Enhanced fuel ethanol production from rice straw hydrolysate by an inhibitor-tolerant mutant strain of Scheffersomyces stipitis

The aim of the present study was to develop an inhibitor-tolerant strain of Scheffersomyces stipitis and establish an efficient ethanol fermentation process for cost-effective ethanol production from lignocellulosic biomass. By a strategy of three successive rounds of UV mutagenesis following adaptation, we isolated a S. stipitis mutant with improved tolerance against ethanol and inhibitors in the form of acetic acid, furfural and vanillin. The mutant strain exhibited excellent ethanol fermentation performance; both the xylose and glucose consumption rate and ethanol productivity were almost two times higher than the parental strain in batch fermentation. To overcome the issue of product inhibition and carbon catabolite repression (CCR) effect, the membrane integrated continuous fermentation system was employed. The maximum ethanol titer of 43.2 g l−1 and productivity of 2.16 g l−1 h−1 was achieved at a dilution rate of 0.05 h−1, higher than the relevant studies ever reported. These results suggested the novel process of cell recycling continuous fermentation using S. stipitis mutant has great potential for commercial ethanol production from lignocelluloses-based biomass

Label-free colorimetric sensor for ultrasensitive detection of heparin based on color quenching of gold nanorods by graphene oxide

A novel label-free colorimetric strategy was developed for ultrasensitive detection of heparin by using the super color quenching capacity of graphene oxide (GO). Hexadecyltrimethylammonium bromide (CTAB)-stabilized gold nanorods (AuNRs) could easily self-assembly onto the surface of GO through electrostatic interaction, resulting in decrease of the surface plasmon resonance (SPR) absorption and consequent color quenching change of the AuNRs from deep to light. Polycationic protamine was used as a medium for disturbing the electrostatic interaction between AuNRs and GO. The AuNRs were prevented from being adsorbed onto the surface of GO because of the stronger interaction between protamine and GO, showing a native color of the AuNRs. On the contrary, in the presence of heparin, which was more easily to combine with protamine, the AuNRs could self-assembly onto the surface of GO, resulting in the native color disappearing of AuNRs. As the concentration of heparin increased, the color of AuNRs would gradually fade until almost colorless. The amounts of self-assembly AuNRs were proportional to the concentration of heparin, and thereby the changes in the SPR absorption and color had been used to monitor heparin levels. Under optimized conditions, good linearity was obtained in a range of 0.02-0.28 mu g/mL (R = 0.9957), and a limit of detection was 5 ng/mL. The simultaneous possession of high sensitivity and selectivity, simplicity, rapidity, and visualization enabled this sensor to be potentially applicable for ultrasensitive and rapid on-site detection toward trace heparin.A novel label-free colorimetric strategy was developed for ultrasensitive detection of heparin by using the super color quenching capacity of graphene oxide (GO). Hexadecyltrimethylammonium bromide (CTAB)-stabilized gold nanorods (AuNRs) could easily self-assembly onto the surface of GO through electrostatic interaction, resulting in decrease of the surface plasmon resonance (SPR) absorption and consequent color quenching change of the AuNRs from deep to light. Polycationic protamine was used as a medium for disturbing the electrostatic interaction between AuNRs and GO. The AuNRs were prevented from being adsorbed onto the surface of GO because of the stronger interaction between protamine and GO, showing a native color of the AuNRs. On the contrary, in the presence of heparin, which was more easily to combine with protamine, the AuNRs could self-assembly onto the surface of GO, resulting in the native color disappearing of AuNRs. As the concentration of heparin increased, the color of AuNRs would gradually fade until almost colorless. The amounts of self-assembly AuNRs were proportional to the concentration of heparin, and thereby the changes in the SPR absorption and color had been used to monitor heparin levels. Under optimized conditions, good linearity was obtained in a range of 0.02-0.28 mu g/mL (R = 0.9957), and a limit of detection was 5 ng/mL. The simultaneous possession of high sensitivity and selectivity, simplicity, rapidity, and visualization enabled this sensor to be potentially applicable for ultrasensitive and rapid on-site detection toward trace heparin. (c) 2012 Elsevier B.V. All rights reserved

Ultrasensitive surface-enhanced Raman scattering nanosensor for mercury ion detection based on functionalized silver nanoparticles

In this work, a simple, rapid and ultrasensitive surface-enhanced Raman scattering (SERS) nanosensor was developed for mercury ion (Hg2+) detection based on 4-mercaptopyridine (4-MPY) functionalized silver nanoparticles (AgNPs) (4-MPY-AgNPs) in the presence of spermine. Here, the spermine would bind AgNPs through Ag-N bonds and induce remarkable aggregation of AgNPs, and thereby would generate significantly enhanced Raman intensity of the reporter molecule 4-MPY. Followed by the addition of Hg2+, the formation of the Hg-Ag alloy blocked the adsorption of 4-MPY and spermine, resulting in the dispersion of 4-MPY-AgNPs and thus decreasing the Raman intensity, by which the Hg2+ could be sensed by SERS. A good linearity was obtained in the range of 1-100 nM (R-2 = 0.987), and the relative standard deviation was between 0.85 and 5.50%. The spermine-induced accumulation of 4-MPY-AgNPs largely enhanced the SERS responses, leading to a high detectability up to 0.34 nM. A real water sample with spiked Hg2+ was also analyzed, presenting satisfactory recoveries ranging from 94.5 to 108.5%, confirming the practicability of the SERS nanosensor based method

A near-infrared fluorescent probe for evaluating endogenous hydrogen peroxide during ischemia/reperfusion injury

Hydrogen peroxide (H2O2), as a major component of reactive oxygen species (ROS), plays an important role in normal physiological processes. A H2O2 burst also occurs in the ischemia/reperfusion (I/R) process and causes a series of physiological and pathological injuries. Therefore, it is important to determine concentration fluctuations of H2O2. Here we develop a ratiometric fluorescent probe, Cy-ArB, which shows high selectivity and sensitivity toward H2O2. The fluorescence response of the probe is triggered by the reaction of borate esters with H2O2, and this process releases a near-infrared heptamethine cyanine fluorophore which has the ability of mitochondrial tracing. Hence, the probe can be used for real-time monitoring of H2O2 fluctuations in the mitochondrial respiration chain. Finally, we explore the fluctuations of H2O2 in cells and in vivo during the I/R process using the probe Cy-ArB. The results of our experiments prove that our probe is a potential candidate for clinical surgery pre-evaluation

Qualitative Recognition of Primary Taste Sensation Based on Surface Electromyography

Based on surface electromyography (sEMG), a novel recognition method to distinguish six types of human primary taste sensations was developed, and the recognition accuracy was 74.46%. The sEMG signals were acquired under the stimuli of no taste substance, distilled vinegar, white granulated sugar, instant coffee powder, refined salt, and Ajinomoto. Then, signals were preprocessed with the following steps: sample augments, removal of trend items, high-pass filter, and adaptive power frequency notch. Signals were classified with random forest and the classifier gave a five-fold cross-validation accuracy of 74.46%, which manifested the feasibility of the recognition task. To further improve the model performance, we explored the impact of feature dimension, electrode distribution, and subject diversity. Accordingly, we provided an optimized feature combination that reduced the number of feature types from 21 to 4, a preferable selection of electrode positions that reduced the number of channels from 6 to 4, and an analysis of the relation between subject diversity and model performance. This study provides guidance for further research on taste sensation recognition with sEMG

A cysteine-selective fluorescent probe for monitoring stress response cysteine fluctuations

Rare studies provided evidence for the real-time monitoring of stress response cysteine fluctuations. Here, we have successfully designed and synthesized a cysteine-selective fluorescent probe 1 to monitor stress response Cys fluctuations, providing visual evidence of Hg2+ regulated cysteine fluctuations for the first time, which may open a new way to help researchers to reveal the mechanism of heavy metal ion poisoning

A twin enrichment method based on dispersive liquid-liquid microextraction and field-amplified sample injection for the simultaneous determination of sulfonamides

A twin enrichment method based on offline dispersive liquid-liquid microextraction (DLLME) coupled with online field-amplified sample injection (FASI) was developed for the simultaneous determination of four sulfonamide (SA) antibiotics, including sulfamethazine (SMZ), sulfamerazine (SMR), sulfadizine (SDZ) and sulfacetamide (SFA), in different environmental waters, followed by capillary electrophoresis (CE). Various parameters that affected the separation performance of CE and the enrichment efficiencies of DLLME and FASI were optimized in detail, and excellent CE separation was attained within 6 min. The DLLME-FASI-CE offered high sensitivity enrichment factors of 206, 166, 185 and 150 for SMZ, SMR, SDZ and SFA, respectively. Highly sensitive detection was realized with low limits of detection (LODs), which ranged from 2.0-23.0, 2.2-26.0 and 4.3-63.0 ng mL(-1) in tap water, lake water and seawater, respectively, as well as limits of quantification (LOQs) within 6.0-63.0, 7.4-96.0 and 14.0-201.0 ng mL(-1), respectively. Satisfactory recoveries in the range of 91-108% were obtained with the three spiked environmental water samples, and the relative standard deviations were from 1.09-7.45%. The simple effective twin enrichment method provided promising perspective for CE determination of SAs in complicated aqueous matrices, with rapidity, sensitivity, and accuracy

Molecularly imprinted polymers-coated gold nanoclusters for fluorescent detection of bisphenol A

A flexible fluorescent sensing strategy for the recognition and detection of bisphenol A (BPA) has been proposed based on molecularly imprinted polymers (MIPs)-coated gold nanoclusters (AuNCs), by taking advantages of the high selectivity of MIPs and the strong fluorescence property of AuNCs. SiO2@AuNCs were initially prepared by making use of the powerful amido bonds between carboxyl-terminated AuNCs and amino-functionalized SiO2 nanoparticles. Then MIPs-coated AuNCs were formed by anchoring MIP layer on the surface of SiO2@AuNCs via a solgel process. In the presence of imprinting template BPA, a Meisenheimer complex could be formed between BPA and the primary amino groups on the surface of the AuNCs, and the photoluminescent energy of AuNCs would be transferred to the complex, and thereby result in the fluorescence quenching of AuNCs. The fluorescence-quenching fractions of the sensor presented a satisfactory linearity with BPA concentrations over the range of 013.1 mu M and the detection limit could reach 0.10 mu M. Distinguished selectivity was also exhibited to BPA over other possibly competing molecules. Moreover, the sensor was successfully applied to determine BPA in seawater, and the average recoveries of BPA at three spiking levels ranged from 91.3 to 96.2% with relative standard deviations below 4.8%. This AuNCs-MIPs based sensor provided great potentials for recognition and determination of phenolic environmental estrogens in complicated samples. (C) 2015 Elsevier B.V. All rights reserved.A flexible fluorescent sensing strategy for the recognition and detection of bisphenol A (BPA) has been proposed based on molecularly imprinted polymers (MIPs)-coated gold nanoclusters (AuNCs), by taking advantages of the high selectivity of MIPs and the strong fluorescence property of AuNCs. SiO2@AuNCs were initially prepared by making use of the powerful amido bonds between carboxyl-terminated AuNCs and amino-functionalized SiO2 nanoparticles. Then MIPs-coated AuNCs were formed by anchoring MIP layer on the surface of SiO2@AuNCs via a solgel process. In the presence of imprinting template BPA, a Meisenheimer complex could be formed between BPA and the primary amino groups on the surface of the AuNCs, and the photoluminescent energy of AuNCs would be transferred to the complex, and thereby result in the fluorescence quenching of AuNCs. The fluorescence-quenching fractions of the sensor presented a satisfactory linearity with BPA concentrations over the range of 013.1 mu M and the detection limit could reach 0.10 mu M. Distinguished selectivity was also exhibited to BPA over other possibly competing molecules. Moreover, the sensor was successfully applied to determine BPA in seawater, and the average recoveries of BPA at three spiking levels ranged from 91.3 to 96.2% with relative standard deviations below 4.8%. This AuNCs-MIPs based sensor provided great potentials for recognition and determination of phenolic environmental estrogens in complicated samples. (C) 2015 Elsevier B.V. All rights reserved