Efficient elimination and detection of phenolic compounds in juice using laccase mimicking nanozymes

Residual phenols in the juice can cause turbidity and affect its sensory quality.Laccase is used to remove phenolic compounds from fruit juice s.In order to overcome the shortcomings of natural laccase instability and high cost,in this work,we prepared a laccase mimic enzyme based on copper ion and adenosine monophosphate(AMP-Cu nanozymes).At the same mass concentration(1 mg·ml^(-1)), the catalytic activity of the nanozyme is about 15 times that of laccase.The AMP-Cu nanozymes had a higher V_(max) and a lower Km than laccase.The laccase mimic enzyme had a good stability under the condition of 30-90 ℃ and pH> 6.It also maintained high catalytic activity at high salt concentrations and 9 days storage time.Furthermore,the AMP-Cu nanozyme s maintained an initial catalytic activity of about 80% after six consecutive cycles of reaction.The linear range of detection of phenolic compounds by AMP-Cu nanozymes was 0.1-100 μmol·L^(-1) with a detection limit of 0.033 μmol·L^(-1).The phenol removal rate of AMP-Cu nanozymes was much higher than that of laccase under different reaction times.When the reaction was performed for 5 h,the phenol removal rate of the fruit juice by AMP-Cu nanozymes was about 65%.The efficient removal of phenolic compounds from different juices by AMP-Cu nanozymes indicate s that they have good application prospect in the food juice industry.

Construction of a Shuttle Vector for Heterologous Gene Expression in Escherichia coli and Microalgae Anabaena

Theconstruction of an integrative shuttle expression vector and potential utility was reported inEscherichiacoliandAnabaena(Nostoc) sp. strain PCC 7120. The vector comprised of the following elements: (a) an intergenic non-coding region fromAnabaenato facilitate its genomic integration (b) a strong functional PpsbAIpromoter fromAnabaenafor desired gene expression and (c) neomycin phosphotransferase gene with its own promoter for the selection of transfor-mants. The constructed vectorpAnFP was evaluated by cloning, transfer and expression of thegfpgene encoding green fluorescent protein. When theE.coliandAnabaenasp. strain PCC 7120 were transformed, intensive green fluorescence produced by the products of GFP protein was observed. This result indicated that the integrative shuttle vector pAnFP can be promisingly used in genome transformation for expression of heterologous genes inE.coliand microalgae such asAnabaenaandNostocstrains.

A Continuous Fault Ride-through Scheme for DFIGs Under Commutation Failures in LCC-HVDC Transmission Systems

Experimental and theoretical studies have confirmed that,relative to a one-shot voltage fault,a doubly-fed induction generator(DFIG)will suffer a greater transient impact during continuous voltage faults.This paper presents the design and application of an effective scheme for DFIGs when a commutation failure(CF)occurs in a line-commutated converter based high-voltage direct current(LCC-HVDC)transmission system.First,transient demagnetization control without filters is proposed to offset the electromotive force(EMF)induced by the natural flux and other low-frequency flux components.Then,a rotor-side integrated impedance circuit is designed to limit the rotor overcurrent to ensure that the rotor-side converter(RSC)is controllable.Furthermore,coordinated control of the demagnetization and segmented reactive currents is implemented in the RSC.Comparative studies have shown that the proposed scheme can limit rotor fault currents and effectively improve the continuous fault ride-through capability of DFIGs.