Biosurfactants: Opportunities for the development of a sustainable future

Changes in the environment in recent years have led to the examination of the role and influence human activities on it. Attempts to quantify the impact of these activities by developing standardized modeling frameworks through life cycle sustainability assessment is one such approach in the context of sustainability seeking to measure the impact of human interventions from a holistic perspective that includes economic, social, and environmental dimensions. Sustainable alternatives to synthetic products are always keenly sought after. Biosurfactants are emerging as suitable alternatives to the predominant less sustainable petroleum-derived counterparts. Several factors surrounding their production, distribution, and end-use, however, still needs to be considered before conclusively confirming their sustainability. Though data are still limited in that subject matter, research showing their impact on some sustainability indicators is highlighted. This review discusses the potential of biosurfactants as sustainable products in the context of social, economic, and environmental aspects.     

Small-angle neutron scattering study of sodium cholate and sodium deoxycholate interacting micelles in aqueous medium

Small angle neutron scattering (SANS) measurements of D₂O solutions (0.1 M) of sodium cholate (NaC) and sodium deoxycholate (NaDC) were carried out atT= 298 K. Under compositions very much above the critical micelle concentration (CMC), the bile salt micelle size growths were monitored by adopting Hayter-Penfold type analysis of the scattering data. NaC and NaDC solutions show presence of correlation peaks atQ = 0.12 and 0.1 ?_-1 respectively. Monodisperse ellipsoids of the micelles produce best fits. For NaC and NaDC systems, aggregation number (9.0, 16.0), fraction of the free counterions per micelle (0.79, 0.62), semi-minor (8.0 ?) and semi-major axes (18.4, 31.7 ?) values for the micelles were deduced. Extent of micellar growth was studied using ESR correlation time measurements on a suitable probe incorporating NaC and NaDC micelles. The growth parameter (axial ratio) values were found to be 2.3 and 4.0 for NaC and NaDC systems respectively. The values agree with those of SANS.     

Biosurfactant Production by <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> Grown in Residual Soybean Oil

Pseudomonas aeruginosa PACL strain, isolated from oil-contaminated soil taken from a lagoon, was used to investigate the efficiency and magnitude of biosurfactant production, using different waste frying soybean oils, by submerged fermentation in stirred tank reactors of 6 and 10 l capacities. A complete factorial experimental design was used, with the goal of optimizing the aeration rate (0.5, 1.0, and 1.5 vvm) and agitation speed (300, 550, and 800 rpm). Aeration was identified as the primary variable affecting the process, with a maximum rhamnose concentration occurring at an aeration rate of 0.5 vvm. At optimum levels, a maximum rhamnose concentration of 3.3 g/l, an emulsification index of 100%, and a minimum surface tension of 26.0 dynes/cm were achieved. Under these conditions, the biosurfactant production derived from using a mixture of waste frying soybean oil (WFSO) as a carbon source was compared to production when non-used soybean oil (NUSO), or waste soybean oils used to fry specific foods, were used. NUSO produced the highest level of rhamnolipids, although the waste soybean oils also resulted in biosurfactant production of 75–90% of the maximum value. Under ideal conditions, the kinetic behavior and the modeling of the rhamnose production, nutrient consumption, and cellular growth were established. The resulting model predicted data points that corresponded well to the empirical information.     

Biofilm inhibition and antimicrobial action of lipopeptide biosurfactant produced by heavy metal tolerant strain Bacillus cereus NK1

Biosurfactants are worthful microbial amphiphilic molecules with efficient surface-active and biological properties applicable to several industries and processes. Among them lipopeptides represent a class of microbial surfactants with increasing scientific, therapeutic and biotechnological interests. A heavy metal tolerant Bacillus strain has been isolated and the biofilm inhibition and antimicrobial activity of biosurfactant produced by the strain have been studied. Biosurfactant production was confirmed by the conventional screening methods including hemolytic activity, drop collapsing test, oil displacement test, emulsification and lipase production assays. The biosurfactant produced by this strain was a lipopeptide and exhibited strong surface activity. The biosurfactant has been characterized using FTIR, TLC and HPLC. The minimum active dose of this biosurfactant when compared with the other chemical surfactants was found as 0.150±0.06 μg. The critical micelle concentration was found to be 45 mg/l. The biosurfactant was found to be stable and active over a wide range of pH, temperature and NaCl concentration. It was also able to emulsify a wide range of hydrocarbons and oils thereby extending its application for the bioremediation of oil contaminated sites. The biosurfactant exhibited significant reduction in biofilm formation by pathogens and showed potent antimicrobial activity against various gram positive, gram negative bacteria and fungi. Agar diffusion assay for heavy metal resistance showed that the isolate was resistant to ferrous, lead and zinc. Considering the biofilm inhibition and antimicrobial property of biosurfactant, it can be utilized as a potential therapeutic molecule for numerous microbial infections. The heavy metal resistance of the strain can also be harnessed as an invaluable biological tool for in situ bioremediation.     

Rational design,properties, and applications of biosurfactants: a short review of recent advances

Biosurfactants combine physicochemical properties with biological activities. Although biosurfactants are often expressed by microorganisms, an increasing amount is produced by chemical synthesis. As many exist in the form of homologous compounds, it is often difficult to purify biosurfactants. But this has not limited the efforts to develop their commercial applications. In this short review, we have featured the recent advances in three important types of biosurfactants, lipopeptides, nucleolipids, and glycolipids. We have focused on comparing some of the key properties and functionalities between modern synthetic versions and their corresponding natural counterparts. We end the review by outlining the needs for not only strengthening their basic structure–property relationships through further research but also developing better technologies, irrespective of direct chemical synthesis or biological synthesis of biosurfactants through constructions of genetically engineered strains, to help advance the commercial use of biosurfactants.     

Biosurfactants production by Pseudomonas aeruginosa FR using palm oil

Biosurfactants production by a strain of Pseudomonas aeruginosa using palm oil as a sole carbon source was investigated. The experiments were carried out in 500-mL conical flasks containing 100 mL of mineral media supplemented with palm oil as the sole carbon source. The P. aeruginosa FR strain was able to reduce surface tension of three tested inorganic media. Rotation velocities from 100 to 150 rpm provided free-cell fermented media with the lowest surface tension of approx 33 mN/m. Emulsification index results of even 100% were achieved when diesel was used as oil phase. Eight surface-active compounds produced by the bacterium were identified by mass spectrometry.     

Biosurfactants: Formulations,properties, and applications

In this review, we attempt to give an overview on the recent progress made on biosurfactants, surface-active biomolecules produced by microorganisms, which are a sustainable alternative to synthetic surfactants. Different biosurfactants, their production techniques, and their physical and chemical properties are discussed. There is a focus on recent studies related to surface properties and rheology of biosurfactants, both being properties which affect their ability to take part in a stable formulation. Biosurfactants can have applications in multiple different industrial sectors, such as agriculture, medicine, personal care, food, petroleum, etc. The specific properties important for applications in these sectors are discussed in detail.     

Synthesis and interfacial properties of sophorolipid derivatives

Biosurfactants made by fermentation from renewable resources provide “environmental friendly” processes and products. A natural sophorolipid mixture was produced by the yeast Candida bombicola when cultured on glucose and oleic acid. The sophorolipid mixture was chemically modified to form the corresponding sophorolipid alkyl (methyl, ethyl, propyl, and butyl) esters by reaction with the corresponding sodium alkoxides. Interfacial properties of these surfactants, such as surface tension reduction, aggregation, and adsorption, were systematically studied. It was found that the critical micelle concentration of sophorolipid esters decreases to about 1/2 per additional one CH₂ group to the alkyl ester moiety. Interestingly, these surfactants were found to adsorb strongly on alumina but weakly on silica. They have properties that make them attractive candidates for uses in detergents, cosmetics, soil remediation, and enhanced oil recovery.