Full length ArticleInnovative, ecofriendly biosorbent-biodegrading biofilms for bioremediation of oil- contaminated water
Graphical abstract
Introduction
Petroleum and its derivatives are among the most serious environmental threat for the oceans [1]. New mitigation measures are urgently needed for the remediation of marine contaminated areas and various physical, chemical and biological methods have been proposed [2]. Bioremediation represents a promising, non-invasive and low cost technology that could provide a more effective and sustainable restoration of contaminated water and sediments [3,4]. Bioremediation exploits the ability of microorganisms to degrade and metabolize different environmental pollutants by assimilating organic molecules into cell biomass and converting them to other products such as carbon dioxide and water [4]. Biostimulation and bioaugmentation are the approaches most often applied. Biostimulation uses nutrients to stimulate the growth of autochthonous hydrocarbon (HC)-degrading microorganisms, while bioaugmentation introduces more efficient allochthonous microorganisms to improve biodegradation at a certain site. HC-degrading bacteria isolated from water, sediment and soil with high biodegradation capacities have been characterized [[5], [6], [7], [8], [9]]. In soil, actinobacteria, well known degraders of recalcitrant biomolecules, are generally abundant [10]; they are resistant to drought and good colonizers of organic and inorganic surfaces [11]. In marine environments, the most actively oil-degrading microorganisms are hydrocarbonoclastic bacteria that live almost exclusively on HC [12].
Environmental microbiological resources can be exploited into biotechnological tools to treat pollution caused by oil HC and its derivatives; an example is the immobilization of HC-degrading bacteria, on different supports, that has been used for the bioremediation of environmental pollutants [[13], [14], [15]]. Immobilization of bacteria on carriers preserves their viability and catalytic functions, as well as providing resistance to unfavorable environmental conditions and high concentrations of pollutants, while displaying a longer half-life [15]. Immobilization processes reduce bioremediation costs and eliminate dispersion and dilution of cells in the environment [14].
Oil removal by adsorption is a widely used approach, with polyethylene being the most used polymer sorbent [16], although inorganic materials, such as titania [17], have also been proposed. A superhydrophobic polyethylene-based shish-kebab membrane has been prepared with self-cleaning and oil/water separation properties [16]. Its membrane adsorption capacity ranged from 15 to 32 g/g, depending on viscosity and density of the organic liquids. Porous polyethylene bundles have been proposed with enhanced hydrophobicity and pumping oil-recovery ability via skin-peeling, able to adsorb up to 3 g/g of oil [18]. These products are quite efficient, but one of the main disadvantages is their non-biodegradability.
For microbial approaches, the creation of a strong and reliable biofilm-based remediation technology remains challenging. The carrier material should be biodegradable, insoluble, non-toxic for the immobilized cells and environment, easily accessible, low cost, available in large quantities, stable and suitable for regeneration.
Recently, the properties of biodegradable polymers from either natural or synthetic sources have aroused great interest by finding applications in various technologically advanced fields [[19], [20], [21]]. The success of synthetic biopolymers such as polylactic acid (PLA), and polycaprolactone (PCL) is due to diverse characteristics, including the relative ease of production and low costs. For instance, a super light 3D hierarchical nanocellulose aerogel foam was prepared with low density (1.50 mg/cm3) and high adsorption capacity (145.2–206.8 g/g for different oils) [22].
Combining technological properties of ecofriendly sorbents with their capacity to host a biodegrading biofilm, allows biodegrading biosorbent biofilms to be obtained which can remove oil from water with high efficiency and economically. Among the different approaches proposed to produce porous biopolymeric structures, electrospinning is one of the most investigated, enabling the production of fibers with diameters potentially ranging from nano- to micro-scale [23,24]. Compared to other porous structures, electrospun nanofiber mats show a higher specific surface area and greater porosity [24,25]. Thus, a wide range of electrospun polymers has been extensively studied for application in oil spill remediation [26] or removal of toxic metal ions from wastewater [27], as well as in the biomedical [23,[28], [29], [30], [31]], catalysis [32] and electronic [33] fields. Here, the bioremediation efficiency of membrane-bacterial systems was analyzed on crude oil using four high performance HC-degrading bacterial strains isolated from different environments: two marine hydrocarbonoclastic gammaproteobacteria Alcanivorax borkumensis SK2 [34] and Oleibacter marinus [5], and two soil, long-chain n-alkane degrading actinobacteria, Gordonia sp. SoCg [35] and Nocardia sp. SoB [9]. The crude oil degrading ability of these formulations was measured and compared with that of the bacterial cells in planktonic form.
Section snippets
Development of the biodegradable membranes
Commercial grade of amorphous PLA (PLA 2002D, Natureworks® LLC, Minnetonka, MN 55345, USA,) was used. PCL (Mw =80 kDa), chloroform (TCM), acetone (Ac), dichloromethane (DCM) and absolute ethanol (EtOH) were from Sigma-Aldrich (Milan, Italy). All solvents were ACS grade (purity > 99 %) and were used as received without further purification. Double distilled water (DDQW) was obtained from MilliQ Plus systems (Millipore, Germany). The polymeric solutions and the electrospun membranes were prepared
PCL and PLA nanofiber membranes
SEM images of the electrospun PCL and PLA are presented in Fig. 1A and B respectively. The images show that the fibers are in the nanoscale for both systems and randomly oriented, even though a slight, non-significant, orientation along the hoop direction could be observed, in particular for the PLA electrospun mats. PCL fibers presented larger diameters and a broader average size distribution (average diameter ϕ: 1.71 ± 0.69 μm) compared to PLA (average diameter ϕ: 1.21 ± 0.48 μm), as
Conclusion
Although many different mechanical, physical and biological remediation strategies have been applied to remove oil from the environment, the best approach is biodegradation by environmental microorganisms, which have been recognized as key players in cleanup events [46]. In this study, we propose a low cost bioremediation tool for sea and fresh water contaminated by crude oil. A multidisciplinary approach enabled synergistic exploitation of the enhanced sorbent capacity of reusable
Compliance with ethical standards
This research was partially funded by the University of Palermo with the “Fondo Finalizzato alla Ricerca di Ateneo” to PQ (FFR-D10) and RS (FFR-D15).
Ethical approval
This article does not contain any studies with human participants or animals.
Declaration of Competing Interest
None.
References (46)
Microbial degradation of petroleum hydrocarbons
Bioresour Technol
(2017)- et al.
Intrinsic bioremediation potential of a chronically polluted marine coastal area
Mar Pollut Bull
(2015) - et al.
Microbial communities of polluted sub-surface marine sediments
Mar Pollut Bull
(2018) - et al.
Flos tectorii degradation of mortars: an example of synergistic action between soluble salts and biodeteriogens
J Cult Herit
(2015) - et al.
Obligate oil-degrading marine bacteria
Curr Opin Biotech
(2007) - et al.
Natural carriers in bioremediation: a review
Electron J Biotechnol
(2016) - et al.
Superlyophobic anti-corrosive and self-cleaning titania robust mesh membrane with enhanced oil/water separation
Sep Purif Technol
(2018) - et al.
Boosted selectivity and enhanced capacity of As (v) removal from polluted water by triethylenetetramine activated lignin-based adsorbents
Int J Biol Macromol
(2019) - et al.
PLA based biocomposites reinforced with Posidonia oceanica leaves
Compos Part B Eng
(2018) - et al.
Structural characterization of lignin and its carbohydrate complexes isolated from bamboo (dendrocalamus sinicus)
Int J Biol Macromol
(2019)
Super light 3D hierarchical nanocellulose aerogel foam with superior oil adsorption
J Colloid Interface Sci
Electrospun PCL/GO-g-PEG structures: processing-morphology-properties relationships
Compos Part A Appl Sci Manuf
Polycaprolactone-based scaffold for oil-selective sorption and improvement of bacteria activity for bioremediation of polluted water: porous PCL system obtained by leaching melt mixed PCL/PEG/NaCl composites: oil uptake performance and bioremediation efficiency
Eur Polym J
A review of polymer nanofibres by electrospinning and their application in oil-water separation for cleaning up marine oil spills
Mar Pollut Bull
Effect of graphene and fabrication technique on the release kinetics of carvacrol from polylactic acid
Compos Sci Technol
Processing, structure, property relationships and release kinetics of electrospun PLA/Carvacrol membranes
Eur Polym J
Effect of hydroxyapatite concentration and size on morpho-mechanical properties of PLA-based randomly oriented and aligned electrospun nanofibrous mats
J Mech Behav Biomed Mater
Biodegradation potentiality of psychrophilic bacterial strain Oleispira antarctica RB-8 T
Mar Pollut Bull
A facile method to determine pore size distribution in porous scaffold by using image processing
Micron
A validated open source nanofiber diameter measurement tool
Biomaterials
Study of oil sorption by expanded perlite at 298.15 K
Sep Purif Technol
Efficiency of recycled wool-based nonwoven material for the removal of oils from water
Chemosphere
Oil removal from aqueous state by natural fibrous sorbent: an overview
Sep Purif Technol
Cited by (50)
A facile two-step method to construct environmental-friendly Janus coconut wood membrane for oil/water separation
2023, Journal of Water Process EngineeringPolyurethane nanofiber membranes immobilized with Bacillus altitudinis LS-1 for bioremediation of diesel-contaminated wastewater
2023, Process Safety and Environmental ProtectionA step closer to real practice: Integrated tandem photocatalysis-biofilm process towards degradation of crude oil
2023, Journal of Environmental ManagementGreen dispersants for oil spill response: A comprehensive review of recent advances
2023, Marine Pollution BulletinRemediation of saline oily water using an algae-based membrane
2023, Journal of Membrane ScienceCitation Excerpt :Thus, there is a pressing need that the water desalination be performed simultaneously with or after oil-water separation. Nowadays, biological-based purification has attracted increasing attention as a more energy efficient and environmentally friendly water treatment technique [19–22]. Algae are a diverse group of photosynthetic microorganisms commonly found in fresh or salt water having different shapes and sizes [22].
- 1
These authors contributed equally to the work.