Electron Beam-Induced Immobilization of Laccase on Porous Supports for Waste Water Treatment Applications

Abstract

Abstract:The versatile oxidase enzyme laccase was immobilized on porous supports such as polymer membranes and cryogels with a view of using such biocatalysts in bioreactors aiming at the degradation of environmental pollutants in wastewater. Besides a large surface area for supporting the biocatalyst, the aforementioned porous systems also offer the possibility for simultaneous filtration applications in wastewater treatment. Herein a "green" water-based, initiator-free, and straightforward route to highly reactive membrane and cryogel-based bioreactors is presented, where laccase was immobilized onto the porous polymer supports using a water-based electron beam-initiated grafting reaction. In a second approach, the laccase redox mediators 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and syringaldehyde were cross-linked instead of the enzyme via electron irradiation in a frozen aqueous poly(acrylate) mixture in a one pot set-up, yielding a mechanical stable macroporous cryogel with interconnected pores ranging from 10 to 50 µm in size. The membranes as well as the cryogels were characterized regarding their morphology, chemical composition, and catalytic activity. The reactivity towards wastewater pollutants was demonstrated by the degradation of the model compound bisphenol A (BPA). Both membrane-and cryogel-immobilized laccase remained highly active after electron beam irradiation. Apparent specific BPA removal rates were higher for cryogelthan for membrane-immobilized and free laccase, whereas membrane-immobilized laccase OPEN ACCESSMolecules 2014, 19 11861 was more stable with respect to maintenance of enzymatic activity and prevention of enzyme leakage from the carrier than cryogel-immobilized laccase. Cryogel-immobilized redox mediators remained functional in accelerating the laccase-catalyzed BPA degradation, and especially ABTS was found to act more efficiently in immobilized than in freely dissolved state.

Biocatalytic Self-Cleaning Polymer Membranes

“…This way, links between the polymer matrix and the enzyme can be formed that are assumed to be side-unspecific. Previous work demonstrated the formation of covalent chemical bonds between the membrane polymer and the immobilized molecules by XPS analysis, which was supported by extensive extraction experiments [22][23][24]26,47]. It is worth emphasizing that the use of an aqueous system is a crucial requirement since different results were obtained in the dry state as also reported in the literature [48].…”

“…The EB treatment results in the generation of a mixture of ions, excited molecules and free radicals as described for the radiolysis of water [45] ensuring the activation of both the dissolved trypsin [25,26,46] as well as of the membranes [22][23][24][27][28][29]47]. The formed radicals/activated species can undergo various reactions, such as cross-linking or recombination reactions.…”

“…This technology enables direct immobilization of functional organic molecules [22,23], engineering polymers [24], or even biomolecules [25,26] on a membrane's surface. The use of low-energy EB radiation combines surface activation (formation of activated species) of the membrane polymer and simultaneous covalent immobilization of the desired compounds from an aqueous system.…”

Potential of Wood-Rotting Fungi to Attack Polystyrene Sulfonate and Its Depolymerisation by Gloeophyllum trabeum via Hydroquinone-Driven Fenton Chemistry

“…Flow rate was adjusted to 0.5 ml/min. A wavelength range from 220 to 400 nm was recorded (detection wavelength: 278 nm) [ 39 ]. External standards of commercial 2,5-DMBQ and self-produced 2,5-DMHQ (see above) were used for calibration.…”

Environmentally Friendly and Recyclable Natural-Mediator-Modified Magnetic Nanoparticles for Laccase-Catalyzed Decolorization

“…It has been reported that mediator immobilization is an effective way to achieve this goal, and the successful immobilization of several artificial on various materials has been reported. For example, a Lac redox mediator (ABTS) was immobilized on a macroporous cryogel by electron irradiation to assist the Laccatalyzed degradation of bisphenol A [32]. In addition, ABTS had been successfully attached to silica nanoparticles and a mesoporous metal-organic framework, and the immobilized ABTS played a similar role to free ABTS in mediating Lac-catalyzed dye decolorization [14,15].…”