Debajyoti Goswami

Abstract: Lipase (triacylglycerol acylhydrolase) is a unique enzyme which can catalyze various types of reactions such as hydrolysis, esterification, alcoholysis etc. In particular, hydrolysis of vegetable oil with lipase as a catalyst is widely studied. Free lipase, lipase immobilized on suitable support, lipase encapsulated in a reverse micelle and lipase immobilized on a suitable membrane to be used in membrane reactor are the most common ways of employing lipase in oil hydrolysis. Castor oil is a unique vegetable oil as it contains high amounts (90%) of a hydroxy monounsaturated fatty acid named ricinoleic acid. This industrially important acid can be obtained by hydrolysis of castor oil. Different conventional hydrolysis processes have certain disadvantages which can be avoided by a lipase-catalyzed process. The degree of hydrolysis varies widely for different lipases depending on the operating range of process variables such as temperature, pH and enzyme loading. Immobilization of lipase on a suitable support can enhance hydrolysis by suppressing thermal inactivation and estolide formation. The presence of metal ions also affects lipase-catalyzed hydrolysis of castor oil. Even a particular ion has different effects on the activity of different lipases. Hydrophobic organic solvents perform better than hydrophilic solvents during the reaction. Sonication considerably increases hydrolysis in case of lipolase. The effects of additives on the same lipase vary with their types. Nonionic surfactants enhance hydrolysis whereas cationic and anionic surfactants decrease it. A single variable optimization method is used to obtain optimum conditions. In order to eliminate its disadvantages, a statistical optimization method is used in recent studies. Statistical optimization shows that interactions between any two of the following pH, enzyme concentration and buffer concentration become significant in presence of a nonionic surfactant named Span 80.

Abstract: In this study, ricinoleic acid was produced on surfactant enhanced castor oil hydrolysis using Candida rugosa lipase. The most effective surfactant was Span 80. Employing fractional factorial design, the most suitable temperature and surfactant concentration were found to be 31 degrees C and 0.257% (w/w in buffer) respectively whereas pH, enzyme concentration, buffer concentration and agitation were identified as the most significant independent variables. A 2(4) full factorial central composite design was applied and the optimal conditions were found to be pH 7.0, enzyme concentration 7.42 mg/g oil, buffer concentration 0.20 g/g oil and agitation 1400 rpm with the maximum response of 76% in 4 h. The most important variable was pH, whereas enzyme and buffer concentrations also showed pronounced effect on response. This is the first report on the application of response surface methodology for optimizing surfactant enhanced ricinoleic acid production using C. rugosa lipase.

Abstract: In this study, response surface methodology was applied to optimize process variables like temperature, pH, enzyme concentration (mg/g oil), and buffer concentration (g/g oil) for hydrolysis of castor oil using Candida rugosa lipase. A 2 4 full factorial central composite design was used to develop the quadratic model that was subsequently optimized and the optimal conditions were as follows: temperature 40 °C, pH 7.72, enzyme concentration 5.28 mg/g oil, buffer concentration 1 g/g oil and there was 65.5% conversion in 6 h. These predicted optimal conditions agreed well with the experimental results. This is the first report on the application of response surface methodology in castor oil hydrolysis using C. rugosa lipase with higher percentage conversion in 6 h.

Abstract: In this study, castor oil is hydrolyzed in presence of Candida rugosa lipase, while in the buffer (aqueous) phase as a dispersion medium. The following conditions were used to optimize the process: speed of agitation, initial pH of buffer phase, temperature, and ratio of buffer phase volume to oil weight. The optimal conditions are 1,100 rpm, pH 6.5, temperature 35°C, and 3:1 buffer phase volume to oil weight ratio. Under these described conditions, the reusability of lipase was tested and it was found that nearly 80% of original hydrolysis percentage was achieved after the first recycle.

Abstract: Selective hydrolysis of brown mustard oil (from Brassica juncea) with regioselective porcine pancreas lipase was studied in this work. Buffer and oil phase were considered as the continuous and dispersed phases, respectively. Effects of speed of agitation, pH of the buffer phase, temperature, buffer-oil ratio and enzyme concentration on hydrolysis were observed. The best combination of process variables was: 900 rpm, pH 9, 35 oC, buffer-oil ratio of 1:1 and enzyme concentration of 10 mg/g oil. These standard conditions led to 50% hydrolysis and selective production of 55% erucic acid in 6 h. Cations like Mg2+ and Ca2+ increased hydrolysis, but Cu2+ strongly inhibited it. Organic solvents decreased hydrolysis, though the decrease was minimum for isooctane. A mixed surfactant comprising of Span 80 and Tween 80 increased erucic acid production by 57% at a buffer-oil ratio of 0.2:1.

Abstract: THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

Abstract: 介绍了Kirk—Othmer Encyclopedia of Chemical Technology（化工技术百科全书）（第五版）电子图书网络版数据库，并对该数据库使用方法和检索途径作出了说明，且结合实例简单地介绍了该数据库的检索方法。

Abstract: We gratefully recognize the financial support from MINECO from the Spanish Government (project number CTQ2017-86170-R, Colciencias, Ministerio de Educacion Nacional, Ministerio de Industria, Comercio y Turismo e ICETEX, Convocatoria Ecosistema Cientifico – Colombia Cientifica. Fondo Francisco Jose de Caldas, Contrato RC-FP44842-212-2018 and Colciencias (Colombia) (project number FP44842-076-2016), Generalitat Valenciana (PROMETEO/2018/076), FAPERGS (project number 17/2551-0000939-8), CONICET (R. Argentina), FUNCAP (project number BP3-0139-00005.01.00/18) and ANPCyT (PICT 2015-0932 and PICT CABBIO 4687).

Abstract: Surfactants are compounds that reduce the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid. Surfactants are characteristically organic compounds containing both hydrophobic groups (their tails) and hydrophilic groups (their heads). Therefore, a surfactant molecule contains both a water insoluble (and oil soluble component) and a water soluble component. Biosurfactants encompass the properties of dropping surface tension, stabilizing emulsions, promoting foaming and are usually non-toxic and biodegradable. Interest in microbial surfactants has been progressively escalating in recent years due to their diversity, environmentally friendly nature, possibility of large-scale production, selectivity, performance under intense circumstances and their impending applications in environmental fortification. These molecules have a potential to be used in a variety of industries like cosmetics, pharmaceuticals, humectants, food preservatives and detergents. Presently the production of biosurfactants is highly expensive due to the use of synthetic culture media. Therefore, greater emphasis is being laid on procurement of various cheap agro-industrial substrates including vegetable oils, distillery and dairy wastes, soya molasses, animal fat, waste and starchy waste as raw materials. These wastes can be used as substrates for large-scale production of biosurfactants with advanced technology which is the matter of future research. This review article represents an exhaustive evaluation of the raw materials, with respect to their commercial production, fermentation mechanisms, current developments and future perspectives of a variety of approaches of biosurfactant production.