Iram Mahmood

Enzymatic hydrolysis of penicillin in mixed ionic liquids/water two-phase system

In this paper, an integrated process involving the mixed ionic liquids/water two‐phase system (MILWS) is proposed to improve the efficiency for enzymatic hydrolysis of penicillin G. First, hydrophilic [C4mim]BF4 (1‐butyl‐3‐methylimidazolium tetrafluoraborate) and NaH2PO4 salt form an ionic liquids aqueous two‐phase system (ILATPS), which could extract penicillin from its fermentation broth efficiently. Second, a hydrophobic [C4mim]PF6 (1‐butyl‐3‐methylimidazolium hexafluoraphosphate) is introduced into the ionic liquids‐rich phase of ILATPS containing penicillin and converses it into MILWS. Penicillin is hydrolyzed by penicillin acylase in the water phase of MILWS at pH 5. The byproduct phenylacetic acid (PAA) is partitioned into the ionic liquids mixture phase, while the intended product 6‐aminopenicillanic acid (6‐APA) is precipitated at this pH. In comparison with a similar butyl acetate/water system (BAWS) at pH 4, MILWS exhibits two advantages. ( 1 ) The selectivity between PAA and penicillin is greatly optimized at pH 5 by varying the mole ratio of [C4mim]PF6/[C4mim]BF4 in MILWS, whereas in BAWS the unalterable nature of the organic solvent restricts the optimized pH for maximum selectivity between PAA and penicillin at pH 4. ( 2 ) The pH for 6‐APA precipitation in BAWS is 4, whereas it shifts to pH 5 in MILWS due to the complexation between negatively charged 6‐APA and the cationic surface of the ionic liquids micelle. As a result, the removal of the two products from the enzyme sphere at relatively high pH is permitted in MILWS, which is beneficial for enzymatic activity and stability in comparison with the acidic pH 4 environment in BAWS.

A new strategy for the synthesis of polyaniline nanostructures using m-CPBA as an oxidant

In this work, we have reported a unique strategy of using Meta-Chloroperoxybenzoic acid (m-CPBA) as an oxidant for Polyaniline (PANI) nanofibers preparation. A templateless rapid mixing method was employed for chemical polymerization of aniline at room temperature under rapid mixing and without use of additional oxidant. PANI nanofibers were fully characterized and their electrochemical properties have been studied in detail. Further, effects of toluene solution on PANI electrochemical properties were also investigated in detail. The results showed that PANI nanofibers, in the presence of toluene as solvent, had relatively high specific capacitance and high columbic efficiency compared to their bulk solution, which was due to the immobile of toluene solution and the fast diffusion of the H+ ions through the polymer material during the redox process.