were Nocardioides (46.48%-56.07%), Gordonia (11.40%-14.61%), Intrasporangiaceae (5.05%-10.58%), Pseudomonas (1.39%-1.92%) and Dietzia (0.64%-2.77%). Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis showed that the abundance of genes associated with crude oil degradation such as ABC transporters (2.89%), fatty acid (1.04%), carbon metabolism (4.5%) and aromatic compound (0.92%) was assigned enhanced after 60 d of remediation. These results indicated that the combination system of the compound bacterium TY and the dehydrocoenzyme activator is a propective option for the bioremediation of oil-contaminated soil.

Pollution characteristics of groundwater in an agricultural hormone-contaminated site and implementation of Fenton oxidation process.

The groundwater polluted by an agricultural hormone site was taken as the research object, and a total of 7 groundwater samples were collected at different locations in the plant. The main pollutants in the research area were determined to be extractable petroleum hydrocarbons (C10-C40); 1,2-dichloroethane; 1,1,2-trichloroethane; carbon tetrachloride; vinyl chloride, and chloroform; the maximum content of these pollutants can reach 271 mg/L, 1.68 × 107 µg/L, 1.56 × 104 µg/L, 9.53 × 104 µg/L, 6.58 × 104 µg/L, and 4.81 × 104 µg/L, respectively. Aiming at the problems of groundwater pollution in this area, two sets of oxidation experiments have been carried out. The addition of NaHSO3 modified Fenton oxidation system was used in this contaminated water, which enhanced (2.2 ~ 46.7%) chemical oxygen demand (COD) removal rate. The highest removal rate of extractable petroleum hydrocarbons (C10-C40) can reach 99%. And the degradation rate of chlorinated hydrocarbon pollutants can reach 99% to 100%, which almost achieved the purpose of complete removal. In the NaHSO3 modified Fenton oxidation system, the addition of NaHSO3 accelerates the cycle of Fe3+/Fe2+ and ensures the continuous existence of Fe2+ in the reaction system, thereby producing more ·OH and further oxidizing and degrading organic pollutants. Our work has provided important insights for this economically important treatment of this type water body and laid the foundation for the engineering of this method.

A novel chitosan-biochar immobilized microorganism strategy to enhance bioremediation of crude oil in soil.

The chitosan-biochar composite is a clean and environmentally friendly immobilized microorganisms carrier. In this study, the chitosan-biochar composite as a carrier to immobilize a compound microbial agent contained Pseudomonas aeruginosa and Bacillus licheniformis, and investigated its role in the remediation of oil-contaminated soil. When using 1% (v/v) acetic acid, 3% (m/v) chitosan solution, 0.1% biochar, 4% (v/v) NaOH solution, freeze-drying 6 h, the optimal chitosan-biochar composite material could be obtained. The specific surfacearea of the material increased to 1.725 m2/g and the average pore size also increased from 130.2260 nm to 165.2980 nm after the addition of biochar through the analysis of specific surface area and pore size, which enlarged the contact area of microorganisms and crude oil with the material. SEM showed that the bacterial successfully adhered to the surface and internal of the material. Using FTIR, the results showed that the synthesis of composite carrier material was the covalent combination of -NH2 on chitosan and -COOH on biochar, forming a new chemical bond -NH-CO-. After 60 days of remediation of oil-contaminated soil, the removal rate of crude oil by chitosan-biochar composite immobilized microorganism method was 45.82%, which was 21.26% higher than that of natural remediation. Simultaneously, several oil-degrading bacteria increased at genus level, including Nocardioides (26.79%-33.09%), Bacillus (3.01%-4.10%), Dietzia (1.84%-5.56%), Pseudomonas (0-0.78%), among which Pseudomonas belongs to exogenous bacteria. The results indicated that the chitosan-biochar composite material has high application value in removing crude oil, and further provides a new strategy for bioremediation of oil-contaminated soil.

Characterization of the simultaneous degradation of pyrene and removal of Cr(VI) by a bacteria consortium YH.

Microorganisms that can simultaneously remediate organic pollutants and heavy metal contamination are great significance in bioremediation. Nevertheless, reports of such microorganisms are still scarce. Here, Pseudomonas sp. YH-1 and Rhodococcus sp. YH-3 were isolated and identified, and they showed greater tolerance to hexavalent (VI) (750 and 800 mg·L-1). The constructed bacteria consortium YH (YH-1:YH-3 = 1:1) could simultaneously degrade 41.69% of pyrene (50 mg·L-1) and remove 76.67% of Cr(VI) (30 mg·L-1) within 5 days. The potential mechanism of Cr(VI) tolerance of YH was further explored by genomic and microscopic analysis. The results showed that YH responded to Cr(VI) stress mainly through efflux of Cr(VI) by chrA and copZ, chromate reduction, DNA-repaired proteases reduces ROS damage, and biosorption by carboxyl, hydroxyl, amino functional groups. Strains YH-1 and YH-3 also contained a variety of genes associated with resistance to other heavy metals, such as cadmium (czcBD), mercury (merAPTR), manganese (mntABC) and copper (copAC, cusABRF and pcoBD). Based on GC-MS and genomic analysis, pyrene was degraded via salicylic acid and phthalic acid pathways. Moreover, a great number of genes related to aromatic hydrocarbon catabolism were identified in the genomes of YH-1 and YH-3. These results confirmed the potential application of the bacteria consortium YH in the bioremediation of water and soil co-contaminated with PAHs-heavy metals.

Degradation characteristics of crude oil by a consortium of bacteria in the existence of chlorophenol.

In order to enhance the degradation effect of microorganisms on crude oil in the existence of chlorophenol compounds, oil-degrading bacteria C4 (Alcaligenes faecails), C5 (Bacillus sp.) and 2,4-dichlorophenol (2,4-DCP) degrading bacteria L3 (Bacillus marisflavi), L4 (Bacillus aquimaris) were isolated to construct a highly efficient consortium named (C4C5 + L3L4). When the compound bacteria agent combination by VC4: VC5: VL3: VL4 = 1:2:2:1, the crude oil degradation efficiency of 7 days was stable at 50.63% ~ 55.43% under different conditions. Degradation mechanism was analyzed by FTIR, GC-MS and IC technology and the following conclusions showed that in the system of adding consortium (C4C5 + L3L4), the heavy components were converted into saturated and unsaturated components. The bacterial consortium could first degrade medium and long chain alkanes into short chain hydrocarbons and then further degrade. And the dechlorination efficiency of 2,4-DCP in the degradation system reached 73.83%. The results suggested that the potential applicability and effectiveness of the selected bacteria consortium for the remediation of oil-contaminated water or soil with the existence of chlorophenol compound.

Ammonium Ions Induce Cellulase Synthesis in Trichoderma koningii.

Cellulase plays an important role in addressing the issue of the energy crisis. However, the yield and degradation efficiency of cellulase remain a major challenge. In the present study, we aimed to verify whether ammonium ion (NH4+) could induce cellulase synthesis from T. koningii AS3.2774 and to explore new functional genes related to the cellulase production. Our results indicated that NH4+ induces cellulase production in a way different from nitrogen sources. NH4+-mediated mycelia displayed a significant increase in transport vesicles. Under NH4+ mediation, CBHI, CBHII, glycoside hydrolase family 5 proteins, Hap2/3/5 complexes, "ribosome biogenesis", and "heme binding" were significantly up-regulated, and differentially expressed genes (DEGs) were mainly involved in "Metabolism". Collectively, our findings illustrated that NH4+ induced the cellulase production at morphological and gene expression levels, which might be related to the Hap2/3/5 complex, ribosomes, and genes involved in various amino acid metabolism, pyruvate metabolism, and glycolysis/gluconeogenesis. Taken together, our results provided valuable insights into the regulatory network of cellulase gene expression in filamentous fungi.

Biodesulfurization of diesel oil in oil-water two phase reaction system by Gordonia sp. SC-10.

OBJECTIVES: Different sulfur contents of diesel oils were used for biodesulfurization to study the desulfurization capacity of Gordonia sp. SC-10 in oil-water two-phase reaction system. RESULTS: Gordonia sp. SC-10 showed great properties in desulfurizing diesel oil with different sulfur contents. This bacterium could decrease sulfur contents in different diesel oils from 194.7 ± 3.7 to 30.4 ± 0.5 mg/l and from 3035.3 ± 23.8 to 1792.8 ± 48.9 mg/l, respectively. Furthermore, this bacterium could desulfurize broad range of organosulfur compounds and had strong desulfurization activity against alkylated DBTs. For low-sulfur diesel oil, sulfur could be removed from 10.2 ± 0.1 to 5.0 ± 0.1 mg/l. CONCLUSIONS: The newly isolated bacteria Gordonia sp. SC-10 showed a good performance in desulfurizing diesel oils, and it might be a useful desulfurizing biocatalyst to enable the industrialized application of biodesulfurization process.

Biodegradation of dibenzothiophene by efficient Pseudomonas sp. LKY-5 with the production of a biosurfactant.

A potent bacterial strain capable of degrading dibenzothiophene (DBT) was isolated and evaluated for its characteristics. The strain, designated as LKY-5, is rod-shaped, gram-negative, and occurs mainly in clusters. It was identified as belonging to the Pseudomonas genus based on the 16S rDNA sequence and phylogenic analysis. Determination of its DBT depletion efficiency by gas chromatography revealed that the isolate was able to completely degrade up to 100 mg L-1 DBT within 144 h. The pH values, DBT concentrations, and biomasses in the medium varied significantly in the initial 24 h. A biosurfactant produced by LKY-5 was extracted and identified as a di-rhamnolipid with the formula Rha-Rha-C8-C8:1 by HPLC-ESI-MS/MS. There were 26 metabolites in the DBT degradation process. Pseudomonas sp. LKY-5 exhibited unusually high DBT degradation efficiency via multiple metabolic pathways. Compared with the reported 4S and Kodama pathways, two more expanded metabolic pathways for the degradation of DBT are proposed. The polycyclic aromatic sulfur heterocycles (PASHs) in diesel, such as C1-DBT, C2-DBT, C3-DBT, 4,6-DMDBT, and 2,4,6-TMDBT, can also be degraded with 28.2-42.3% efficiency. The results showed that LKY-5 is an excellent bacterial candidate for the bioremediation of PASH-contaminated sites and sediments.

Thermophilic biodesulfurization and its application in oil desulfurization.

To reduce the harm caused to the environment by fuel combustion and meet the increasingly stringent emission standards, the sulfur content of fuels should be reduced. Dibenzothiophene, benzothiophene, and their derivatives are sulfur-containing components of fuels that are difficult to desulfurize and can therefore cause great environmental damage. Biodesulfurization is a desulfurization method that has the advantage of being able to remove dibenzothiophene and its derivatives removed easily under conditions that are relatively mild when compared with hydrodesulfurization. This paper introduces the advantages of thermophilic biodesulfurization compared with mesophilic biodesulfurization; analyzes the desulfurization mechanism, including the desulfurization pathways and enzymic systems of desulfurization bacteria; and discusses the application of biodesulfurization in oil desulfurization. The main problems existing in biodesulfurization and possible solutions are also analyzed in this paper. Biological desulfurization is a promising method for desulfurization; accordingly, more studies investigating biodesulfurization of actual oil are needed to enable the industrialized application of biodesulfurization.