Acrylic modified kraft lignin microspheres as novel support for immobilization of laccase from M.Thermophila expressed in A. oryzae (Novozym® 51003) and application in degradation of anthraquinone textile dyes

Abstract

The novel lignin-based microspheres (LMS-DEGDMA) were produced through a two-step modification procedure consisting of kraft lignin (KL) modification with acrylic acid synthesized from fructose; and suspension and copolymerization of acrylic acid modified KL (KL-A) with diethylene glycol dimethacrylate (DEGDMA). The applied procedure provided LMS-DEGDMA microspheres in the size range of 50-90 μm with specific surface area of 39 m2/g, porosity ϵp 62, pore diameters of 4-20 nm and total pore volume of 0.14 cm3/g. Immobilization of laccase from Myceliophthora thermophilia expressed in Aspergillus oryzae (Novozyme® 51003) on LMS-DEGDMA was explored. By optimization of the immobilization process, it was demonstrated that laccase immobilization on LMS-DEGDMA exhibited the best results (protein immobilization yield of 70 %, activity yield of 27 %, and catalytic activity of 262 IU/g of support) when the immobilization was carried out at pH 5.0 and 100 mg of offered protein per g support during 1 h. Additionally, the LMS-DEGDMA-laccase preparation showed efficiency (>80 %, 5-7 cycles) in decolorization of anthraquinone dyes (Lanaset® violet B, Lanaset® blue 2 R and C.I. Acid Green 40) and their mixture. In case of Lanaset® violet B, LMS-DEGDMA improved laccase's kinetics characteristics (90 % over 24 h) along with operational stability (> 63 % catalytic activity, 7 cycles).