There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Short protocols in molecular biology

Microorganisms synthesise a wide range of surface-active compounds (SAC), generally called biosurfactants. These compounds are mainly classified according to their molecular weight, physico-chemical properties and mode of action. The low-molecular-weight SACs or biosurfactants reduce the surface tension at the air/water interfaces and the interfacial tension at oil/water interfaces, whereas the high-molecular-weight SACs, also called bioemulsifiers, are more effective in stabilising oil-in-water emulsions. Biosurfactants are attracting much interest due to their potential advantages over their synthetic counterparts in many fields spanning environmental, food, biomedical, and other industrial applications. Their large-scale application and production, however, are currently limited by the high cost of production and by limited understanding of their interactions with cells and with the abiotic environment. In this paper, we review the current knowledge and the latest advances in biosurfactant applications and the biotechnological strategies being developed for improving production processes and future potential.

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Microbial biosurfactants production, applications and future potential

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Studies in Surface Science and Catalysis

In the era of global industrialisation, the exploration of natural resources has served as a source of experimentation for science and advanced technologies, giving rise to the manufacturing of products with high aggregate value in the world market, such as biosurfactants. Biosurfactants are amphiphilic microbial molecules with hydrophilic and hydrophobic moieties that partition at liquid/liquid, liquid/gas or liquid/solid interfaces. Such characteristics allow these biomolecules to play a key role in emulsification, foam formation, detergency and dispersal, which are desirable qualities in different industries. Biosurfactant production is considered one of the key technologies for development in the 21st century. Besides exerting a strong positive impact on the main global problems, biosurfactant production has considerable importance to the implantation of sustainable industrial processes, such as the use of renewable resources and “green” products. Biodegradability and low toxicity have led to the intensification of scientific studies on a wide range of industrial applications for biosurfactants in the field of bioremediation as well as the petroleum, food processing, health, chemical, agricultural and cosmetic industries. In this paper, we offer an extensive review regarding knowledge accumulated over the years and advances achieved in the incorporation of biomolecules in different industries.

Biosurfactants: Multifunctional Biomolecules of the 21st Century

Biosurfactant production was studied by Bacillus licheniformis K51, B. subtilis 20B, B. subtilis R1 and Bacillus strain HS3 using molasses or cheese whey as a sole source of nutrition at 45 � C. The isolates were able to grow and produce biosurfactant under shaking as well as static conditions. Maximum biosurfactant production was achieved with molasses at 5.0–7.0% (w/v). The biosurfactant retained its surface-active properties after incubation at 80 � C at a wide range of pH values and salt concentrations for nine days. Oil displacement experiments in sand pack columns with crude oil showed 25–33% recovery of residual oil. � 2007 Published by Elsevier Ltd.

Short Communication Biosurfactant production using molasses and whey under thermophilic conditions

Biosurfactant production using molasses and whey under thermophilic conditions.

Biosurfactant production by Bacillus subtilis B30 and its application in enhancing oil recovery.

Production of biosurfactant and antifungal compound by fermented food isolate Bacillus subtilis 20B.

Microbial enhanced oil recovery (MEOR) is a type of enhanced oil recovery (EOR) technology, generally employed as a tertiary stage where oil recovery using primary and secondary traditional methods is not feasible anymore. Amongst several potential biological agents useful for MEOR, biosurfactants (biologically produced amphiphilic surfactants) play key roles. They are mostly equivalent to or better than their chemical counterparts in several aspects including; better environmental compatibility, production from renewable waste substrates, maintaining activity at harsh environmental conditions, lower or no environmental toxicity. Biosurfactants are still not cost-competitive when compared to chemical surfactants. Different strategies like the use of cheaper raw materials, optimization of media components, fermentation processes and downstream processes, use of hyperproducers are currently explored to improve biosurfactant production economics. Biosurfactant mediated MEOR (BS-MEOR) could be applied by either in-situ or ex-situ techniques. In-situ BS-MEOR could be applied by injecting biosurfactant producing microorganisms in the oil well with or without additional nutrients. Generally followed by shut-in phase and subsequently monitoring microbial activities, metabolites production and oil recovery from the producer wells. Whereas for ex-situ BS-MEOR applications, the biosurfactant is produced outside the oil well and injected directly for enhancing oil recovery. This review highlights the biosurfactant production and economics, general protocols for applications from lab-to-field scale, different successful trials along with pros and cons of both in-situ and ex-situ BS-MEOR applications.

Sanket J. Joshi

Papers

Short Communication Biosurfactant production using molasses and whey under thermophilic conditions

Biosurfactant production using molasses and whey under thermophilic conditions.

Biosurfactant production by Bacillus subtilis B30 and its application in enhancing oil recovery.

Production of biosurfactant and antifungal compound by fermented food isolate Bacillus subtilis 20B.

Biosurfactants: Production and potential applications in microbial enhanced oil recovery (MEOR)