The effects of deletion of cellobiohydrolase genes on carbon source-dependent growth and enzymatic lignocellulose hydrolysis in Trichoderma reesei

Ren Meibin,Wang Yifan,Liu Guoxin,Zuo Bin,Zhang Yuancheng,Wang Yunhe,Liu Weifeng,Liu Xiangmei,Zhong Yaohua 한국미생물학회 2020 The journal of microbiology Vol.58 No.8

The saprophytic fungus Trichoderma reesei has long been used as a model to study microbial degradation of lignocellulosic biomass. The major cellulolytic enzymes of T. reesei are the cellobiohydrolases CBH1 and CBH2, which constitute more than 70% of total proteins secreted by the fungus. However, their physiological functions and effects on enzymatic hydrolysis of cellulose substrates are not sufficiently elucidated. Here, the cellobiohydrolase-encoding genes cbh1 and cbh2 were deleted, individually or combinatively, by using an auxotrophic marker-recycling technique in T. reesei. When cultured on media with different soluble carbon sources, all three deletion strains (Δcbh1, Δcbh2, and Δcbh1Δcbh2) exhibited no dramatic variation in morphological phenotypes, but their growth rates increased apparently when cultured on soluble cellulase-inducing carbon sources. In addition, Δcbh1 showed dramatically reduced growth and Δcbh1Δcbh2 could hardly grew on microcrystalline cellulose (MCC), whereas all strains grew equally on sodium carboxymethyl cellulose (CMC-Na), suggesting that the influence of the CBHs on growth was carbon source-dependent. Moreover, five representative cellulose substrates were used to analyse the influence of the absence of CBHs on saccharification efficiency. CBH1 deficiency significantly affected the enzymatic hydrolysis rates of various cellulose substrates, where acid pre-treated corn stover (PCS) was influenced the least. CBH2 deficiency reduced the hydrolysis of MCC, PCS, and acid pre-treated and delignified corncob but improved the hydrolysis ability of filter paper. These results demonstrate the specific contributions of CBHs to the hydrolysis of different types of biomass, which could facilitate the development of tailor-made strains with highly efficient hydrolysis enzymes for certain biomass types in the biofuel industry.

Torsional Vibration Analysis of Hydro-Generator Set Considered Electromagnetic and Hydraulic Vibration Resources Coupling

Zhiqiang Song,Yunhe Liu,Pengcheng Guo,Jianjun Feng 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.7

The torsional vibration characteristics of the hydro-generator set considering the electromagnetic and hydraulic vibration resources coupling are studied. The moment of rotation consists of water flow driving and magnetic torques caused by the air gap magnetic field in the generator rotor in the case of ignoring the mechanical friction. A coupling torque vibration model of hydro-generator shaft system was established. The model considered the coupling action of hydraulic and electromagnetic excitations, as well as the elastic effect of rotor spiders. The influences of the rotor moment inertia, rotor stiffness, and mass of turbine water added into the torsional natural vibration of the unit shaft system were studied. The effect of hydraulic excitation frequency on torsional vibration response was also investigated. The frequency response curves of shaft torque, torsional vibration angle, and electromagnetic torque were presented. The electromagnetic and hydraulic coupling resonance was studied when hydraulic excitation frequency was equal to zero and first-order frequencies. The excitation electric current and internal active power angle on torsional vibration was further analyzed. This study provides an analysis model and method considering the coupling of electromagnetic and hydraulic vibration resources for design and stable operation of water turbine generator sets.

Experimental and Analytical Study of Eccentrically Braced Frames Combined with High-Strength Steel

Shen Li,Yunhe Liu,JianBo Tian 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.2

In the structure of high-strength steel composite eccentrically braced steel frames (HSS–EBFs), the links and braces are made of Q345 steel, while the non-energy-dissipation segments (columns and beams) are made of high-strength steel (HSS). HSS reduces the cross-section of the members and increases the economic effi ciency. Here, four groups of K-HSS–EBFs are designed by performance-based plastic design method in this paper, which includes 5-storey, 10-storey, 15-storey and 20-storey, and each group contain four diff erent link length (900, 1000, 1100 and 1200 mm). The cyclic test loading was applied to 1:2 scale three-storey K-type HSS–EBFs (K-HSS–EBFs) with shear links to investigate their seismic performance. The results indicate that the as-prepared K-HSS–EBF structure exhibits excellent bearing capacity, ductility, and energy dissipation. We also fi nd that the fracture of the link web in the second storey led to the degradation of the load-carrying capacity. The non-designated yield members remained in the elastic stage, whereas the links ultimately experience inelastic rotations, and thus dissipate the energy in the K-HSS–EBFs. Moreover, nonlinear pushover analyses and nonlinear dynamic analyses are conducted, and the loading capacity, link rotations, ductility, interstory drifts and failure mode under rare earthquake of all models are compared. The results indicate that K-HSS–EBFs with diff erent link length have similar deformation characteristic and failure mode under pushover analysis or rare earthquakes, and the interstory drifts, link rotations and ductility of HSS–EBFs are increased with rising the link length.

Effects of xylanase supplementation to wheat-based diets on growth performance, nutrient digestibility and gut microbes in weanling pigs

Dong, Bing,Liu, Shaoshuai,Wang, Chunlin,Cao, Yunhe Asian Australasian Association of Animal Productio 2018 Animal Bioscience Vol.31 No.9

Objective: This study was designed to investigate the effects of an Aspergillus sulphureus xylanase expressed in Pichia pastoris on the growth performance, nutrient digestibility and gut microbes in weanling pigs. Methods: A total of 180 weanling pigs (initial body weights were $8.47{\pm}1.40kg$) were assigned randomly to 5 dietary treatments. Each treatment had 6 replicates with 6 pigs per replicate. The experimental diets were wheat based with supplementation of 0, 500, 1,000, 2,000, and 4,000 U xylanase/kg. The experiment lasted 28 days (early phase, d 0 to 14; late phase, d 15 to 28). Results: In the early phase, compared to the control, average daily gain (ADG) was higher for pigs fed diets supplemented with xylanase and there was a quadratic response in ADG (p<0.05). In the entire phase, ADG was higher for the pigs fed 1,000 or 2,000 U/kg xylanase compared to the control (p<0.05). The gain to feed ratio was higher for pigs fed diets supplemented with 1,000 or 2,000 U/kg xylanase compared to the control (p<0.05). Increasing the amount of xylanase improved the apparent total tract digestibility of dry matter, crude protein, neutral detergent fiber, calcium, and phosphorus during both periods (p<0.05). Xylanase supplementation (2,000 U/kg) decreased the proportion of Lachnospiraceae (by 50%) in Firmicutes, but increased Prevotellaceae (by 175%) in Bacteroidetes and almost diminished Enterobacteriaceae (Escherichia-Shigella) in Proteobacteria. Conclusion: Xylanase supplementation increased growth performance and nutrient digestibility up to 2,000 U/kg. Supplementation of xylanase (2,000 U/kg) decreased the richness of gut bacteria but diminished the growth of harmful pathogenic bacteria, such as Escherichia-Shigella, in the colon.

Study on Mechanical Properties of Press-Bending Members Based on Transmission Towers Diagonal Member Reinforcement In-Situ

Zhenke Xin,Huanhuan Wei,Yunhe Liu,Gang Liang 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.4

According to the reinforcement requirements of load-bearing members of existing transmission tower, a new type of in-situ reinforcement scheme for the angle steel T-shaped composite section is proposed. Through the compression test of 10 groups of members, the infl uence of slenderness ratio, the number of fi xtures, the number of bolt rows and other parameters on the failure mode and bearing performance of members was studied. A simulation model was established using ABAQUS software, the load-displacement curve, failure models and other aspects verify the reliability and validity of simulation results. The results show that when the slenderness ratio of member reaches a certain value, the ultimate bearing capacity of member reinforced with the reinforcement angle steel of same specifi cation and strength can be multiplied and increased several times, the slenderness ratio has little eff ect on the force transmission effi ciency of reinforcement angle steel. The number of bolt rows has a small eff ect on the ultimate bearing capacity of member, the increase rate of ultimate bearing capacity, the failure mode and the force transmission effi ciency of reinforcement angle steel, the infl uence of strength of reinforcement angle steel, the specifi cation of reinforcement angle steel on the ultimate bearing capacity, and the increase rate of ultimate bearing capacity of member obviously, the higher strength and specifi cation of reinforcement, the greater the ultimate bearing capacity of reinforced member, and the higher the rate of improvement of ultimate bearing capacity, the smaller the thickness of fi ller plate, that is the smaller the eccentricity, the higher force transmission effi ciency of reinforcement. The research results can provide experimental and theoretical basis for the reinforcement of tower structure and engineering design.

Compressive performance of RAC filled GFRP tube-profile steel composite columns under axial loads

Ma, Hui,Bai, Hengyu,Zhao, Yanli,Liu, Yunhe,Zhang, Peng Techno-Press 2019 Advances in concrete construction Vol.8 No.4

To investigate the axial compressive performance of the recycled aggregate concrete (RAC) filled glass fiber reinforced polymer (GFRP) tube and profile steel composite columns, static loading tests were carried out on 18 specimens under axial loads in this study, including 7 RAC filled GFRP tube columns and 11 RAC filled GFRP tube-profile steel composite columns. The design parameters include recycled coarse aggregate (RCA) replacement percentage, profile steel ratio, slenderness ratio and RAC strength. The failure process, failure modes, axial stress-strain curves, strain development and axial bearing capacity of all specimens were mainly analyzed in detail. The experimental results show that the GFRP tube had strong restraint ability to RAC material and the profile steel could improve the axial compressive performance of the columns. The failure modes of the columns can be summarized as follow: the profile steel in the composite columns yielded first, then the internal RAC material was crushed, and finally the fiberglass of the external GFRP tube was seriously torn, resulting in the final failure of columns. The axial bearing capacity of the columns decreased with the increase of RCA replacement percentage and the maximum decreasing amplitude was 11.10%. In addition, the slenderness ratio had an adverse effect on the axial bearing capacity of the columns. However, the strength of the RAC material could effectively improve the axial bearing capacity of the columns, but their deformability decreased. In addition, the increasing profile steel ratio contributed to the axial compressive capacity of the composite columns. Based on the above analysis, a formula for calculating the bearing capacity of composite columns under axial compression load is proposed, and the adverse effects of slenderness ratio and RCA replacement percentage are considered.

Shear behavior of composite frame inner joints of SRRC column-steel beam subjected to cyclic loading

Hui Ma,Sanzhi Li,Zhe Li,Yunhe Liu,Jing Dong,Peng Zhang 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.27 No.4

In this paper, cyclic loading tests on composite frame inner joints of steel-reinforced recycled concrete (SRRC) column.steel beam were conducted. The main objective of the test was to obtain the shear behavior and analyze the shear strength of the joints. The main design parameters in the test were recycled coarse aggregate (RCA) replacement percentage and axial compression ratio. The failure process, failure modes, hysteresis curves and strain characteristics of the joints were obtained, and the influences of design parameters on the shear strength of the joints have been also analysed in detail. Results show that the failure modes of the joints area are typical shear failure. The shear bearing capacity of the joints maximally decreased by 10.07% with the increase in the RCA replacement percentage, whereas the shear bearing capacity of the joints maximally increased by 16.6% with the increase in the axial compression ratio. A specific strain analysis suggests that the shear bearing capacity of the joints was mainly provided by the three shear elements of the recycled aggregate concrete (RAC) diagonal compression strut, steel webs and stirrups of the joint area. According to the shear mechanism and test results, the calculation formulas of the shear bearing capacity of the three main shear elements were deduced separately. Thus, the calculation model of the shear bearing capacity of the composite joints considering the adverse effects of the RCA replacement percentage was established through a superposition method. The calculated values of shear strength based on the calculation model were in good agreement with the test values. It indicates that the calculation method in this study can reasonably predict the shear bearing capacity of the composite frame inner joints of SRRC column–steel beam.

Numerical analysis and horizontal bearing capacity of steel reinforced recycled concrete columns

Hui Ma,Jian-yang Xue,Yunhe Liu,Jing Dong 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.22 No.4

This paper simulates the hysteretic behavior of steel reinforced recycled concrete (SRRC) columns under cyclic loads using OpenSees software. The effective fiber model and displacement-based beam-column element in OpenSees is applied to each SRRC columns. The Concrete01 material model for recycled aggregate concrete (RAC) and Steel02 material model is proposed to perform the numerical simulation of columns. The constitutive models of RAC, profile steel and rebars in columns were assigned to each fiber element. Based on the modelling method, the analytical models of SRRC columns are established. It shows that the calculated hysteresis loops of most SRRC columns agree well with the test curves. In addition, the parameter studies (i.e., strength grade of RAC, stirrups strength, steel strength and steel ratio) on seismic performance of SRRC columns were also investigated in detail by OpenSees. The calculation results of parameter analysis show that SRRC columns suffered from flexural failure has good seismic performance through the reasonable design. The ductility and bearing capacity of columns increases as the increasing magnitude of steel strength, steel ratio and stirrups strength. Although the bearing capacity of columns increases as the strength grade of RAC increases, the ductility and energy dissipation capacity decreases gradually. Based on the test and numerical results, the flexural failure mechanism of SRRC columns were analysed in detail. The computing theories of the normal section of bearing capacity for the eccentrically loaded columns were adopted to calculate the nominal bending strength of SRRC columns subjected to vertical axial force under lateral cyclic loads. The calculation formulas of horizontal bearing capacity for SRRC columns were proposed based on their nominal bending strength.

Finite element analysis and axial bearing capacity of steel reinforced recycled concrete filled square steel tube columns

Jing Dong,Hui Ma,Changming Zou,Yunhe Liu,Chen Huang 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.72 No.1

This paper presents a finite element model which can simulate the axial compression behavior of steel reinforced recycled concrete (SRRC) filled square steel tube columns using the ABAQUS software. The analytical model was established by selecting the reasonable nonlinear analysis theory and the constitutive relationship of material in the columns. The nonlinear analysis of failure modes, deformation characteristics, stress nephogram, and load-strain curves of columns under axial loads was performed in detail. Meanwhile, the influences of recycled coarse aggregate (RCA) replacement percentage, profile steel ratio, width thickness ratio of square steel tube, RAC strength and slenderness ratio on the axial compression behavior of columns were also analyzed carefully. It shows that the results of finite element analysis are in good agreement with the experimental results, which verifies the validity of the analytical model. The axial bearing capacity of columns decreased with the increase of RCA replacement percentage. While the increase of wall thickness of square steel tube, profile steel ratio and RAC strength were all beneficial to improve the bearing capacity of columns. Additionally, the parameter analysis of finite element analysis on the columns was also carried out by using the above numerical model. In general, the SRRC filled square steel tube columns have high bearing capacity and good deformation ability. On the basis of the above analysis, a modified formula based on the American ANSI/AISC 360-10 was proposed to calculate the nominal axial bearing capacity of the columns under axial loads. The research conclusions can provide some references for the engineering application of this kind of columns.

Enhanced recovery after surgery strategy for cirrhosis patients undergoing hepatectomy: experience in a single research center

Yiling Zheng,Liming Wang,Fan Wu,Weiqi Rong,Yunhe Liu,Kai Zhang,Jianxiong Wu 대한외과학회 2020 Annals of Surgical Treatment and Research(ASRT) Vol.98 No.5

Purpose: To evaluate the safety and effectiveness of an enhanced recovery after surgery (ERAS) programme after curative liver resection in cirrhotic hepatocellular carcinoma (HCC) patients. Methods: One hundred sixty-two patients were enrolled in the study; 80 patients whose data were collected prospectively were assigned to the ERAS group, and 82 patients whose data were collected retrospectively were assigned to the control group. Preoperative clinicopathologic factors, surgical factors, and postoperative outcomes of the 2 groups were compared. Logistic regression was applied to explore potential predictors of hospital stay and morbidity. Results: The postoperative hospital stay, postoperative complication rate, and recovery of liver function on postoperative day 5 seemed to be better in the ERAS group. The composition of complications was different in the 2 groups; pleural effusion and postoperative ascites were more common in the control group, and indocyanine green retention at 15 minutes, operation time, preoperative alanine aminotransferase, and number of liver segmentectomies were associated with postoperative complications rather than ERAS intervention. Conclusion: The ERAS programme is safe and effective for HCC patients with chronic liver disease undergoing hepatectomy, but it seems that surgical factors, such as operation type, have a greater impact on morbidity than other factors. Operative characteristics such as the method of blood loss control and the volume of liver resection should be augmented into ERAS protocol of hepatectomy.