Razi Ahmad

Development of cellulase-nanoconjugates with enhanced ionic liquid and thermal stability for in situ lignocellulose saccharification

The present work aimed to improve catalytic efficiency of Trichoderma reesei cellulase for enhanced saccharification. The cellulase was immobilized on two nanomatrices i.e. magnetic and silica nanoparticles with immobilization efficiency of 85% and 76% respectively. The nanobioconjugates exhibited increase in Vmax, temperature optimum, pH and thermal stability as compared with free enzyme. These could be efficiently reused for five repeated cycles and were stable in 1-ethyl-3-methylimidazoliumacetate [EMIM][Ac], an ionic liquid. Ionic liquids (IL) are used as green solvents to dissolve lignocellulosic biomass and facilitate better saccharification. The cellulase immobilized on magnetic nanoparticles was used for in situ saccharification of [EMIM][Ac] pretreated sugarcane bagasse and wheat straw for two cycles. The structural deconstruction and decrease in biomass crystallinity was confirmed by SEM, XRD and FTIR. The high hydrolysis yields (∼89%) obtained in this one-pot process coupled with IL stability and recycled use of immobilized cellulase, potentiates its usefulness in biorefineries.

Immobilization of Aspergillus niger cellulase on multiwall carbon nanotubes for cellulose hydrolysis

In present study, Aspergillus niger cellulase was immobilized onto functionalized multiwalled carbon nanotubes (MWCNTs) via carbodiimide coupling. MWCNTs offer unique advantages including enhanced electronics properties, a large edge to basal plane ratio, rapid electrode kinetics and its possess higher tensile strength properties due to their structural arrangements. The immobilization was confirmed by FTIR (Fourier transform infrared spectroscopy) and SEM (scanning electron microscope). The bionanoconjugates prepared under optimized condition retained 85% activity with improved pH and thermal stability. The t1/2 of immobilized cellulase at 70 °C was four fold higher than free enzyme. The Km value indicates that affinity of bionanoconjugates towards substrate has increased by two times. The preparation could be reused ten times without much loss in enzyme activity. The enhanced catalytic efficiency, stability and reusability makes it useful for efficient cellulose hydrolysis.

Functionalized Molybdenum Disulfide Nanosheets for 0D–2D Hybrid Nanostructures: Photoinduced Charge Transfer and Enhanced Photoresponse

The high-concentration stable dispersion of free-standing mono- or few-layer transition metal dichalcogenide (TMD) nanosheets (NSs) remains a significant barrier for their application in solution-processed optoelectronic devices. Here, we report oleylamine (OLA)- and dodecanethiol (DDT)-assisted exfoliation of MoS2 NSs in nonpolar organic solvent 1,2-dichlorobenzene (DCB), which enables high-concentration stable dispersion of free-standing mono- or few-layer NSs. The functionalized MoS2 NSs were further utilized for the fabrication of solution-processed 0D-2D hybrids of CuInS2 quantum dots (CIS QDs) and MoS2 NSs. The strong photoluminescence (PL) quenching and decreased PL lifetimes of CIS QDs attached to MoS2 NSs indicates efficient charge transfer from photoexcited CIS to MoS2 NSs. The photocurrent of CIS/MoS2 hybrid devices is dramatically enhanced compared to that of pure CIS and pristine MoS2-based devices, confirming that efficient charge separation and transfer occur from CIS QDs to MoS2 NSs.

Improved Performance of Organic LEDs with Modified Metal-Organic Interface

Incorporation of thin layers of strong acceptor tetrafluro-tetracyanoquinodi methane (F4TCNQ) over conducting substrate Indium-Tin-Oxide (ITO) modified its work function. The enhancement depended on the thickness of F4TCNQ film. These modified ITO substrates were used as hole injection contacts in OLEDs which show enhanced device current, lower operating voltages and enhanced current efficiency.

Cholesterol-oxidase-magnetic nanobioconjugates for the production of 4-cholesten-3-one and 4-cholesten-3, 7-dione

Cholesterol oxidase(ChOx) enzyme isolated from Pseudomonas aeruginosa PseA(ChOxP) and Rhodococcus erythropolis MTCC 3951(ChOxR) strains as well as a commercial variant produced by Streptomyces sp.(ChOxS) were immobilized on silane modified iron(II, III)oxide magnetic nanoparticles(MNP) by covalent coupling methods. The nanobiocatalysts in case of ChOxP, ChOxR and ChOxS, retained 71, 91 and 86% of cholesterol oxidase activity respectively, as compared to their soluble counterparts. The catalytic efficiency of the immobilized enzymes on nanoparticles was more than 2.0 times higher than the free enzyme. They also showed enhanced pH and thermal stability. After 10 cycles of operation, the MNP-bioconjugates retained 50, 52 and 51% of residual activity in case of ChOxP, ChOxR and ChOxS respectively. The presence of enzyme on nanoparticles was confirmed by FTIR, SEM and TEM. The nanobiocatalysts were used for the biotransformation of cholesterol and 7-ketocholesterol to 4-cholesten-3-one and 4-cholesten-3, 7-dione respectively, which are industrially and medically important steroid precursors.

Functionalized 2D-MoS2-Incorporated Polymer Ternary Solar Cells: Role of Nanosheet-Induced Long-Range Ordering of Polymer Chains on Charge Transport

In this paper, we demonstrated the enhancement in power conversion efficiency (PCE) of solar cells based on poly(3-hexylthiophene-2,5-diyl) (P3HT)/[6,6]-phenyl C71 butyric acid methyl ester (PC71BM) by incorporation of functionalized 2D-MoS2 nanosheets (NSs) as an additional charge-transporting material. The enhancement in PCE of ternary solar cells arises due to the synergic enhancement in exciton dissociation and the improvement in mobility of both electrons and holes through the active layer of the solar cells. The improved hole mobility is attributed to the formation of the long-range ordered nanofibrillar structure of polymer phases and improved crystallinity in the presence of 2D-MoS2 NSs. The improved electron mobility arises due to the highly conducting 2D network of MoS2 NSs which provides additional electron transport channels within the active layer. The nanosheet-incorporated ternary blend solar cells exhibit 32% enhancement in PCE relative to the binary blend P3HT/PC71BM.

Asparaginase conjugated magnetic nanoparticles used for reducing acrylamide formation in food model system

Acrylamide is a potent carcinogen and neurotoxin formed by the Maillard reaction when l-asparagine reacts with starch at high temperature. It is formed in food materials mainly deep fried and bakery products. Enzymatic pretreatment of these food products with asparaginase enzyme leads to reduction in acrylamide. However, enzymatic process is quite expensive due to high cost, low catalytic efficiency as well as problem with enzyme reusability. Present work deals with these problems by exploring l-asparaginase from Bacillus aryabhattai. Asparaginase enzyme was immobilized on APTES modified magnetic nanoparticles. It was found to be more than three-fold increase their thermal stability from free enzyme and retained 90% activity after fifth cycle. The immobilized enzyme also showed better affinity towards its substrate. During pretreatment of asparagine in a starch-asparagine food model system and it was clearly demonstrated that asparaginase nanoconjugates had reduced the formation of acrylamide by more than 90% within 30 min.

Biodegradation of waste grease by Penicillium chrysogenum for production of fatty acid.

The aim of present work was to effectively remediate grease waste by Penicillium chrysogenum. For efficient degradation, grease waste was pre-treated using various lipases, among them lipolase was the best. The pretreated grease was used as a substrate by P. chrysogenum resulting into the production of fatty acids. Process was optimized by response surface methodology (RSM) using four variables viz; FeCl2 (mM), spore concentration (spores/ml), time period (days) and amount of grease (g). The optimized conditions viz; FeCl2 1.25mM, culture amount 5×1011spores/ml and time period 16days led to the production of 6.6mg/g fatty acid from 10.0g of pre-treated grease mixed with 5.0g wheat bran in 10.0ml czapek-dox medium under solid state fermentation. The fermented media was extracted with hexane and subjected to GCMS analysis, which showed the presence of higher amount of palmitic acid. It was purified by crystallization method and 2.8g of palmitic acid was recovered from 1.0kg grease waste in tray fermentation.