Sharif Digital Repository

Biodiesel has drawn the attention of many researches to itself as a replacing source for crude oil, recently. Transesterification is one of the most popular methods used for biodiesel production. Enzyme transesterification is a more simple method in comparison with acidic or basic transesterification. However, the high price and low yield of enzyme transesterification has caused many obstacles in its application. Enzyme engineering has gained much attention as a way to improve enzyme performance. In this thesis, biodiesel production by a native enzyme named Bacillus thermocatenulatus, and two engineered-enzymes is studied. First, effective parameters and variables in biodiesel production by... 

The enzymatic transesterification of castor oil with methanol in a solvent free media is carried out using lipase catalyst. The influence of several operation conditions on the production of biodiesel was analyzed i.e. the amount of enzyme, molar ratio of methanol to castor oil, reaction temperature and reaction time. It is observed that with increase in molar ratio, reaction time and enzyme amount, the amount of product (biodiesel) increased. When reaction temperature increased, the amount of biodiesel increased firstly and then decreased. The optimum conditions for the reaction were as follows: enzyme amount 300 mg, molar ratio of methanol to oil 9:1 and temperature 55°C. The maximum... 

In this study, biodiesel production using enzymatic method for transestrification of castor oil was investigated. It was found that the yield of biodiesel production is affected by methanol to oil molar ratio, temperature, enzyme amount, water content and reaction time. Effective factors were determined first, using two-factorial design method. Methanol to oil molar ratio was found as the most effective factor. Response surface methodology coupled with central composite design was utilized for statistical modeling of enzymatic biodiesel production and the reaction time was found as a non-significant factor. In another attempt, three factors including methanol to oil molar ratio, temperature,... 

Fats and oils are one of the main human food diet components that provide the necessary fatty acids for our body. So the fatty acids available in consuming oils are so important. In this research the mixture of palm and sunflower oils with different compounds: (80:20, 60:40, 50:50, 40:60, 20:80) were used for preparing free- trans shortening by interesterification. For this purpose a special stabilized lipase (Lipozyme TLIM) were used and performed the physicochemical properties: free fatty acids, peroxide value, iodine value, slip melting point, solid fat content, P-anisidine value, soap, oxidative stability at 110 0C, and the profile of fatty acids on the primitive blends and final samples... 

In this study, the polysulfon ultrafilteration membranes were prepared and applied to concentrate the Lipase enzymes produced in the laboratory and the commercial enzymes of Novozymes Company. Using Design Expert software. The effect of membrane preparation conditions including polysulfone and polyvinylpyrrolidone concentration and the solvent type were investigated. The prepared membranes were characterized by measuring of distilled water flux, enzyme liquor flux, and enzyme activity in permeate and the Retentate flows. The results showed that increasing of polysulfone concentration reduced the flux of distilled water and enzyme activity in permeate and enhanced the enzyme activity in the... 

In this study, Pseudomonas aeruginosa BBRC-10036 was used for lipase production. The organism secreted the enzyme extracellulary. First of all, effect of initial pH of the culture broth on lipase activity was studied in order to determine the optimum condition for lipase production. After production, this enzyme must be separated from culture and after that the enzyme must be purified for using in analysis and industry. Different methods are used for purification of the enzyme. In this research, first precipitation was used and then this lipase has been purified by Ion exchange Chromatography leading to 2.33- fold purification and 11.47% recovery. In precipitation by acetone, maximum... 

Lipases (triacylglycerol acylhydrolases) are industrial enzymes that have wide applications in the detergent, pharmaceutical and food industries. Pseudomonas aeruginosa strain is known to be suitable for lipase production due to its stability in organic solvents, resistance to temperature and pH. Lipases are usually secreted extracellularly, and its isolation from the culture medium is very important. The most cost-effective separation method is filtration which is more economical than centrifuge. Here, the use of filtration method is important from two aspects of creating clearance and maintaining enzyme activity. The equipment in this research is the filter press, whose initial tests are... 

In this study, polyelectrolyte-coated magnetic silica nanocomposites were prepared via the covalent attachment of polyelectrolytes onto the as-prepared magnetite-silica particles with core-shell structures and average diameter of 210±50 nm, and subsequently applied for the immobilization of lipase molecules. In this regard, polyethyleneimine (PEI) with two molecular weights of 10000 and 750000 and polyacrylic acid (PAA) with two molecular weights of 1800 and 100000 were utilized. The type and molecular weight of the polyelectrolyte molecules greatly impacted the concentration of binding sites on the particles surface and consequently on the lipase immobilization efficiency and loading... 

Dietary CLA production for medicinal purposes needs a safe and selective process. Biological production methods meet this goal. In this study, the microbial species that was suitable for CLA production was selected; then the CLA produced by bioconversion methods was utilized to produce CLA-enriched triglycerides by trans-esterification. Also the biochemical kinetics of CLA production and esterification reactions to produce CLA-enriched triglycerides was studied. In the presence of two substrates, the kinetics of enzymatic reaction was studied. Then the factors influencing on the microbial yield and CLA production including reaction conditions (reaction time, cell concentration and substrate... 

Superparamagnetic core/shell nonporous (S1) and core/shell/shell mesoporous (S2 and S3) nanocomposite magnetite/silica particles with a magnetite cluster core of 130±30 nm, a nonporous silica shell of 90±10 nm thickness, and a mesoporous silica shell of 70±15 nm thickness were prepared thorough a simple method. Mesoporous particles were prepared with two BJH pore sizes (2.44 for S2 and 3.76 nm for S3 particles, respectively). The fabricated S1, S2 and S3 particles present high saturation magnetization values of 20, 13 and 17 emu/g, respectively. As a biological application, the lipase from Pseudomonas cepacia was successfully immobilized onto the amino-functionalized nanocomposite particles... 

Lipases (Triacyl Glycerol Acyl Hydrolase, EC.3.1.1.3) are multidimensional biocatalysts which have many applications in food industrials, dairy, fats and oils processing, detergents, synthesis of pure chemical and pharmaceutical materials, paper industrial and cosmetics. Generally, industrial enzymes are produced extracellularly, so their separation from a low-cost complex medium (usually used for production) is one of the cost stages in their production process. Filtration is the most economical method of separation in the production of enzymes, but due to the small size of colloidal particles and cell masses present in the fermentation environment, its use is subject to limitations. In...