Cloning of a gene encoding glycosyltransferase from Pueraria lobata (Wild.) Ohwi and its expression in Pichia pastoris

The key enzyme of puerarin biosynthesis in Pueraria lobata (Willd.) Ohwi was unclear but may involve glycosylation. To investigate the regulation of puerarin biosynthesis, a putative UDP-dependent glycosyltransferase (UGT) gene, PlUGT1 was isolated from P. lobata root, which contained abundant puerarin. PlUGT1 encoded 480 deduced amino acid residues with a conserved UDP-glucose-binding domain, which has 61 to 84% similarity to homologues from other plant species. SDS polyacrylamide gel electrophoresis and western blotting results showed that, fusion protein migrated as a single protein band with a molecular weight of 55 kDa. A yeast expression vector pPICZA-PlUGT1 was constructed and was transformed into Pichia pastoris strain GS115. Several recombinants containing multi-copy expression cassettes were obtained on the zeocin-YPD plate and confirmed by southern dot blotting. The yield of PlUGT1 attained 0.05 g/l when recombinant cells were cultured at pH 5.5, 30°C and induced with 0.5% methanol for 72 h. The expression of PlUGT1 protein correlates positively with the copy numbers of PlUGT1 in transformed yeast cells. These results suggest that, the PlUGT1 protein can be expressed efficiently in the P. pastoris expression system and may supply a new economic and convenient way for the production of PlUGT1 protein.Keywords: Pueraria lobata (Willd.) Ohwi, glycosyltransferase, cloning, expression, Pichia pastori

Interaction of whey protein with polyphenols from salal fruits (Gaultheria shallon) and the effects on protein structure and hydrolysis pattern by Flavourzyme®

This work is part of the Strategic Research Programme 2016-2021 and is funded by the Scottish Government's Rural and Environment Science and Analytical Services Division (RESAS). This work was also supported by Guangdong Provincial Science and Technology Program (No. 2017A030310031).Peer reviewedPostprin

Active arc suppression device based on voltage-source convertor with consideration of line impedance in distribution networks

Abstract In the non‐effectively grounding distribution system, residual current under single‐line‐to‐ground (SLG) fault threatens the safety of human being and power supply equipment. Active arc suppression device has been proved to be effective for SLG fault arc suppression when the line impedance is ignored. However, in practice, line impedance varies with the fault location and the load current flowing through the impedance brings about additional voltage drop, which increases the fault current and is not dealt with by the conventional methods. To achieve accurate SLG fault arc suppression with the existence of line impedance, the neutral‐to‐ground voltage reference for full ground‐fault current compensation is firstly derived and a detection method is then proposed. The pre‐fault and post‐fault line currents are used to eliminate the influence of load current on the line impedance voltage drop. A dual‐loop voltage and current controller is then designed. The prototype of active arc suppression device was developed. The results of simulation and prototype experiment validate the effectiveness of the proposed method

A new, improved method to identify reaction mechanisms based on the shape of derivative thermogravimetric curves

This study firstly presents a summary of using differential thermogravimetric (DTG) data for identifying reaction mechanisms of solid-state reactions. It shows that applying features delineated in currently-used models for initial and final temperatures are problematic during the classification of reaction mechanisms. Secondly, it develops a relationship linking the number of distinct peaks in second derivative thermogravimetric (DDTG) curves for selecting reaction mechanisms. An analysis is also given discussing the maximum conversion rates and relevant values of half widths in DTG curves, and recommends modified limits of these parameters which cover a greater majority of solid-state reactions. Based on the revised parameters, a new flow chart is developed to define reaction mechanisms. This flow chart is applied to the experimental combustion of three different of coal samples for which data analyses proved to be simple and reliable, and then from which distinct reaction mechanisms were determined successfully

Determination of smoke point of laminar acetylene diffusion flames under subatmospheric pressures

An experimental study on smoke point of acetylene laminar jet diffusion flames was performed in a chamber with sub-atmospheric pressures of 0.03–0.1 MPa. A combined normal video and the CH filtering technique were employed in the flame image recording to facilitate determining the smoke point. The measured smoke point flame height, fuel flow rate, and residence time was found to vary with pressure to power laws. In this article, both jet inertia and buoyancy effects were considered for calculating smoke point residence time of reacting jets

Using Fuzzy C-Means Clustering to Determine First Arrival of Microseismic Recordings

Accurate and automatic first-arrival picking is one of the most crucial steps in microseismic monitoring. We propose a method based on fuzzy c-means clustering (FCC) to accurately divide microseismic data into useful waveform and noise sections. The microseismic recordings’ polarization linearity, variance, and energy are employed as inputs for the fuzzy clustering algorithm. The FCC produces a membership degree matrix that calculates the membership degree of each feature belonging to each cluster. The data section with the higher membership degree is identified as the useful waveform section, whose first point is determined as the first arrival. The extracted polarization linearity improves the classification performance of the fuzzy clustering algorithm, thereby enhancing the accuracy of first-arrival picking. Comparison tests using synthetic data with different signal-to-noise ratios (SNRs) demonstrate that the proposed method ensures that 94.3% of the first arrivals picked have an error within 2 ms when SNR = −5 dB, surpassing the residual U-Net, Akaike information criterion, and short/long time average ratio approaches. In addition, the proposed method achieves a picking accuracy of over 95% in the real dataset tests without requiring labelled data