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Yang Chengwei,Zhang Ting,Zhu Jing,Wei Yunyi,Zhu Furong,Cheng Zhong 한국미생물·생명공학회 2023 Journal of microbiology and biotechnology Vol.33 No.4
Exo-polygalacturonase (exo-PG) hydrolyzes pectin acids and liberates mono-galacturonate, which plays an important role in juice extraction, and has rarely been reported. Exo-PG (AfumExoPG28A) from Aspergillus fumigatus belongs to the glycoside hydrolase 28 family. In this study, its gene was cloned and the protein was expressed and secreted in Pichia pastoris with a maximal activity of 4.44 U/ml. The optimal temperature and pH of AfumExoPG28A were 55°C and 4.0, respectively. The enzyme exhibited activity over almost the entire acidic pH range (>20.0% activity at pH 2.5-6.5) and remained stable at pH 2.5–10.0 for 24 h. The Km and Vmax values of AfumExoPG28A were calculated by the substrate of polygalacturonic acid as 25.4 mg/ml and 23.6 U/mg, respectively. Addition of AfumExoPG28A (0.8 U/mg) increased the light transmittance and juice yield of plantain pulp by 11.7% and 9%, respectively. Combining AfumExoPG28A (0.8 U/mg) with an endo-PG (0.8 U/mg) from our laboratory, the enzymes increased the light transmittance and juice yield of plantain pulp by 45.7% and 10%, respectively. Thus, the enzyme’s potential value in juice production was revealed by the remarkable acidic properties and catalytic activity in fruit pulp.
A novel preparation and formation mechanism of carbon nanotubes aerogel
Li Shaolong,He Yan,Jing Chengwei,Gong Xiubin,Cui Lianlei,Cheng Zhongyue,Zhang Chuanqi,Nan Fei 한국탄소학회 2018 Carbon Letters Vol.28 No.-
A novel, unique, and effective method for carbon nanotube (CNT) dispersion by the free arc stimulation is proposed. CNTs are introduced as an aerogel into the air space via the dispersion method and can be utilized as a solution by adding it to solvents. The volume of the original generated CNT aerogel with a high-volume expansion ratio displays a performance two orders of magnitudes better than that of raw CNTs, which is considered a powerful characterization of the dispersion effect. The CNT aerogel, which was observed by scanning electron microscopy also showed a satisfactory dispersion morphology. Its structure and properties were tested before and after dispersion by Raman spectroscopy and great consistency was observed, which proved that the CNTs were undamaged. This approach may greatly promote the large-scale application of CNTs.
( Bo Lu ),( Liang Xian ),( Jing Zhu ),( Yunyi Wei ),( Chengwei Yang ),( Zhong Cheng ) 한국미생물생명공학회 2022 Journal of microbiology and biotechnology Vol.32 No.4
An endo-polygalacturonase (endo-PGase) exhibiting excellent performance during acidic fruit juice production would be highly attractive to the fruit juice industry. However, candidate endo-PGases for this purpose have rarely been reported. In this study, we expressed a gene from Penicillium oxalicum in Pichia pastoris. The recombinant enzyme PoxaEnPG28C had an optimal enzyme activity at pH 4.5 and 45℃ and was stable at pH 3.0-6.5 and < 45℃. The enzyme had a specific activity of 4,377.65 ± 55.37 U/mg towards polygalacturonic acid, and the K<sub>m</sub> and V<sub>max</sub> values of PoxaEnPG28C were calculated as 1.64 g/l and 6127.45 U/mg, respectively. PoxaEnPG28C increased the light transmittance of orange, lemon, strawberry and hawthorn juice by 13.9 ± 0.3%, 29.4 ± 3.8%, 95.7 ± 10.2% and 79.8 ± 1.7%, respectively; it reduced the viscosity of the same juices by 25.7 ± 1.6%, 52.0 ± 4.5%, 48.2 ± 0.7% and 80.5 ± 2.3%, respectively, and it increased the yield of the juices by 24.5 ± 0.7%, 12.7 ± 2.2%, 48.5 ± 4.2% and 104.5 ± 6.4%, respectively. Thus, PoxaEnPG28C could be considered an excellent candidate enzyme for acidic fruit juice production. Remarkably, fruit juice production using hawthorn as an material was reported for the first time.