Rational design of a 500 m3 fermenter for erythromycin production by Saccharopolyspora erythraea / 生物工程学报

Erythromycin is a macrolide antibiotic produced by Saccharopolyspora erythraea. Its yield is greatly affected by the fermentation conditions and the bioreactor configurations. In this study, a novel scale-up method for erythromycin fermentation was developed based on computational fluid dynamics (CFD) and time constant analysis. Firstly, the dissolved oxygen (DO) was determined as a key parameter according to the physiological properties of S. erythraea cultivated in a 50 L bioreactor. It was found that the time constant of oxygen supply (tmt) in a 500 m3 bioreactor should be less than 6.25 s in order to satisfy the organism's oxygen uptake rate (OUR). Subsequently, a 500 m3 bioreactor was designed using the time constant method combined with empirical correlations. The impeller combination with one BDT8 impeller at bottom and two MSX4 impellers at upper part was determined, and then validated by numerical simulation. The results indicated that the tmt of the bioreactor (< 6.25 s) and the fluid properties, including gas hold-up, shear stress and fluid vector, met the requirements of erythromycin fermentation. Finally, the industrial production of erythromycin in the 500 m3 showed the design method was applicable in large scale fermentation.

High-throughput "read-on-ski" automated imaging and label-free detection system for toxicity screening of compounds using personalised human kidney organoids / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Organoid models are used to study kidney physiology, such as the assessment of nephrotoxicity and underlying disease processes. Personalized human pluripotent stem cell-derived kidney organoids are ideal models for compound toxicity studies, but there is a need to accelerate basic and translational research in the field. Here, we developed an automated continuous imaging setup with the "read-on-ski" law of control to maximize temporal resolution with minimum culture plate vibration. High-accuracy performance was achieved: organoid screening and imaging were performed at a spatial resolution of 1.1 μm for the entire multi-well plate under 3 min. We used the in-house developed multi-well spinning device and cisplatin-induced nephrotoxicity model to evaluate the toxicity in kidney organoids using this system. The acquired images were processed via machine learning-based classification and segmentation algorithms, and the toxicity in kidney organoids was determined with 95% accuracy. The results obtained by the automated "read-on-ski" imaging device, combined with label-free and non-invasive algorithms for detection, were verified using conventional biological procedures. Taking advantage of the close-to-in vivo-kidney organoid model, this new development opens the door for further application of scaled-up screening using organoids in basic research and drug discovery.

Ultrasonographic features of cervical lymph node metastasis and their relationship with the expression of cell proliferation-associated nuclear antigen / 中国基层医药

Objective:To observe the ultrasonographic features of cervical lymph node metastasis and analyze their relationship with the expression of cell proliferation-associated nuclear antigen (Ki-67).Methods:The clinical data of 92 patients with cervical lymph node metastasis who received treatment in Zhejiang Quhua Hospital, China between June 2017 and July 2019 were retrospectively analyzed. The correlation between ultrasonographic features of cervical lymph node metastasis and Ki-67 expression was analyzed.Results:Among the 92 patients, 158 metastatic lymph nodes were confirmed by pathological examination. The main ultrasonic imaging features were the length ratio of long diameter to short diameter < 2 in 119 (75.32%) lymph nodes, disappearance of portal hyperechoic signal in 127 (80.38%) lymph nodes, punctate hyperechoic signal in 108 (68.35%) lymph nodes, cystic degeneration in 57 (36.08%) lymph nodes, mixed types of peripheral blood flow signal in 124 (78.48%) lymph nodes, microcalcification in 123 (77.85%) lymph nodes. The length ratio of long diameter to short diameter < 2, punctate hyperechoic signal and mixed types of peripheral blood flow signal were correlated with high expression of Ki-67 ( χ2 = 24.252, 15.732, 17.033, all P < 0.05). Conclusion:High expression of Ki-67 is correlated with the length ratio of long diameter to short diameter < 2, punctate hyperechoic signal and mixed types of peripheral blood flow signal in cervical lymph node metastasis.

Numerical simulation and optimization of impeller combination used in stirred bioreactor / 生物工程学报

Bioreactors have been central in monoclonal antibodies and vaccines manufacturing by mammalian cells in suspension culture. Numerical simulation of five impeller combinations in a stirred bioreactor was conducted, and characteristics of velocity vectors, distributions of gas hold-up, distributions of shear rate in the bioreactor using 5 impeller combinations were numerically elucidated. In addition, genetically engineered CHO cells were cultivated in bioreactor installed with 5 different impeller combinations in fed-batch culture mode. The cell growth and antibody level were directly related to the maximum shear rate in the bioreactor, and the highest viable cell density and the peak antibody level were achieved in FBMI3 impeller combination, indicating that CHO cells are sensitive to shear force produced by impeller movement when cells were cultivated in bioreactor at large scale, and the maximum shear rate would play key roles in scaling-up of bioreactor at industrial scale.

Rapid cryopreservation for Siraitia grosvenorii cells based on cells' capacitance detection / 生物工程学报

A rapid quantitative evaluation method for Siraitia grosvenorii cells was successfully developed based on plant cells' capacitance value detected by a viable cell mass monitor and the cryopreservation of S. grosvenorii suspension cells was optimized. The survival rate of S. grosvenorii cells was quantitatively measured by viable cell mass monitor and 2, 3, 5-triphenyltetrazolium chloride (TTC). An optimum cryoprotectant recipe is that the growth medium contained 10% sucrose and 10% DMSO. The experimental results also showed higher cell survival rates and cell viabilities were achieved when suspension cells were treated with pretreatment of 0.2 mol/L sucrose. With the increase of concentration of sucrose, however, the cell survival rate was decreased. And the cell survival rate represented a bell shape with the increase of pretreatment time. The highest cell survival rate and cell viability were obtained with the 9 h' s pretreatment. In addition, there was a good correlation between the cell survival rate measured by cell recovery test and that measured by viable cell mass monitor, while there were no significant differences in the cell morphology and the ability of mogrosides V production by S. grosvenorii cells cultured in suspension after cryopreservation. Therefore, the evaluation method developed based on the viable cell mass monitor has good feasibility and reliability.

Agrobacterium tumefaciens-mediated transformation of Aureobasidium pullulans and high-efficient screening for polymalic acid producing strain / 生物工程学报

To develop a genetic transformation method of Aureobasidium pullulans and T-DNA insertion for high-efficient screening of polymalic acid (PMA) producing strain. Agrobacterium tumefaciens-AGL1, containing the selection genes encoding hygromycin B phosphotase or phosphinothricin acetyltranferase, was used to transform Aureobasidium pullulans CCTCC M2012223 and transformants were confirmed by colony PCR method. Transferred DNA (T-DNA) insertional mutants were cultured in microwell plate, and screened for high-titer PMA producing strain according to the pH response model. DNA walking was used to detect the insertion sites in the mutant. Results show that the selection markers could stably generated in the transformants, and 80 to 120 transformants could be found per 10(7) single cells. A high-titer PMA mutant H27 was obtained, giving a good PMA production caused by the disruption of phosphoglycerate mutase, that increased by 24.5% compared with the control. Agrobacterium tumefaciens-mediated transformation and high-efficient screening method were successfully developed, which will be helpful for genetic transformation of Aureobasidium pullulans and its functional genes discovery.

Optimization and application of chemically defined medium for 13C metabolic flux analysis of Streptomyces rimosus M4018 / 生物工程学报

The aim of this study is to develop a synthetic medium suitable for 13C metabolic flux analysis (13C-MFA) of Streptomyces rimosus. The cell growth rate and oxytetracycline production by S. rimosus M4018 were compared when M4018 cells were growth on the optimized chemically defined media with organic nitrogen sources or inorganic nitrogen sources. First, a synthetic medium contained KNO3 as the main nitrogen source was screened, then optimized by a response surface method. Using this new medium, the oxytetracycline yield was increased from 75.2 to 145.6 mg/L. Furthermore, based on the 13C-MFA, we identified that Entner-Doudoroff pathway does not exist in S. rimosus cells cultured in a chemically defined medium with feed of 100% 1-13C labeled glucose. This study is helpful for subsequent 13C-MFA application of S. rimosus.

Metabolic characterization of rat sertoli cell in vitro culture / 生物工程学报

Sertoli cell (SC) is intrinsic to the testis and provides an appropriate growth environment for the germ cells. It was separated from rat's testis and identified by hematoxylin and eosin staining(HE) and immunocytochemical reaction, then cultivated in vitro. Culture conditions such as pH, osmotic pressure and metabolic parameters that include consumption rates of glucose, glutamine, amino acids and formation rates of lactic acid, ammonium ion were investigated. It was showed that adhesion process of SCs was accomplished within 2-4 hours after inoculation. It was also observed that the SCs entered into the decline phase when the concentration of ammonium ion and lactic acid were above 2.3 mmol/L and 14 mmol/L, respectively, which caused osmotic pressure above 326 mosm/kg and pH below 6.8 in the medium. As the changes of amino acids during culture were concerned, Glu and Ala accumulated rapidly, while Val, Leu, Ile reduced slightly and at the same time Ser, Arg, and Gly were stable. The restrict factors for SCs grown in static culture might be high osmotic pressure and low pH, which were generated when glutamine and glucose were metabolized into lactic acid. The findings could be fundamental in the process optimization of large scale Sertoli cells in vitro culture.

STUDIES ON CONDITIONS OF CELL HIGH DENSITY CULTIVATION FOR GENETICALLY ENGINEERED METHYLOTROPHIC PICHIA PASTORIS / 微生物学通报

Recently the methylotrophic Pichia pastoris,with many advantages such as high expression,stable genetics and protein secretion,has been used extensively as a host expressing heterologous proteins.The optimal seed medium among seven media MM,MD,MGY,BMGY,YMPD,YMPGy and MGyB is BMGY with addition of 4mL/L PTM1 The high density synthesized medium in shake flask culture is as follows: Glycerol 4%(NH 4) 2SO 4 10g/L,CaSO 4 0.93g/L,K 2SO 4 18 2g/L,MgSO 4?7H 2O 14 9g/L,add 0.1mol/L PBS(pH=6 0) to 1 0 liter.The harvested yeast cell optical density (OD 600 ) reached 65 or more after 26 hours cultivation.By analysis of SDS\|PAGE,the results of Pichia pastoris culture by methanol inducement for 72 hours showed that the expression of recombinant human serum albumin had been achieved by methanol inducement after 12 hours,and the mount of targeted protein reached the summit after 24 hours inducement by methanol.The high density synthesized medium in shake flask culture in this experiment,which is similar to the mediums of batch fermentation and batch\|fed fermentation,is benefit to direct the P.pastoris fermentation in the fermentor.