Laccase immobilization onto natural polysaccharides for biosensing and biodegradation.

Over the last few years, the focus of researchers have been set on enzyme engineering and enzyme immobilization technology using natural polysaccharides as promising and green supporting materials to address the challenges of free enzymes for various applications. Polysaccharides have been extensively implemented as enzyme carriers because they can be easily modified chemically according to the nature of immobilization. This process improves the stability and lifetime of laccase in catalytic reactions. Additionally, the selectivity of the enzymes can be preserved for particular application after immobilization onto polysaccharides. This review paper reveals the significance and potential of natural polysaccharides (including cellulose, chitosan, and alginate) and their composites as support materials for the laccases immobilization to expand the modified biocatalysts for industrial applications. Moreover, the roles of immobilized laccases are discussed from a fundamental point of view to elucidate their catalytic mechanisms as biocatalysts in the detection and degradation of environmental contaminants.

Aerobic oxidative synthesis of quinazolinones and benzothiazoles in the presence of laccase/DDQ as a bioinspired cooperative catalytic system under mild conditions.

The current study applied laccase/DDQ as a bioinspired cooperative catalytic system for the synthesis of quinazolinones (80-95% yield) and benzothiazoles (65-98% yield) using air or O2 as ideal oxidants in aqueous media at ambient temperature. The aerobic oxidative cyclization reactions occur in two steps: (i) chemical cyclization; (ii) chemoenzymatic oxidation. These methods are more environment-friendly, efficient, simple and practical than other reported methods due to the use of O2 as an oxidant, laccase as an eco-friendly biocatalyst, aqueous media as the solvent and free from any toxic transition metal and halide catalysts. Therefore, these methods can be applied in pharmaceutical and other sensitive synthetic procedures.

Magnetic Fe3O4/Graphene Oxide/Copper-Based Nanocomposite as a Reusable Catalyst for the Reduction of 4-Nitrophenol.

In the present investigation, Fe3O4/Graphene oxide/Pr-NH2-CuII was reported as a novel magnetically recoverable nanocomposite and characterized using various analytical techniques such as FT-IR spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), vibrating sample magnetometry (VSM), X-ray diffraction (XRD), and inductively coupled plasma (ICP). The catalytic performance of the synthesized catalyst was evaluated in the reduction of 4-nitrophenol to 4-aminophenol by an excess amount of sodium borohydride as the source of hydrogen in aqueous solution. The reaction was monitored by UV-vis spectroscopy at ambient temperature. Magnetic nature of the catalyst led to its simple recovery by a permanent magnet and excellent recyclability without appreciable loss of the catalytic activity.

Synthesis and characterization of NiFe2O4@Cu nanoparticles as a magnetically recoverable catalyst for reduction of nitroarenes to arylamines with NaBH4.

In this research, a simple and efficient method for synthesis of magnetically separable NiFe2O4@Cu nanocomposite under co-precipitation conditions was described. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), atomic absorption spectroscopy (AAS), Brunauer-Emmett-Teller (BET) and vibrating sample magnetometer (VSM) analyses confirmed the construction of NiFe2O4@Cu nanoparticles. The prepared core-shell nanocomposite showed a satisfactory catalytic activity for NaBH4 reduction of nitroarenes to arylamines. All reactions were carried out in a mixture of H2O-EtOH (1.5:0.5mL) within 1-12min under reflux conditions. The Cu nanocatalyst can be easily separated by a magnet and reused seven consecutive runs with no obvious loss of activity.

One-pot reductive-acetylation of nitroarenes with NaBH4 catalyzed by separable core-shell Fe3O4@Cu(OH)x nanoparticles.

One-pot reductive-acetylation of nitroarenes to acetanilides was carried out efficiently with NaBH4 in the presence of magnetically separable core-shell Fe3O4@Cu(OH)x nanoparticles. All reactions were carried out in H2O followed by acetylation with acetic anhydride within 5-17min giving the N-arylacetamides in high to excellent yields. Reusability of the catalyst was examined 9 times without significant loss of its catalytic activity.

Factors affecting viability of Bifidobacterium bifidum during spray drying.

BACKGROUND: There is substantial clinical data supporting the role of Bifidobacterium bifidum in human health particularly in benefiting the immune system and suppressing intestinal infections. Compared to the traditional lyophilization, spray-drying is an economical process for preparing large quantities of viable microorganisms. The technique offers high production rates and low operating costs but is not usually used for drying of substances prone to high temperature. The aim of this study was to establish the optimized environmental factors in spray drying of cultured bifidobacteria to obtain a viable and stable powder. METHODS: The experiments were designed to test variables such as inlet air temperature, air pressure and also maltodextrin content. The combined effect of these variables on survival rateand moisture content of bacterial powder was studied using a central composite design (CCD). Sub-lethal heat-adaptation of a B. bifidum strain which was previously adapted to acid-bile-NaCl led to much more resistance to high outlet temperature during spray drying. The resistant B. bifidum was supplemented with cost friendly permeate, sucrose, yeast extract and different amount of maltodextrin before it was fed into a Buchi B-191 mini spray-dryer. RESULTS: Second-order polynomials were established to identify the relationship between the responses andthe three variables. Results of verification experiments and predicted values from fitted correlations were in close agreement at 95% confidence interval. The optimal values of the variables for maximum survival and minimum moisture content of B. bifidum powder were as follows: inlet air temperature of 111.15°C, air pressure of 4.5 bar and maltodextrin concentration of 6%. Under optimum conditions, the maximum survival of 28.38% was achieved while moisture was maintained at 4.05%. CONCLUSION: Viable and cost effective spray drying of Bifidobacterium bifidum could be achieved by cultivating heat and acid adapted strain into the culture media containing nutritional protective agents.