Special Issue "Biosurfactants: Trends and Applications"

A special issue of Colloids and Interfaces (ISSN 2504-5377).

Deadline for manuscript submissions: closed (31 August 2018)

Special Issue Editor

Guest Editor
Prof. Dr. Angela F. Cunha

Department of Biology, University of Aveiro, Aveiro, Portugal
Website | E-Mail
Phone: +351234370784
Interests: bacterial biosurfactants; bioremediation; biofilms; plant-bacteria interactions; quorum sensing; photodynamic inactivation

Special Issue Information

Dear Colleagues,

Biosurfactants are surface active agents produced by microorganisms that have higher efficiency and stability, lower toxicity and higher biocompatibility and biodegradability than chemical surfactants. These molecules have a wide range of applications in environmental and industrial processes and as ingredients in antifouling formulations, foods, detergents, cosmetics and personal care products.

The generalized use of biosurfactants is still limited by the high production costs when compared to petrochemically-derived surfactants. As a result, the development of biosurfactant-based industrial products must overcome important challenges in order to attain economic viability.

In the attempt of reducing production costs, “super-producing” strains have been surveyed from a wide range of habitats and bacterial co-cultures have been tested. The use of industrial waste materials as low-cost substrates has also been successfully demonstrated. Furthermore, the production of biosurfactants by microaerophilic facultative anaerobic bacteria has been tested as a strategy of reducing the need for aeration and associated foaming.

During the last few decades, biosurfactants have been demonstrated as mediators of the antifouling effects of some marine microbes. “Blue Biotechnology” represents, therefore, a new breath on bacterial biosurfactant prospection. The encapsulation within release-controlled systems for the long-term prevention of microbial colonization is a second line of approaches to enhance efficiency and optimize cost-benefit ratio.

This Special Issue will address these topics, as well as other perspectives on current research and future perspectives for microbial biosurfactant production and applications:

  • Producing organisms and molecules
  • Biosurfactants from extremophiles
  • Anaerobes as biosurfactant producers
  • Physiology and biochemistry of biosurfactant production
  • Optimized cultivation strategies for reducing production costs
  • Biosurfactant expression in heterologous hosts
  • Industrial and environmental applications
  • Applications in MEOR and petroleum industry
  • Biomedical and therapeutic applications
  • Biosurfactant-based antifouling materials

SI Best Paper Award (300 CHF) will be selected from this SI.

Prof. Dr. Angela F. Cunha
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Colloids and Interfaces is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (10 papers)

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Research

Jump to: Review

Open AccessArticle
Release of Pharmaceutical Peptides in an Aggregated State: Using Fibrillar Polymorphism to Modulate Release Levels
Colloids Interfaces 2019, 3(1), 42; https://doi.org/10.3390/colloids3010042
Received: 8 October 2018 / Revised: 15 March 2019 / Accepted: 15 March 2019 / Published: 26 March 2019
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Abstract
Traditional approaches to achieve sustained delivery of pharmaceutical peptides traditionally use co-excipients (e.g., microspheres and hydrogels). Here, we investigate the release of an amyloidogenic glucagon analogue (3474) from an aggregated state and the influence of surfactants on this process. The formulation of peptide [...] Read more.
Traditional approaches to achieve sustained delivery of pharmaceutical peptides traditionally use co-excipients (e.g., microspheres and hydrogels). Here, we investigate the release of an amyloidogenic glucagon analogue (3474) from an aggregated state and the influence of surfactants on this process. The formulation of peptide 3474 in dodecyl maltoside (DDM), rhamnolipid (RL), and sophorolipid (SL) led to faster fibrillation. When the aggregates were subjected to multiple cycles of release by repeated resuspension in fresh buffer, the kinetics of the release of soluble peptide 3474 from different surfactant aggregates all followed a simple exponential decay fit, with half-lives of 5–18 min and relatively constant levels of release in each cycle. However, different amounts of peptide are released from different aggregates, ranging from 0.015 mg/mL (3475-buffer) up to 0.03 mg/mL (3474-DDM), with 3474-buffer and 3474-RL in between. In addition to higher release levels, 3474-DDM aggregates showed a different amyloid FTIR structure, compared to 3474-RL and 3474-SL aggregates and a faster rate of degradation by proteinase K. This demonstrates that the stability of organized peptide aggregates can be modulated to achieve differences in release of soluble peptides, thus coupling aggregate polymorphism to differential release profiles. We achieved aggregate polymorphism by the addition of different surfactants, but polymorphism may also be reached through other approaches, including different excipients as well as changes in pH and salinity, providing a versatile handle to control release profiles. Full article
(This article belongs to the Special Issue Biosurfactants: Trends and Applications)
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Open AccessArticle
Production of a Biosurfactant by Cunninghamella echinulata Using Renewable Substrates and Its Applications in Enhanced Oil Spill Recovery
Colloids Interfaces 2018, 2(4), 63; https://doi.org/10.3390/colloids2040063
Received: 1 September 2018 / Revised: 5 November 2018 / Accepted: 14 November 2018 / Published: 24 November 2018
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Abstract
This study aimed to evaluate the production of a surfactant by Cunninghamella echinulata, using agro-industrial residues, corn steep liquor (CSL), and soybean oil waste (SOW). The study had a factorial design, using as a variable response to the reduction of surface tension. [...] Read more.
This study aimed to evaluate the production of a surfactant by Cunninghamella echinulata, using agro-industrial residues, corn steep liquor (CSL), and soybean oil waste (SOW). The study had a factorial design, using as a variable response to the reduction of surface tension. C. echinulata was able to produce biosurfactant in assay, CSL (8.82%) and SOW (2%). The results showed that the biosurfactant was successfully produced by C. echinulata and had attractive properties, such as a low surface tension (31.7 mN/m), a yield of 5.18 g/L at 120 h of cultivation, and an anionic profile. It also achieved a reduction in surface tension stability in a wide range of pH values, temperatures, and salinity values. The biosurfactant produced by C. echinulata showed an absence of toxicity to Artemia salina. The influence of the biosurfactant on the viscosity of engine oil, burnt engine oil, diesel, soybean oil post-frying, canola oil, and water was investigated. The results reveal a mechanism for the decrease of the viscosity using hydrophobic substrates and the new biosurfactant solution at 1.5% of the (CMC). This enables the formulation of a low-cost culture medium alternative, based on corn steep liquor and the reuse of soybean oil after frying to produce a biosurfactant. Additionally, performance of the biosurfactant isolated from C. echinulata showed an excellent ability to remove spilled oil, such as diesel (98.7%) and kerosene (92.3%) from marine sand. Full article
(This article belongs to the Special Issue Biosurfactants: Trends and Applications)
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Open AccessArticle
An Efficient Bioemulsifier-Producing Bacillus subtilis UCP 0146 Isolated from Mangrove Sediments
Colloids Interfaces 2018, 2(4), 58; https://doi.org/10.3390/colloids2040058
Received: 1 September 2018 / Revised: 24 October 2018 / Accepted: 6 November 2018 / Published: 13 November 2018
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Abstract
In this work, we investigated the potential of Bacillus subtilis UCP 0146 in the bioconversion of a medium containing 100% cassava flour wastewater to obtain a bioemulsifier. The evaluation of the production was carried out by the emulsification index (IE24) and [...] Read more.
In this work, we investigated the potential of Bacillus subtilis UCP 0146 in the bioconversion of a medium containing 100% cassava flour wastewater to obtain a bioemulsifier. The evaluation of the production was carried out by the emulsification index (IE24) and the surface tension (ST). The ionic charge, stability (temperature, salinity, and pH measured by IE24 and viscosity), and ability to remove and disperse oil and textile dye were investigated. B. subtilis produced an anionic bioemulsifier in the medium containing 100% cassava wastewater under Condition 4 of the factorial design (inoculum 9% at a temperature of 35 °C and shaken at 100 rpm), and showed a surface tension of 39 mN/m, an IE24 of 95.2%, and a yield of 2.69 g·L−1. The bioemulsifier showed stability at different pH (2–8), temperatures (0–120 °C), and NaCl concentrations, a dispersion oil displacement area (ODA) test of 55.83 cm2, and a reduction of the viscosity of the burned engine oil (90.5 Cp). The bioemulsifier was able to remove petroleum (94.4%) and methylene blue azo dye (62.2%). The bioemulsifier and its synthesis from bacteria also emphasizes the role of surfactants in oil remediation. Full article
(This article belongs to the Special Issue Biosurfactants: Trends and Applications)
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Open AccessArticle
Culture Medium Optimization for Production of Rhamnolipids by Burkholderia glumae
Colloids Interfaces 2018, 2(4), 49; https://doi.org/10.3390/colloids2040049
Received: 6 September 2018 / Revised: 10 October 2018 / Accepted: 15 October 2018 / Published: 18 October 2018
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Abstract
Burkholderia glumae is a biosafety level 1 bacterium capable of producing rhamnolipid biosurfactant with longer 3-hydroxy fatty acid chains moieties than those produced by the prototypal producer, the opportunistic pathogen Pseudomonas aeruginosa. Although the capacity of production of rhamnolipid, and the parameters [...] Read more.
Burkholderia glumae is a biosafety level 1 bacterium capable of producing rhamnolipid biosurfactant with longer 3-hydroxy fatty acid chains moieties than those produced by the prototypal producer, the opportunistic pathogen Pseudomonas aeruginosa. Although the capacity of production of rhamnolipid, and the parameters affecting this production, are well established for P. aeruginosa, little is known about the factors that may affect their production in B. glumae. Hence, to evaluate and enhance the production of rhamnolipids in B. glumae, following the selection of best carbon and nitrogen sources, a two-level fractional factorial design experiment was performed to identify the limiting factors significantly affecting the production of rhamnolipids in this bacterial species. Effects of six inorganic nutrients and two physical parameters were studied, and mannitol, urea, CaCl2, and potassium phosphate buffer were selected for further optimization by applying a response surface methodology (RSM). Under the identified optimized conditions, a rhamnolipid production of 1.66 g/L was obtained, about five times higher than that of the initial non-optimized conditions. This represents a key step in the development of large-scale production processes. Full article
(This article belongs to the Special Issue Biosurfactants: Trends and Applications)
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Open AccessArticle
Ion Flotation of La3+, Cd2+, and Cs+ using Monorhamnolipid Collector
Colloids Interfaces 2018, 2(4), 43; https://doi.org/10.3390/colloids2040043
Received: 28 August 2018 / Revised: 1 October 2018 / Accepted: 2 October 2018 / Published: 4 October 2018
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Abstract
Water scarcity is a global issue that is expected to continue increasing in importance in the coming decades. Reclaimed water is one important source available to meet future needs. The reclamation process for wastewaters, particularly from industrial sources, involves the need to remove [...] Read more.
Water scarcity is a global issue that is expected to continue increasing in importance in the coming decades. Reclaimed water is one important source available to meet future needs. The reclamation process for wastewaters, particularly from industrial sources, involves the need to remove low-level contaminants. Here we report the efficacy of an ion flotation process that uses the biosurfactant monorhamnolipid as a metal collector to recover Cs+, Cd2+, and La3+ from water. These elements were tested at collector-to-colligend ratios of 2, 5, and 10. The collector-to-colligend ratio and metal valence play a large role in determining flotation success with removal efficiencies varying widely. The maximum removal efficiency for the metals when floated individually were 46.2, 99.8, and 98.6% for Cs+, Cd2+, and La3+, respectively. When mixed together at near equimolar concentrations removal efficiencies were 39.4, 98.4, and 88.1%, respectively. Removal efficiency for Cs+, Cd2+, and La3+ were up to 49.9, 99.5, and 51.5% when mixed at a ratio of 200:10:1, whereas conditional stability constants predict a removal order of La3+ > Cd2+> Cs+. Future research should examine parameters, including pH and ionic strength, that may affect the flotation process as well as actual metal-contaminated waste streams to evaluate the usefulness of this technology. Full article
(This article belongs to the Special Issue Biosurfactants: Trends and Applications)
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Open AccessArticle
Increasing Uniformity of Biosurfactant Production in Starmerella bombicola via the Expression of Chimeric Cytochrome P450s
Colloids Interfaces 2018, 2(4), 42; https://doi.org/10.3390/colloids2040042
Received: 17 August 2018 / Revised: 21 September 2018 / Accepted: 26 September 2018 / Published: 3 October 2018
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Abstract
Sophorolipids are one of the best known microbial biosurfactants and are produced by several yeast species. The best studied producer is Starmerella bombicola, a non-pathogenic yeast associated in nature with bumblebees. Sophorolipids are built up of the rare disaccharide sophorose, which is [...] Read more.
Sophorolipids are one of the best known microbial biosurfactants and are produced by several yeast species. The best studied producer is Starmerella bombicola, a non-pathogenic yeast associated in nature with bumblebees. Sophorolipids are built up of the rare disaccharide sophorose, which is attached to a fatty acid through a glyosidic bound. Sophorolipids produced by S. bombicola mainly contain oleic acid as the incorporated hydrophobic group. Other chain lengths can, to a certain content, be incorporated by feeding the yeast with substrates of alternative chain lengths. However, the efficiency for such substrates is low as compared to the preferred C18 chain length and defined by the substrate specificity of the first enzymatic step in sophorolipid biosynthesis, i.e., the cytochrome P450 enzyme CYP52M1. To increase product uniformity and diversity at the same time, a new strain of S. bombicola was developed that produces sophorolipids with a palmitic acid acyl chain. This was achieved by heterologous expression of the cytochrome P450 cyp1 gene of Ustilago maydis and feeding with palmitic acid. Optimization of the production was done by protein and process engineering. Full article
(This article belongs to the Special Issue Biosurfactants: Trends and Applications)
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Open AccessArticle
Cholate Adsorption Behavior at Carbon Electrode Interface and Its Promotional Effect in Laccase Direct Bioelectrocatalysis
Colloids Interfaces 2018, 2(3), 33; https://doi.org/10.3390/colloids2030033
Received: 11 July 2018 / Revised: 4 August 2018 / Accepted: 12 August 2018 / Published: 21 August 2018
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Abstract
Fast electron transfer between laccase (Lac) and single-walled carbon nanotubes (SWCNTs) can be achieved at a cholate-modified SWCNT interface. Furthermore, the catalytic reduction of O2 starts at a high potential, close to the equilibrium redox potential of the O2/H2 [...] Read more.
Fast electron transfer between laccase (Lac) and single-walled carbon nanotubes (SWCNTs) can be achieved at a cholate-modified SWCNT interface. Furthermore, the catalytic reduction of O2 starts at a high potential, close to the equilibrium redox potential of the O2/H2O couple. A sodium cholate (SC)-modified electrode interface provides suitable conditions for Lac direct bioelectrocatalysis. In the present study, the SC promotional effect in Lac direct bioelectrocatalysis was investigated using various types of electrode materials. The fully hydrophilic surface of indium tin oxide and an Au electrode surface did not show a SC promotional effect, because SC did not bind to these surfaces. A carbon surface with a large number of defects was unsuitable for SC binding because of hydrophilic functional groups at the defect sites. Carbon surfaces with few defects, for example, basal-plane highly oriented pyrolytic graphite (HOPG), gave a SC promotional effect. Full article
(This article belongs to the Special Issue Biosurfactants: Trends and Applications)
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Review

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Open AccessReview
Molecular Dynamics Simulation of Protein Biosurfactants
Colloids Interfaces 2018, 2(3), 39; https://doi.org/10.3390/colloids2030039
Received: 19 August 2018 / Revised: 4 September 2018 / Accepted: 6 September 2018 / Published: 8 September 2018
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Abstract
Surfaces and interfaces are ubiquitous in nature and are involved in many biological processes. Due to this, natural organisms have evolved a number of methods to control interfacial and surface properties. Many of these methods involve the use of specialised protein biosurfactants, which [...] Read more.
Surfaces and interfaces are ubiquitous in nature and are involved in many biological processes. Due to this, natural organisms have evolved a number of methods to control interfacial and surface properties. Many of these methods involve the use of specialised protein biosurfactants, which due to the competing demands of high surface activity, biocompatibility, and low solution aggregation may take structures that differ from the traditional head–tail structure of small molecule surfactants. As well as their biological functions, these proteins have also attracted interest for industrial applications, in areas including food technology, surface modification, and drug delivery. To understand the biological functions and technological applications of protein biosurfactants, it is necessary to have a molecular level description of their behaviour, in particular at surfaces and interfaces, for which molecular simulation is well suited to investigate. In this review, we will give an overview of simulation studies of a number of examples of protein biosurfactants (hydrophobins, surfactin, and ranaspumin). We will also outline some of the key challenges and future directions for molecular simulation in the investigation of protein biosurfactants and how this can help guide future developments. Full article
(This article belongs to the Special Issue Biosurfactants: Trends and Applications)
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Open AccessReview
Statistical Design, a Powerful Tool for Optimizing Biosurfactant Production: A Review
Colloids Interfaces 2018, 2(3), 36; https://doi.org/10.3390/colloids2030036
Received: 24 July 2018 / Revised: 11 August 2018 / Accepted: 27 August 2018 / Published: 2 September 2018
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Abstract
Biosurfactants (Bs) have been studied for decades and applied in different industrial sectors because of their competitive biochemical characteristics, and the fact that they are environmentally friendly. Current scientific investigations mainly involve the search for novel Bs producing organisms with attractive characteristics. Bs [...] Read more.
Biosurfactants (Bs) have been studied for decades and applied in different industrial sectors because of their competitive biochemical characteristics, and the fact that they are environmentally friendly. Current scientific investigations mainly involve the search for novel Bs producing organisms with attractive characteristics. Bs are expected to replace synthetic surfactants in the near future, but low production yields and inefficient downstream processes have prevented their widespread use. Although there are numerous reports on Bs optimization, to date there has been no critical compilation or revision of the statistical designs and strategies employed for improved production. The purpose of this mini review is to briefly discuss the factors that affect Bs production and the importance of statistical design as an essential tool for increasing production. Full article
(This article belongs to the Special Issue Biosurfactants: Trends and Applications)
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Open AccessFeature PaperReview
The Impact of Biosurfactants on Microbial Cell Properties Leading to Hydrocarbon Bioavailability Increase
Colloids Interfaces 2018, 2(3), 35; https://doi.org/10.3390/colloids2030035
Received: 1 August 2018 / Revised: 20 August 2018 / Accepted: 23 August 2018 / Published: 26 August 2018
Cited by 1 | PDF Full-text (2789 KB) | HTML Full-text | XML Full-text
Abstract
The environment pollution with hydrophobic hydrocarbons is a serious problem that requires development of efficient strategies that would lead to bioremediation of contaminated areas. One of the common methods used for enhancement of biodegradation of pollutants is the addition of biosurfactants. Several mechanisms [...] Read more.
The environment pollution with hydrophobic hydrocarbons is a serious problem that requires development of efficient strategies that would lead to bioremediation of contaminated areas. One of the common methods used for enhancement of biodegradation of pollutants is the addition of biosurfactants. Several mechanisms have been postulated as responsible for hydrocarbons bioavailability enhancement with biosurfactants. They include solubilization and desorption of pollutants as well as modification of bacteria cell surface properties. The presented review contains a wide discussion of these mechanisms in the context of alteration of bioremediation efficiency with biosurfactants. It brings new light to such a complex and important issue. Full article
(This article belongs to the Special Issue Biosurfactants: Trends and Applications)
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