Biosurfactants are microbially synthesized surfactants that are environmental friendly due to low toxicity. Sophorolipid is one of the simplest biosurfactants with well-defined structure produced by Starmerella bombicola(ATCC 22214) on glucose and vegetable oil as the carbon source. The raw material cost accounts for 10-30% of the overall cost. Glycerol is readily available from a commercial fat-splitting process as sweetwater at a very low cost. Sophorolipids was synthesized using glycerol and sweetwater as a cost-effective carbon source. The glycerol was further replaced with sweetwater as a source of glycerol. Optimum glycerol concentration was 15% w/v with 10% w/v sunflower oil, giving 6.6 g/L of sophorolipids. The crude sophorolipid contains two major components; both of them were lactonic sophorolipids as analyzed by reverse-phase high-performance liquid chromatography (RP-HPLC), liquid chromatography-mass spectroscopy (LC-MS), and nuclear magnetic resonance ((1)H-NMR).

Vegetable edible oils and fats are mainly used for frying purposes in households and the food industry. The oil undergoes degradation during frying and hence has to be replaced from time to time. Rhamnolipids are produced by microbial cultivation using refined vegetable oils as a carbon source and Pseudomonas aeruginosa (ATCC 10145). The raw material cost accounts for 10-30% of the overall cost of biosurfactant production and can be reduced by using low-cost substrates. In this research, attention was focused on the preparation of rhamnolipids, which are biosurfactants, using potential frying edible oils as a carbon source via a microbial fermentation technique. The use of low-cost substrates as a carbon source was emphasized to tilt the cost of production for rhamnolipids. The yield was 2.8 g/L and 7.5 g/L from waste frying oil before and after activated earth treatment, respectively. The crude product contained mainly dirhamnolipids, confirmed by thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), liquid chromatography-mass spectroscopy (LC-MS), and (1)H-nuclear magnetic resonance (NMR). Hence, the treatment can be used to convert waste frying oil as a low-cost substrate into a cost-effective carbon source.

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The procedure for the classical chemical refining of vegetable oils consists of degumming, alkali neutralization, bleaching, and deodorization. Conventional refining of rice bran oil using alkali gives oil of acceptable quality, but the refining losses are very high. A critical work has been carried out to study the application of membrane technology in the pretreatment of crude rice bran oil. Oils intended for physical refining should have a low phosphorus content, and this is not readily achievable by the conventional acid/ water degumming process. The application of membrane technology for the pretreatment of rice bran oil has been investigated. The process has already been successfully applied to other vegetable oils. Ceramic membranes, which are important from the commercial point of view, were examined for this purpose. The results showed that the membrane-filtered oils met the requirements of physical refining, with a substantial reduction in color. It was observed that most of the waxy material was also rejected. Experiments were carried out to establish the relationship between permeate flux and rejection with membrane pore size, trans-membrane pressure and micellar solute concentration.

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Oils and fats serve as one of the most important renewable feedstocks for various chemicals such as lubricants, textiles auxiliaries, biodiesel and surfactants. The oils have also proved themselves to be better substrates than glucose for production of biosurfactants such as rhamnolipids. Cost is major hindrance in the commercialization of these biosurfactants and fresh refined oils cannot be used for rhamnolipid production. Non-traditional oils such as jatropha oil, karanja oil and neem oil can be used as newer feedstock for the synthesis of rhamnolipids. Jatropha oil gave the highest production of rhamnolipids, 4.55 g/L in non-traditional oils and the rhamnolipid concentration was comparable to that of most common oils, sunflower oil giving 5.08 g/L of rhamnolipids. The jatropha oil contained mainly linoleic acid that showed the highest consumption rate as compared to oleic and palmitic acid. Neem oil produced a lower concentration of rhamnolipids (2.63 g/L) than other oils. Both monorhamnolipids and dirhamnolipids were synthesized using these oils. The product obtained can find high value specialty applications such as biomedical drug delivery and cosmetics.

Frying is one of the most common processes in households, restaurants and food industries. During frying, oil undergoes degradation and hence has to be replaced time to time. This creates large amounts of waste causing disposal and environmental problems. Sophorolipids are produced by microbial bioconversion of refined vegetable oils along with glucose. The raw material cost accounts for 10-30% of the overall cost of biosurfactant production that can be reduced by using a low cost substrate like waste frying oil. In the present work, waste frying oils were used in the production of sophorolipids at the shake flask level. It gave mainly (70-80%) the acidic form of sophorolipids. It was observed that the linoleic acid was preferentially consumed over other fatty acids by the organism (Starmerella bombicola). The activated earth treatment was found to improve the yield of sophorolipids and hence the treatment can be used to convert waste frying oil as a low cost substrate into a cost effective carbon source.

Biosurfactants such as sophorolipids are natural and eco‐friendly surfactants that are used in cosmetics and health care products. In addition to surfactant properties, sophorolipids also possess antimicrobial and skin healing properties. In the present work, castor oil (10%) was used as a non‐conventional carbon source in combination with glucose (10%) or with glycerol (15%) for fermentative production of novel sophorolipids by using Starmerella bombicola (ATCC 22214). The yields of sophorolipids are 6.1 g/L on castor oil with glucose as a carbon source and 2.7 g/L on castor oil with glycerol as a carbon source analyzed by anthrone method and HPLC. The structures of sophorolipids synthesized on castor oil were elucidated by liquid chromatography–mass spectrometry and 1H NMR of the purified compounds. The results indicated the incorporation of ricinoleic acid into sophorolipids without omega‐1 oxygenation step that is required for incorporation of oleic acid into sophorolipids. It resulted in the production of novel sophorolipids that can find various applications as cosmetic ingredients and antimicrobial agents. Practical applications: Castor oil, widely produced in India, contains palmitic acid (1–2%), strearic acid (1–2%), oleic acid (6–8%), linoleic acid (0.5–1%), and mainly ricinoleic acid (80–90%). The presence of hydroxyl fatty acid as ricinoleic acid makes castor oil different from other vegetable oils. Therefore, castor oil is being used as a valuable raw material in various chemicals industries. The present work proved that castor oil can be used as a new substrate for the production of sophorolipids with a novel structure having hydroxyl group on the moiety. The end product can be used for enhancement of surfactant properties in combination with a chemically synthesized surfactant.