D. N. Bhowmick

Pesticides as Microemulsion Formulations

Conventional systems like wettable powders, emulsifiable concentrates (ECs), oil in water emulsions (O/W emulsions), water in oil emulsions (W/O emulsions), aqueous suspension concentrates etc. are popularly used as the pesticide formulations. However, the microemulsion systems are preferred for their long-term thermodynamic stability, low viscosity, cost economy, and aesthetic appeal. Such systems provide a method for preparing an isotropic mixture of oil and water. Major advantage of microemulsion is in usage of the widely, easily available, environmentally friendly, and least expensive diluents, water. Formulation of pesticide microemulsion is a difficult task. The present investigation deals with the systematic study to arrive at the economical composition for microemulsion and solubilized systems. These compositions gave maximum stability with the optimum usage of surfactants. The microemulsion and solubilized systems when further diluted with water gave macroemulsion and microemulsion respectively, which were stable over an extended period of time.

MICROBIAL SYNTHESIS OF RHAMNOLIPIDS BY Pseudomonas aeruginosa (ATCC 10145) ON WASTE FRYING OIL AS LOW COST CARBON SOURCE

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 1H-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.

Study of Glycerol and Sweet Water as a Carbon Source for Production of Rhamnolipids by Naturally Occurring Strains of Pseudomonas aeruginosa (ATCC 10145 and ATCC 9027)

Abstract The interest in biosurfactant has increased considerably due to their large potential for industrial applications. Rhamnolipid is a simplest class of biosurfactants with well defined structure. The main obstacle in commercialization of biosurfactant especially rhamnolipids is the higher cost of the production. Glycerol is readily available from commercial fat-splitting process in the form of sweet water (up to 20% w/v) at very low cost. Two natural strains of Pseudomonas aeruginosa (ATCC 10145 and ATCC 9027) were compared for rhamnolipid production. The neotype strain of Pseudomonas aeruginosa (ATCC 10145) was found to produce more amounts of rhamnolipids than Pseudomonas aeruginosa (ATCC 9027) on glucose and glycerol as carbon source. The microbial growth (0.94 g/L) and formation of rhamnolipids (2.75 g/L) was maximum at 5% (w/v) glycerol concentration by Pseudomonas aeruginosa (ATCC 10145). The fermentation was monitored for 8 days on shake flask and magnetically stirred batch culture. In magnetically stirred batch culture, microbial growth was 0.69 g/L and 2.73 g/L of rhamnolipid was formed. Sweet water was also used as a source of glycerol.

Study of Glycerol Residue as a Carbon Source for Production of Rhamnolipids by Pseudomonas aeruginosa (ATCC 10145)

Abstract Rhamnolipid is the simplest class of biosurfactants with a well defined structure. The main obstacle in commercialization of biosurfactant especially rhamnolipids is the higher cost of the production. The production cost can be reduced by using economical carbon sources. Glycerol residue is available from glycerin distillation plant at low cost. It can be used as carbon source for rhamnolipid production using Pseudomonas aeruginosa (ATCC 10145). The optimum concentration of glycerol residue was 5% weight by volume (w/v) yielding maximum rhamnolipids at 2.50 g/L in the broth. From batch monitoring of polyglycerol and monoglycerol consumption, it appeared that polyglycerols were first hydrolyzed to monoglycerol in the broth itself and consumed as carbon source. The product had components similar to rhamnolipids synthesized on pure glycerol under the same conditions. This indicated the potential of glycerol residue as economic substrate for production of rhamnolipids.

Stabilization of Foam Produced by Sodium Lauryl Sulphate with Mannosylerythritol Lipids Synthesized on Soybean Oil and Sucrose by Pseudozyma antarctica (ATCC 32657)

Abstract Biosurfactants are gaining importance due their large potential for industrial applications and their eco-friendly nature. The properties of biosurfactants can vary with their structure which is dependent upon strain, cultivation conditions and carbon source. A mannosylerythritol lipid (MEL) is one of the simplest biosurfactants with a well-defined structure produced by Pseudozyma antarctica (ATCC 32657). The study includes the surfactant properties of MEL produced on soybean oil with sucrose as substrate. MEL showed surface activity at very low concentrations. The various properties were explained on the basis of the structural similarity between MEL and Gemini surfactant. The performance properties of SLS like foaming, emulsification and wetting were improved when SLS was partially substituted (5–20 %) by MEL. Based on the study, MEL can be used in various cosmetic products like shaving creams, skin creams and lotions, where MEL will not only enhance foaming property but also provide moisturizing and healing properties on skin.