An inexpensive strategy for facilitated recovery of metals and fermentation products by foam fractionation process

Sophorolipids: A comprehensive review on properties and applications

Sophorolipids are surface-active glycolipids produced by several non-pathogenic yeast species and are widely used as biosurfactants in several industrial applications. Sophorolipids provide a plethora of benefits over chemically synthesized surfactants for certain applications like bioremediation, oil recovery, and pharmaceuticals. They are, for instance less toxic, more benign and environment friendly in nature, biodegradable, freely adsorb to different surfaces, self-assembly in hydrated solutions, robustness for industrial applications etc. These miraculous properties result in valuable physicochemical attributes such as low critical micelle concentrations (CMCs), reduced interfacial surface tension, and capacity to dissolve non-polar components. Moreover, they exhibit a diverse range of physicochemical, functional, and biological attributes due to their unique molecular composition and structure. In this article, we highlight the physico-chemical properties of sophorolipids, how these properties are exploited by the human community for extensive benefits and the conditions which lead to their unique tailor-made structures and how they entail their interfacial behavior. Besides, we discuss the advantages and disadvantages associated with the use of these sophorolipids. We also review their physiological and functional attributes, along with their potential commercial applications, in real-world scenario. Biosurfactants are compared to their man-made equivalents to show the variations in structure-property correlations and possible benefits. Those attempting to manufacture purported natural or green surfactant with innovative and valuable qualities can benefit from an understanding of biosurfactant features structured along the same principles. The uniqueness of this review article is the detailed physico-chemical study of the sophorolipid biosurfactant and how these properties helps in their usage and detailed explicit study of their applications in the current scenario and also covering their pros and cons.

A novel method for the separation of saponin from soybean meal by colloidal gas aphrons: optimization based on response surface methodology

Natural surfactants, such as soy saponins, are rich in triterpenoid saponins, which have significant biological activities and are used in different applications, such as cosmetics, food, and pharmaceutical industries. In this research, it was used colloidal gas aphrons (CGAs) as a green and cost-effective method to concentrate soy saponin from soybean meal extract. The production of micro-nano bubbles, in conjunction with the investigation of the effect of different chemical and process variables, significantly impacted the purity and recovery of saponins in this method. The response surface methodology (RSM) was employed to optimize the process. The purity and recovery percentage of saponins were found to be 75.12 and 25.87 in optimal conditions, respectively. Furthermore, when the maximum value for both responses was selected, the purity and recovery reached 57.61% and 71.94%, respectively. Eventually, the results indicate that this method is technically promising, straightforward, and cost-effective in separating saponins for various applications.

Foam Fractionation Methods in Aerobic Fermentation Processes

Inherently occurring foam formation during aerobic fermentations of surface-active compounds can be exploited by fractionating the foam. This also serves as the first downstream processing step for product concentration and is used for in situ product recovery. Compared to other foam prevention methods, it does not interfere with fermentation parameters or alter broth composition. Nevertheless, parameters affecting the foaming behaviour are complex. Therefore, the specific foam fractionation designs need to be engineered for each fermentation individually. This still hinders a widespread industrial application. However, few available commercial approaches demonstrate the applicability of foam columns on an industrial scale. This systematic literature review highlights relevant design aspects and process demands that need to be considered for an application to fermentations and proposes a classification of foam fractionation designs and methods. It further analyses substance-specific characteristics associated with foam fractionation. Finally, solutions for current challenges are presented, and future perspectives are discussed. This article is protected by copyright. All rights reserved.

A critical review on the environmental application of lipopeptide micelles

The importance of lipopeptide micelles in environmental applications has been highlighted. These vessels exhibit various sizes, shapes, and surface properties under different environmental conditions. An in-depth understanding of the tunable assembling behavior of biosurfactant micelles is of great importance for their applications. However, a systematic review of such behaviors with assorted micro/nano micellar structures under given environmental conditions, particularly under low temperature and high salinity, remains untapped. Such impacts on their environmental applications have yet to be summarized. This review tried to fill the knowledge gaps by providing a comprehensive summary of the recent knowledge advancement in genetically regulated lipopeptides production, micelles associated decontamination mechanisms in low temperature and high salinity environments, and up-to-date environmental applications. This work is expected to deliver valuable insights to guide lipopeptide design and discovery. The mechanisms concluded in this study could inspire the forthcoming research efforts in the advanced environmental application of lipopeptide micelles.

Biophysical approaches for exploring lipopeptide-lipid interactions

In recent years, lipopeptides (LPs) have attracted a lot of attention in the pharmaceutical industry due to their broad-spectrum of antimicrobial activity against a variety of pathogens and their unique mode of action. This class of compounds has enormous potential for application as an alternative to conventional antibiotics and for pest control. Understanding how LPs work from a structural and biophysical standpoint through investigating their interaction with cell membranes is crucial for the rational design of these biomolecules. Various analytical techniques have been developed for studying intramolecular interactions with high resolution. However, these tools have been barely exploited in lipopeptide-lipid interactions studies. These biophysical approaches would give precise insight on these interactions. Here, we reviewed these state-of-the-art analytical techniques. Knowledge at this level is indispensable for understanding LPs activity and particularly their potential specificity, which is relevant information for safe application. Additionally, the principle of each analytical technique is presented and the information acquired is discussed. The key challenges, such as the selection of the membrane model are also been briefly reviewed.

In situ downstream strategies for cost-effective bio/surfactant recovery

Since 60-80% of total costs of production are usually associated with downstream collection, separation, and purification processes, it has become advantageous to investigate how to replace traditional methods with efficient and cost-effective alternative techniques for recovery and purification of biosurfactants. In the traditional techniques, large volumes of organic solvents are usually used for increasing production cost and the overall environmental burden. In addition, traditional production and separation methods typically carried out in batch cultures reduce biosurfactant yields due to product inhibition and lower biosurfactants activity as a result of interaction with the organic solvents used. However, some in situ recovery methods that allow continuous separation of bioproducts from culture broth leading to an improvement in yield production and fermentation efficiency. For biosurfactants commercialization, enhancement of product capacity of the separation methods and the rate of product removal is critical. Recently, interest in the integration of separation methods with a production step as rapid and efficient techniques has been increasing. This review focuses on the technology gains and potentials for the most common methods used in in situ product removal: foam fractionation and ultrafiltration, especially used to recover and purify two well-known biosurfactants: glycolipids (rhamnolipids) and lipopeptides (surfactins).

Biosurfactant-biopolymer driven microbial enhanced oil recovery (MEOR) and its optimization by an ANN-GA hybrid technique

A lipopeptide biosurfactant produced by marine Bacillus megaterium and a biopolymer produced by thermophilic Bacillus licheniformis were tested for their application potential in the enhanced oil recovery. The crude biosurfactant obtained after acid precipitation effectively reduced the surface tension of deionized water from 70.5 to 28.25mN/m and the interfacial tension between lube oil and water from 18.6 to 1.5mN/m at a concentration of 250mgL^-1. The biosurfactant exhibited a maximum emulsification activity (E₂₄) of 81.66% against lube oil. The lipopeptide micelles were stabilized by addition of Ca²⁺ ions to the biosurfactant solution. The oil recovery efficiency of Ca²⁺ conditioned lipopeptide solution from a sand-packed column was optimized by using artificial neural network (ANN) modelling coupled with genetic algorithm (GA) optimization. Three important parameters namely lipopeptide concentration, Ca²⁺ concentration and solution pH were considered for optimization studies. In order to further improve the recovery efficiency, a water soluble biopolymer produced by Bacillus licheniformis was used as a flooding agent after biosurfactant incubation. Upon ANN-GA optimization, 45% tertiary oil recovery was achieved, when biopolymer at a concentration of 3gL^-1 was used as a flooding agent. Oil recovery was only 29% at optimal conditions predicted by ANN-GA, when only water was used as flooding solution. The important characteristics of biopolymers such as its viscosity, pore plugging capabilities and bio-cementing ability have also been tested. Thus, as a result of biosurfactant incubation and biopolymer flooding under the optimal process conditions, a maximum oil recovery of 45% was achieved. Therefore, this study is novel, timely and interesting for it showed the combined influence of biosurfactant and biopolymer on solubilisation and mobilization of oil from the soil.

Screening concepts, characterization and structural analysis of microbial-derived bioactive lipopeptides: a review

Lipopeptide biosurfactants are surface active biomolecules that are produced by a variety of microorganisms. Microbial lipopeptides have gained the interest of microbiologists, chemists and biochemists for their high biodiversity as well as efficient action, low toxicity and good biodegradability in comparison to synthetic counterparts. In this report, we review methods for the production, isolation and screening, purification and structural characterization of microbial lipopeptides. Several techniques are currently available for each step, and we describe the most commonly utilized and recently developed techniques in this review. Investigations on lipopeptide biosurfactants in natural products require efficient isolation techniques for the characterization and evaluation of chemical and biological properties. A combination of chromatographic and spectroscopic techniques offer opportunities for a better characterization of lipopeptide structures, which in turn can lead to the application of lipopeptides in food, pharmaceutical, cosmetics, agricultural and bioremediation industries.

Biosurfactants: Multifunctional Biomolecules of the 21st Century

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.

Role of pH-induced structural change in protein aggregation in foam fractionation of bovine serum albumin

For reducing protein aggregation in foam fractionation, the role of pH-induced structural change in the interface-induced protein aggregation was analyzed using bovine serum albumin (BSA) as a model protein. The results show that the decrease in pH from 7.0 to 3.0 gradually unfolded the BSA structure to increase the molecular size and the relative content of β-sheet and thus reduced the stability of BSA in the aqueous solution. At the isoelectric point (pH 4.7), BSA suffered the lowest level in protein aggregation induced by the gas-liquid interface. In the pH range from 7.0 to 4.7, most BSA aggregates were formed in the defoaming process while in the pH range from 4.7 to 3.0, the BSA aggregates were formed at the gas-liquid interface due to the unfolded BSA structure and they further aggregated to form insoluble ones in the desorption process.

Rhamnolipid biosurfactants: evolutionary implications, applications and future prospects from untapped marine resource

Rhamnolipid-biosurfactants are known to be produced by the genus Pseudomonas, however recent literature reported that rhamnolipids (RLs) are distributed among diverse microbial genera. To integrate the evolutionary implications of rhamnosyl transferase among various groups of microorganisms, a comprehensive comparative motif analysis was performed amongst bacterial producers. Findings on new RL-producing microorganism is helpful from a biotechnological perspective and to replace infective P. aeruginosa strains which ultimately ensure industrially safe production of RLs. Halotolerant biosurfactants are required for efficient bioremediation of marine oil spills. An insight on the exploitation of marine microbes as the potential source of RL biosurfactants is highlighted in the present review. An economic production process, solid-state fermentation using agro-industrial and industrial waste would increase the scope of biosurfactants commercialization. Potential and prospective applications of RL-biosurfactants including hydrocarbon bioremediation, heavy metal removal, antibiofilm activity/biofilm disruption and greener synthesis of nanoparticles are highlighted in this review.