Showing papers by "Anju Chadha published in 2010"

Asymmetric synthesis of (S)-ethyl-4-chloro-3-hydroxybutanoate using Candida parapsilosis ATCC 7330

Abstract: Asymmetric reduction of ethyl-4-chloro-3-oxobutanoate to (S)-ethyl-4-chloro-3-hydroxybutanoate in aqueous medium by resting cells of Candida parapsilosis ATCC 7330 was optimized. The influence of culture parameters (inoculum size, inoculum age and biocatalyst harvest time) and reaction parameters (co-substrate, resting cell, pH and substrate concentrations) on the asymmetric reduction were studied. It was found that these parameters significantly influenced the rate of the asymmetric reduction. Under the optimum conditions, the final concentration of (S)-ethyl-4-chloro-3-hydroxybutanoate, enantiomeric excess and the isolated yield of (S)-ethyl-4-chloro-3-hydroxybutanoate were 1.38 M (230 g/l), >99 and 95%, respectively. The space time yield was 115 mmol/lh, which is significantly higher than other whole cell biocatalysts reported so far.

Biocatalytic deracemization of alkyl-2-hydroxy-4-arylbut-3-ynoates using whole cells of Candida parapsilosis ATCC 7330

Abstract: Racemic alkyl-2-hydroxy-4-arylbut-3-ynoates were deracemized to the (S)-alkyl-2-hydroxy-4-arylbut-3-ynoates in excellent enantiomeric excesses (up to >99%) and good isolated yields (up to 81%) with the biocatalyst Candida parapsilosis ATCC 7330. The absolute configuration of the resulting enantiomer was assigned by 1H NMR using Mosher’s method.

Pseudomonas cepacia lipase catalyzed esterification and transesterification of 3-(furan-2-yl) propanoic acid/ethyl ester: A comparison in ionic liquids vs hexane

Abstract: A comparison of the Pseudomonas cepacia lipase (lipase PS) catalyzed esterification of 3-(furan-2-yl) propanoic acid and transesterification of ethyl 3-(furan-2-yl) propanoate with six straight chain alcohols (propanol to octanol) in ionic liquids and hexane was carried out. The ionic liquids selected, [Bmim]BF 4 , [Bmim]PF 6 ,and [ Bmim]Tf 2 N, consisted of an identical cation and different anions. This is the first report on the biocatalyzed synthesis of these esters. In all the media, lipase PS catalyzed esterification of 3-(furan-2-yl) propanoic acid resulted in high yields of the esters compared to the transesterification of ethyl 3-(furan-2-yl) propanoate. [Bmim]Tf 2 N proved to be the best; yielding 98-67% of the product by lipase PS catalyzed esterification. The lipase PS-[Bmim]Tf 2 N and lipase PS-[Bmim]PF 6 mixture was recycled five times without any decrease in the yields of the products and was found to be operationally stable up to 10 months at room temperature.

Resolution of N-protected amino acid esters using whole cells of Candida parapsilosis ATCC 7330

Abstract: Whole cells of Candida parapsilosis ATCC 7330 were used for the resolution of N -acetyl amino acid esters. Excellent enantioselectivities ( E = 40 to >500) were achieved for the resolution of N-protected protein and non-protein amino acid esters giving good yields (28–50%) and high enantiomeric excesses (up to >99%) for both enantiomers.

A Novel Method for Monitoring the Transesterification Reaction of Oil in Biodiesel Production by Estimation of Glycerol

Abstract: A quantitative method is reported for the estimation of glycerol during transesterification of oil to form biodiesel. The reagent used to derivatize glycerol was 9,9-dimethoxyfluorene. Glycerol is estimated by both UV–visible spectrophotometric and high performance liquid chromatography methods. Using the former method, detection limits of 0.05% w/w of glycerol in biodiesel was established. Validation of the developed method was done using the Greenhill method for determination of free glycerol formed during the transesterification reaction.

Dynamic response of polysilicon microcantilevers to enzymatic hydrolysis of urea

Abstract: Micromolar levels of urea [1–20 mM] on surface micromachined polysilicon cantilever beams immobilized with the enzyme urease was studied. Urea hydrolyses to ammonia and carbon dioxide which are volatile in nature. Monitoring the change in resonance frequency of a urease immobilized cantilever beam during the course of urea hydrolysis, mediated by the immobilized enzyme can give us information on the reaction rates. The change in the resonance frequency of the cantilever beams as a result of urea hydrolysis was measured using Doppler Vibrometry. The reaction kinetics of the enzyme urease was studied by analyzing the dynamic response of the enzyme immobilized microcantilevers for various concentrations of urea.

Packaged bulk micromachined triglyceride biosensor

Abstract: Estimation of triglyceride concentration is important for the health and food industries. Use of solid state biosensors like Electrolyte Insulator Semiconductor Capacitors (EISCAP) ensures ease in operation with good accuracy and sensitivity when compared to conventional sensors. In this paper we report on packaging of miniaturized EISCAP sensors on silicon. The packaging involves glass to silicon bonding using adhesive. Since this kind of packaging is done at room temperature, it cannot damage the thin dielectric layers on the silicon wafer unlike the high temperature anodic bonding technique and can be used for sensors with immobilized enzyme without denaturing the enzyme. The packaging also involves a teflon capping arrangement which helps in easy handling of the bio-analyte solutions. The capping solves two problems. Firstly, it helps in the immobilization process where it ensures the enzyme immobilization happens only on one pit and secondly it helps with easy transport of the bio-analyte into the sensor pit for measurements.