Synthesis and high expression of chitin deacetylase from Colletotrichum lindemuthianum in Pichia pastoris GS115

A gene, ClCDA, encoding chitin deacetylase from Colletotrichum lindemuthianum, was optimized according to the codon usage bias of Pichia pastoris and synthesized in vitro by overlap extension PCR. It was secretorily expressed in P. pastoris GS115 using the constitutive expression vector pHMB905A. The expression level reached the highest with 110 mg/l culture supernatant after 72 h of methanol induction, which comprised 77.27 U/mg chitin deacetylase activity. SDS-PAGE, mass spectrometry, and deglycosylation assays demonstrated that partial recombinant protein was glycosylated with an apparent molecular mass of 33 kDa. The amino acid sequences of recombinant proteins were confirmed by mass spectrometry.     

Knockout of fatty acid desaturase genes in Pichia pastoris GS115 and its effect on the fatty acid biosynthesis and physiological consequences

Unsaturated fatty acids (UFAs), including oleic acid (OA, C18:1n-9), linoleic acid (LA, C18:2n-6) and α-linolenic acid (ALA, C18:3n-3), are major components of membrane lipids in Pichia pastoris GS115. In order to clarify the biosynthesis pathway of UFAs on the molecular level and investigate their possible roles in growth and development of this strain, we here report modified strains with disrupted desaturase gene by homologous recombination. Gas chromatography analysis of fatty acid composition in the corresponding mutants confirmed that ?¹²-desaturase encoded by Fad12 was responsible for the formation of LA, and ALA was synthesized by ?¹⁵-desaturase encoded by Fad15. Simultaneous deletion of Fad9A and Fad9B was lethal and supplementation of OA could restore growth, indicating that possibly both Fad9A and Fad9B encoded ?⁹-desaturase that converted SA into OA. Phenotypic analysis demonstrated that wild type and Fad15 mutant grew at almost the same rate, Fad12 mutant grew much slower than these two strains. Moreover, OA was positively correlated to cold tolerance and ethanol tolerance of GS115, whereas LA and ALA did not affect cold tolerance and ethanol tolerance of it. In addition, we showed that tolerance of GS115 to high concentration of methanol was independent of these three UFAs.     

Fast development of Pichia pastoris GS115 Mut+ cultures employing batch-to-batch control and hybrid semi-parametric modeling

In this paper, we implemented a model-based optimization platform for fast development of Pichia pastoris cultures employing batch-to-batch control and hybrid semi-parametric modeling. We illustrate the methodology with a P. pastoris GS115 strain expressing a single-chain antibody fragment (scFv) by determining the optimal time profiles of temperature, pH, glycerol feeding and methanol feeding that maximize the endpoint scFv titer. The first hybrid model was identified from data of six exploratory experiments carried out in a pilot 50-L reactor. This model was subsequently used to maximize the final scFv titer of the proceeding batch employing a dynamic optimization program. Thereupon, the optimized time profiles of control variables were implemented in the pilot reactor and the resulting new data set was used to re-identify the hybrid model and to re-optimize the next batch. The iterative batch-to-batch optimization was stopped after 4 complete optimized batches with the final scFv titer stabilizing at 49.5 mg/L. In relation to the baseline batch (executed according to the Pichia fermentation guidelines by Invitrogen) a more than fourfold increase in scFv titer was achieved. The biomass concentration at induction and the methanol feeding rate profile were found to be the most critical control degrees of freedom to maximize scFv titer.     

Expression, purification, and bioactivity of (GLP-1A2G)2-HSA analogs in Pichia pastoris GS115

We developed (GLP-1_A2G)₂-HSA (GGH) analogs that are resistant to degradation and also show high serum glucose-reducing activity in vivo. Five analogs with N-terminal extensions were designed based on the protein GGH. Next, we constructed recombinant plasmids capable of expressing the five analogs in methylotrophic yeast Pichia pastoris GS115. Expression reached 150 mg/L in a small-scale incubation. Fusion proteins were successfully purified from the supernatant using ultrafiltration concentration, affinity absorption chromatography, hydrophobic chromatography, ion exchange chromatography and gel filtration. A single band was observed on SDS-PAGE and the purity was 97%. Activity test results suggested that both A-GGH and G-GGH showed better activity in vitro and that their cAMP levels were significantly increased by 10-fold compared to GGH without N-terminal extension. Additionally, A-GGH efficiently enhanced the glucoselowering effect, which was maintained after the administration for 24 h. A-GGH is a potential drug for treating type 2 diabetes.     

苦瓜MAP30基因的毕赤酵母表达载体构建及重组菌株的筛选

目的:从苦瓜中克隆MAP30全长基因,并将该基因连接至表达载体pPIC9中,建立酵母菌落PCR筛选方法。方法采用改良SDS法从苦瓜表皮中提取基因组DNA,设计特异性的引物,通过PCR技术扩增出全长861bp的MAP30基因。该基因经XhoⅠ和EcoRⅠ双酶切,连接至毕赤酵母表达载体pPIC9中。重组载体转化GS115菌株,运用菌落PCR鉴定重组菌株。结果:基因测序表明,该基因已成功插入酵母表达载体pPIC9α-factor分泌信号下游,同源性分析表明该基因与GeneBank(AF284811)的核苷酸同源性达99.9%,氨基酸同源性达100%。菌落PCR显示外源基因已整合入酵母GS115菌株中。结论:成功地克隆了MAP30全长基因,并构建了含MAP30基因的重组毕赤酵母表达载体,并获得了整合菌株,为下一步研究奠定了基础。     

Effect of disruption of Pichia pastoris YPS1 gene on viability and production of recombinant proteins

In the present study, we constructed a Pichia pastoris mutant strain PS111 that lacks one member of the yapsin family through disruption of the YPS1 gene coding for aspartic protease yapsin 1. Under normal growth conditions, the PS111 mutant strain did not show detectable growth defects. Unlike the S. cerevisiae yps1 mutant, the P. pastoris PS111 strain showed no sensitivity when grown in the presence of CaCl₂, elevated temperature (37°C), under acid (pH 4.9) and alkaline (pH 8.3) conditions. Unlike the S. cerevisiae, the P. pastoris yps1 mutant showed decreased growth phenotype induced by cell wall-perturbing reagent sodium dodecyl sulfate (SDS) only when the concentration of SDS was increased by ten times. The use of the yps1 disruptant to produce human interferon alpha16 (hINF-α16) prevents proteolysis, which occurs in the wildtype strain. It was found that the degradation of recombinant protein Alburon composed of human serum albumin (HSA) and hINF-α16 was slightly decreased in the strain lacking yapsin 1.     

Purification and scale-up of a recombinant heavy chain fragment C of botulinum neurotoxin serotype E in Pichia pastoris GS115

A recombinant C-terminus heavy chain fragment from botulinum neurotoxin serotype E (BoNT/E) is proposed as a vaccine against the serotype E neurotoxin. This fragment, rBoNTE(Hc), was produced intracellular in Pichia pastoris GS115 by a three-step fermentation process, i.e., glycerol batch phase and a glycerol fed-batch phase to achieve high cell densities, followed by a methanol fed-batch induction phase. The rBoNTE(Hc) protein was purified from the soluble fraction of cell lysates using three ion-exchange chromatography steps (SP Sepharose Fast Flow, Q Sepharose Fast Flow, Sp Sepharose High Performance) and polished with a hydrophobic charge induction chromatography step (MEP HyperCel). Method development at the bench scale was achieved using 7-380 mL columns and the process was performed at the pilot scale using 0.5-3.1 L columns in preparation for technology transfer to cGMP manufacturing. The purification process resulted in greater than 98% pure rBoNTE(Hc) based on HPLC and yielded up to 1.01g of rBoNTE(Hc)/kg cells at the bench scale and 580mg vaccine/kg cells at the pilot scale. N-terminal sequencing showed that the purified rBoNTE(Hc) N-terminus is intact and was found to protect mice against a challenge of 1000 mouse intraperitoneal LD50's of BoNT/E.     

Expression of the bovine papillomavirus type 1, 2 and 4 L1 genes in the yeast Pichia pastoris

Papillomaviruses are known to cause benign or malignant lesions in various animals. In cattle, bovine papillomavirus (BPV) is the etiologic agent of papillomatosis and neoplasia of the upper gastrointestinal tract and urinary bladder. Currently, there are no standard diagnostic tests or prophylactic vaccines. Protection against papillomavirus infection is conferred by neutralizing antibodies directed towards the major structural protein L1. These antibodies can be efficiently induced by immunization with virus-like particles that are formed spontaneously after L1 gene expression in recombinant systems. The yeast Pichia pastoris is known to provide an efficient system for expression of proteins due to reduced cost and high levels of protein production. We evaluated P. pastoris for expression of the L1 gene from BPV1, BPV2 and BPV4. After methanol induction, the recombinants were able to produce L1 proteins of the three different BPV types. To increase heterologous L1 protein levels, a codon optimization strategy was used for production under bioreactor conditions. The BPV1 L1 protein was identified by monoclonal antibody anti-6xHis. This is the first report of BPV L1 expression in yeast.     

Assignment of 115 genes from HSA9 and HSA14 to SSC1q by RH mapping to generate a dense human-pig comparative map

A large number of significant QTL for economically important traits including average daily gain have been located on SSC1q, which, as shown by chromosome painting, corresponds to four human chromosomes (HSA9, 14, 15 and 18). To provide a comprehensive comparative map for efficient selection of candidate genes, 81 and 34 genes localized on HSA9 and HSA14 respectively were mapped to SSC1q using a porcine 7000-rad radiation hybrid panel (IMpRH). This study, together with the cytogenetic map (http://www2.toulouse.inra.fr/lgc/pig/cyto/genmar/htm/1GM.HTM), demonstrates that SSC1q2.1-q2.13 corresponds to the region ranging from 44.6 to 63.2 Mb on HSA14q21.1-q23.1, the region from 86.5 to 86.8 Mb on HSA15q24-q25, the region from 0.9 to 27.2 Mb on HSA9p24.3-p21, the region from 35.1 to 38.0 Mb on HSA9p13, the region from 70.3 to 79.3 Mb on HSA9q13-q21 and the region from 96.4 to 140.0 Mb on HSA9q22.3-q34. The conserved synteny between HSA9 and SSC1q is interrupted by at least six sites, and the synteny between HSA14 and SSC1q is interrupted by at least one site.     

Reduced proteolysis of secreted gelatin and Yps1-mediated alpha-factor leader processing in a Pichia pastoris kex2 disruptant

Heterologous proteins secreted by yeast and fungal expression hosts are occasionally degraded at basic amino acids. We cloned Pichia pastoris homologs of the Saccharomyces cerevisiae basic residue-specific endoproteases Kex2 and Yps1 to evaluate their involvement in the degradation of a secreted mammalian gelatin. Disruption of the P. pastoris KEX2 gene prevented proteolysis of the foreign protein at specific monoarginylic sites. The S. cerevisiae alpha-factor preproleader used to direct high-level gelatin secretion was correctly processed at its dibasic site in the absence of the prototypical proprotein convertase Kex2. Disruption of the YPS1 gene had no effect on gelatin degradation or processing of the alpha-factor propeptide. When both the KEX2 and YPS1 genes were disrupted, correct precursor maturation no longer occurred. The different substrate specificities of both proteases and their mutual redundancy for propeptide processing indicate that P. pastoris kex2 and yps1 single-gene disruptants can be used for the alpha-factor leader-directed secretion of heterologous proteins otherwise degraded at basic residues.     

Recombinant expression of ShPI-1A, a non-specific BPTI-Kunitz-type inhibitor, and its protection effect on proteolytic degradation of recombinant human miniproinsulin expressed in Pichia pastoris

Pichia pastoris is a highly successful system for the large-scale expression of heterologous proteins, with the added capability of performing most eukaryotic post-translational modifications. However, this system has one significant disadvantage - frequent proteolytic degradation by P. pastoris proteases of heterologously expressed proteins. Several methods have been proposed to address this problem, but none has proven fully effective. We tested the effectiveness of a broad specificity protease inhibitor to control proteolysis. A recombinant variant of the BPTI-Kunitz protease inhibitor ShPI-1 isolated from the sea anemone Stichodactyla helianthus, was expressed in P. pastoris. The recombinant inhibitor (rShPI-1A), containing four additional amino acids (EAEA) at the N-terminus, was folded similarly to the natural inhibitor, as assessed by circular dichroism. rShPI-1A had broad protease specificity, inhibiting serine, aspartic, and cysteine proteases similarly to the natural inhibitor. rShPI-1A protected a model protein, recombinant human miniproinsulin (rhMPI), from proteolytic degradation during expression in P. pastoris. The addition of purified rShPI-1A at the beginning of the induction phase significantly protected rhMPI from proteolysis in culture broth. The results suggest that a broad specificity protease inhibitor such as rShPI-1A can be used to improve the yield of recombinant proteins secreted from P. pastoris.     

Biotransformation of β‐hydroxypyruvate and glycolaldehyde to l‐erythrulose by Pichia pastoris strain GS115 overexpressing native transketolase

Transketolase is a proven biocatalytic tool for asymmetric carbon‐carbon bond formation, both as a purified enzyme and within bacterial whole‐cell biocatalysts. The performance of Pichia pastoris as a host for transketolase whole‐cell biocatalysis was investigated using a transketolase‐overexpressing strain to catalyze formation of l ‐erythrulose from β‐hydroxypyruvic acid and glycolaldehyde substrates. Pichia pastoris transketolase coding sequence from the locus PAS_chr1‐4_0150 was subcloned downstream of the methanol‐inducible AOX1 promoter in a plasmid for transformation of strain GS115, generating strain TK150. Whole and disrupted TK150 cells from shake flasks achieved 62% and 65% conversion, respectively, under optimal pH and methanol induction conditions. In a 300 μL reaction, TK150 samples from a 1L fed‐batch fermentation achieved a maximum l ‐erythrulose space time yield (STY) of 46.58 g L^?1 h^?1, specific activity of 155 U , product yield on substrate (Y_p/s) of 0.52 mol mol^?1 and product yield on catalyst (Y_p/x) of 2.23g . We have successfully exploited the rapid growth and high biomass characteristics of Pichia pastoris in whole cell biocatalysis. At high cell density, the engineered TK150 Pichia pastoris strain tolerated high concentrations of substrate and product to achieve high STY of the chiral sugar l ‐erythrulose. © 2017 The Authors Biotechnology Progress published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers Biotechnol. Prog., 34:99–106, 2018     

Degradation of HSA-AX15(R13K) when expressed in Pichia pastoris can be reduced via the disruption of YPS1 gene in this yeast

Expression of recombinant protein HSA-AX15(R13K) in Pichia pastoris GS115 strain produced both the intact protein and its two degradation products with molecular weights of around 43kDa and 66.2kDa, respectively. To reduce or avoid the degradation, a modified P. pastoris GS115 stain, in which YPS1 gene was disrupted, was constructed via homologous recombination and used as a host strain for the HSA-AX15(R13K) expression. After 60h of induction during culture, it was found that the degradation product of around 66.2kDa was reduced significantly in the supernatant of yps1-disrupted strain compared with that in the supernatant of wild-type strain. By the Western blot analysis of culture supernatants from wild-type and yps1-disrupted strains expressing HSA-AX15(R13K), the significant improvement was also seen in the degradation product of around 43kDa. Comparison of cell growth between the two strains demonstrated a similar growth tendency, thereby indicating that the disruption of YPS1 gene has no effect on the normal physiology of GS115 strain. Following induction for 60h, the yield of intact HSA-AX15(R13K) in the yps1 disruptant was three-fold higher than that in the wild-type strain. Therefore, such a P. pastoris mutant deficient in YPS1 activity is suitable for the high-level expression of recombinant protein HSA-AX15(R13K).     

Selective expression of nonsecreted triple-helical and secreted single-chain recombinant collagen fragments in the yeast Pichia pastoris

High-level recombinant expression systems for the production of stable triple-helical human collagens and collagen fragments have been developed in the yeast Pichia pastoris. Collagen fragments are secreted as single-chain polypeptides by the yeast alpha-mating factor pre-pro sequence, but secretion of full-length triple-helical procollagen molecules has not been achieved despite the use of the same secretory signal. We studied here the effects of the secretory signal and the conformation and size of the collagen polypeptide on its secretion in P. pastoris. Unlike the collagen signal sequence, the alpha-mating factor pre-pro sequence led to efficient secretion of single-chain 45 and 9 kDa type I collagen fragments. The efficiency was dependent on the length of the collagen polypeptide, as secretion of single-chain full-length 90 kDa alpha1(I) polypeptides was less efficient than that of the 45 kDa fragment. Furthermore, the conformation of the collagen polypeptides had a marked effect on secretion, as induction of trimerization of the 45 and 9 kDa fragments by either the C propeptide or the small trimerizing domain foldon led to an accumulation of triple-helical molecules inside the cells despite the presence of the alpha-mating factor pre-pro sequence. Our results show that P. pastoris is a suitable host for the development of tailored expression systems aimed at selective production of nonsecreted triple-helical and secreted single-chain collagen fragments of varying lengths for specific purposes.     

High-level expression and characterization of a secreted recombinant cation-dependent mannose 6-phosphate receptor in Pichia pastoris

Mannose 6-phosphate receptors (MPRs) form essential components of the lysosomal enzyme targeting system by binding newly synthesized acid hydrolases with high (nM) affinity. We report the use of Pichia pastoris as a host to efficiently express the extracytoplasmic ligand-binding domain of the cation-dependent mannose 6-phosphate receptor. A truncated and glycosylation-deficient form of the receptor AF-Asn(81)/Stop(155) was secreted into the culture medium, yielding approximately 28mg/L after purification, which is an improvement of 10-100-fold compared to expression in baculovirus-infected insect cells and mammalian cells, respectively. Enzymatic deglycosylation indicated high-mannose sugars at the single potential glycosylation site of Asn 81. The extent and heterogeneity of N-glycans were revealed by applying matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). In the case of AF-Asn(81)/Stop(155), the majority (75%) of the oligosaccharides contained chain lengths of Man(8-10)GlcNAc(2) while Man(11-12)GlcNAc(2) comprised the remaining (25%) N-linked sugars. A comparative MALDI-TOF spectra of Asn(81)/Stop(155) purified from insect cells indicated that Man(2-3)GlcNAc(2) and GlcNAcMan(2-3)GlcNAc(2) share the oligosaccharide pool. The receptor isolated from yeast was functional with respect to ligand binding and acid-dependent dissociation properties, as determined by pentamannosyl phosphate-agarose affinity chromatography. In addition, the protein was biochemically and functionally similar to Asn(81)/Stop(155) expressed in insect cells concerning its oligomeric state and binding affinity to the lysosomal enzyme, beta-glucuronidase (K(d)=1.4nM). These results demonstrate that P. pastoris is a convenient system for the production of large quantities of functional recombinant MPRs suitable for structure-function studies.     

Physiological response of Pichia pastoris GS115 to methanol-induced high level production of the Hepatitis B surface antigen: catabolic adaptation, stress responses, and autophagic processes

ABSTRACT: BACKGROUND: Pichia pastoris is an established eukaryotic host for the production of recombinant proteins. Most often, protein production is under the control of the strong methanol-inducible aox1 promoter. However, detailed information about the physiological alterations in P. pastoris accompanying the shift from growth on glycerol to methanol-induced protein production under industrial relevant conditions is missing. Here, we provide an analysis of the physiological response of P. pastoris GS115 to methanol-induced high-level production of the Hepatitis B virus surface antigen (HBsAg). High product titers and the retention of the protein in the endoplasmic reticulum (ER) are supposedly of major impact on the host physiology. For a more detailed understanding of the cellular response to methanol-induced HBsAg production, the time-dependent changes in the yeast proteome and ultrastructural cell morphology were analyzed during the production process. RESULTS: The shift from growth on glycerol to growth and HBsAg production on methanol was accompanied by a drastic change in the yeast proteome. In particular, enzymes from the methanol dissimilation pathway started to dominate the proteome while enzymes from the methanol assimilation pathway, e.g. the transketolase DAS1, increased only moderately. The majority of methanol was metabolized via the energy generating dissimilatory pathway leading to a corresponding increase in mitochondrial size and numbers. The methanol-metabolism related generation of reactive oxygen species induced a pronounced oxidative stress response (e.g. strong increase of the peroxiredoxin PMP20). Moreover, the accumulation of HBsAg in the ER resulted in the induction of the unfolded protein response (e.g. strong increase of the ER-resident disulfide isomerase, PDI) and the ER associated degradation (ERAD) pathway (e.g. increase of two cytosolic chaperones and members of the AAA ATPase superfamily) indicating that potential degradation of HBsAg could proceed via the ERAD pathway and through the proteasome. However, the amount of HBsAg did not show any significant decline during the cultivation revealing its general protection from proteolytic degradation. During the methanol fed-batch phase, induction of vacuolar proteases (e.g. strong increase of APR1) and constitutive autophagic processes were observed. Vacuolar enclosures were mainly found around peroxisomes and not close to HBsAg deposits and, thus, were most likely provoked by peroxisomal components damaged by reactive oxygen species generated by methanol oxidation. CONCLUSIONS: In the methanol fed-batch phase P. pastoris is exposed to dual stress; stress resulting from methanol degradation and stress resulting from the production of the recombinant protein leading to the induction of oxidative stress and unfolded protein response pathways, respectively. Finally, the modest increase of methanol assimilatory enzymes compared to the strong increase of methanol dissimilatory enzymes suggests here a potential to increase methanol incorporation into biomass/product through metabolic enhancement of the methanol assimilatory pathway.     

Human pS2/trefoil factor 1: production and characterization in Pichia pastoris

The recombinant protein human trefoil factor 1 (hTFF1), formerly called hpS2, has been produced for the first time in a yeast-based expression in Pichia pastoris. hTFF1 was secreted in large amounts in the extracellular medium of P. pastoris under the control of the glyceraldehyde-3-phosphate dehydrogenase promoter. The fermentation broth containing hTFF1 was concentrated by tangential flow filtration prior to purification by anion- and cation-exchange chromatography, followed by preparative high-performance liquid chromatography. The resulting hTFF1 was found to be intact by Western blot analysis. Further analysis revealed mainly the presence of the monomeric form of the hTFF1 peptide. Finally, in vitro, the recombinant hTFF1 was shown to decrease proliferation of the HCT116 cancer cells.     

Expression and purification of soluble porcine CTLA-4 in yeast Pichia pastoris

Co-stimulation blockade can be used to modulate the immune response for induction of organ transplantation tolerance, treatment of autoimmune disease as well as cancer treatment. Cytotoxic T-Lymphocyte Antigen-4 (CTLA-4), also known as CD152, is an important co-stimulatory molecule which serves as a negative regulator for T cell proliferation and differentiation. CTLA-4/CD28-CD80/CD86 pathway is a critical co-stimulatory pathway for adaptive immune response. T cell activation through the T cell receptor and CD28 leads to increased expression of CTLA-4, an inhibitory receptor for CD80 and CD86. MGH MHC-defined miniature swine provide a unique large animal model useful for preclinical studies of transplantation tolerance and immune regulation. In this study, we have expressed the codon-optimized soluble porcine CTLA-4 in the yeast Pichia pastoris system. The secreted porcine CTLA-4 was captured using Ni-Sepharose 6 fast flow resin and further purified using strong anion exchange resin Poros 50HQ. Glycosylation analysis using PNGase F demonstrated the N-linked glycosylation on P. pastoris expressed soluble porcine CTLA-4. To improve the expression level and facilitate the downstream purification we mutated the two potential N-linked glycosylation sites with non-polarized alanines by site-directed mutagenesis. Removal of the two N-glycosylation sites significantly improved the production level from ～2 to ～8mg/L. Biotinylated glycosylated and non-N-glycosylated soluble porcine CTLA-4 both bind to a porcine CD80-expressing B-cell lymphoma cell line (K(D)=13nM) and competitively inhibit the binding of an anti-CD80 monoclonal antibody. The availability of soluble porcine CTLA-4, especially the non-N-glycosylated CTLA-4, will provide a very valuable tool for assessing co-stimulatory blockade treatment for translational studies in the clinically relevant porcine model.