Integrating phytoremediation and mycoremediation with biosurfactant-producing fungi for hydrocarbon removal and the potential production of secondary resources

Treatment of petroleum-contaminated soil to a less toxic medium via physical and chemical treatment is too costly and requires posttreatment. This review focuses on the employment of phytoremediation and mycoremediation technologies in cleaning hydrocarbon-contaminated soil which is currently rare. It is considered environmentally beneficial and possibly cost-effective as it implements the synergistic interaction between plants and biosurfactant producing mycorrhiza to degrade hydrocarbon contaminants. This review also covers possible sources of hydrocarbon pollution in water and soil, toxicity effects, and current technologies for hydrocarbon removal and degradation. In addition to these problems, this review also discusses the challenges and opportunities of transforming the resultant treated sludge and treating plants into potential by-products for a higher quality of life for future generations.

Main Factors Determining the Scale-Up Effectiveness of Mycoremediation for the Decontamination of Aliphatic Hydrocarbons in Soil

Soil contamination constitutes a significant threat to the health of soil ecosystems in terms of complexity, toxicity, and recalcitrance. Among all contaminants, aliphatic petroleum hydrocarbons (APH) are of particular concern due to their abundance and persistence in the environment and the need of remediation technologies to ensure their removal in an environmentally, socially, and economically sustainable way. Soil remediation technologies presently available on the market to tackle soil contamination by petroleum hydrocarbons (PH) include landfilling, physical treatments (e.g., thermal desorption), chemical treatments (e.g., oxidation), and conventional bioremediation. The first two solutions are costly and energy-intensive approaches. Conversely, bioremediation of on-site excavated soil arranged in biopiles is a more sustainable procedure. Biopiles are engineered heaps able to stimulate microbial activity and enhance biodegradation, thus ensuring the removal of organic pollutants. This soil remediation technology is currently the most environmentally friendly solution available on the market, as it is less energy-intensive and has no detrimental impact on biological soil functions. However, its major limitation is its low removal efficiency, especially for long-chain hydrocarbons (LCH), compared to thermal desorption. Nevertheless, the use of fungi for remediation of environmental contaminants retains the benefits of bioremediation treatments, including low economic, social, and environmental costs, while attaining removal efficiencies similar to thermal desorption. Mycoremediation is a widely studied technology at lab scale, but there are few experiences at pilot scale. Several factors may reduce the overall efficiency of on-site mycoremediation biopiles (mycopiles), and the efficiency detected in the bench scale. These factors include the bioavailability of hydrocarbons, the selection of fungal species and bulking agents and their application rate, the interaction between the inoculated fungi and the indigenous microbiota, soil properties and nutrients, and other environmental factors (e.g., humidity, oxygen, and temperature). The identification of these factors at an early stage of biotreatability experiments would allow the application of this on-site technology to be refined and fine-tuned. This review brings together all mycoremediation work applied to aliphatic petroleum hydrocarbons (APH) and identifies the key factors in making mycoremediation effective. It also includes technological advances that reduce the effect of these factors, such as the structure of mycopiles, the application of surfactants, and the control of environmental factors.

Microbial surfactants: characteristics, production and broader application prospects in environment and industry

Microbial surfactants are green molecules with high surface activities having the most promising advantages over chemical surfactants including their ability to efficiently reducing surface and interfacial tension, nontoxic emulsion-based formulations, biocompatibility, biodegradability, simplicity of preparation from low cost materials such as residual by-products and renewable resources at large scales, effectiveness and stabilization under extreme conditions and broad spectrum antagonism of pathogens to be part of the biocontrol strategy. Thus, biosurfactants are universal tools of great current interest. The present work describes the major types and microbial origin of surfactants and their production optimization from agro-industrial wastes in the batch shake-flasks and bioreactor systems through solid-state and submerged fermentation industries. Various downstream strategies that had been developed to extract and purify biosurfactants are discussed. Further, the physicochemical properties and functional characteristics of biosurfactants open new future prospects for the development of efficient and eco-friendly commercially successful biotechnological product compounds with diverse potential applications in environment, industry, biomedicine, nanotechnology and energy-saving technology as well.

Microbial surfactants: A journey from fundamentals to recent advances

Microbial surfactants are amphiphilic surface-active substances aid to reduce surface and interfacial tensions by accumulating between two fluid phases. They can be generically classified as low or high molecular weight biosurfactants based on their molecular weight, whilst overall chemical makeup determines whether they are neutral or anionic molecules. They demonstrate a variety of fundamental characteristics, including the lowering of surface tension, emulsification, adsorption, micelle formation, etc. Microbial genera like Bacillus spp., Pseudomonas spp., Candida spp., and Pseudozyma spp. are studied extensively for their production. The type of biosurfactant produced is reliant on the substrate utilized and the pathway pursued by the generating microorganisms. Some advantages of biosurfactants over synthetic surfactants comprise biodegradability, low toxicity, bioavailability, specificity of action, structural diversity, and effectiveness in harsh environments. Biosurfactants are physiologically crucial molecules for producing microorganisms which help the cells to grasp substrates in adverse conditions and also have antimicrobial, anti-adhesive, and antioxidant properties. Biosurfactants are in high demand as a potential product in industries like petroleum, cosmetics, detergents, agriculture, medicine, and food due to their beneficial properties. Biosurfactants are the significant natural biodegradable substances employed to replace the chemical surfactants on a global scale in order to make a cleaner and more sustainable environment.

Bioremediation of an agricultural saline soil contaminated with endosulfan and Escherichia coli by an active surface agent induced in a Penicillium crustosum culture

This study evaluates the production of a biological active surface agent (BASA) through its surface tension (ST) and emulsifying activity (E₂₄) for endosulfan degradation (ED) and Escherichia coli growth inhibition (EcGI) in an agricultural saline soil. The fungus, identified as Penicillium crustosum was isolated from the Citrus sinensis peel (CsP), then the surface properties were evaluated in 9 culture media through a Taguchi L9 experimental design. The culture conditions included: stirring speed, pH, carbon (C) and nitrogen (N) sources; being glucose, NH₄N0₃, 120 rpm and pH of 5, the most significant parameters in the BASA production. The BASA identified as a lipopeptide type, showed a ST = 38 mN m^-1 and E₂₄=71%. Both properties were stable at 80 °C, while ST presented stability in the pH range of 2 - 12, and a saline concentration of 200 g L^-1; E₂₄ was also stable at a pH between 8-12. Further application of BASA and fungal inoculum to a contaminated agricultural saline soil presented an EcGI of 99.8% on the 8th day, and ED of 92.9 ± 4.7% in 30 days, respectively; being the first report that uses this fungus for pesticide and bacteria elimination from an agricultural saline soil.

Fungal biosurfactants, from nature to biotechnological product: bioprospection, production and potential applications

Biosurfactants are in demand by the global market as natural commodities that can be added to commercial products or use in environmental applications. These biomolecules reduce the surface/interfacial tension between fluid phases and exhibit superior stability to chemical surfactants under different physico-chemical conditions. Biotechnological production of biosurfactants is still emerging. Fungi are promising producers of these molecules with unique chemical structures, such as sophorolipids, mannosylerythritol lipids, cellobiose lipids, xylolipids, polyol lipids and hydrophobins. In this review, we aimed to contextualize concepts related to fungal biosurfactant production and its application in industry and the environment. Concepts related to the thermodynamic and physico-chemical properties of biosurfactants are presented, which allows detailed analysis of their structural and application. Promising niches for isolating biosurfactant-producing fungi are presented, as well as screening methodologies are discussed. Finally, strategies related to process parameters and variables, simultaneous production, process optimization through statistical and genetic tools, downstream processing and some aspects of commercial products formulations are presented.

A review on biosurfactants: properties, applications and current developments

Microbial surfactants are a large number of amphipathic biomolecules with a myriad of biomolecule constituents from various microbial sources that have been studied for their surface tension reduction activities. With unique properties, their applications have been increased in different areas including environment, medicine, healthcare, agriculture and industries. The present review aims to study the biochemistry and biosynthesis of biosurfactants exhibiting varying biomolecular structures which are produced by different microbial sources. It also provides details on roles played by biosurfactants in nature as well as their potential applications in various sectors. Basic biomolecule content of all the biosurfactants studied showed presence of carbohydrates, aminoacids, lipids and fattyacids. The data presented here would help in designing, synthesis and application of tailor-made novel biosurfactants. This would pave a way for perspectives of research on biosurfactants to overcome the existing bottlenecks in this field.

Production of Biosurfactants by Ascomycetes

Surfactants are utilized to reduce surface tension in aqueous and nonaqueous systems. Currently, most synthetic surfactants are derived from petroleum. However, these surfactants are usually highly toxic and are poorly degraded by microorganisms. To overcome these problems associated with synthetic surfactants, the production of microbial surfactants (called biosurfactants) has been studied in recent years. Most studies investigating the production of biosurfactants have been associated mainly with bacteria and yeasts; however, there is emerging evidence that those derived from fungi are promising. The filamentous fungi ascomycetes have been studied for the production of biosurfactants from renewable substrates. However, the yield of biosurfactants by ascomycetes depends on several factors, such as the species, nutritional sources, and environmental conditions. In this review, we explored the production, chemical characterization, and application of biosurfactants by ascomycetes.

Extraction and characterization of polysaccharide-enriched fractions from Phoma dimorpha mycelial biomass

Ultrasound-assisted extraction (UAE) and pressurized hot water extraction (PHWE) were tested as advanced clean methods to obtain polysaccharides from Phoma dimorpha mycelial biomass. These methods were compared to conventional extraction (hot water extraction, HWE) in terms of polysaccharides-enriched fractions (PEF) yield. A central composite rotational design was performed for each extraction method to investigate the influence of independent variables on the yield and to help the selection of the condition with the highest yield using water as an extraction solvent. The best extraction condition of PEF yielded 12.02 wt% and was achieved when using UAE with direct sonication for 30 min under the intensity of 75.11 W/cm² and pulse factor of 0.57. In the kinetic profiles, the highest yield (15.28 wt%) was obtained at 50 °C under an ultrasound intensity of 75.11 W/cm² and a pulse factor of 0.93. Structural analysis of extracted polysaccharide was performed using Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and thermal property. The water solubility index, water holding capacity, and emulsification index of PEF were 31.3 ± 1.5%, 138.1 ± 3.2%, and 62.9 ± 2.3%, respectively. The submerged fermentation demonstrates the huge potential of Phoma dimorpha to produce polysaccharides with bioemulsifying properties as a biotechnologically cleaner alternative if compared to commercial petroleum-derived compounds. Furthermore, UAE and PHWE are green technologies, which can be operated at an industrial scale for PEF extraction.

Eco-Friendly Bioemulsifier Production by Mucor circinelloides UCP0001 Isolated from Mangrove Sediments Using Renewable Substrates for Environmental Applications

The successful production of a biosurfactant is dependent on the development of processes using low cost raw materials. In the present work, an economically attractive medium composed of corn steep liquor and waste cooking oil was formulated to maximize the production of bioemulsifier by Mucor circinelloides UCP0001. A central rotational composite design was applied to statistical validation of the production. The emulsifying properties, stability under extreme conditions, its toxicity character, and the characterization of the bioemulsifier were determined. The best condition for biomolecule synthesis occurred in the assay 2 containing 4% of corn steep liquor and 3% waste soybean oil and exhibited 100% emulsification index for canola oil and petroleum, as well as excellent emulsifying activity for canola oil and burned engine oil. The nutritional factors studied showed statistical relevance, since all linear, quadratic effects and their interactions were significant. The bioemulsifier showed 2.69 g/L yield and the chemical character of the molecule structure was identified by FT-IR (Fourier Transform Infrared) spectroscopy. The bioemulsifier showed no toxicity to Artemia salina and Chlorella vulgaris. Stable emulsions were obtained under extreme conditions of temperature, pH, and salinity. These findings contribute to understanding of the relationship between production, physical properties, chemical composition, and stability of bioemulsifier for their potential applications in biotechnology, such as bioremediation of hydrocarbon-contaminated soil and water.

Biosurfactant production of Piper hispidum endophytic fungi

AIMS

To evaluate the production of biosurfactants by fungi isolated from the Amazonian species Piper hispidum (Piperaceae), and to determine the physico-chemical properties of the crude biosurfactant obtained from the most promising fungi.

METHODS AND RESULTS

A total of 117 endophytic fungi were isolated, and 50 were used to verify the production of biosurfactants. Of these, eight presented positive results in the drop collapse test, and emulsification index ranging from 20 to 78%. The most promising fungi, Ph III 23L and Ph II 22S (identified as Aspergillus niger and Glomerella cingulata, respectively) were recultivated for extraction and analysis of the biosurfactant's physico-chemical characteristics. The cultivation broth that presented the greatest decrease in surface tension (36%) was that of the A. niger, which reduced it from 68·0 to 44·0 mN m^-1 . The lowest critical micellar concentration value was found for the same endophyte (14·93 mg ml^-1 ).

CONCLUSIONS

Endophytes of P. hispidum proved to be interesting producers of biosurfactants and presented promising physico-chemical characteristics for applications in diverse industrial sectors.

SIGNIFICANCE AND IMPACT OF THE STUDY

Piper hispidum endophytic fungi can be used as a new source of biosurfactants, as these molecules present a significant market due to their wide industrial applications.

Efficient production of tri-acetylated mono-acylated mannosylerythritol lipids by Sporisorium sp. aff. sorghi SAM20

AIMS

The aim of this study was to isolate a novel yeast strain, evaluate biosurfactant production by the strain and characterize the major product.

METHODS AND RESULTS

The strain SAM20, isolated from grass, identified as Sporisorium sp. aff. sorghi based on phylogenetic analyses. The strain produced approximately 32 g l^-1 glycolipid biosurfactants from 40 g l^-1 soybean oil after 7 days at 28°C. The glycolipids showed a unique pattern of mannosylerythritol lipids (MELs) on thin layer chromatography plate compared to those hitherto reported. Structural characterization of the major product, called GL-A, revealed that it was mainly tri-acetylated mono-acylated MELs (MEL-A2) with C14:0, C16:0, C12:0 or C14:1 as the hydrophobic chain. The critical micelle concentration (CMC), the surface tension at CMC and hydrophilic-lipophilic balance value for GL-A were estimated to be 20 mg l^-1 , 30·0 mN m^-1 and 8·7, respectively.

CONCLUSIONS

A MEL-A2 with novel composition and surface activities was efficiently produced from a novel MEL producer. This is the first report on production of MEL-A2 as the major product and from soybean oil. The biosurfactant has potential application as a wetting agent and oil-in-water emulsifier.

SIGNIFICANCE AND IMPACT OF THE STUDY

Discovery of novel structures and novel strains is valuable for further commercial development and application of MELs. Sporisorium sp. aff. sorghi SAM20 can be considered as a potential candidate for commercial production of biosurfactants.