Green Surfactants (Biosurfactants): A Petroleum-Free Substitute for Sustainability-Comparison, Applications, Market, and Future Prospects

Surfactants are a group of amphiphilic molecules (i.e., having both hydrophobic and hydrophilic domains) that are a vital part of nearly every contemporary industrial process such as in agriculture, medicine, personal care, food, and petroleum. In general surfactants can be derived from (i) petroleum-based sources or (ii) microbial/plant origins. Petroleum-based surfactants are obvious results from petroleum products, which lead to petroleum pollution and thus pose severe problems to the environment leading to various ecological damages. Thus, newer techniques have been suggested for deriving surfactant molecules and maintaining environmental sustainability. Biosurfactants are surfactants of microbial or plant origins and offer much added advantages such as high biodegradability, lesser toxicity, ease of raw material availability, and easy applicability. Thus, they are also termed "green surfactants". In this regard, this review focused on the advantages of biosurfactants over the synthetic surfactants produced from petroleum-based products along with their potential applications in different industries. We also provided their market aspects and future directions that can be considered with selections of biosurfactants. This would open up new avenues for surfactant research by overcoming the existing bottlenecks in this field.

Formulation and evaluation of antidandruff shampoo using mannosylerythritol lipid (MEL) as a bio-surfactant

Dandruff is a dermatological, harmless, non-inflammatory, chronic scalp condition caused by Malassezia species and recognisable by the white flakes of dead skin in the hair. Mannosylerythritol lipids (MEL) are non-ionic glycolipid surfactants (biosurfactants) with excellent surface-active properties. Their skin compatibility, biocompatibility, biodegradability and remarkable antimicrobial properties make them a potential alternative to conventional surfactants. In the current study, an anti-dandruff shampoo was formulated with different concentrations of sodium lauryl sulphate (SLS) and MEL as surfactants. Two anti-dandruff agents, salicylic acid and benzoic acid, were used. The other ingredients used were xanthan gum, sodium EDTA, urea, Tween 80 and distilled water. The various physicochemical parameters evaluated were colour, clarity, odour, texture, pH, skin irritation, percentage of solid content, dispersibility for dirt, foam formation and foam stability, critical micelle concentration, washability, surface tension, visual stability and antimicrobial test using recommended procedures. The pH ranged from 5.15 to 6.5, the physical appearance was golden yellow, the solids content ranged from 25.1% to 28%, surface tension ranged from 30.64 mN m−1 to 38.00 mN m−1, CMC concentration ranged from 30.14 g/L to 30.16 g/L and foam value ranged from 190 mL to 105 mL. Antimicrobial activity was determined with Staphylococcus aureus (DSM 3463) and Malassezia furfur (ATCC14521). The zone of inhibition ranged from 10 mm to 17 mm (S. aureus) and 14.5 mm to 24 mm (M. furfur), respectively. The shampoo formulated with MEL only (formulation C) showed lower foaming and anti-dandruff activity than the synthetic shampoo (formulation A). However, the anti-dandruff activity increased when MEL was used in combination with SLS (formulation B). This shows that the antimicrobial properties of MEL and SLS together with other antimicrobial agents such as salicylic acid and benzoic acid enhance the properties of the shampoo. SLS can be completely replaced by a combination with biosurfactants to reduce the use of chemical surfactants and improve the anti-dandruff properties.

Optimization of the primary purification process of extracting sphorolipid from the fermentation broth to achieve a higher yield and purity

Sophorolipid (SL) is a surface-active glycolipid biosurfactant with promising industrial applications. It is synthesised by fermentation of hydrophobic and hydrophilic substrates using selected non-pathogenic yeasts. However, its applications are limited by high production costs and ineffective product recovery in downstream purification stages. Natural sophorolipids are produced in six to nine different hydrophobic sophorosides, where the carboxyl end of the fatty acid is either free, which is known as the acidic or open form, or it can be esterified internally to produce the lactonic form. The present study deals with the screening and selection of suitable solvents for the extraction of acidic and lactonic SL from fermentation broth. The optimisation study involves exhaustive extraction with the six different immiscible solvents ethyl acetate, butyl acetate, methylene dichloride, methyl tert.-butyl ether, methyl iso-butyl ketone and methyl ethyl ketone. The partition coefficient (Kd), which is the ratio of the solute concentration in the organic layer compared to the aqueous layer, determines the performance measurement of the extraction process in terms of yield and purity of the desired solute. The factors that influence exhaustive extraction were the broth to solvent ratio and the extraction stages. The optimal extraction conditions for the highest possible yield were a broth to solvent ratio of 1:1 and a number of extraction steps of 2. Methylene dichloride showed better results in terms of yield and selectivity in the extraction of acidic and lactonic SL from the fermentation broth compared to the other solvents investigated. For lactonic SL, the highest Kd value determined was 36.6 and for acidic SL the highest Kd value was 1.14.

Production of mannosylerythritol lipids: biosynthesis, multi-omics approaches, and commercial exploitation

Compilation of resources regarding MEL biosynthesis, key production parameters; available omics resources and current commercial applications, for smut fungi known to produce MELs.