Exploring the effects of Qijiao Shengbai capsule on leukopenic mice from the perspective of intestinbased on metabolomics and 16S rRNA sequencing

Qijiao Shengbai capsule (QJSB) is formulated according to the traditional Chinese medicine formula, its function is to nourish Qi and blood, improve the body's immunity. Leukopenia has been treated with it in clinical settings. However, the mechanism of leukopenia from the perspective of intestinal tract has not been reported. This study combined metabolomics and 16S rRNA sequencing technologies to investigate the mechanism of QJSB on leukopenia from the intestine. As a result of cyclophosphamide induction in mice, the results demonstrated that QJSB may greatly increase the quantity of peripheral leukocytes (including neutrophils). Meanwhile, QJSB had a restorative effect on the colon of leukopenic mice; it also increased the level of IL-2, IL-6 and G-CSF in the intestine, further enhancing the immunity and hematopoietic function of mice. Metabolic studies showed that QJSB altered 27 metabolites, most notably amino acid metabolism. In addition, QJSB had a positive regulatory effect on the intestinal microbiota, and could alter community composition by improving the diversity and abundance of the intestinal microbial, which mainly involved 6 related bacterial groups, and primarily regulates three associated SCFAs (acetic acid, butyrate acid and valeric acid). Therefore, this study suggests that QJSB can improve hematopoietic function, enhance the immune system, relieve leucopenia and improve the gut in leucopenic mice by modulating metabolic response pathways, fecal metabolites and intestinal microbiota.

Systems biology approach in the formulation of chemically defined media for recombinant protein overproduction

The cell culture medium is an intricate mixture of components which has a tremendous effect on cell growth and recombinant protein production. Regular cell culture medium includes various components, and the decision about which component should be included in the formulation and its optimum amount is an underlying issue in biotechnology industries. Applying conventional techniques to design an optimal medium for the production of a recombinant protein requires meticulous and immense research. Moreover, since the medium formulation for the production of one protein could not be the best choice for another protein, hence, the most suitable media should be determined for each recombinant cell line. Accordingly, medium formulation becomes a laborious, time-consuming, and costly process in biomanufacturing of recombinant protein, and finding alternative strategies for medium development seems to be crucial. In silico modeling is an attractive concept to be adapted for medium formulation due to its high potential to supersede laboratory examinations. By emerging the high-throughput datasets, scientists can disclose the knowledge about the effect of medium components on cell growth and metabolism, and via applying this information through systems biology approach, medium formulation optimization could be accomplished in silico with no need of significant amount of experimentation. This review demonstrates some of the applications of systems biology as a powerful tool for medium development and illustrates the effect of medium optimization with system-level analysis on the production of recombinant proteins in different host cells.

High cell density culture of baker's yeast FX-2 based on pH-stat coupling with respiratory quotient

The high cell density culture of baker's yeast FX-2 was investigated in a 50 L(A) automatic bioreactor. Herein, it was found firstly that the Crabtree effect clearly existed in batch fermentation with higher glucose content, then the critical initial glucose content range (≤2.00 g L^-1 ) was reasonably ascertained to effectively avoid Crabtree effect. In the next fed-batch fermentations with different strategies, the second strategy (maintain ethanol concentration lower than 0.10% and pH around 4.80) was confirmed to be more beneficial to yeast growth than the first strategy (keep reducing sugar not more than 2.00 g L^-1 and control steady Carbon/Nitrogen ratio 3.05:1.00). After that, one optimal control strategy (maintain pH around 4.80 and keep respiratory quotient in the range of 0.90-1.00) was constructed to further enhance cell yield. Under an optimal control strategy, four schemes with the aim of achieving pH-stat were compared, and yeast extract instead of other alkaline materials was selected as a better regulator. As a result, 148.37 g L^-1 dry cell weight, 38.25 × 10⁸ mL^-1 living cells, and 8.24 g L^-1  h^-1 productivity were harvested, which respectively elevated 23.74%, 135.38%, and 24.47% compared to that obtained under the traditional scheme (regulate pH with ammonia); meanwhile, the maximum oxygen uptake rate and carbon dioxide excretion rate were both more than 250.00 mmol L^-1  min^-1 .

Expression of a collagen-binding domain fusion protein: effect of amino acid supplementation, inducer type, and culture conditions

Collagen binding domain fusion proteins are of significant importance because of their potential as therapeutic biomaterials. In this paper, we investigate the production of such therapeutic proteins via fermentation of Escherichia coli on both an undefined medium and a defined medium. Defined media with amino acid supplementation provided higher amounts of therapeutic protein than undefined media with no supplementation. Additionally, utilizing lactose instead of isopropyl-β-d-thio-galactoside (IPTG) for induction and extending batch time yielded higher amounts of the model therapeutic.

Enhancing toxic protein expression in Escherichia coli fed-batch culture using kinetic parameters: Human granulocyte-macrophage colony-stimulating factor as a model system

The kinetics of recombinant human granulocyte-macrophage colony-stimulating factor (hGM-CSF) expression was studied under the strong T7 promoter in continuous culture of Escherichia coli using complex medium to design an optimum feeding strategy for high cell density cultivation. Continuous culture studies were done at different dilution rates and the growth and product formation profiles were monitored post-induction. Recombinant protein expression was in the form of inclusion bodies with a maximum specific product formation rate (q(p)) of 63.5 mg g(-1) DCW h(-1) at a dilution rate (D) of 0.3 h(-1). The maximum volumetric product concentration achieved at this dilution rate was 474 mg l(-1), which translated a ~1.4 and ~1.75 folds increase than the values obtained at dilution rates of 0.2 h(-1) and 0.4 h(-1) respectively. The specific product yield (Y(P/x)) peaked at 138 mg g(-1) DCW, demonstrating a ~1.6 folds increase in the values obtained at other dilution rates. A drop in q(p) was observed within 5-6 h of induction at all the dilution rates, possibly due to protein toxicity and metabolic stress associated with protein expression. The data from the continuous culture studies allowed us to design an optimal feeding strategy and induction time in fed-batch cultures which resulted in a maximum product concentration of 3.95 g l(-1) with a specific hGM-CSF yield (Y(P/x)) of 107 mg g(-1) DCW.

Metabolic responses to recombinant bioprocesses in Escherichia coli

Escherichia coli has been widely used for the production of recombinant proteins. However, the unbalances between host metabolism and recombinant biosynthesis continue to hamper the efficiency of these recombinant bioprocesses. The additional drainage of biosynthetic precursors toward recombinant processes burdens severely the metabolism of cells that, ultimately, elicits a series of stress responses, reducing biomass growth and recombinant protein production. Several strategies to overcome these metabolic limitations have been implemented; however, in most cases, improvements in recombinant protein expression were achieved at the expense of biomass growth arrest, which significantly hampers the efficiency of recombinant bioprocesses. With the advent of high throughput techniques and modelling approaches that provide a system-level understanding of the cellular systems, it is now expected that new advances in recombinant bioprocesses are achieved. By providing means to deal with these systems, our understanding on the metabolic behaviour of recombinant cells will advance and can be further explored to the design of suitable hosts and more efficient and cost-effective bioprocesses. Here, we review the major metabolic responses associated with recombinant processes and the engineering strategies relevant to overcome these stresses. Moreover, the advantages of applying systems levels engineering strategies to enhance recombinant protein production in E. coli cells are discussed and future perspectives on the advances of mathematical modelling approaches to study these systems are exposed.