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.

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

Microbial biosurfactants with high ability to reduce surface and interfacial surface tension and conferring important properties such as emulsification, detergency, solubilization, lubrication and phase dispersion have a wide range of potential applications in many industries. Significant interest in these compounds has been demonstrated by environmental, bioremediation, oil, petroleum, food, beverage, cosmetic and pharmaceutical industries attracted by their low toxicity, biodegradability and sustainable production technologies. Despite having significant potentials associated with emulsion formation, stabilization, antiadhesive and antimicrobial activities, significantly less output and applications have been reported in food industry. This has been exacerbated by uneconomical or uncompetitive costing issues for their production when compared to plant or chemical counterparts. In this review, biosurfactants properties, present uses and potential future applications as food additives acting as thickening, emulsifying, dispersing or stabilising agents in addition to the use of sustainable economic processes utilising agro-industrial wastes as alternative substrates for their production are discussed. V C 2013 American Institute of Chemical Engineers Biotechnol. Prog., 000:000–000, 2013

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Microbial biosurfactants as additives for food industries

Synthetic surfactants are becoming increasingly unpopular in many applications due to previously disregarded effects on biological systems and this has led to a new focus on replacing such products with biosurfactants that are biodegradable and produced from renewal resources. Microbially derived biosurfactants have been investigated in numerous studies in areas including: increasing feed digestibility in an agricultural context, improving seed protection and fertility, plant pathogen control, antimicrobial activity, antibiofilm activity, wound healing and dermatological care, improved oral cavity care, drug delivery systems and anticancer treatments. The development of the potential of biosurfactants has been hindered somewhat by the myriad of approaches taken in their investigations, the focus on pathogens as source species and the costs associated with large-scale production. Here, we focus on various microbial sources of biosurfactants and the current trends in terms of agricultural and biomedical applications.

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Microbial biosurfactants: current trends and applications in agricultural and biomedical industries.

In this work, biosurfactant production by Bacillus subtilis #573 was evaluated using corn steep liquor (CSL) as culture medium The best results were obtained in a culture medium consisting of 10% (v/v) of CSL, with a biosurfactant production of about 13 g/l To the best of our knowledge, this is the first report describing biosurfactant production by B subtilis using CSL as culture medium Subsequently, the effect of different metals (iron, manganese and magnesium) on biosurfactant production was evaluated using the medium CSL 10% It was found that for all the metals tested, the biosurfactant production was increased (up to 41, 44 and 35 g/l for iron, manganese and magnesium, respectively) When the culture medium was supplemented with the optimum concentration of the three metals simultaneously, the biosurfactant production was increased up to 48 g/l Furthermore, the biosurfactant exhibited a good performance in oil recovery assays when compared with chemical surfactants, which suggests its possible application in microbial enhanced oil recovery or bioremediation

https://repositorium.sdum.uminho.pt/bitstream/1822/34587/1/document_19839_1.pdf

Biosurfactant production by Bacillus subtilis using corn steep liquor as culture medium.

Lipopeptide surfactants: Production, recovery and pore forming capacity.

During the last years, several applications of biosurfactants with medical purposes have been reported. Biosurfactants are considered relevant molecules for applications in combating many diseases. However, their use is currently extremely limited due to their high cost in relation to that of chemical surfactants. Use of inexpensive substrates can drastically decrease its production cost. Here, twelve solid substrates were screened for the production of Bacillus subtilis SPB1 biosurfactant and the maximum yield was found with millet. A Plackett-Burman design was then used to evaluate the effects of five variables (temperature, moisture, initial pH, inoculum age, and inoculum size). Statistical analyses showed that temperature, inoculum age, and moisture content had significantly positive effect on SPB1 biosurfactant production. Their values were further optimized using a central composite design and a response surface methodology. The optimal conditions of temperature, inoculum age, and moisture content obtained under the conditions of study were 37°C, 14 h, and 88%, respectively. The evaluation of the antimicrobial activity of this compound was carried out against 11 bacteria and 8 fungi. The results demonstrated that this biosurfactant exhibited an important antimicrobial activity against microorganisms with multidrug-resistant profiles. Its activity was very effective against Staphylococcus aureus, Staphylococcus xylosus, Enterococcus faecalis, Klebsiella pneumonia, and so forth.

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Investigation of antimicrobial activity and statistical optimization of Bacillus subtilis SPB1 biosurfactant production in solid-state fermentation.

Nutritional requirements can contribute considerably to the production cost and the bioprocess economics. Media optimisation using response surface methodology is one of the used methods to ameliorate the bioprocess economics. In the present study, biosurfactant production by Bacillus subtilis SPB1 was effectively enhanced by response surface methodology. A Plackett-Burman-based statistical screening procedure was adopted to determine the most important factor affecting lipopeptide production. Eleven variables are screened and results show that glucose, K2HPO4, and urea concentrations influence the most biosurfactant production. A Central Composite Design was conducted to optimize the three selected factors. Statistical analyses of the data of model fitting were done by using NemrodW. Results show a maximum predicted biosurfactant concentration of 2.93 (±0.32) g/L when using 15 g/L glucose, 6 g/L urea, and 1 g/L K2HPO4. The predicted value is approximately 1.65 much higher than the original production determined by the conventional one-factor-at-a-time optimization method.

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Optimization of the Nutritional Parameters for Enhanced Production of B. subtilis SPB1 Biosurfactant in Submerged Culture Using Response Surface Methodology

Semia Chaabouni-Ellouze

Papers

Investigation of antimicrobial activity and statistical optimization of Bacillus subtilis SPB1 biosurfactant production in solid-state fermentation.

Optimization of the Nutritional Parameters for Enhanced Production of B. subtilis SPB1 Biosurfactant in Submerged Culture Using Response Surface Methodology