Synergetic Sensing Effect of Sodium Carboxymethyl Cellulose and Bismuth on Cadmium Detection by Differential Pulse Anodic Stripping Voltammetry.

In the present work, a novel electrochemical sensor was developed for the detection of trace cadmium with high sensitivity and selectivity in an easy and eco-friendly way. Firstly, a glassy carbon electrode (GCE) was modified with nontoxic sodium carboxymethyl cellulose (CMC) by a simple drop-casting method, which was applied to detect cadmium by differential pulse anodic stripping voltammetry (DPASV) in a solution containing both target cadmium and eco-friendly bismuth ions, based on a quick electro-codeposition of these two metal ions on the surface of the modified electrode (CMC-GCE). Investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FT-IR), both CMC (with good film-forming ability) and bismuth (with well-defined stripping signal) were found to be well complexed with target cadmium, leading to vital signal amplification for cadmium detection at a sub-nanomolar level. Under the optimal conditions, the proposed sensor exhibited a good linear stripping signal response to cadmium (Ⅱ) ion, in a concentration range of 0.001 µmol/L-1 µmol/L with a limit of detection of 0.75 nmol/L (S/N = 3). Meanwhile, the results demonstrate that this novel electrochemical sensor has excellent sensitivity and reproducibility, which can be used as a promising detection technique for testing natural samples such as tap water.

Isolation, identification and application on soy sauce fermentation flavor bacteria of CS1.03.

Bacillus is a common bacterial genus in Chinese traditional sun-brewed moromi. Some Bacillus species can metabolize sauce flavour and aroma substances. To address the insufficiency of flavour microbes in soy sauce fermentation, we used 16S rDNA sequence analysis to identify the CS1.03 strain, which was isolated from moromi produced through the traditional and natural sun brewing methods. A Box-Behnken design was used to optimize the addition technology of CS1.03, and ammoniacal nitrogen content and sensory evaluation were adopted as determination indices. GC-MS analysis was also performed to analyse the flavour components. Results identified CS1.03 as Bacillus subtilis. The optimal conditions yielded 10.7 g/L ammoniacal nitrogen in fermented soy sauce with rich aroma and flavour, and a sensory evaluation score of 90.5. GC-MS analysis revealed that the contents of phenol, aldehyde and ketone are all increased. These results demonstrated that CS1.03 could improve the flavour of soy sauce and shows good potential for application in soy sauce fermentation.

A high performance Pb(II) electrochemical sensor based on spherical CuS nanoparticle anchored g-C3N4.

A new electrochemical sensor has been constructed for ultra-sensitive detection of lead ions (Pb2+) by square wave anodic stripping voltammetry (SWASV), based on the copper sulfide/graphitic carbon nitride nanocomposite modified glassy carbon electrode (CuS/g-C3N4/GCE). First, spherical CuS nanoparticles with good electrical conductivity were anchored on layered g-C3N4 with high coordination activity, affording an excellent electrode modifier CuS/g-C3N4 nanocomposite. Then, the performance of the CuS/g-C3N4/GCE and its electrochemical response to Pb2+ were thoroughly studied, and the sensing mechanism was investigated. On the one hand, the CuS/g-C3N4 nanocomposite has greatly improved the electron transportation and electrode performance through functional complementarity - CuS endows g-C3N4 with a good electrical conductivity and a large active specific surface area, while g-C3N4 endows CuS with high dispersibility and strong adsorption. On the other hand, the CuS/g-C3N4 modifier has effectively promoted the deposition of trace Pb2+ from the solution onto the electrode surface by means of synergistic enrichment (crucial for amplification of detection signals) - g-C3N4 can coordinate with Pb2+ by its large number of conjugated triazine heterocyclic rings in its molecular framework, while CuS can adsorb Pb2+ due to its inherent size effect of nanomaterials. The proposed sensor can efficiently detect Pb2+ in the concentration range of 0.050-5.000 µM with a limit of detection (LOD) as low as 4.00 nM, and can be well applied for the detection of trace Pb2+ in actual tea samples.

Effect of aroma-producing yeasts in high-salt liquid-state fermentation soy sauce and the biosynthesis pathways of the dominant esters.

Fermentation with excellent aroma-producing yeasts can enhance the flavour of soy sauce. In this work, Millerozyma farinosa CS2.23, Zygosaccharomyces rouxii CS2.42, and Candida parapsilosis CS2.53 were added to the high-salt liquid-state moromi to promote soy sauce fermentation. All three yeasts improved the TE of soy sauce, the highest of which reached 1.03 g/L with added CS2.42. Other quality indexes of soy sauce, including RS, TA, and AN, were not greatly affected. The volatile esters of soy sauce added to the three yeasts increased by 108.85%, 166.71%, and 113.61% compared with the control through GC-MS analysis. Obviously, CS2.42 had an excellent ability to produce esters. Studying the biosynthesis pathway of esters, CS2.42 has the best esterification ability, while CS2.53 has the advantage of alcoholysis ability. The exploration of the biosynthetic pathway of acetate and ethyl esters has laid a foundation for regulating esters in soy sauce fermentation.