Anju Chadha

A wide range of primary and secondary multifunctional alcohols, α-hydroxyamides, and α-hydroxyesters were oxidized to their corresponding aldehydes, ketones, α-ketoamides, and α-ketoesters under mild reaction conditions using 2,2,6,6-tetramethylpiperidine-1-oxyl as a catalyst with calcium hypochlorite as an oxidant [TEMPO-Ca(OCl) 2]. This simplified method does not require any transition metals, acids, or bases and demonstrates controlled and selective oxidation of structurally diverse alcohols, affording moderate to excellent yields at room temperature. © 2012 Taylor & Francis Group, LLC.

We present an FTIR based assay to monitor the whole cell mediated oxidation of aryl alcohols by measuring the characteristic IR absorption of the hydroxyl group [OH] of the substrate and the carbonyl group [CO] of the corresponding oxidized product. This method expedites the analysis of whole cell mediated catalysis which is usually done by GC and/or HPLC. The FTIR assay had linearity with R²≥0.980 and sensitivity up to 10μM. The accuracy and precision of FTIR assay was found ≥81% and ≥94%, respectively. This assay was validated by GC which exhibited ≥82% accuracy and ≥79% precision. The time of analysis taken by this assay was 2-3min per sample in comparison with 20-40min by GC.

Biocatalysis, one of the most ecologically friendly methods for synthesising chiral synthons, has emerged as a desirable process for manufacturing active pharmaceutical ingredients and agrochemicals, most of which contain one or more chiral amine moieties. Compared with the traditional biocatalytic processes for the synthesis of chiral amines involving lipases or transaminases, enzymatic imine reduction is a more promising approach. The single-step enzymatic reduction of prochiral imines to the corresponding amines can yield 100% of the required enantiomer without any by-products. Furthermore, the reduction of imines generated in situ through the condensation of amines and carbonyl compounds can be used to synthesise almost any primary, secondary, or tertiary amine. In the past decade, several imine-reducing enzyme families, such as Streptomyces imine reductases (IReds), native amine dehydrogenases and engineered leucine/phenylalanine dehydrogenases and opine dehydrogenases, have been explored. The ornithine cyclodeaminase/µ-crystallin (OCD/CRYM) superfamily consists of proteins capable of imine reduction, which have been relatively unexplored regarding the synthesis of chiral amines. The proteins in this family are ubiquitously distributed in all three domains of life and catalyse diverse and unique reactions. This review is aimed at summarising current knowledge on this superfamily and exploring its potential in biocatalysis. After a brief discussion of their discovery, the known members of the OCD/CRYM superfamily are broadly classified on the basis of the reactions that they catalyse, and their biochemical characteristics and biological roles are described in detail. This is followed by a discussion of the overall structure, active sites and proposed reaction mechanisms, with common themes drawn among members. Finally, the applications of these enzymes, particularly in the synthesis of various chiral synthons, are summarised.

Biocatalytic deracemisation of racemic allylic alcohols by whole cells of Candida parapsilosis ATCC 7330 resulted in the formation of the (R)-enantiomers in high enantiomeric excesses (up to >99%) and isolated yields (up to 79%). © 2008 Elsevier Ltd. All rights reserved.

Cyclotides are unique plant cyclic-peptides that can serve as agrochemicals, pharmaceutical scaffolds for drug delivery, and therapeutic agents. Currently, cyclotides are obtained only via direct extraction from limited plants. Hence, they serve as valuable candidates for synthesis via plant cell bioprocesses. In this study, callus lines (47 in total) were successfully induced from the leaf and petiole explants of the Indian medicinal plant, V. odorata, on a solidified woody plant medium (WPM) supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D) (4.5 mg/l). Two fast growing callus lines, VOP-4 and VOL-44, were selected for the development of cell suspension cultures having a doubling time of 8 and 6 days, respectively. Further, known (15) and novel (9) cyclotides were identified for the first time in the callus and cell suspension cultures of V. odorata, using liquid chromatography and Fourier transform mass spectrometry. The cyclotides were identified based on their monoisotopic mass (2.5–4 kDa), hydrophobic nature, disulfide bonds, circular structure and amino acid sequence. Some of the cyclotides identified in the study (vodo I96, vodo I97, vodo I98) were exclusively produced in callus/cell suspension cultures and not in the parent plant. The study revealed that besides germplasm conservation, plant cell bioprocessing of V. odorata could be a potential alternative for in vitro production of known and novel cyclotides.

Optically pure aliphatic β-hydroxy esters were prepared from their racemates by deracemisation using the biocatalyst Candida parapsilosis ATCC 7330. High optical purity (up to >99 %) and good yields (up to 71 %) of the product secondary alcohols were obtained. This study highlights the importance of optimization of reaction conditions using ethyl-3-hydroxybutanoate as the model substrate to improve the enantioselectivity (enantiomeric excess from 9 to 98 %). The present study emphasises the broad substrate scope of the biocatalyst towards deracemisation. This is the first report of Candida parapsilosis ATCC 7330-mediated deracemisation of various alkyl-3-hydroxybutanoates to produce either the (R)-enantiomers (methyl, ethyl, propyl, butyl, t-butyl, allyl-3-hydroxybutanoates) or (S)-enantiomers (pentyl, iso-amyl and iso-propyl-3-hydroxybutanoates).

The non-edible oils of mahua and jatropha were transesterified using methanol and 1 wt % KOH as the catalyst. The effect of co-solvent and the kinetic study of the transesterification of mahua oil is being reported here for the first time. Kinetics, modeled as a single-step reaction, revealed that the order of the reaction is 2 with respect to the triglyceride concentration and 1 with respect to the methanol concentration in both oils. In the presence of co-solvent, tetrahydrofuran (THF), methanolysis of mahua oil resulted in the increase of the rate constants from 0.08 to 1.17 L2 mol-2 min-1 at 28 °C and from 0.43 to 3.18 L2 mol -2 min-1 at 45 °C. The corresponding values for jatropha oil were found to be 0.50 and 2.76 L2 mol-2 min-1 at 28 °C and 1.26 and 4.56 L2 mol-2 min-1 at 45 °C. © 2011 American Chemical Society.

Biocatalytic reduction of alkyl 2-oxopropanoates were carried out by utilizing the whole cells of Candida parapsilosis ATCC 7330 to form the optically enriched alkyl 2-hydroxypropanoates with good enantiomeric excess (ee) (≤91%) and isolated yields (≤68%). Enantiomerically enriched (S)-ethyl 3-bromo-2-hydroxypropanoate thus synthesized by biocatalytic reduction of ethyl 3-bromo-2-oxopropanoate is presented in this study for the first time in water under ambient reaction conditions in a reaction time of 4 h which is considerably less than earlier reported procedures.

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. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Aromatic β-hydroxy acid esters were found to undergo deracemisation using whole cells of Candida parapsilosis. The conditions for the deracemisation reaction were optimised where ∼75% isolated yield and >95% enantiomeric excess of the product was achieved. The effect of electron donating as well as electron withdrawing groups present in the standard substrate, ethyl 3-hydroxy 3-phenyl propionate was studied to establish the generality of the reaction. The enantiomeric excess of the product remains high (>95%) irrespective of the different substituents in the para position but substitution at the ortho position obstructs the process. Similarly, ethyl and methyl esters of the standard substrate undergo deracemisation reaction giving high ee of the product, but the benzyl ester of the standard substrate did not undergo deracemisation. © 2004 Elsevier B.V. All rights reserved.