Diesel oil removal by Serratia sp. W4-01 immobilized in chitosan-activated carbon beads

Simultaneous immobilization enhances synergistic interactions and crude oil removal of bacterial consortium

Oil spillage has serious adverse effects on marine environments. The degradation of crude oil by microorganisms may be an effective and sustainable approach. In this study, the removal of crude oil from seawater by immobilized bacterial consortium was performed and the enhancement of crude oil degradation efficiency by varying immobilization methods and inoculum volume ratio was examined. The nonpathogenic and heavy metal-tolerant bacterial consortium of Sphingobium naphthae MO2-4 and Priestia aryabhattai TL01-2 was immobilized by biofilm formation on aquaporousgels. The simultaneous immobilization of strains MO2-4 and TL01-2 showed better crude oil removal efficiency than independent immobilization, which indicated positive interactions among consortium members in the mixed-culture immobilized systems. Moreover, the immobilized consortium at a 2:1 (MO2-4:TL01-2) inoculum volume ratio showed the best crude oil removal capacity. The immobilized consortium removed 77% of 2000 mg L-1 crude oil in seawater over 7 days. The immobilized consortium maintained crude oil removal efficacy in semicontinuous experiments. In addition, the immobilized consortium was used to remediate seawater contaminated with 1000 mg L-1 crude oil in a 20 L wave tank. After 28 days, the crude oil degradation efficiency of immobilized consortium was approximately 70%, and crude oil degradation through natural attenuation was not observed. Moreover, the genomic features of strains MO2-4 and TL01-2 are reported. Genomic analyses of both strains confirmed the presence of many genes involved in hydrocarbon degradation, heavy metal resistance, biosurfactant synthesis, and biofilm formation, supporting the biodegradation results and characterizing strain properties. The results of this work introduce the potential benefit of simultaneous immobilization of bacterial consortia to improve efficiency of crude oil biodegradation and has motivated further investigations into large-scale remediation of crude oil-contaminated seawater.

Effective diesel removal by a novel electrospun composite nanofibrous membrane with immobilized Bacillus cereus LY-1

Nanofiber membranes have recently been considered as promising supports for the immobilization of microorganisms due to the simplicity and cost-effectiveness of electrostatic spinning technology and the ability to control fiber morphology, such as obtaining higher surface area and porosity. In this study, electrospun polyvinyl alcohol/sodium alginate/attapulgite (PVA/SA/ATP) nanofiber membrane was prepared as support for immobilized Bacillus cereus LY-1 for diesel degradation in an aqueous medium and a significant improvement in diesel removal efficiency was realized. The effect of modified ATP concentration on diesel removal was investigated. The results showed that the nanofiber membranes complexed with cetyl trimethyl ammonium bromide (CTAB) and 1% ATP (w/w) had the best capacity for diesel removing. When the initial diesel concentration was 2 g L-1, about 87.8% of diesel was removed by the immobilized LY-1 cells after 72 h. Immobilization of bacteria improves the ability of bacteria to survive in adverse environments. Immobilized LY-1 cells maintain the nature to remove diesel at high salinity or pH range of 6-9. Furthermore, the reusability of the LY-1 cells-immobilized PVA/SA/CTAB-ATP nanofiber membrane was tested. A diesel removal rate of 64.9% could be achieved after 4 times of use. PVA/SA/CTAB-ATP nanofibrous membranes with immobilized LY-1 cells are feasible, economical and environmentally friendly for remediation of diesel contamination in the aqueous medium, and have potential applications in the future.

Study on the preparation conditions and degradation performance of an efficient immobilized microbial agent for marine oil pollution

In the process of handling marine oil spills accidents, the biological method has attracted wide attention due to its low cost and no secondary pollution. However, in the process of practical application, there are problems such as low microbial density and great influence of environmental factors when the oil is treated by spraying microorganisms on the sea surface. This study used immobilized microorganism technology to solve the above-mentioned problems. In this study, the bacteria immobilized on cinnamon shell (CS) with good degradation performance were obtained by optimizing preparation conditions. Under the optimal conditions of sodium alginate (SA) concentration of 4.57%, CS concentration of 1.28%, and the CaCl₂ concentration of 2.45%, the degradation rate of diesel in 5 days reached 74.04%. The reusability of immobilized microbial agents was further studied. The study designed three cycles of repeated degradation experiments. The results showed that the degradation rate of diesel can still reach 60.12% after three times of reuse, which indicated the reusability of the immobilized microbial agents was excellent. The decrease in degradation rate of diesel was mainly related to the fragmentation of immobilized microbial agents and the decrease in microbial biomass.

Phenol biodegradation by immobilized Rhodococcus qingshengii isolated from coking effluent on Na-alginate and magnetic chitosan-alginate nanocomposite

Phenol is a hazardous organic solvent to living organisms, even in its small amounts. In order to bioremediation of phenol from aqueous solution, a novel bacterial strain was isolated from coking wastewater, identified as Rhodococcus qingshengii based on 16S rRNA sequence analysis and named as strain Sahand110. The phenol-biodegrading capabilities of the free and immobilized cells of Sahand110 on the beads of Na-alginate (NA) and magnetic chitosan-alginate (MCA) nanocomposite were evaluated under different initial phenol concentrations (200, 400, 600, 800 and 1000 mg/L). Results illustrated that Sahand110 was able to grow and complete degrade phenol up to 600 mg/L, as the sole carbon and energy source. Immobilized cells of Sahand110 on NA and MCA were more competent than its free cells in degradation of high phenol concentrations, 100% of 1000 mg/L phenol within 96 h, indicating the improved tolerance and performance of the immobilized cells against phenol toxicity. Therefore, the immobilized Sahand110 on the studied beads, especially MCA bead regarding its suitable properties, has significant potential to enhanced bioremediation of phenol-rich wastewaters.

Bioaugmentation with zeolite-immobilized bacterial consortium OPK results in a bacterial community shift and enhances the bioremediation of crude oil-polluted marine sandy soil microcosms

A pyrene-degrading consortium OPK containing Mycolicibacterium strains PO1 and PO2, Novosphingobium pentaromativorans PY1 and Bacillus subtilis FW1 effectively biodegraded medium- and long-chain alkanes as well as mixed hydrocarbons in crude oil. The detection of alkB and CYP153 genes in the genome of OPK members supports its phenotypic ability to effectively degrade a broad range of saturated hydrocarbons in crude oil. Zeolite-immobilized OPK was developed as a ready-to-use bioproduct and it exhibited 74% removal of 1000 mg L^-1 crude oil within 96 h in sterilized seawater without nutrient supplementation and maintained high crude oil-removal activity under a broad range of pH values (5.0-9.0), temperatures (30-40 °C) and salinities (20-60‰). In addition, the immobilized OPK retained a high crude oil removal efficacy in semicontinuous experiments and showed reusability for at least 5 cycles. Remarkably, bioaugmentation with zeolite-immobilized OPK in sandy soil microcosms significantly increased crude oil (10,000 mg kg^-1 soil) removal from 45% to 80.67% within 21 days compared to biostimulation and natural attenuation. Moreover, bioaugmentation with exogenous immobilized OPK stimulated an increase in the relative abundances of Alcanivorax genus, indigenous hydrocarbon-degrading bacteria, which in turn enhanced removal efficiency of crude oil contamination from sandy soil microcosms. The results indicate positive interactions between the bioaugmented immobilized consortium, harboring Mycolicibacterium as a key player, and indigenous Alcanivorax, which exhibited crucial functions for improving crude oil removal efficacy. The knowledge obtained forms an important basis for further synthesis and handling of a promising bio-based product for enhancing the in situ bioremediation of crude oil-polluted marine environments.

A comprehensive review on the applications of functionalized chitosan in petroleum industry

The biomaterials have gained the attention for utilization as sustainable alternatives for petroleum-derived products due to the rapid depletion of petroleum resources and environmental issues. Chitosan is an economical, renewable and abundant polysaccharide having unique molecular characteristics. Chitosan is derived by deacetylation of chitin, a natural polysaccharide existing in insects' exoskeleton, outer shells of crustaceans, and some fungi cell walls. Chitosan is widely used in numerous domains like agriculture, food, water treatment, medicine, cosmetics, fisheries, packaging, and chemical industry. This review aims to account for all the efforts made towards chitosan and its derivatives for utilization in the petroleum industry and related processes including exploration, extraction, refining, transporting oil spillages, and wastewater treatment. This review includes a compilation of various chemical modifications of chitosan to enhance the petroleum field's performance and applicability.

Chitin- and Chitosan-Based Derivatives in Plant Protection against Biotic and Abiotic Stresses and in Recovery of Contaminated Soil and Water

Biotic, abiotic stresses and their unpredictable combinations severely reduce plant growth and crop yield worldwide. The different chemicals (pesticides, fertilizers, phytoregulators) so far used to enhance crop tolerance to multistress have a great environmental impact. In the search of more eco-friendly systems to manage plant stresses, chitin, a polysaccharide polymer composed of N-acetyl-D-glucosamine and D-glucosamine and its deacetylated derivative chitosan appear as promising tools to solve this problem. In fact, these molecules, easily obtainable from crustacean shells and from the cell wall of many fungi, are non-toxic, biodegradable, biocompatible and able to stimulate plant productivity and to protect crops against pathogens. In addition, chitin and chitosan can act as bioadsorbents for remediation of contaminated soil and water. In this review we summarize recent results obtained using chitin- and chitosan-based derivatives in plant protection against biotic and abiotic stresses and in recovery of contaminated soil and water.

Shewanella oneidensis MR-1 impregnated Ca-alginate capsule for efficient Cr(VI) reduction and Cr(III) adsorption

Shewanella oneidensis MR-1 (MR-1)-impregnated alginate capsules with 3D porous structure were prepared through cation crossing-linking and was used for the Cr(VI) reduction and removal. After being encapsulated by alginate, the endurance of the MR-1 was largely enhanced under conditions of high Cr(VI) concentrations (up to 4 mM) and low pH (pH 5). The Cr(VI) reduction over the MR-1-impregnated alginate capsules could be fitted by pseudo first-order kinetic model. With the Cr(VI) initial concentration increasing from 1 to 4 mM, the first-order rate constant for the encapsulated MR-1 (k_capsules) and free cells (k_cells) fell by 26.3% and 82.4%, respectively. At pH 5, the k_capsules value was 0.19 h^{- 1}, which was about 3.7 times higher than k_cells. Moreover, the encapsulated MR-1 held 90.5% of the Cr(VI) reduction ability after 15 days of resting time, while the free MR-1 held 19.7%. After bioreduction, 73.6% of total chromium was adsorbed on the MR-1 impregnated Ca-alginate capsules. XPS results showed 85% of the adsorbed chromium was Cr(III). The mechanism for chromium removal over the MR-1-impregnated Ca-alginate capsules was proposed with the following steps: (1) Cr(VI) was bioreduced via the encapsulated MR-1; (2) the reduced soluble Cr(III) was adsorbed by alginate selectively. In the study, the Ca-alginate shell of the cabbage-like MR-1 impregnated capsules could be a shelter for encapsulated MR-1 to endure unfavorable conditions (e.g., low pH and high concentration of Cr(VI)) and immobilize the soluble chromium. Considering the obtained capsules derived from biomolecules were environment-friendly, the MR-1-impregnated Ca-alginate capsules were potential for the application in the remediation of environmental pollution. Graphical abstract.

Systematic degradation mechanism and pathways analysis of the immobilized bacteria: Permeability and biodegradation, kinetic and molecular simulation

In order to effectively improve the degradation rate of diesel, a systematic analysis of the degradation mechanism used by immobilized bacteria is necessary. In the present study, diesel degradation mechanisms were assessed by analyzing permeability, biodegradation, adsorption kinetics, and molecular simulation. We found that bacteria immobilized on cinnamon shells and peanut shells degraded relatively high amounts of diesel (69.94% and 64.41%, respectively). The primary degradation pathways used by immobilized bacteria included surface adsorption, internal uptake, and biodegradation. Surface adsorption was dominant in the early stage of degradation, whereas biodegradation was dominant in later stages. The diesel adsorption rate of the immobilized bacteria was in agreement with the pseudo second-order kinetic model. The immobilized bacteria and diesel interacted through hydrogen bonds.

Adsorptive bioremediation of soil highly contaminated with crude oil

Due to the extended oil extraction and transportation in Russia and other oil-producing countries, many lands remain contaminated because of accidental spills. This situation requires the cost-effective and efficient remediation of petroleum-contaminated soils. Bioremediation of soils contaminated with high concentrations of crude oil is usually hampered by high toxicity thresholds for microbial degraders. We have performed a two-year microfield experiment on the influence of a mixed adsorbent (ACD) composed of granular activated carbon and diatomite on bioremediation of a grey forest soil contaminated with crude oil at concentrations (5-15 % w/w) that would theoretically not result in a successful pollutant removal due to toxicity. Remediation of these soils was evaluated after treating with the ACD adsorbent (from 4 to 12% w/w) and a biopreparation (BP) containing hydrocarbon-degrading bacteria, separately or in combination. Reduction of total petroleum hydrocarbons content was significantly greater in highly contaminated soils with the combined amendments than in the respective controls (through the activation of indigenous degrading microorganisms by fertilizing and mixing) by 9-10% and 5-8% at the end of the first and second years, respectively, depending on the contamination level. Significantly higher counts of petroleum-degrading microorganisms (as indigenous and introduced by the BP), as well as much less phytotoxicity was detected in the ACD-amended soils, as compared with the samples without adsorbent. In addition, the ACD mixture drastically reduced the wash-out of polar petroleum metabolites (evidently oxidized hydrocarbons) and the phytotoxicity of the lysimetric waters, especially in highly contaminated soils. The results indicate that the mixture of activated carbon and diatomite is a prospective adsorbent for the in situ bioremediation of soils highly contaminated with crude oil.

Enhanced removal of trichlorfon and Cd(II) from aqueous solution by magnetically separable chitosan beads immobilized Aspergillus sydowii

Simultaneous removal of heavy metals and organics from wastewater has always been an environmental problem with great concern. In this study, a novel ecofriendly bioborbent, magnetic chitosan beads immobilized Aspergillus sydowii (MCBAs) were synthesized and used to simultaneously remove trichlorfon (TCF) and Cd(II) from aqueous solution. MCBAs showed an increased special surface area (55.38 m²·g^-1) through immobilizing A. sydowii and its saturation magnetization reached 14.62 emu·g^-1. The equilibrium removal capacities of TCF and Cd(II) were 135.43 mg·g^-1 and 56.40 mg·g^-1 in the co-system with 200 mg·L^-1 TCF and 50 mg·L^-1 Cd(II), respectively. The removal capacities of TCF and Cd(II) were strongly depended on the immobilized A. sydowii spore concentration, initial concentrations of TCF and Cd(II), and MCBAs dose. TCF biodegradation intermediates were identified by gas chromatography-mass spectrometry system. Fourier transform infrared spectra displayed that -OH and -NH groups on MCBAs mainly participated in the Cd(II) sequestration and the CO stretching vibration was possibly related to the degradation intermediates of TCF. MCBAs exhibited excellent recyclability upto four cycles. Therefore, MCBAs are suitable and effective for the simultaneous removal of TCF and Cd(II) from wastewater.

Study on the degradation performance and kinetics of immobilized cells in straw-alginate beads in marine environment

In this study, two strains Halomonas and Aneurinibacillus were mixed in equal proportions as free cells that could degrade diesel and produce biosurfactant. A new type of immobilized cells, free cells immobilized in beads combined with sodium alginate and straw, was studied. The components of straw-alginate beads were optimized by Response Surface Method, and the degradation performance of immobilized cells was determined. The result indicated that the density, strength and broken rate of straw-alginate beads were 1.04 g/cm³, 216 g and 4%, respectively. The best degradation rate of immobilized cells in straw-alginate beads could be 68.68%. Lately, by analyzing the Monod model, v_max (maximum specific degradation rate of diesel) and K_S (half saturation rate constant) of immobilized cells in straw-alginate beads were 1.84 d^-1 and 3.23 g/L, respectively, which explained the higher degradation performance.