Mausumi Mukhopadhyay

Overview of Fungal Lipase: A Review

Lipases (triacylglycerolacyl hydrolases, EC3.1.1.3) are class of enzymes which catalyze the hydrolysis of long-chain triglycerides. In this review paper, an overview regarding the fungal lipase production, purification, and application is discussed. The review describes various industrial applications of lipase in pulp and paper, food, detergent, and textile industries. Some important lipase-producing fungal genera include Aspergillus, Penicillium, Rhizopus, Candida, etc. Current fermentation process techniques such as batch, fed-batch, and continuous mode of lipase production in submerged and solid-state fermentations are discussed in details. The purification of lipase by hydrophobic interaction chromatography is also discussed. The development of mathematical models applied to lipase production is discussed with special emphasis on lipase engineering.

Treatment of Chlorophenols from Wastewaters by Advanced Oxidation Processes

The ubiquitous presence of chlorophenols (CPs) in the natural environment illustrates the seriousness of CP pollution and the importance of an effective method for treating wastewaters containing CPs. The limitations of conventional wastewater treatment methods to effectively degrade/remove CPs having recalcitrant properties mandates the search for newer cost effective treatment technologies to be developed to meet the stringent environmental regulations. Advanced oxidation processes (AOPs) have evolved as the most promising techniques as they facilitate a substantial amount of chemical oxygen demand (COD) and total organic carbon (TOC) removal from industrial effluents. An extensive literature review of the widely used methods for CPs degradation is presented with due focus on AOPs. The overall objective is to review CP degradation by AOPs at length, with regard to specific reaction conditions, UV irradiation intensity, oxidants, degradation kinetics and intermediates/products formed thereof.

Agro-industrial waste-mediated synthesis and characterization of gold and silver nanoparticles and their catalytic activity for 4-nitroaniline hydrogenation

The biosynthesis of gold (Au-NPs) and silver nanoparticles (Ag-NPs) using agro-industrial waste Citrus aurantifolia peel extract as a bio-reducing agent is reported. Catalytic activity of nanoparticles (NPs) was evaluated for hydrogenation of anthropogenic pollutant 4-nitroaniline (4-NA). Both synthesized NPs were nearly spherical and distributed in size range of 6–46 and 10–32 nm for Au-NPs and Ag-NPs, respectively. XRD analysis revealed face centered cubic (fcc) structure of both NPs. ζ potential value obtained from colloidal solution of Au-NPs and Ag-NPs was −28.0 and −26.1mV, respectively, indicating the stability of the NPs in colloidal solution. FTIR spectra supported the role of citric and ascorbic acids of peel extract for biosynthesis and stabilization of NPs. The biosynthesized NPs exhibited excellent catalytic activity for hydrogenation of 4-NA in the presence of NaBH4.

Lipase-catalyzed glycerolysis of olive oil in organic solvent medium: Optimization using response surface methodology

Enzymatic glycerolysis of olive oil for mono- (MG) and diglycerides (DG) synthesis was investigated. Several pure organic solvents and co-solvent mixtures were screened in a batch reaction system. The yields of MG and DG in co-solvent mixtures exceeded those of the corresponding pure organic solvents. Batch reaction conditions of the glycerolysis reaction, the lipase amount, the glycerol to oil molar ratio, the reaction time, and temperature, were studied. In these systems, the high content of reaction products, especially MG (55.8 wt%) and DG (16.4wt%) was achieved at 40 °C temperature and 0.025 g of lipase with relatively low glycerol to oil molar ratio (2: 1) within 4 h of reaction time in isopropanol/tert-butanol (1: 3) solvent mixture. Glycerolysis reaction was optimized with the assistance of response surface methodology (RSM). Optimal condition for reaction conversion was recommended as lipase amount 0.025 g, glycerol to oil molar ratio 2: 1, reaction time 4 h and temperature 40 °C.

Immobilization of Candida antarctica lipase onto cellulose acetate-coated Fe2O3 nanoparticles for glycerolysis of olive oil

Candida antarctica lipase was covalently immobilized onto the surface of cellulose acetate-coated Fe2O3 nanoparticles. The characterizations of immobilized lipase were examined by Fourier transform infrared spectrophotometer (FTIR) and field emission gun-scanning electron microscopy (FEG-SEM). The immobilized lipase was assayed for production of monoglycerides (MG) and diglycerides (DG) by glycerolysis of olive oil in a solvent medium. The effect of various reaction conditions on the MG and DG production such as reaction time, temperature, the molar ratio of glycerol to oil and amount of immobilized lipase was investigated. The optimum condition for MG and DG production was found at 50 °C temperature and 0.025 g of lipase with the molar ratio of glycerol to oil 1.5: 1 in 5 h of reaction time. The effect of substrate concentration on enzymatic activity of the free and immobilized lipase showed the best fits to the Lineweaver-Burk plots. The Km and Vmax values of immobilized lipase were found to be 25mM and 0.58mM/min, whereas that for free lipase was 52.63mM and 1.75mM/min, respectively. The activation and deactivation energy was found to decrease for immobilization of lipase on cellulose acetate-coated Fe2O3 nanoparticles.

Photochemical degradation of 4-chlorophenol in the aqueous phase using peroxyacetic acid (PAA)

The photochemical degradation of 4-chlorophenol (4-CP) using ultraviolet irradiation (UV) of 6, 12 and 18 W with peroxyacetic acid (PAA) was studied in a batch reactor. The objective of this work was to investigate degradation and mineralization of 4-CP by PAA. The degradation efficiency increased with increasing UV input. The degradation process was also pH and initial PAA concentration dependent. The optimum conditions for the photochemical degradation of 4-CP as UV input, pH and PAA concentration was found to be 18 W, 9.5 and 3,040 ppm. The reaction efficiency decreased with increasing initial 4-CP concentrations. More than 95% mineralization of 4-CP was achieved with the UV/PAA process. The chloride ion concentration and chemical oxygen demand (COD) was evaluated. The chloride ion concentration and COD were decreased gradually with increasing UV input. Samples were analyzed by high pressure liquid chromatography (HPLC), UV spectrophotometry and gas chromatography-mass spectrometry (GC-MS) for residual concentration and identification of final degraded products.

Comparative Study of Separation of Acetonitrile from Aqueous Solutions by Pervaporation using Different Membranes

Pervaporation of acetonitrile-water mixtures was carried out using three commercial membranes, viz: polydimethylsiloxane (PDMS), polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF). The effects of feed concentration and feed temperature on the pervaporation performance, total and partial permeate fluxes, as well as acetonitrile selectivity, were investigated. It was found that increase in temperature yields higher total fluxes and lower selectivity for acetonitrile-water system. Changing concentration of acetonitrile in the range concerned leads to significant effect on total flux and selectivity. PDMS membrane was found to be most selective for acetonitrile separation. The total flux through the membranes was found to be in the order of PTFE > PVDF > PDMS, and the acetonitrile selectivity was found to be in the order of PDMS > PVDF > PTFE. The activation energies of water and acetonitrile associated with the permeation process for the PDMS, PTFE, and PVDF membranes were calculated to be in the ranges of 0.29–0.99, 0.6–0.87, 0.45–2.73 kJ/mol for acetonitrile and 1.23–1.95, 1.37–1.71, 1.16–3.37 kJ/mol for water at different concentrations, respectively.

Surface-Modified Nanocomposite Membranes

Access to enough clean and safe water requires improvement over the current state of filtration technology. Membrane technology is one of the best tools for removing dissolved matters and/or particulates during the cleaning process, but some unavoidable intrinsic properties, like flux decline and fouling, reduce the membrane life, stability and separation capacity. To improve membrane performances, researchers reported the significant role played by associating nanoparticles to membrane polymers. Nanoparticles create a path in the membrane for selective water permeation and pose a barrier for undesired matters. There are two different methods for incorporating nanoparticles in membranes: (i) adding nanoparticles to the polymeric matrix and (ii) depositing nanoparticles on the membrane surface. The deposition/coating of nanoparticles on the membrane surface allows opportunities for water/wastewater treatment. In this review, focus has been given to the development of different nanoparticle-deposited membranes and their possible applications to large-scale water purification processes, where antifouling, permeate quality and self-cleaning properties are required.

Removal of arsenic from aqueous media using zeolite/chitosan nanocomposite membrane

ABSTRACT In this work, the removal of arsenic (III) using zeolite/chitosan nanocomposite membranes was studied and characterized using scanning electron microscopy (SEM), atomic force microscope (AFM), etc. The water contact angle of the membrane decreased from 74.2 to 59.2° and the porosity of the prepared membranes increased from 20.38 to 45.81% with an increase in the concentration of zeolite. The rejection of arsenic (III) increases with increase in the zeolite loading for 500 and 1000 µg/L; but at 100 and 150 µg/L, the trend was opposite. The membrane with 1.0 [Chi-Z (1.0)] and 1.25 [Chi-Z (1.25)] wt% zeolite showed the highest rejection (>94%) for 1000 µg/L concentration of arsenic trioxide aqueous solution.

Flux improvement, rejection, surface energy and antibacterial properties of synthesized TiO2-Mo.HNTs/PVC nanocomposite ultrafiltration membranes

The present work demonstrates the preparation of modified halloysite loaded with titanium dioxide (TiO2) nanoparticles and its use as a nanofiller in a poly(vinyl chloride) (PVC) hybrid ultrafiltration (UF) membrane for advanced water treatment. Modification of raw halloysite nanotubes (rHNTs) with 3-aminopropyltriethoxysilane (APTES) was performed, after which TiO2 nanoparticles were synthesized using titanium(IV) isopropoxide (TIP) solution on the surface of the modified HNTs (Mo.HNTs) using the sol–gel method. Novel hybrid UF membranes (TiO2-Mo.HNTs/PVC) were prepared by blending of TiO2-Mo.HNTs nanofiller in different concentrations using a classical phase inversion method. Pure water flux of the hybrid UF membrane (197.5 ± 3.6 L m−2 h−1 in 2 wt% hybrid UF membrane) improved consistently with an increasing amount of nanofiller in the membrane matrix. The hydrophilicity of the membrane samples increased (contact angle as low as 68.8° ± 5.6° in 3 wt% hybrid UF membrane) and interfacial surface free energy was also high (−ΔGSL 98.22 mJ m−2 in 3 wt% membrane), as compared to the membrane without nanofiller. The rejection of BSA and HA by all TiO2-Mo.HNTs/PVC (1–3 wt%) membranes was greater than 80%. TiO2-Mo.HNTs played an important role in stopping pollutants during membrane filtration; and antibacterial activity of the TiO2-Mo.HNTs/PVC hybrid UF membranes against E. coli was high (95–97.5% in 2 wt% and 3 wt% hybrid membrane). Thus TiO2-Mo.HNTs played an important role in the separation processes.