This paper demonstrates carbon quantum dots (CQDs) with triangular silver nanoparticles (AgNPs) as the sensing materials of localized surface plasmon resonance (LSPR) sensors for chlorophyll detection. The CQDs and AgNPs were prepared by a one-step hydrothermal process and a direct chemical reduction process, respectively. FTIR analysis shows that a CQD consists of NH2, OH, and COOH functional groups. The appearance of C=O and NH2 at 399.5 eV and 529.6 eV in XPS analysis indicates that functional groups are available for adsorption sites for chlorophyll interaction. A AgNP-CQD composite was coated on the glass slide surface using (3-aminopropyl) triethoxysilane (APTES) as a coupling agent and acted as the active sensing layer for chlorophyll detection. In LSPR sensing, the linear response detection for AgNP-CQD demonstrates R2 = 0.9581 and a sensitivity of 0.80 nm ppm-1, with a detection limit of 4.71 ppm ranging from 0.2 to 10.0 ppm. Meanwhile, a AgNP shows a linear response of R2 = 0.1541 and a sensitivity of 0.25 nm ppm-1, with the detection limit of 52.76 ppm upon exposure to chlorophyll. Based on these results, the AgNP-CQD composite shows a better linearity response and a higher sensitivity than bare AgNPs when exposed to chlorophyll, highlighting the potential of AgNP-CQD as a sensing material in this study.
A series of 2-methoxypyridine-3-carbonitrile (5a-i)-bearing aryl substituents were successfully synthesized in good yields by the condensation of chalcones (4a-i) with malononitrile in basic medium. The condensation process, in most cases, offers a route to a variety of methoxypyridine derivatives (6a-g) as side products in poor yields. All new compounds were fully characterized using different spectroscopic methods. Mass ESI-HMRS measurements were also performed. Furthermore, these compounds were screened for their in vitro cytotoxicity activities against three cancer cell lines; namely, those of the liver (line HepG2), prostate (line DU145) and breast (line MBA-MB-231). The cytotoxicity assessment revealed that compounds 5d, 5g, 5h and 5i exhibit promising antiproliferative effects (IC50 1-5 µM) against those three cancer cell lines.
The partitioning of β-mannanase derived from Bacillus subtilis ATCC 11774 in aqueous two-phase system (ATPS) was studied. The ATPS containing different molecular weight of polyethylene glycol (PEG) and types of salt were employed in this study. The PEG/salt composition for the partitioning of β-mannanase was optimized using response surface methodology. The study demonstrated that ATPS consists of 25% (w/w) of PEG 6000 and 12.52% (w/w) of potassium citrate is the optimum composition for the purification of β-mannanase with a purification fold (PF) of 2.28 and partition coefficient (K) of 1.14. The study on influences of pH and crude loading showed that ATPS with pH 8.0 and 1.5% (w/w) of crude loading gave highest PF of 3.1. To enhance the partitioning of β-mannanase, four ionic liquids namely 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4), 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim]BF4), 1-butyl-3-methylimidazolium bromide ([Bmim]Br), 1-ethyl-3-methylimidazolium bromide ([Emim]Br) was added into the system as an adjuvant. The highest recovery yield (89.65%) was obtained with addition of 3% (w/w) of [Bmim]BF4. The SDS-PAGE analysis revealed that the β-mannanase was successfully recovered in the top phase of ATPS with the molecular size of 36.7kDa. Therefore, ATPS demonstrated a simple and efficient approach for recovery and purification of β-mannanase from fermentation broth in one single-step strategy.
A conventional reactor in microbial electrochemical technology (MET) consists of anode and cathode compartments divided by a separator, which is usually a proton exchange membrane (PEM), such as Nafion 117. In this study, a novel porous clay earthenware (NCE) was fabricated as the separator to replace the highly cost PEM. The fabrication of NCEs is with raw clay powder and starch powder that acts as a pore-forming agent at different starch powder contents (10 vol%, 20 vol%, and 30 vol%), ball-milled before hydraulically pressed to form green ceramic pellets and sintered up to 1200 °C. The highest power density of 2250 ± 21 mW/m2 (6.0 A/m2), the internal resistance of 75 ± 24 Ω and coulombic efficiency (CE) of 44 ± 21% were produced for MFC-NCE from 30 vol% starch powder content under batch mode operation. The MFC-PEM combination produced the lowest power density, CE and the highest internal resistance up to 1350 ± 17 mW/m2 (3.0 A/m2), 23 ± 15% and 326 ± 13 Ω, respectively.
This study aimed at recovery of thermostable lipase from Escherichia coli BL21 using porous glass beads grafted with polyethylene glycol (PEG) in aqueous impregnated resins system (AIRS). The influencing parameters such as concentration and pH of extraction solution, concentration of NaCl, size of the beads, and pH of the desorption solution on the partition behaviour of lipase were evaluated. Smaller adsorbent (4 mm) had a 65.5% of recovery yield with approximately two-fold higher purification factor compared to that obtained with the larger adsorbent. Recombinant lipase was purified successfully using AIRS with a purification factor of 7.6 and yield of 78.4% under optimum conditions of 18% (w/w) PEG 4000, 10% (w/w) of potassium citrate at pH 9 with 3% (w/w) of NaCl. Optimum desorption was obtained with 4.0 mm of porous glass beads at pH 9.