Enhancement of recombinant BmK AngM1 production in Pichia pastoris by regulating gene dosage, co-expressing with chaperones and fermenting in fed-batch mode

Advances in the biosynthesis and metabolic engineering of rare ginsenosides

Rare ginsenosides are the deglycosylated secondary metabolic derivatives of major ginsenosides, and they are more readily absorbed into the bloodstream and function as active substances. The traditional preparation methods hindered the potential application of these effective components. The continuous elucidation of ginsenoside biosynthesis pathways has rendered the production of rare ginsenosides using synthetic biology techniques effective for their large-scale production. Previously, only the progress in the biosynthesis and biotechnological production of major ginsenosides was highlighted. In this review, we summarized the recent advances in the identification of key enzymes involved in the biosynthetic pathways of rare ginsenosides, especially the glycosyltransferases (GTs). Then the construction of microbial chassis for the production of rare ginsenosides, mainly in Saccharomyces cerevisiae, was presented. In the future, discovery of more GTs and improving their catalytic efficiencies are essential for the metabolic engineering of rare ginsenosides. This review will give more clues and be helpful for the characterization of the biosynthesis and metabolic engineering of rare ginsenosides. KEY POINTS: • The key enzymes involved in the biosynthetic pathways of rare ginsenosides are summarized. • The recent progress in metabolic engineering of rare ginsenosides is presented. • The discovery of glycosyltransferases is essential for the microbial production of rare ginsenosides in the future.

Pathway engineering facilitates efficient protein expression in Pichia pastoris

Pichia pastoris has been recognized as an important platform for the production of various heterologous proteins in recent years. The strong promoter AOX1, induced by methanol, with the help of the α-pre-pro signal sequence, can lead to a high expression level of extracellular protein. However, this combination was not always efficient, as protein secretion in P. pastoris involves numerous procedures mediated by several cellular proteins, including folding assisted by endoplasmic reticulum (ER) molecular chaperones, degradation through ubiquitination, and an efficient vesicular transport system. Efficient protein expression requires the cooperation of various intracellular pathways. This article summarizes the process of protein secretion, modification, and transportation in P. pastoris. In addition, the roles played by the key proteins in these processes and the corresponding co-expression effects are also listed. It is expected to lay the foundation for the industrial protein production of P. pastoris. KEY POINTS: • Mechanisms of chaperones in protein folding and their co-expression effects are summarized. • Protein glycosylation modifications are comprehensively reviewed. • Current dilemmas in the overall protein secretion pathway of Pichia pastoris and corresponding solutions are demonstrated.

Astragalus–Scorpion Drug Pair Inhibits the Development of Prostate Cancer by Regulating GDPD4-2/PI3K/AKT/mTOR Pathway and Autophagy

Objective: Prostate cancer (PCa) is an epithelial malignancy of the prostate that currently lacks effective treatment. Traditional Chinese medicine (TCM) can play an anticancer role through regulating the immune system, anti-tumor angiogenesis, regulating tumor cell apoptosis, autophagy dysfunction, and other mechanisms. This study attempted to explore the active ingredients and potential mechanism of action of the Astragalus–Scorpion (A–S) drug pair in PCa, in order to provide new insights into the treatment of PCa.

Methods: Network pharmacology was used to analyze the A–S drug pair and PCa targets. Bioinformatics analysis was used to analyze the LncRNAs with significant differences in PCa. The expression of LC3 protein was detected by immunofluorescence. CCK8 was used to detect cell proliferation. The expressions of GDPD4-2, AC144450.1, LINC01513, AC004009.2, AL096869.1, AP005210.1, and BX119924.1 were detected by RT-qPCR. The expression of the PI3K/AKT/mTOR pathway and autophagy-related proteins were detected by western blot. LC-MS/MS was used to identify the active components of Astragalus and Scorpion.

Results: A–S drug pair and PCa have a total of 163 targets, which were mainly related to the prostate cancer and PI3K/AKT pathways. A–S drug pair inhibited the formation of PCa, promoted the expression of LC3Ⅱ and Beclin1 proteins, and inhibited the expression of P62 and PI3K–AKT pathway proteins in PCa mice. Astragaloside IV and polypeptide extract from scorpion venom (PESV) were identified as the main active components of the A–S drug pair. GDPD4-2 was involved in the treatment of PCa by Astragaloside IV-PESV. Silencing GDPD4-2 reversed the therapeutic effects of Astragaloside IV-PESV by regulating the PI3K/AKT/mTOR pathway.

Conclusion: Astragaloside IV-PESV is the main active components of A–S drug pair treated PCa by regulating the GDPD4-2/PI3K–AKT/mTOR pathway and autophagy.

Metabolic engineering of yeasts for green and sustainable production of bioactive ginsenosides F2 and 3β,20S-Di-O-Glc-DM

Both natural ginsenoside F2 and unnatural ginsenoside 3β,20S-Di-O-Glc-DM were reported to exhibit anti-tumor activity. Traditional approaches for producing them rely on direct extraction from Panax ginseng, enzymatic catalysis or chemical synthesis, all of which result in low yield and high cost. Metabolic engineering of microbes has been recognized as a green and sustainable biotechnology to produce natural and unnatural products. Hence we engineered the complete biosynthetic pathways of F2 and 3β,20S-Di-O-Glc-DM in Saccharomyces cerevisiae via the CRISPR/Cas9 system. The titers of F2 and 3β,20S-Di-O-Glc-DM were increased from 1.2 to 21.0 mg/L and from 82.0 to 346.1 mg/L at shake flask level, respectively, by multistep metabolic engineering strategies. Additionally, pharmacological evaluation showed that both F2 and 3β,20S-Di-O-Glc-DM exhibited anti-pancreatic cancer activity and the activity of 3β,20S-Di-O-Glc-DM was even better. Furthermore, the titer of 3β,20S-Di-O-Glc-DM reached 2.6 g/L by fed-batch fermentation in a 3 L bioreactor. To our knowledge, this is the first report on demonstrating the anti-pancreatic cancer activity of F2 and 3β,20S-Di-O-Glc-DM, and achieving their de novo biosynthesis by the engineered yeasts. Our work presents an alternative approach to produce F2 and 3β,20S-Di-O-Glc-DM from renewable biomass, which lays a foundation for drug research and development.

Increased expression of recombinant chitosanase by co-expression of Hac1p in the yeast Pichia pastoris

BACKGROUND

Pichia pastoris is one of the most popular eukaryotic hosts for producing heterologous proteins, while increasing secretion of target proteins is still a top priority for their application in industrial fields. Recently, the research effort to enhance protein production therein has focused on up-regulating the unfolded protein response (UPR).

OBJECTIVE

We evaluated the effects of activated UPR via Hac1p co-expression with the promoter AOX1 (PAOX1) or GAP (PGAP) on expression of recombinant chitosanase (rCBS) in P. pastoris.

METHOD

The DNA sequence encoding the chitosanase was chemically synthesized and cloned into pPICZαA and the resulted pPICZαA/rCBS was transformed into P. pastoris for expressing rCBS. The P. pastoris HAC1i cDNA was chemically synthesized and cloned into pPIC3.5K to give pPIC3.5K/Hac1p. The HAC1i cDNA was cloned into pGAPZB and then inserted with HIS4 gene from pAO815 to construct the vector pGAPZB/Hac1p/HIS4. For co-expression of Hac1p, the two plasmids pPIC3.5K/Hac1p and pGAPZB/Hac1p/HIS4 were transformed into P. pastoris harboring the CBS gene. The rCBS was assessed based on chitosanase activity and analyzed by SDS-PAGE. The enhanced Kar2p was detected with western blotting to evaluate UPR.

RESULTS

Hac1p co-expression with PAOX1 enhanced rCBS secretion by 41% at 28°C. Although the level of UPR resulted from Hac1p co-expression with PAOX1 was equivalent to that with PGAP in terms of the quantity of Kar2p (a hallmark of the UPR), substitution of PGAP for PAOX1 further increased rCBS production by 21%. The methanol-utilizing phenotype of P. pastoris did not affect rCBS secretion with co-expression of Hac1p or not. Finally, Hac1p co-expression with PAOX1 or PGAP promoted rCBS secretion from 22 to 30°C and raised the optimum induction temperature.

CONCLUSION

The study indicated that Hac1p co-expression with PAOX1 or PGAP is an effective strategy to trigger UPR of P. pastoris and a feasible means for improving production of rCBS therein.

Medium optimization for high yield production of human serum albumin in Pichia pastoris and its efficient purification

OBJECTIVE

To improve the yield of recombinant human serum albumin (HSA) in Pichia pastoris by medium optimization and establish the related purification scheme.

RESULTS

A simplified version of the generally used buffered glycerol complex medium (BMGY), which contained yeast extract, glycerol and potassium salts, was found to be applicable. By decreasing the salt concentration of basal salt medium (BSM) to half of the original formula further, we achieved a high yield of 17.47 g/L HSA in the supernatant within a 192 h induction, which is the highest rHSA yield ever reported as far as we know. Accompanied with a three-step purification procedure which recovered two thirds of the desired protein at high purity, our work lays a solid foundation for large-scale industrial production of HSA.

CONCLUSION

Medium optimization plays a significant role in improving the yield of desired protein, lowering the production cost and helping to explore the producing strain's character.

Development of a New High-Cell Density Fermentation Strategy for Enhanced Production of a Fungus β-Glucosidase in Pichia pastoris

Traditional diosgenin manufacturing process has led to serious environmental contamination and wastewater. Clean processes are needed that can alternate the diosgenin production. The β-glucosidase FBG1, cloned from Fusarium sp. CPCC 400709, can biotransform trillin and produce diosgenin. In this study, Pichia pastoris production of recombinant FBG1 was implemented to investigate various conventional methanol induction strategies, mainly including DO-stat (constant induction DO), μ-stat (constant exponential feeding rate) and m-stat (constant methanol concentration). The new co-stat strategy combining μ-stat and m-stat strategies was then developed for enhanced FBG1 production during fed-batch high-cell density fermentation on methanol. The fermentation process was characterized with respect to cell growth, methanol consumption, FBG1 production and methanol metabolism. It was found that large amounts of formaldehyde were released by the enhanced dissimilation pathway when the co-stat strategy was implemented, and therefore the energy generation was enhanced because of improved methanol metabolism. Using co-stat feeding, the highest volumetric activity reached ∼89 × 10⁴ U/L, with the maximum specific activity of ∼90 × 10² U/g. After 108 h induction, the highest volumetric production reached ∼403 mg/L, which was ∼91, 154, and 183 mg/L higher than the maximal production obtained at m-stat, μ-stat, and DO-stat strategies, respectively. FBG1 is the first P. pastoris produced recombinant enzyme for diosgenin production through the biotransformation of trillin. Moreover, this newly developed co-stat induction strategy represents the highest expression of FBG1 in P. pastoris, and the strategy can be used to produce FBG1 from similar Pichia strains harboring Fbg1 gene, which lays solid foundation for clean and sustainable production of diosgenin. The current work provides unique information on cell growth, substrate metabolism and protein biosynthesis for enhanced β-glucosidase production using a P. pastoris strain under controlled fermentation conditions. This information may be applicable for expression of similar proteins from P. pastoris strains.

Expression of multidrug transporter P-glycoprotein in Pichia pastoris affects the host's methanol metabolism

Pichia pastoris KM71H (MutS ) is an efficient producer of hard-to-express proteins such as the membrane protein P-glycoprotein (Pgp), an ATP-powered efflux pump which is expressed properly, but at very low concentration, using the conventional induction strategy. Evaluation of different induction strategies indicated that it was possible to increase Pgp expression by inducing the culture with 20% media containing 2.5% methanol. By quantifying methanol, formaldehyde, hydrogen peroxide and formate, and by measuring alcohol oxidase, catalase, formaldehyde dehydrogenase, formate dehydrogenase, malate dehydrogenase, isocitrate dehydrogenase and α-ketoglutarate dehydrogenases, it was possible to correlate Pgp expression to the induction strategy. Inducing the culture by adding methanol with fresh media was associated with decreases in formaldehyde and hydrogen peroxide, and increases in formaldehyde dehydrogenase, formate dehydrogenase, isocitrate dehydrogenase and α-ketoglutarate dehydrogenases. At these conditions, Pgp expression was 1400-fold higher, an indication that Pgp expression is affected by increases in formaldehyde and hydrogen peroxide. It is possible that Pgp is responsible for this behaviour, since the increased metabolite concentrations and decreased enzymatic activities were not observed when parental Pichia was subjected to the same growth conditions. This report adds information on methanol metabolism during expression of Pgp from P. pastoris MutS strain and suggests an expression procedure for hard-to-express proteins from P. pastoris.