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.

Fermentative production of rhamnolipid and purification by adsorption chromatography.

Glycolipids are one of the major classes of biosurfactants in which the rhamnolipids are best studied. The present work investigates the optimization of inoculum age and batch time for maximizing the yield of rhamnolipid from Pseudomonas aeruginosa (MTCC 2453). The yield and titer of rhamnolipids were maximum in the fermentation batch with an inoculum age of 24 hr. Batch time studies were performed on biomass production, rhamnolipid production, and sunflower oil utilization. The maximum yield of rhamnolipid was achieved at 96 hr when the culture cells were in the late exponential/early stationary phase. At optimum substrate concentration, maximum yield of 10.8 g/L was achieved. Further, downstream processing of crude rhamnolipid from broth using organic solvent extraction and subsequent purification using adsorption chromatography was done. In this study, chromatographic method was developed for purification of rhamnolipid by adsorption phenomena with more than 88.7% purity and 86.5% recovery. The present study provides new perspective on concepts involving separation by adsorption. Further antimicrobial properties and surfactant properties were studied for rhamnolipid production.

Ultrasound-assisted lipase catalyzed hydrolysis of aspirin methyl ester.

The ultrasound-assisted hydrolysis of aspirin methyl ester (AME) was investigated using immobilized Candida antarctica lipase B (CALB) (1%) in the presence of solvents like triolein, chloroform (CHCl3) and dichloromethane (DCM). The effect of ultrasound and the role of water on the conversion rates have also been investigated. Proton nuclear magnetic resonance spectroscopic (1H NMR) was chosen to calculate hydrolysis convertion rates. We observed that lipase-ultrasound assisted hydrolysis of AME in the presence of triolein and water showed the highest hydrolysis conversion rate (65.3%). Herein low water amount played an important role as a nucleophile being crucial for the hydrolysis yields obtained. Lipase activity was affected by the conjugated action of ultrasound and solvents (35.75% of decrease), however not disturbing its hydrolytic efficiency. It was demonstrated that lipase is able to hydrolyse AME to methyl 2-hydroxy benzoate (methyl salicylate), which applications include fragrance agents in food, beverages and cosmetics, or analgesic agent in liniments.

Ultrasound Assisted Synthesis of Hydroxylated Soybean Lecithin from Crude Soybean Lecithin as an Emulsifier.

Soybean lecithin is a by-product obtained during degumming step of crude soybean oil refining. Crude soybean lecithin (CSL) contains major amount of phospholipids (PLs) along with minor amount of acylglycerols, bioactive components, etc. Due to presence of PLs, CSL can be used as an emulsifier. Crude soybean lecithin (CSL) was utilized to synthesize hydroxylated soybean lecithin (HSL) by hydroxylation using hydrogen peroxide and catalytic amount of lactic acid to enhance the hydrophilicity and emulsifying properties of CSL. To reduce the reaction time and to increase rate of reaction, HSL was synthesized under ultrasound irradiation. The effect of different operating parameters such as lactic acid, hydrogen peroxide, temperature, ultrasonic power and duty cycle in synthesis of HSL were studied and optimized. The surface tension (SFT), interfacial tension (IFT) and the critical micelle concentration (CMC) of the HSL (26.11 mN/m, 2.67 mN/m, 112 mg/L) were compared to CSL (37.53 mN/m, 6.22 mN/m, 291 mg/L) respectively. The HSL has better emulsion stability and low foaming characteristics as compared to CSL. Therefore, the product as an effective emulsifier can be used in food, pharmacy, lubricant, cosmetics, etc.

Comparative Studies between Conventional and Microwave Assisted Extraction for Rice Bran Oil.

The present work deals with comparison of microwave assisted extraction to that of conventional solvent extraction for the extraction of rice bran oil (RBO); focusing on extraction yield and oil composition. Microwave assisted extraction act as a green process over other method and proved that it is effective method for extraction of oil. The investigation also focuses on the study of functional group and component present in oil. Natural antioxidant component; its activity was confirmed by DPPH assay. The oryzanol content was also determined by measuring the optical density of the sample at 315 nm in n-heptane using UV visible spectrophotometer.

Rice Bran Oil: A Versatile Source for Edible and Industrial Applications.

Rice bran oil (RBO) is healthy gift generously given by nature to mankind. RBO is obtained from rice husk, a byproduct of rice milling industry and is gaining lot of importance as cooking oil due to presence of important micronutrient, gamma oryzanol. Its high smoke point is beneficial for its use for frying and deep frying of food stuff. It is popular because of balanced fatty acid profile (most ideal ratio of saturated, monounsaturated and polyunsaturated fatty acids), antioxidant capacity, and cholesterollowering abilities. Rice bran wax which is secondary by-product obtained as tank settling from RBO is used as a substitute for carnauba wax in cosmetics, confectionery, shoe creams etc. It can be also used as a source for fatty acid and fatty alcohol. The article is intended to highlight for the importance of RBO and its applications.

Diester-containing Zwitterionic Gemini Surfactants with Different Spacer and Its Impact on Micellization Properties and Viscosity of Aqueous Micellar Solution.

A series of diester containing zwitterionic gemini surfactants, N,N-dimethyl-N-alkyl-2-[[hydroxy (alkoxy) phosphinyl]oxy]-alkylammonium designated as C8(-)-S-Cn(+), S = 2 and 3, n = 12, 14 and 16, were synthesized and characterized by instrumental techniques namely FT-IR, (1)H NMR, (13)C NMR, (31)P NMR and Mass spectral studies. These new gemini surfactants further investigated for their various surfactant properties. The critical micelle concentration (cmc) and the effectiveness of surface tension reduction (Πcmc) were determined as a function of surfactant concentration by means of surface tension measurement. Micellization and viscosity properties were investigated by surface tension, electrical conductivity, dye micellization and rheology techniques. The findings of the aqueous surfactant system obtained were impacted by polarity, size and the nature of zwitterions as the surface. The thermodynamic and viscosity properties of these surfactants found to be based on the structures of gemini surfactants.

Synthesis and Performance Properties of Cationic Fabric Softeners Derived from Free Fatty Acid of Tallow Fat.

Esterquat cationic softener is basically the class of surface active quaternary ammonium compounds. Esterquat compounds were synthesized and their surface behavior, antibacterial activity and Textile softening properties were investigated. Easily found cheap material was used to synthesize cationic fabric softeners. This fabric softener will be a good for commercially and industrially important because their emulsify activity, rewettability dispersing power and softness. Free fatty acids were derived from tallow oil and were treated with triethanolamine and mono-ethanolamine at 140°C. This diester was quaternaries with dimethyl sulphate and benzyl chloride. The synthesized esterquat compounds were characterized by its cationic content, 1H NMR and FT-IR analysis. In addition to the cationic content, surface tension, CMC (critical micelle concentration), rewettability, fabric softening, emulsification and dispersing power were determined as their surface-active properties. The fabric softening activity of esterquat and esteramide prepared from DMS was better softening activity of fabrics compared to untreated cotton and polyester fabrics cloth. The presented result shows that the esterquat made from BCl exhibit the best dispersing power. The esterquat made from DMS both in TEA and MEA shows good rewettability was determined.

Preparation of Zirconia Supported Basic Nanocatalyst: A Physicochemical and Kinetic Study of Biodiesel Production from Soybean Oil.

Zirconia supported cadmium oxide basic nanocatalyst was prepared by simple co-precipitation method using aq. ammonia as precipitating reagent. The catalyst was characterised by X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy technique (TEM), Brunauer-Emmet-Teller surface area measurement (BET), temperature program desorption (TPD-CO2) etc. The transesterificaton of soybean oil with methanol into biodiesel was catalysed by employing zirconia supported nanocatalyst. Kinetics of transesterificaton of oil was studied and obeyed the pseudo first order equation. While, the activation energy (Ea) for the transesterification of oil was found to be 41.18 kJ mol(-1). The 97% yield of biodiesel was observed using 7% catalyst loading (with respect of oil), 1:40 molar ratio of oil to methanol at 135°C.

Choline Chloride Catalyzed Amidation of Fatty Acid Ester to Monoethanolamide: A Green Approach.

Choline chloride catalyzed efficient method for amidation of fatty acid methyl ester to monoethanolamide respectively. This is a solvent free, ecofriendly, 100% chemo selective and economically viable path for alkanolamide synthesis. The Kinetics of amidation of methyl ester were studied and found to be first order with respect to the concentration of ethanolamine. The activation energy (Ea) for the amidation of lauric acid methyl ester catalyzed by choline chloride was found to be 50.20 KJ mol(-1). The 98% conversion of lauric acid monoethanolamide was obtained at 110°C in 1 h with 6% weight of catalyst and 1:1.5 molar ratio of methyl ester to ethanolamine under nitrogen atmosphere.

Ultrasound assisted transesterification of waste cooking oil using heterogeneous solid catalyst.

Transesterification based biodiesel production from waste cooking oil in the presence of heterogeneous solid catalyst has been investigated in the present work. The effect of different operating parameters such as type of catalyst, catalyst concentration, oil to methanol molar ratio and the reaction temperature on the progress of the reaction was studied. Some studies related to catalyst reusability have also been performed. The important physicochemical properties of the synthesized biodiesel have also been investigated. The results showed that tri-potassium phosphate exhibits high catalytic activity for the transesterification of waste cooking oil. Under the optimal conditions, viz. catalyst concentration of 3wt% K3PO4, oil to methanol molar ratio of 1:6 and temperature of 50°C, 92.0% of biodiesel yield was obtained in 90min of reaction time. Higher yield was obtained in the presence of ultrasound as compared to conventional approach under otherwise similar conditions, which can be attributed to the cavitational effects. Kinetic studies have been carried out to determine the rate constant at different operating temperatures. It was observed that the kinetic rate constant increased with an increase in the temperature and the activation energy was found to be 64.241kJ/mol.

Synthesis and effect of fatty acid amides as friction modifiers in petroleum base stock.

Fatty acid amides were prepared by using Lewis acid as a catalyst. The products from reaction was subjected to solvent extraction with chloroform and then followed by purification with n-hexane, ethanol and acetonitrile. Fatty acid amide, characterized by various physicochemical and tribological properties like wear scar, weld load and coefficient of friction. These compounds found good antiwear (AW) and extreme pressure (EP) additive. The addition of various EP and AW additives in lubricating oil is an important and effective way to reduce friction and wear. Fatty acid amides were used as antiwear and friction modifier additive and a comparative study was carried out for 1%, 3%, 5% additive blend with commercial petroleum base stocks 150N and 500N.

Green synthesis of isopropyl ricinoleate.

Increased environmental awareness is slowly driving the industry to develop alternatives to chemical routes for synthesis. Lipase catalysed synthesis is one such alternative route that is environmentally more acceptable. In this study, immobilized Candida antarctica lipase (Lipozyme 435) was used for the esterification of ricinoleic acid and isopropyl alcohol. Molecular sieves were used to remove the water formed during esterification to drive the reaction in forward direction. The optimal conditions observed were 40°C temperature, 4% enzyme concentration, 1:1 acid: alcohol ratio and 4 hours time interval. Under the described conditions, the reusability of lipase was tested and it was found that above 80% esterification was observed for over three cycles.

Synthesis of polymers from fatty alcohol and acrylic acid and its impact on tribological properties.

Anhydride copolymers were synthesized from acrylic acid and fatty alcohols (C12- C18, C18:1). These n-alkyl acrylates were treated with maleic anhydride in presence of hydrogen peroxide in second step, to form anhydride copolymer. The anhydride copolymer further reacted to n-butylamine to form poly (n-acrylate-co-nbutylmalemide). The compounds were used as pour point depressant (PPD) additive. The synthesized experimental pour point depressants were added in different concentrations to conventional base stock (150N and 500N), which had no other additive content before. Synthesized additives were effective as viscosity index improver but also lowered the pour point. These results were comparable with industrial product. Furthermore all additives showed antiwear (AW) and extreme pressure (EP) properties. The resultant anhydride copolymer can act as multifunctional additive, which is novelty of the work.

Effect of wax esters as friction modifiers in petroleum base stock.

Condensation product of fatty acids and fatty alcohols is termed as wax esters. A series of fatty acids and fatty alcohols both saturated & unsaturated ranging from C 12 to C 22 were synthesised using p-TSA as a catalyst. Carbonyl functionality was confirmed by infrared spectrophotometer. Wax esters were used as friction modifier additives at 1%, 3%, 5% in 150N and 500N commercial petroleum base stocks. These base stocks were characterized by tribological properties like wear scar, weld load and coefficient of friction. All the tribological properties were better for saturated products than the unsaturated ones.

Stabilization of emulsion and butter like products containing essential fatty acids using kalonji seeds extract and curcuminoids.

Owing to the tendency of essential fatty acids (EFAs) to undergo autoxidation, their storage becomes a key problem. Generally, they are stabilized by synthetic antioxidants like TBHQ that are toxic in nature. Recently many studies were reported where these EFAs are stabilized by natural antioxidants. In the present study, curcuminoids and kalonji seeds ethanol extract (KEE) were used to stabilize these EFAs in refined sunflower oil (RSFO), water-in-oil (w/o) emulsion and butter like products (BLPs). In RSFO, though curcuminoids alone exerted pro-oxidant effect, KEE and curcuminoids showed synergistic antioxidant activity that was comparable to TBHQ. KEE exhibited good antioxidant activity in emulsions and BLPs, providing fine physical properties like slipping point, dropping point and spreadability. EFAs increased the nutritional value of BLPs and antioxidants added for their stabilization provided their medicinal benefits.