No abstract

Compact-siro spinning is a new kind of spinning technique that combines compact spinning and siro spinning, and is widely put into practice. In this paper, a simulation and characterization of the flow field in the condensing zone are made by computational fluid dynamics software. It mainly includes the distribution rules of static pressure and velocity. According to the relative references and factory condition, several orthogonal and control experiments have been done. Through testing the strength, evenness and hairiness properties and analyzing and comparing the results with the data of three different suction slots, we select the compact-siro spinning suction device whose yarn has the best overall performance. The theory analysis gives foundation and explanation for the experiment, and also provides a theoretical basis for optimizing the properties of compact-siro yarn in production practice.Compact-siro spinning 1 is a new kind of spinning technique that combines compact spinning 2 and siro spinning, 3 and is widely put into practice. Siro spinning parallelly feeds two rovings with a certain pitch into the same drafting zone of the spinning frame. Then the two rovings are twisted on one spindle after the draft parallelly. The structure of siro spun yarn is similar to plied yarn, with good strength, hairiness 4 and evenness properties. However, it has disadvantage of worse twist stability and indistinctive plied yarn characteristic. As previous research shows, the compact spinning system 5 can decrease the twisting triangle zone and make the fiber tangled. Therefore, considering the advantage of the two spinning techniques, compactsiro spinning can give the yarn a stable and obvious twisting structure under negative pressure. 6 Yang 7 studied an advanced spinning technology that combined compact spinning and siro-spinning in a traditional ring spinning machine. Wang 8 studied the spinning mechanism and the yarn structure of compact-siro spinning. Wang 9 made a systematic analysis for the causes of the increase in compact-siro spun yarn strength, evenness and the decrease in hairiness in theory. Lu 10 studied influences of airflow on fiber movement on compact-siro spinning with a lattice apron. If the technique is mature enough, it will result in savings in cost, energy and labor force, leading to better market prospects. In this paper, the numerical simulation of airflow in the condensing zone of compact-siro spinning is studied, and the impact factors of the agglomeration effects are analyzed. The comprehensive performances of three different suction slots are compared, and the compact-siro spinning suction device whose yarn has the best overall performance is selected.

No abstract

Background Adding acid protease to feed can enhance protein digestibility, boost feed utilization, and stimulate the growth of animals in breading industry. In order to obtain an acid protease with high hydrolysis efficiency to plant protein, in this study, an aspartic protease from Aspergillus niger was heterologous expressed in Pichia pastoris (P. pastoris). The enzymatic properties and application in soybean protein degradation were also studied. Results In our investigation, the high aspartic protease (Apa1) activity level of 1500 U/mL was achieved in 3 L bioreactor. After dialysis and anion exchange chromatography, the total enzyme activity and specific enzyme activity were 9412 U and 4852 U/mg, respectively. The molecular weight of the purified protease was 50 kDa, while the optimal pH and temperature were 3.0 and 50 °C, respectively. It was stable at pH 2.0–5.0 and 30–60 °C. Apa1 was used to hydrolyze soybean isolate protein (SPI) at 40 °C and pH 3.0, and a high hydrolysis degree (DH) of 61.65% was achieved. In addition, the molecular weight distribution of SPI hydrolysis products was studied, the result showed that the hydrolysis products were primarily oligopeptides with molecular weights of 189 Da or below. Conclusions In this study, Apa1 was successfully expressed in P. pastoris and high expression level was obtained. In addition, the highest protein hydrolysis rate to SPI degradation so far was achieved. The acid protease in this study provides a new protease that is suitable for the feed industry, which will be very helpful to improve the feed utilization and promote the development of the breeding industry.

No abstract