A highly-sensitive sensor based on carbon nanohorns@reduced graphene oxide coated by gold platinum core-shell nanoparticles for electrochemical detection of carbendazim in fruit and vegetable juice.

Carbendazim (CBZ) is beneficial to fruit and vegetable cultivation, but its residue will cause fruit and vegetable juice pollution. In this work, an electrochemical sensor based on carbon nanohorns@reduced graphene oxide coated by gold platinum core-shell nanoparticles (Au@Pt/CNHs@RGO/GCE) was prepared for CBZ detection. The results showed that the assembly of CNHs and RGO assisted by ultrasound improved the electron transfer ability and electrochemical active surface area of CNHs@RGO. Moreover, the coating of Au@Pt nanoparticles further enhanced the sensitivity of the sensor. With the synergistic effect of the three materials, the sensor had a wider linear range (0.05 µmol/L-50 µmol/L), a lower limit of detection (1.64 nmol/L), and satisfactory recovery rates (90.60 % ∼ 97.60 %, carrot juice; 94.00-114.43 %, orange juice). Additionally, the sensor presented good anti-interference and repeatability. This work provides a simple, rapid, economical, sensitive, and accurate sensor for CBZ quantification in fruit and vegetable juice.

Inhibition of Fusarium graminearum growth and deoxynivalenol accumulation in barley malt by protonated g-C3N4/oxygen-doped g-C3N4 homojunction.

Barley malt, the main raw material for beer production, is at risk of Fusarium graminearum (F. graminearum) infection, leading to the possible production of large amounts of deoxynivalenol (DON) in malt. DON in malt can migrate into the final beer product, posing a food safety risk to consumers. In our work, a protonated g-C3N4/oxygen-doped g-C3N4 (CNH/OCN) composite was prepared and used for the inhibition of F. graminearum growth and DON accumulation in barley malt under visible light irradiation. The results showed that the inhibition rate of F. graminearum reached 100 % after 2.5 h of visible light irradiation, and the inhibition effect was still stable after 3 rounds of reuse. The possible pathway of inhibiting F. graminearum spores was that the photogenerated carriers in the CNH/OCN composite transferred in the form of a type II homojunction under visible light and stimulated O2 in the catalytic system to produce a large amount of O2- to kill spores. Compared with the untreated malt, the photocatalytic inhibition rates of the CNH/OCN composite material for ergosterol and DON in malt reached 73.33 % and 67.25 %, respectively. Although photocatalysis had a certain effect on the physicochemical indices of malt, the malt after photocatalysis still met the first-grade standard of Chinese industry standard QB/T 1686-2008.

Enhancement Effect of Chitosan Coating on Inhibition of Deoxynivalenol Accumulation by Litsea cubeba Essential Oil Emulsion during Malting.

The purpose of this work was to study the enhancement effect of chitosan coating on inhibition of deoxynivalenol (DON) accumulation by Litsea cubeba essential oil emulsion during malting. Firstly, the primary emulsion suitable for malting process was screened and the improvement effect of chitosan coating on the properties of primary emulsion was studied. On this basis, chitosan-based Litsea cubeba essential oil emulsion was applied to malting processing. The results showed that the primary emulsion of Litsea cubeba essential oil had good antifungal properties and a minimal effect on the germinability of barley compared with other primary emulsions. The addition of chitosan can improve the physical stability and antifungal ability of the emulsion and reduce the effect of the emulsion on barley germination. When 100 g of chitosan-based Litsea cubeba essential oil emulsion (40 mg/g) was applied to the malting process, the germination rate of barley was 87.7% and the DON concentration of finished malt was reduced to 690 µg/kg, which was 20.9% lower than that of the control. Meanwhile, the other indexes of malt produced by secondary emulsion treatment (after adding chitosan) increased significantly compared with those of malt produced by primary emulsion. This study was of great significance for the application of emulsion to inhibit the accumulation of mycotoxin during malting.

High efficiency preparation and characterization of intact poly(vinyl alcohol) dehydrogenase from Sphingopyxis sp.113P3 in Escherichia coli by inclusion bodies renaturation.

Poly(vinyl alcohol) dehydrogenase (PVADH, EC 1.1.99.23) is an enzyme which has potential application in textile industry to degrade the poly(vinyl alcohol) (PVA) in waste water. Previously, a 1,965-bp fragment encoding a PVADH from Sphingopyxis sp. 113P3 was synthesized based on the replacement of the rare codons in Escherichia coli (E. coli). In this work, the deduced mature PVADH (mPVADH) gene of 1,887 bp was amplified by polymerase chain reaction (PCR) and inserted into the site between NcoI and HindIII in pET-32a(+). The constructed recombinant plasmid was transformed into E. coli Rosetta (DE3). In shake flask, the fusion protein of thioredoxin (Trx)-mPVADH was expressed precisely; however, Trx-mPVADH was found to accumulate mainly as inclusion bodies. After isolating, dissolving in buffer containing urea, purification, dialysis renaturation, and digesting with recombinant enterokinase/His (rEK/His), the bioactive mPVADH fragments were obtained with protein concentration of 0.56 g/L and enzymatic activity of 194 U/mL. The K m and V max values for PVA 1799 were 2.33 mg/mL and 15.7 nmol/(min·mg protein), respectively. (1)H-NMR and infrared (IR) spectrum demonstrated that its biological function was oxidizing hydroxyl groups of PVA 1799 to form diketone, and PVA 1799 could be degraded completely by successive treatment with mPVADH and oxidized PVA hydrolase (OPH).