Purification and Characterization of a Thermo- and pH-Stable Laccase From the Litter-Decomposing Fungus Gymnopus luxurians and Laccase Mediator Systems for Dye Decolorization

An extracellular laccase (GLL) was purified from fermentation broth of the litter-decomposing fungus Gymnopus luxurians by four chromatography steps, which resulted in a high specific activity of 118.82 U/mg, purification fold of 41.22, and recovery rate of 42.05%. It is a monomeric protein with a molecular weight of 64 kDa and N-terminal amino acid sequence of AIGPV TDLHI, suggesting that GLL is a typical fungal laccase. GLL demonstrated an optimum temperature range of 55°C–65°C and an optimum pH 2.2 toward 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). It displayed considerably high thermostability and pH stability with about 63% activity retained after 24 h at 50°C, and 86% activity retained after 24 h at pH 2.2, respectively. GLL was significantly enhanced in the presence of K+, Na+, and Mg2+ ions. It demonstrated Km of 539 μM and kcat/Km of 140 mM–1⋅s–1 toward ABTS at pH 2.2 and 37°C. Acetosyringone (AS) and syringaldehyde (SA) were the optimal mediators of GLL (0.4 U/ml) for dye decolorization with decolorization rates of about 60%–90% toward 11 of the 14 synthetic dyes. The optimum reaction conditions were determined to be mediator concentration of 0.1 mM, temperature range of 25°C –60°C, and pH 4.0. The purified laccase was the first laccase isolated from genus Gymnopus with high thermostability, pH stability, and effective decolorization toward dyes, suggesting that it has potentials for textile and environmental applications.

Production of Highly Thermostable Laccase from Penicillium spinulosum for Enhanced Delignification of Untreated Wheat Bran

Background: Lignin confers rigidity on plant cell wall and poses a challenge to hydrolysis of cellulose, which makes production of biofuels from lignocellulose an overwhelming problem. This prompts continuous search for novel ligninolytic enzymes, especially, laccases for delignification of lignocellulose for improved saccharification of biomass. Objective: This study reports production, physicochemical properties and delignification efficiency of laccases from Penicillium and Trichoderma species on untreated wheat bran. Methods: Fungal laccases were produced using different agroresidues (wheat bran, coconut shell and palm kernel shell) as substrates in submerged fermentation. Best substrate for laccase production was determined. Physicochemical properties of crude enzymes and delignification efficiency of the laccases were determined on untreated wheat bran using pure laccase as control. Results: Wheat bran supported maximum laccase production from fungi under study. Highest laccase yield of 22.5 U/mL was obtained from P. spinulosum. Laccase from P. spinulosum was optimally active at pH 7.0 and 50 °C and exhibited remarkable high thermostability with 61.6% residual activity at 90 °C after 2 h incubation. The activity of the thermostable enzyme was enhanced in the presence of Cu2+. Biodelignification efficiency of cell-free extract from P. spinulosum, T. koningii, and P. restrictum on wheat bran were 95%, 81.5% and 63.5%, respectively. Surprisingly, a much lower delignification efficiency of 33.42% was obtained with commercial laccase from Trametes versicolor. Conclusion: The high thermostability and striking delignification efficiency of laccase from P. spinulosum make the enzyme a good bioresource for biodelignification of untreated lignocellulose for biofuel production.

Photochromism and photoresponsive luminescence in naphthalenediimide coordination polymers with high thermostability

Two novel photochromic complexes [Zn2(bpdc)2(m-DPNDI)2]·H2O (1) and [Cd(bpdc)(m-DPNDI)]·H2O (2) (H2bpdc = 4,4′-diphenic acid, m-DPNDI = N,N′-bis(3-pyridyl)-1,4,5,8-naphthalenetetracarboxydiimide) were prepared through a solvothermal method.

New Organic-Inorganic Hybrid Materials: High Refractive Index Polymers Based on Cyclotriphophazene with High Thermostability and Transparency

Two flexible and colorless high refractive index films based on cyclotriphophazene have been successfully prepared by the thiol-ene reaction of hexa-substituted cyclotriphophazene monomer (CVP) and commercial bifunctional aromatic thiol. The...