Optimization for the extraction of polyphenols from Inonotus obliquus and its antioxidation activity.

In order to study the extraction process and antioxidative activity of Inonotus obliquus polyphenols (IOP), the optimal extraction process was determined by orthogonal experiment optimization. The clearance rate of DPPH and hydroxyl radicals were used as indicators to evaluate the antioxidant activity of IOP. The results showed that the optimum extraction conditions were as follows: ethanol concentration of 50%, solid-liquid ratio of 1:20, temperature of 60 °C, and 90 min. Under these conditions, the extraction yield of IOP was 2.84%. The antioxidant capacity of extracts appeared to be IOP dose-dependent, while it also presented stronger ferric reducing antioxidant power (FRAP). High Performance Liquid Chromatography (HPLC-MS) analysis indicated that the major identified polyphenol compounds extracted at the optimal conditions were ten compounds (procyanidin, caffeic acid, p-coumaric acid, isorhamnetin-3-O-glucoside, astilbin, tangeretin, gallic acid, kaempferol, quercetin, and catechin 7-xyloside). These findings indicate that I. obliquus polyphenols have the potential to be developed as a natural antioxidant and have a good application prospect.

Freezing/thawing pretreatment of dormant Aspergillus niger spores to increase the Cr(vi) adsorption capacity: process and mechanism.

Hexavalent chromium is a widespread pollutant that threatens ecological and human health. However, its removal from the environment is limited by the high cost and energy consumption rate of current technologies. In this study, the Cr(vi) biosorption mechanism of Aspergillus niger spores pretreated by freezing/thawing was studied by batch experiments and surface chemistry analyses. The results indicated that pretreatment enhanced the spores' Cr(vi) removal efficiency. The cell surface, internal functional groups, and morphology of the freezing/thawing-pretreated spores (FTPS) before and after Cr(vi) loading were characterized by advanced spectroscopy techniques such as SEM-EDAX, XPS, FTIR, and FETEM analyses. The SEM and BET data showed that the surface of FTPS was rougher than that of untreated spores. The XPS data showed that FTPS bio-transformed Cr(vi) into Cr(iii). The intracellular localization of chromium was visualized by FETEM, and both surface and intracellular structures removed Cr(vi) following pseudo-second-order biosorption kinetics. The biosorption dynamics of Cr(vi) fit the Langmuir isotherm model describing a monolayer. These results suggest that freezing/thawing pretreatment of A. niger spores could lead to the development of a novel, efficient biomaterial for the removal of Cr(vi).

Enhanced catalytic efficiency of CotA-laccase by DNA shuffling.

Bacterial CotA-laccases exhibit higher activity in alkaline pH and salt concentration conditions compared to laccases from white-rot fungi. They are considered as green catalysts in decolorizing of industrial dyes. However, CotA-laccases are limited due to the low yield and catalytic efficiency as the spore-bound nature of CotA. A DNA shuffling strategy was applied to generate a random mutation library. To improve laccase activities, a mutant (T232P/Q367R 5E29) with two amino acid substitutions was identified. The catalytic efficiency of mutant 5E29 was 1.21 fold higher compared with that of the wild-type. The Km and kcat values of 5E29 for SGZ were of 20.3 ± 1.3 µM and 7.6 ± 2.7 s-1. The thermal stability was a slight enhancement. Indigo Carmine and Congo red were efficiently decolorized by using this mutant at pH 9.0. These results provide that 5E29 CotA-laccase is a good candidate for biotechnology applications under alkaline condition, with an effective decolorization capability.

AKT signalling and mitochondrial pathways are involved in mushroom polysaccharide-induced apoptosis and G1 or S phase arrest in human hepatoma cells.

This study describes molecular mechanisms for inhibiting tumour cell proliferation using polysaccharides from medicinal mushrooms in human hepatoma cells. The results show that regarding cell cycle-related proteins, three types of polysaccharides significantly enhance the expression of p27(Kip) in HepG2 and Bel-7404 cells, while suppressing the activity of cyclin D1/CDK4 and/or cyclin E/CDK2. Considering apoptosis-related factors, the polysaccharides suppressed AKT activity through the inhibition of AKT phosphorylation at Thr(308) and/or Ser(473). The growth of HepG2 and Bel-7404 cells was suppressed by the up-regulation of a subunit of PI3K and phospho-PTEN, which are modulators of AKT activity. The polysaccharides also activated the mitochondria-mediated apoptosis pathway by stimulating the activation of Bcl-2 family proteins to release cytochrome c and Smac and cleave caspase-9 and caspase-3 in HepG2 and Bel-7404 cells. These factors have a potent effect on cell cycle arrest in G(1) and/or S phase and induce apoptosis in HepG2 and Bel-7404 cells.