Project description:In recent years, cell-free protein synthesis (CFPS) systems have been used to synthesize proteins, prototype genetic elements, manufacture chemicals, and diagnose diseases. These exciting, novel applications lead to a new wave of interest in the development of new CFPS systems that are derived from prokaryotic and eukaryotic organisms. The eukaryotic Pichia pastoris is emerging as a robust chassis host for recombinant protein production. To expand the current CFPS repertoire, we report here the development and optimization of a eukaryotic CFPS system, which is derived from a protease-deficient strain P. pastoris SMD1163. By developing a simple crude extract preparation protocol and optimizing CFPS reaction conditions, we were able to achieve superfolder green fluorescent protein (sfGFP) yields of 50.16 ± 7.49 μg/ml in 5 h batch reactions. Our newly developed P. pastoris CFPS system fits to the range of the productivity achieved by other eukaryotic CFPS platforms, normally ranging from several to tens of micrograms protein per milliliter in batch mode reactions. Looking forward, we believe that our P. pastoris CFPS system will not only expand the CFPS toolbox for synthetic biology applications, but also provide a novel platform for cost-effective, high-yielding production of complex proteins that need post-translational modification and functionalization.
Project description:Cell-free protein synthesis systems derived from eukaryotic sources often provide comparatively low amounts of several μg per ml of de novo synthesized membrane protein. In order to overcome this, we herein demonstrate the high-yield cell-free synthesis of the human EGFR in a microsome-containing system derived from cultured Sf21 cells. Yields were increased more than 100-fold to more than 285 μg/ml by combination of IRES-mediated protein translation with a continuous exchange cell-free reaction format that allowed for prolonged reaction lifetimes exceeding 24 hours. In addition, an orthogonal cell-free translation system is presented that enabled the site-directed incorporation of p-Azido-L-phenylalanine by amber suppression. Functionality of cell-free synthesized receptor molecules is demonstrated by investigation of autophosphorylation activity in the absence of ligand and interaction with the cell-free synthesized adapter molecule Grb2.
Project description:Protein production in yeasts is related to the specific growth rate μ. To elucidate on this correlation, we studied the transcriptome of Pichia pastoris at different specific growth rates by cultivating a strain secreting human serum albumin at μ = 0.015 to 0.15 h(-1) in glucose-limited chemostats. Genome-wide regulation revealed that translation-related as well as mitochondrial genes were upregulated with increasing μ, while autophagy and other proteolytic processes, carbon source-responsive genes and other targets of the TOR pathway as well as many transcriptional regulators were downregulated at higher μ. Mating and sporulation genes were most active at intermediate μ of 0.05 and 0.075 h(-1) . At very slow growth (μ = 0.015 h(-1) ) gene regulation differs significantly, affecting many transporters and glucose sensing. Analysis of a subset of genes related to protein folding and secretion reveals that unfolded protein response targets such as translocation, endoplasmic reticulum genes, and cytosolic chaperones are upregulated with increasing growth rate while proteolytic degradation of secretory proteins is downregulated. We conclude that a high μ positively affects specific protein secretion rates by acting on multiple cellular processes.
Project description:BackgroundPichia pastoris (syn. Komagataella phaffii) is a widely used generally recognized as safe host for heterologous expression of proteins in both industry and academia. Recently, it has been shown to be a potentially good chassis host for the production of high-value pharmaceuticals and chemicals. Nevertheless, limited availability of selective markers and low efficiency of homologous recombination make this process difficult and time-consuming, particularly in the case of multistep biosynthetic pathways. Therefore, it is crucial to develop an efficient and marker-free multiloci gene knock-in method in P. pastoris.ResultsA non-homologous-end-joining defective strain (Δku70) was first constructed using the CRISPR-Cas9 based gene deficiency approach. It was then used as a parent strain for multiloci gene integration. Ten guide RNA (gRNA) targets were designed within 100 bp upstream of the promoters or downstream of terminator, and then tested using an eGFP reporter and confirmed as suitable single-locus integration sites. Three high-efficiency gRNA targets (PAOX1UP-g2, PTEF1UP-g1, and PFLD1UP-g1) were selected for double- and triple-locus co-integration. The integration efficiency ranged from 57.7 to 70% and 12.5 to 32.1% for double-locus and triple-locus integration, respectively. In addition, biosynthetic pathways of 6-methylsalicylic acid and 3-methylcatechol were successfully assembled using the developed method by one-step integration of functional genes. The desired products were obtained, which further established the effectiveness and applicability of the developed CRISPR-Cas9-mediated gene co-integration method in P. pastoris.ConclusionsA CRISPR-Cas9-mediated multiloci gene integration method was developed with efficient gRNA targets in P. pastoris. Using this method, multiple gene cassettes can be simultaneously integrated into the genome without employing selective markers. The multiloci integration strategy is beneficial for pathway assembly of complicated pharmaceuticals and chemicals expressed in P. pastoris.
Project description:Materials science and genetic engineering have joined forces over the last three decades in the development of so-called protein-based polymers. These are proteins, typically with repetitive amino acid sequences, that have such physical properties that they can be used as functional materials. Well-known natural examples are collagen, silk, and elastin, but also artificial sequences have been devised. These proteins can be produced in a suitable host via recombinant DNA technology, and it is this inherent control over monomer sequence and molecular size that renders this class of polymers of particular interest to the fields of nanomaterials and biomedical research. Traditionally, Escherichia coli has been the main workhorse for the production of these polymers, but the methylotrophic yeast Pichia pastoris is finding increased use in view of the often high yields and potential bioprocessing benefits. We here provide an overview of protein-based polymers produced in P. pastoris. We summarize their physicochemical properties, briefly note possible applications, and detail their biosynthesis. Some challenges that may be faced when using P. pastoris for polymer production are identified: (i) low yields and poor process control in shake flask cultures; i.e., the need for bioreactors, (ii) proteolytic degradation, and (iii) self-assembly in vivo. Strategies to overcome these challenges are discussed, which we anticipate will be of interest also to readers involved in protein expression in P. pastoris in general.
Project description:ObjectiveGlucuronoyl esterase (GE) is an emerging enzyme that improves fractionation of lignin-carbohydrate complexes. However, the commercial availability of GE is limited, which hinders the research of GE-based bioprocesses for its industrial application in lignocellulose biorefineries. This study evaluated a workable, cost-effective, and commercially scalable production strategy to improve the ease of GE-based research. This strategy consisted of a constitutive and methanol-free enzyme production step coupled with a two-step filtration process. The aim was to determine if this strategy can yield copious amounts of GE, by secretion into the extracellular medium with an acceptable purity that could allow its direct application. This approach was further validated for cellobiose dehydrogenase, another emerging lignocellulose degrading enzyme which is scarcely available at high cost.ResultsThe secreted recombinant enzymes were functionally produced in excess of levels previously reported for constitutive production (1489-2780 mg L-1), and were secreted at moderate to high percentages of the total extracellular protein (51-94%). The constant glycerol feed, implemented during fed-batch fermentation, lead to a decline in growth rate and plateaued productivity. Tangential flow ultrafiltration was used to concentrate cell-free enzyme extracts 5-6-fold, reaching enzyme activity levels (1020-202 U L-1) that could allow their direct application.
Project description:Comparison of transcription profile of Pichia pastoris cells grown on Glucose medium with Pichia pastoris cells grown on Methanol/Glycerol medium, the fermentations were done in a chemostat.
Project description:BackgroundMethanol, synthesized from CO2, is a potentially sustainable one-carbon (C1) resource for biomanufacturing. The use of methanol as a feedstock to produce single cell protein (SCP) has been investigated for decades as an alternative to alleviate the high global demand for animal-derived proteins. The methylotrophic yeast Pichia pastoris is an ideal host for methanol-based SCP synthesis due to its natural methanol assimilation ability. However, improving methanol utilization, tolerance to higher temperature, and the protein content of P. pastoris are also current challenges, which are of great significance to the economical industrial application using methanol as a feedstock for SCP production.ResultsIn the present work, adaptive laboratory evolution (ALE) has been employed to overcome the low methanol utilization efficiency and intolerance to a higher temperature of 33 °C in P. pastoris, associated with reduced carbon loss due to the lessened detoxification of intracellular formaldehyde through the dissimilation pathway and cell wall rearrangement to temperature stress resistance following long-term evolution as revealed by transcriptomic and phenotypic analysis. By strengthening nitrogen metabolism and impairing cell wall synthesis, metabolic engineering further increased protein content. Finally, the engineered strain via multi-strategy produced high levels of SCP from methanol in a pilot-scale fed-batch culture at 33 °C with a biomass of 63.37 g DCW/L, methanol conversion rate of 0.43 g DCW/g, and protein content of 0.506 g/g DCW. SCP obtained from P. pastoris contains a higher percentage of protein compared to conventional foods like soy, fish, meat, whole milk, and is a source of essential amino acids, including methionine, lysine, and branched-chain amino acids (BCAAs: valine, isoleucine, leucine).ConclusionsThis study clarified the unique mechanism of P. pastoris for efficient methanol utilization, higher temperature resistance, and high protein synthesis, providing a P. pastoris cell factory for SCP production with environmental, economic, and nutritional benefits.
Project description:The methylotrophic yeast, Pichiapastoris, is an important organism used for the production of therapeutic proteins. However, the presence of fungal-like glycans, either N-linked or O-linked, can elicit an immune response or enable the expressed protein to bind to mannose receptors, thus reducing their efficacy. Previously we have reported the elimination of β-linked glycans in this organism. In the current report we have focused on reducing the O-linked mannose content of proteins produced in P. pastoris, thereby reducing the potential to bind to mannose receptors. The initial step in the synthesis of O-linked glycans in P. pastoris is the transfer of mannose from dolichol-phosphomannose to a target protein in the yeast secretory pathway by members of the protein-O-mannosyltransferase (PMT) family. In this report we identify and characterize the members of the P. pastoris PMT family. Like Candida albicans, P. pastoris has five PMT genes. Based on sequence homology, these PMTs can be grouped into three sub-families, with both PMT1 and PMT2 sub-families possessing two members each (PMT1 and PMT5, and PMT2 and PMT6, respectively). The remaining sub-family, PMT4, has only one member (PMT4). Through gene knockouts we show that PMT1 and PMT2 each play a significant role in O-glycosylation. Both, by gene knockouts and the use of Pmt inhibitors we were able to significantly reduce not only the degree of O-mannosylation, but also the chain-length of these glycans. Taken together, this reduction of O-glycosylation represents an important step forward in developing the P. pastoris platform as a suitable system for the production of therapeutic glycoproteins.
Project description:Snakebite envenomation is a neglected condition that constitutes a public health problem in tropical and subtropical countries, including Brazil. Interestingly, some animals are resistant to snake envenomation due to the presence of inhibitory glycoproteins in their serum that target toxic venom components. DM64 is an acidic glycoprotein isolated from Didelphis aurita (opossum) serum that has been characterized as an inhibitor of the myotoxicity induced by bothropic toxins bearing phospholipase A2 (PLA2) structures. This antitoxic protein can serve as an excellent starting template for the design of novel therapeutics against snakebite envenomation, particularly venom-induced local tissue damage. Therefore, the aim of this work was to produce a recombinant DM64 (rDM64) in the methylotrophic yeast Pichia pastoris and to compare its biological properties with those of native DM64. Yeast fermentation in the presence of Pefabloc, a serine protease inhibitor, stimulated cell growth (~1.5-fold), increased the rDM64 production yield approximately 10-fold and significantly reduced the susceptibility of rDM64 to proteolytic degradation. P. pastoris fermentation products were identified by mass spectrometry and Western blotting. The heterologous protein was efficiently purified from the culture medium by affinity chromatography (with immobilized PLA2 myotoxin) and/or an ion exchange column. Although both native and recombinant DM64 exhibit different glycosylation patterns, they show very similar electrophoretic mobilities after PNGase F treatment. rDM64 formed a noncovalent complex with myotoxin II (Lys49-PLA2) from Bothrops asper and displayed biological activity that was similar to that of native DM64, inhibiting the cytotoxicity of myotoxin II by 92% at a 1:1 molar ratio.