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Herein, we demonstrate the immobilization of Pseudomonas fluorescens lipase (PFL) on polyaniline nanofibers (PANFs) via physical adsorption. Polyaniline nanofibers (PANFs) were synthesized by the oxidative polymerization of aniline. The developed robust nanobiocatalyst (PANFs-PFL) exhibited eight times higher activity than free PFL. In addition, immobilization of lipase on PANFs imparted operational stability of the nanobioconjugate. The various reaction parameters for immobilization (viz. reaction time, pH, stirring rate and enzyme-support ratio) were optimized using statistical design in terms of lipase activity and loading. Furthermore, facile separation, enhanced reusability (upto 6 cycles) and thermostability (upto 75 °C) were additional advantages of the nanobioconjugate. The catalytic prowess of nanobioconjugate was examined in the kinetic resolution of (RS)-N-(4-(3-chloro-2-hydroxypropoxy)phenyl)acetamide and (RS)-1-(1-naphthyl) ethanol in comparison to free PFL. PANFs-PFL demonstrated 49.9% and 48.1% conversion for (RS)-N-(4-(3-chloro-2-hydroxypropoxy)phenyl)acetamide and (RS)-1-(1-naphthyl) ethanol, respectively which signified its importance as a nanobiocatalyst.

Immobilization of surfactant treated Burkholderia cepacia lipase on the surface of carbon nanofibers was performed via two different methods: adsorption and covalent attachment. Simple adsorption of lipase on carbon nanofibers turned out to be a poor strategy, exhibiting an immobilization efficiency of 36%, while covalent coupling using 1-ethyl-3-[3-dimethylaminopropyl] carbodiimide (EDC)/N-hydroxysuccinimide (NHS) showed better immobilization efficiency (56%). The nanobioconjugate fabricated using the latter method showed an eleven-fold increase in enzyme activity towards the hydrolysis of p-nitrophenyl palmitate and enhanced dispersion in organic solvents. At 80 °C, the half-life of lipase in the nanobioconjugate was almost 20 fold higher than that of free lipase, demonstrating its thermal stability. The as-prepared nanobioconjugate was reused for nine consecutive reaction cycles achieving 100% yield in the hydrolysis of p-nitrophenol palmitate but losing almost 50% of the initial activity after seven operational cycles. Finally, this heterogeneous nanobioconjugate was more active and enantioselective [C = 47.8, eep = 97.0 and E = 194] than free lipase [C = 35.4, eep = 97.1 and E = 88] towards the kinetic resolution of a racemic intermediate of atenolol yielding the S enantiomer, which signifies its importance as a nanobiocatalyst.

The present work reports covalent immobilization of Pseudomonas fluorescens lipase (PFL) on functionalized multiwalled carbon nanotubes (MWCNTs) as a nanobiocatalyst (NBC). This nanobiocatalyst facilitates efficient kinetic resolution of (RS)-1-phenylethanol into (S)-1-phenylethanol [C = 49.7%, eep = 99.5%, ees = 98.1% and E value = 191.4]. The immobilized preparation (MWCNTs-PFL) showed ten-fold increase in activity, thermal stability upto 80 °C and recyclability (8 cycles). MWCNTs-PFL nanobioconjugate demonstrated better stability and enhanced activity compared to covalently immobilized PFL on other matrices (silver nanoparticles, gold nanoparticles and chitosan beads) used for the study. A statistical design [response surface methodology (RSM)] employed for the optimization of enzyme immobilization parameters made this study statistically more significant. Overall, the newly developed nanobiocatalyst has applications towards the kinetic resolution of racemic compounds.

In the present study Pseudomonas fluorescens lipase (PFL) was screened as a time efficient biocatalyst for the kinetic resolution of a racemic intermediate [(RS)-1-chloro-3-(4-(2-methoxyethyl)phenoxy)propan-2-ol] of metoprolol, an important selective β1-blocker drug. PFL selectively acylated the R-form of this racemic intermediate in a short duration of 3 h. Different reaction parameters were optimized to achieve maximum enantioselectivity. It was found that at 30 °C, enzyme activity of 400 units and substrate concentration of 10 mM gave a high enantioselectivity and conversion in an optimum time of 3 hours (C = 50.5%, eep = 97.2%, ees = 95.4%, E = 182). To validate these experimental results, the 3D structure of PFL was built using homology modelling. Validation of the model through Ramachandran plot (92.7% in favored region), Errat plot (overall quality factor, 79.27%), Verify-3D score (86.19) and ProSA_Z score (−6.24) depicted the overall good quality of the model. Molecular docking of the R- and S-enantiomers of the intermediate, which was performed on this model, demonstrated a strong H-bond interaction (1.6 A) between the hydroxyl group of the R-enantiomer and Arg54, a key binding residue of the catalytic site of PFL, while no significant interaction with the S-enantiomer was observed. Thus, the outcome of this docking study was in agreement with the experimental data, clarifying that PFL preferentially catalysed the transesterification of the R-enantiomer into the corresponding ester, leaving the S-enantiomer intact.

Polyaniline nanofibers were synthesized by the oxidative polymerization of aniline. Surfactant treated lipase from Burkholdaria cepacia was immobilized on these polyaniline nanofibers by adsorption. The activity of immobilized preparation was six times higher than that of free lipase with an enhanced dispersion in organic solvents. Five-level-four-factor central composite design was applied for the optimization of immobilization parameters (viz. reaction time, pH, stirring rate and enzyme-support ratio) which were evaluated on the basis of lipase loading and activity. The thermal stability of the lipase in the nanobioconjugate, demonstrated in terms of the half-life at 80 °C was almost sixteen-fold higher than in the free form. The reusability data revealed the utility of the nanoconjugate for seven consecutive cycles with a slow and gradual decline in the activity. However, the nanoconjugate retained almost 30% of their initial activity after seven cycles of reuse revealing its utility of in industrial applications. The nanoconjugate was used in the kinetic resolution of (RS)-1-(7-(3-chloro-2-hydroxypropoxy)benzofuran-2-yl) ethanone, racemic intermediate of an important β-blocker (Befunolol), with a high conversion rate of 48.2%, 98% ee-value and enantioselectivity (E) of 188, which signify its importance as a nanobiocatalyst.

Pseudomonas fluorescens lipase (PFL) was covalently immobilized on carbon nanofiber (CNF) using 1‑ethyl‑3‑[3‑dimethylaminopropyl] carbodiimide (EDC)/N‑hydroxysuccinimide (NHS). Surface functionalization of carbon nanofiber augments dispersibility as well as efficiency of covalent immobilization. Crucial parameters for immobilization such as pH, enzyme-support ratio, reaction time and mixing rate were optimized using one factor at a time (OFAT) approach. The nanobiocatalyst prepared under optimized conditions demonstrated a ten-fold increase in enzyme activity and the advantage of high thermal stability (up to 85 °C) along with 10 cycles of reusability. Subsequently practical application of the nanobiocatalyst was explored in the kinetic resolution of racemic 1‑phenylethanol into (S)‑1‑phenylethanol [C = 49.1%, eep = 99.5%, ees = 98.5% and E value = 151.4] followed by Mitsunobu reaction with a substituted pyrrole, giving an enantiopure (R)-carboetomidate analogue (yield = 83%).

Tinospora cordifolia is a popular medicinal plant which is used in several traditional medicines to cure various diseases. The common names are Amrita and Guduchi and belong to the family of Menispermaceae. It is considered an essential herbal plant of Indian system of medicine (ISM) and has been used in the treatment of fever, urinary problem, dysentery, skin diseases leprosy, diabetes, and many more diseases. The plant reported containing chemical compound including Alkaloids, Terpenoids, Lignans, Steroids and others that establish the phytochemistry and pharmacological activity of Tinospora cordifolia. The present review highlights the pharmacological importance viz antioxidant activity, antimicrobial activity, antibacterial activity, antifungal activity, anti-diabetic activity, antistress activity, hypolipidaemic effect, hepatic disorder, anticancer anti HIV potential, antiosteoporotic effects, antitoxic effects, wound healing, anticomplementary activity, and immunomodulating activity, systemic infection and Parkinson ̓s disease.