Expression of enzymes for the usage in food and feed industry with Pichia pastoris

Improvement of bread making quality by supplementation with a recombinant xylanase produced by Pichia pastoris

Xylanases (EC 3.2.1.8) are hydrolytic enzymes, which randomly cleave the β-1,4-linked xylose residues from xylan. The synthetic gene xynBS27 from Streptomyces sp. S27 was successfully cloned and expressed in Pichia pastoris. The full-length gene consists of 729 bp and encodes 243 amino acids including 51 residues of a putative signal peptide. This enzyme was purified in two steps and was shown to have a molecular weight of 20 kDa. The purified r-XynBS27 was active against beechwood xylan and oat spelt xylan as expected for GH 11 family. The optimum pH and temperature values for the enzyme were 6.0 and 75 °C, respectively. The Km and Vmax were 12.38 mg/mL and 13.68 μmol min/mg, respectively. The r-XynBS27 showed high xylose tolerance and was inhibited by some metal ions and by SDS. r-XynBS27 was employed as an additive in the bread making process. A decrease in firmness, stiffness and consistency, and improvements in specific volume and reducing sugar content were recorded.

High level production of a recombinant acid stable exoinulinase from Aspergillus kawachii

Exoinulinases-enzymes extensively studied in recent decades because of their industrial applications-need to be produced in suitable quantities in order to meet production demands. We describe here the production of an acid-stable recombinant inulinase from Aspergillus kawachii in the Pichia pastoris system and the recombinant enzyme's biochemical characteristics and potential application to industrial processes. After an appropriate cloning strategy, this genetically engineered inulinase was successfully overproduced in fed-batch fermentations, reaching up to 840 U/ml after a 72-h cultivation. The protein, purified to homogeneity by chromatographic techniques, was obtained at a 42% yield. The following biochemical characteristics were determined: the enzyme had an optimal pH of 3, was stable for at least 3 h at 55 °C, and was inhibited in catalytic activity almost completely by Hg⁺². The respective K_m and V_max for the recombinant inulinase with inulin as substrate were 1.35 mM and 2673 μmol/min/mg. The recombinant enzyme is an exoinulinase but also possesses synthetic activity (i. e., fructosyl transferase). The high level of production of this recombinant plus its relevant biochemical properties would argue that the process presented here is a possible recourse for industrial applications in carbohydrate processing.

Evaluating Potential Risks of Food Allergy and Toxicity of Soy Leghemoglobin Expressed in Pichia pastoris

SCOPE

The Soybean (Glycine max) leghemoglobin c2 (LegHb) gene was introduced into Pichia pastoris yeast for sustainable production of a heme-carrying protein, for organoleptic use in plant-based meat. The potential allergenicity and toxicity of LegHb and 17 Pichia host-proteins each representing ≥1% of total protein in production batches are evaluated by literature review, bioinformatics sequence comparisons to known allergens or toxins, and in vitro pepsin digestion.

METHODS AND RESULTS

Literature searches found no evidence of allergenicity or toxicity for these proteins. There are no significant sequence matches of LegHb to known allergens or toxins. Eleven Pichia proteins have modest identity matches to minor environmental allergens and 13 Pichia proteins have significant matches to proteins from toxic sources. Yet the matched allergens and toxins have similar matches to proteins from the commonly consumed yeast Saccharomyces cerevisiae, without evidence of food allergy or toxicity. The demonstrated history of safe use indicates additional tests for allergenicity and toxicity are not needed. The LegHb and Pichia sp. proteins were rapidly digested by pepsin at pH 2.

CONCLUSION

These results demonstrate that foods containing recombinant soy LegHb produced in Pichia sp. are unlikely to present an unacceptable risk of allergenicity or toxicity to consumers.

Identification of novel factors enhancing recombinant protein production in multi-copy Komagataella phaffii based on transcriptomic analysis of overexpression effects

The methylotrophic yeast Komagataella phaffii (Pichia pastoris) has been developed into a highly successful system for heterologous protein expression in both academia and industry. However, overexpression of recombinant protein often leads to severe burden on the physiology of K. phaffii and triggers cellular stress. To elucidate the global effect of protein overexpression, we set out to analyze the differential transcriptome of recombinant strains with 12 copies and a single copy of phospholipase A₂ gene (PLA₂) from Streptomyces violaceoruber. Through GO, KEGG and heat map analysis of significantly differentially expressed genes, the results indicated that the 12-copy strain suffered heavy cellular stress. The genes involved in protein processing and stress response were significantly upregulated due to the burden of protein folding and secretion, while the genes in ribosome and DNA replication were significantly downregulated possibly contributing to the reduced cell growth rate under protein overexpression stress. Three most upregulated heat shock response genes (CPR6, FES1, and STI1) were co-overexpressed in K. phaffii and proved their positive effect on the secretion of reporter enzymes (PLA₂ and prolyl endopeptidase) by increasing the production up to 1.41-fold, providing novel helper factors for rational engineering of K. phaffii.

Engineering strategies for enhanced production of protein and bio-products in Pichia pastoris: A review

Pichia pastoris has been recognized as one of the most industrially important hosts for heterologous protein production. Despite its high protein productivity, the optimization of P. pastoris cultivation is still imperative due to strain- and product-specific challenges such as promoter strength, methanol utilization type and oxygen demand. To address the issues, strategies involving genetic and process engineering have been employed. Optimization of codon usage and gene dosage, as well as engineering of promoters, protein secretion pathways and methanol metabolic pathways have proved beneficial to innate protein expression levels. Large-scale production of proteins via high cell density fermentation additionally relies on the optimization of process parameters including methanol feed rate, induction temperature and specific growth rate. Recent progress related to the enhanced production of proteins in P. pastoris via various genetic engineering and cultivation strategies are reviewed. Insight into the regulation of the P. pastoris alcohol oxidase 1 (AOX1) promoter and the development of methanol-free systems are highlighted. Novel cultivation strategies such as mixed substrate feeding are discussed. Recent advances regarding substrate and product monitoring techniques are also summarized. Application of P. pastoris to the production of biodiesel and other value-added products via metabolic engineering are also reviewed. P. pastoris is becoming an indispensable platform through the use of these combined engineering strategies.

A novel bi-directional promoter system allows tunable recombinant protein production in Pichia pastoris

Background

The methylotrophic yeast Pichia pastoris is a well-studied host organism for recombinant protein production, which is usually regulated either by a constitutive promoter (e.g. promoter of glyceraldehyde-3-phosphate dehydrogenase; P_GAP) or an inducible promoter (e.g. promoter of alcohol oxidase 1; P_AOX1). Both promoter systems have several advantages and disadvantages; with one of the main disadvantages being their lack of tunability. Various novel promoter systems, which are either inducible or de-repressed, allowing higher degrees of freedom, have been reported. Recently, bi-directional promoter systems in P. pastoris with two promoter systems regulating recombinant expression of one or more genes were developed. In this study, we introduce a novel bi-directional promoter system combining a modified catalase promoter system (P_DC; derepressible and inducible) and the traditional P_AOX1, allowing tunable recombinant protein production.

Results

We characterized a recombinant P. pastoris strain, carrying the novel bi-directional promoter system, during growth and production in three dynamic bioreactor cultivations. We cloned the model enzyme cellobiohydralase downstream of either promoter and applied different feeding strategies to determine the physiological boundaries of the strain. We succeeded in demonstrating tunability of recombinant protein production solely in response to the different feeding strategies and identified a mixed feed regime allowing highest productivity.

Conclusion

In this feasibility study, we present the first controlled bioreactor experiments with a recombinant P. pastoris strain carrying a novel bi-directional promotor combination of a catalase promoter variant (P_DC) and the traditional P_AOX1. We demonstrated that this bi-directional promoter system allows tunable recombinant protein expression only in response to the available C-sources. This bi-directional promoter system offers a high degree of freedom for bioprocess design and development, making bi-directional promoters in P. pastoris highly attractive for recombinant protein production.

Recycling of a selectable marker with a self-excisable plasmid in Pichia pastoris

Pichia pastoris is a widely used heterologous protein production workhorse. However, with its multiple genetic modifications to solve bottlenecks for heterologous protein productivity, P. pastoris lacks selectable markers. Existing selectable marker recycling plasmids have drawbacks (e.g., slow growth and conditional lethality). Here, zeocin-resistance marker recycling vectors were constructed using the Cre/loxP recombination system. The vectors were used to (i) knock in heterologous phytase, xylanase and lipase expression cassettes, (ii) increase the phytase, xylanase and lipase gene copy number to 13, 5, and 5, respectively, with vector introduction and (iii) engineer the secretion pathway by co-overexpressing secretion helper factors (Sly1p and Sec1p) without introducing selectable markers, giving a phytase field of 0.833 g/L. The vectors allow selectable marker recycling and would be a useful tool to engineer P. pastoris for high heterologous protein productivity.

A Novel Vector for Construction of Markerless Multicopy Overexpression Transformants in Pichia pastoris

Pichia pastoris is widely used as a platform for heterologous protein expression because of its high volumetric productivity. Multicopy integration of the target gene is commonly used to improve the production of the target protein. Cre/lox recombination system is a powerful tool for the marker rescue during multiple integrations with one selection marker. Here we reported a novel expression vector based on the Cre/lox recombination system for multiple integrations of target gene to construct multicopy expression strain of P. pastoris. P_AOX1 promoter was fused to cre to construct a methanol inducible Cre recombinase. The leakage expression of Cre recombinase in Escherichia coli was blocked by introducing the operator gene lacO. The expression vector designed pMCO-AOXα was stable in E. coli and could effectively rescue the Zeocin resistance gene for next round of integration in P. pastoris. Phytase AppA from E. coli was chosen as a reporter gene. Transformants with 2-16 copies of appA were constructed by using a single antibiotic. Expression of appA was gene dosage dependent when <12 copies were integrated. The protein yield increased 4.45-folds when 12 copies of appA were integrated comparing with the single copy integration. Our results showed that pMCO-AOXα was highly effective for rational construction of multicopy transformat in P. pastoris.

Genome and metabolic engineering in non-conventional yeasts: Current advances and applications

Microbial production of chemicals and proteins from biomass-derived and waste sugar streams is a rapidly growing area of research and development. While the model yeast Saccharomyces cerevisiae is an excellent host for the conversion of glucose to ethanol, production of other chemicals from alternative substrates often requires extensive strain engineering. To avoid complex and intensive engineering of S. cerevisiae, other yeasts are often selected as hosts for bioprocessing based on their natural capacity to produce a desired product: for example, the efficient production and secretion of proteins, lipids, and primary metabolites that have value as commodity chemicals. Even when using yeasts with beneficial native phenotypes, metabolic engineering to increase yield, titer, and production rate is essential. The non-conventional yeasts Kluyveromyces lactis, K. marxianus, Scheffersomyces stipitis, Yarrowia lipolytica, Hansenula polymorpha and Pichia pastoris have been developed as eukaryotic hosts because of their desirable phenotypes, including thermotolerance, assimilation of diverse carbon sources, and high protein secretion. However, advanced metabolic engineering in these yeasts has been limited. This review outlines the challenges of using non-conventional yeasts for strain and pathway engineering, and discusses the developed solutions to these problems and the resulting applications in industrial biotechnology.

N-Glycosylation Engineering to Improve the Constitutive Expression of Rhizopus oryzae Lipase in Komagataella phaffii

Our previous studies demonstrated that the N-glycans in Rhizopus chinensis lipase (RCL) was important for its secretion. In order to improve the secretion of Rhizopus oryzae lipase (ROL) under the control of the GAP promoter in Komagataella phaffii, two extra N-glycosylation sites were introduced in ROL according to the position of the N-glycosylation sites of RCL by sequence alignment. The results indicated that the secretion level of ROL was strongly improved by N-glycosylation engineering, and the highest value of extracellular enzyme activity was increased from 0.4 ± 0.2 U/mL to 207 ± 6 U/mL in a shake flask. In the 7-L fermenter, the extracellular enzyme activity of the mutant (2600 ± 43 U/mL) and the total protein concentration (2.5 ± 0.2 g/L) were 218- and 6.25-fold higher than these of the parent, respectively. This study presents a strategy for constitutive recombinant expression of ROL using the GAP promoter combined with N-glycosylation engineering, providing a potential enzyme for application in the food industry.

Production of Chimeric Acidic α-Amylase by the Recombinant Pichia pastoris and Its Applications

Recombinant chimeric α-amylase (Ba-Gt-amy) has been produced extracellularly in Pichia pastoris under AOX promoter. Clones of P. pastoris with multiple gene copies have been generated by multiple transformations and post-transformational vector amplification, which led to 10.7-fold enhancement in α-amylase titre as compared to a clone with a copy of the gene. The recombinant P. pastoris integrated eight copies of Ba-Gt-amy in the genome of P. pastoris, as revealed by real time PCR data analysis. Heterologous protein expression as well as mRNA level of Ba-Gt-amy was higher in multi-copy clone than that with single copy. The pure Ba-Gt-amy expressed in P. pastoris is a glycoprotein of 75 kDa, which is optimally active at pH 4.0 and 60°C with T_1/2 of 40 min at 70°C. The Kinetic parameters and end product analysis suggested that glycosylation has no effect on catalytic properties of Ba-Gt-amy. The enzyme saccharifies soluble as well as raw starches efficiently and generates maltose and maltooligosaccharides, thus, useful in baking and sugar syrup industries. The strategy for generating multi-copy clones is being reported for the first time, which could be useful in enhancing the production of other recombinant proteins.

Discovering Protein-Coding Genes from the Environment: Time for the Eukaryotes?

Eukaryotic microorganisms from diverse environments encompass a large number of taxa, many of them still unknown to science. One strategy to mine these organisms for genes of biotechnological relevance is to use a pool of eukaryotic mRNA directly extracted from environmental samples. Recent reports demonstrate that the resulting metatranscriptomic cDNA libraries can be screened by expression in yeast for a wide range of genes and functions from many of the different eukaryotic taxa. In combination with novel emerging high-throughput technologies, we anticipate that this approach should contribute to exploring the functional diversity of the eukaryotic microbiota.

A high-throughput expression screening platform to optimize the production of antimicrobial peptides

Background

Antimicrobial peptides (AMPs) are promising candidates for the development of novel antibiotics, but it is difficult to produce sufficient quantities for preclinical and clinical studies due to their toxicity towards microbial expression hosts. To avoid laborious trial-and-error testing for the identification of suitable expression constructs, we have developed a small-scale expression screening platform based on a combinatorial plasmid library.

Results

The combinatorial library is based on the Golden Gate cloning system. In each reaction, six donor plasmids (each containing one component: a promoter, fusion partner 1, fusion partner 2, protease cleavage site, gene of interest, or transcriptional terminator) were combined with one acceptor plasmid to yield the final expression construct. As a proof of concept, screening was carried out in Escherichia coli and Pichia pastoris to study the expression of three different model AMPs with challenging characteristics, such as host toxicity or multiple disulfide bonds. The corresponding genes were successfully cloned in 27 E. coli and 18 P. pastoris expression plasmids, each in a one-step Golden Gate reaction. After transformation, small-scale expression screening in microtiter plates was followed by AMP quantification using a His₆ tag-specific ELISA. Depending on the plasmid features and the expression host, the protein yields differed by more than an order of magnitude. This allowed the identification of high producers suitable for larger-scale protein expression.

Conclusions

The optimization of recombinant protein production is best achieved from first principles by initially optimizing the genetic construct. The unrestricted combination of multiple plasmid features yields a comprehensive library of expression strains that can be screened for optimal productivity. The availability of such a platform could benefit all laboratories working in the field of recombinant protein expression.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-017-0637-5) contains supplementary material, which is available to authorized users.

Recent advances in the production of recombinant subunit vaccines in Pichia pastoris

Recombinant protein subunit vaccines are formulated using defined protein antigens that can be produced in heterologous expression systems. The methylotrophic yeast Pichia pastoris has become an important host system for the production of recombinant subunit vaccines. Although many basic elements of P. pastoris expression system are now well developed, there is still room for further optimization of protein production. Codon bias, gene dosage, endoplasmic reticulum protein folding and culture condition are important considerations for improved production of recombinant vaccine antigens. Here we comment on current advances in the application of P. pastoris for the synthesis of recombinant subunit vaccines.

Production and Anti-Melanoma Activity of Methoxyisoflavones from the Biotransformation of Genistein by Two Recombinant Escherichia coli Strains

Biotransformation of the soy isoflavone genistein by sequential 3'-hydroxylation using recombinant Escherichia coli expressing tyrosinase from Bacillus megaterium and then methylation using another recombinant E. coli expressing O-methyltransferase from Streptomyces peucetius was conducted. The results showed that two metabolites were produced from the biotransformation, identified as 5,7,4'-trihydroxy-3'-methoxyisoflavone and 5,7,3'-trihydroxy-4'-methoxyisoflavone, respectively, based on their mass and nuclear magnetic resonance spectral data. 5,7,4'-Trihydroxy-3'-methoxyisoflavone showed potent antiproliferative activity toward mouse B16 melanoma cells with an IC₅₀ value of 68.8 μM. In contrast, the compound did not show any cytotoxicity toward mouse normal fibroblast cells, even at 350 μM concentration. The results of the present study offer insight on the production of both 5,7,4'-trihydroxy-3'-methoxyisoflavone and 5,7,3'-trihydroxy-4'-methoxyisoflavone by two recombinant E. coli strains and the potential anti-melanoma applications of 5,7,4'-trihydroxy-3'-methoxyisoflavone.

High-level expression and characterization of a novel cutinase from Malbranchea cinnamomea suitable for butyl butyrate production

BACKGROUND

Butyl butyrate has been considered as a promising fuel source because it is a kind of natural ester which can be converted from renewable and sustainable lignocellulosic biomass. Compared with the conventional chemical methods for butyl butyrate production, the enzymatic approach has been demonstrated to be more attractive, mainly owing to the mild reaction conditions, high specificity, low energy consumption, and environmental friendliness. Cutinases play an important role in the butyl butyrate production process. However, the production level of cutinases is still relatively low. Thus, to identify novel cutinases suitable for butyl butyrate synthesis and enhance their yields is of great value in biofuel industry.

RESULTS

A novel cutinase gene (McCut) was cloned from a thermophilic fungus Malbranchea cinnamomea and expressed in Pichia pastoris. The highest cutinase activity of 12, 536 U/mL was achieved in 5-L fermentor, which is by far the highest production for a cutinase. McCut was optimally active at pH 8.0 and 45 °C. It exhibited excellent stability within the pH range of 3.0-10.5 and up to 75 °C. The cutinase displayed broad substrate specificity with the highest activity towards p-nitrophenyl butyrate and tributyrin. It was capable of hydrolyzing cutin, polycaprolactone, and poly(butylene succinate). Moreover, McCut efficiently synthesized butyl butyrate with a maximum esterification efficiency of 96.9% at 4 h. The overall structure of McCut was resolved as a typical α/β-hydrolase fold. The structural differences between McCut and Aspergillus oryzae cutinase in groove and loop provide valuable information for redesign of McCut. These excellent features make it useful in biosynthesis and biodegradation fields.

CONCLUSIONS

A novel cutinase from M. cinnamomea was identified and characterized for the first time. High-level expression by P. pastoris is by far the highest for a cutinase. The enzyme exhibited excellent stability and high esterification efficiency for butyl butyrate production, which may make it a good candidate in biofuel and chemical industries.

Recent advances of molecular toolbox construction expand Pichia pastoris in synthetic biology applications

Pichia pastoris: (reclassified as Komagataella phaffii), a methylotrophic yeast strain has been widely used for heterologous protein production because of its unique advantages, such as readily achievable high-density fermentation, tractable genetic modifications and typical eukaryotic post-translational modifications. More recently, P. pastoris as a metabolic pathway engineering platform has also gained much attention. In this mini-review, we addressed recent advances of molecular toolboxes, including synthetic promoters, signal peptides, and genome engineering tools that established for P. pastoris. Furthermore, the applications of P. pastoris towards synthetic biology were also discussed and prospected especially in the context of genome-scale metabolic pathway analysis.

Expression and characterization of a Talaromyces marneffei active phospholipase B expressed in a Pichia pastoris expression system

Phospholipase B is a virulence factor for several clinically important pathogenic fungi, including Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus, but its role in the thermally dimorphic fungus Talaromyces marneffei remains unclear. Here, we provide the first report of the expression of a novel phospholipase gene, designated TmPlb1, from T. marneffei in the eukaryotic expression system of Pichia pastoris GS115. Sensitive real-time quantitative reverse-transcription PCR (qRT-PCR) demonstrated that the expression of TmPlb1 increased 1.85-fold in the yeast phase compared with the mycelial phase. TmPlb1 contains an open reading frame (ORF) of 732 bp that encodes a protein of 243 amino acids. The conserved serine, aspartate and histidine catalytic triad and the G-X-S-X-G domain of TmPLB1 provide the structural basis for its molecular activity. The ORF of TmPlb1 was successfully cloned into a pPIC9K vector containing an α-mating factor secretion signal that allowed the secretory expression of TmPLB1 in P. pastoris. The heterologous protein expression began 12 h after methanol induction and peaked at 96 h. Through analysis with SDS-polyacrylamide gel electrophoresis (SDS-PAGE), western blotting and mass spectrometry, we confirmed that TmPLB1 was successfully expressed. Through Ni-affinity chromatography, TmPLB1 was highly purified, and its concentration reached 240.4 mg/L of culture medium. With specific substrates, the phospholipase A1 and phospholipase A2 activities of TmPLB1 were calculated to be 5.96 and 1.59 U/mg, respectively. The high purity and activity of the TmPLB1 obtained here lay a solid foundation for further investigation.

Beyond bread and beer: whole cell protein extracts from baker's yeast as a bulk source for 3D cell culture matrices

Here, we present a novel approach to form hydrogels from yeast whole cell protein. Countless hydrogels are available for sophisticated research, but their fabrication is often difficult to reproduce, with the gels being complicated to handle or simply too expensive. The yeast hydrogels presented here are polymerized using a four-armed, amine reactive crosslinker and show a high chemical and thermal resistance. The free water content was determined by measuring swelling ratios for different protein concentrations, and in a freeze-drying approach, pore sizes of up to 100 μm in the gel could be created without destabilizing the 3D network. Elasticity was proofed to be adjustable with the help of atomic force microscopy by merely changing the amount of used protein. Furthermore, the material was tested for possible cell culture applications; diffusion rates in the network are high enough for sufficient supply of human breast cancer cells and adenocarcinomic human alveolar basal epithelial cells with nutrition, and cells showed high viabilities when tested for compatibility with the material. Furthermore, hydrogels could be functionalized with RGD peptide and the optimal concentration for sufficient cell adhesion was determined to be 150 μM. Given that yeast protein is one of the cheapest and easiest available protein sources and that hydrogels are extremely easy to handle, the developed material has highly promising potential for both sophisticated cell culture techniques as well as for larger scale industrial applications.

Structural characterization of the α-mating factor prepro-peptide for secretion of recombinant proteins in Pichia pastoris

The methylotrophic yeast Pichia pastoris has been used extensively for expressing recombinant proteins because it combines the ease of genetic manipulation, the ability to provide complex posttranslational modifications and the capacity for efficient protein secretion. The most successful and commonly used secretion signal leader in Pichia pastoris has been the alpha mating factor (MATα) prepro secretion signal. However, limitations exist as some proteins cannot be secreted efficiently, leading to strategies to enhance secretion efficiency by modifying the secretion signal leader. Based on a Jpred secondary structure prediction and knob-socket modeling of tertiary structure, numerous deletions and duplications of the MATα prepro leader were engineered to evaluate the correlation between predicted secondary structure and the secretion level of the reporters horseradish peroxidase (HRP) and Candida antarctica lipase B. In addition, circular dichroism analyses were completed for the wild type and several mutant pro-peptides to evaluate actual differences in secondary structure. The results lead to a new model of MATα pro-peptide signal leader, which suggests that the N and C-termini of MATα pro-peptide need to be presented in a specific orientation for proper interaction with the cellular secretion machinery and for efficient protein secretion.

A Novel Phytase Derived from an Acidic Peat-Soil Microbiome Showing High Stability under Acidic Plus Pepsin Conditions

Four novel phytases of the histidine acid phosphatase family were identified in two publicly available metagenomic datasets of an acidic peat-soil microbiome in northeastern Bavaria, Germany. These enzymes have low similarity to all the reported phytases. They were overexpressed in <i>Escherichia coli</i> and purified. Catalytic efficacy in simulated gastric fluid was measured and compared among the four candidates. The phytase named rPhyPt4 was selected for its high activity. It is the first phytase identified from unculturable Acidobacteria. The phytase showed a longer half-life than all the gastric-stable phytases that have been reported to date, suggesting a strong resistance to low pH and pepsin. A wide pH profile was observed between pH 1.5 and 5.0. At the optimum pH (2.5) the activity was 2,790 μmol/min/mg at the physiological temperature of 37°C and 3,989 μmol/min/mg at the optimum temperature of 60°C. Due to the competent activity level as well as the high gastric stability, the phytase could be a potential candidate for practical use in livestock and poultry feeding

The bud tip is the cellular hot spot of protein secretion in yeasts

Yeasts are valuable hosts for recombinant protein production. Among them, Pichia pastoris is frequently used for production of secreted proteins, and much effort was made to improve the secretion efficiency of this expression platform. However, the knowledge on the secretion machinery is mainly based on studies in Saccharomyces cerevisiae. Therefore, it is of great interest for targeted improvement of the system to learn more about the secretion process in P. pastoris. Using human serum albumin, a protein which is produced in high quantities in P. pastoris, we show here the secretion pathway of this protein. During passage of the secretory route, the recombinant protein is mainly localized in the endoplasmic reticulum (ER) and in COPII vesicles, and is inherited to the daughter cell via the perinuclear ER. The final release to the cell exterior occurs at the bud, initiating at the bud tip and later spreading over the entire bud surface. The same polarized secretion pattern was observed for a recombinant antibody light chain and the native secretory protein Epx1 of P. pastoris. Clarifying the point of release of secretory proteins will have major impact on engineering the secretory pathway of P. pastoris and other budding yeasts.

Heterologous expression of Aspergillus terreus fructosyltransferase in Kluyveromyces lactis

Fructo-oligosaccharides are prebiotic and hypocaloric sweeteners that are usually extracted from chicory. They can also be produced from sucrose using fructosyltransferases, but the only commercial enzyme suitable for this purpose is Pectinex Ultra, which is produced with Aspergillus aculeatus. Here we used the yeast Kluyveromyces lactis to express a secreted recombinant fructosyltransferase from the inulin-producing fungus Aspergillus terreus. A synthetic codon-optimised version of the putative β-fructofuranosidase ATEG 04996 (XP 001214174.1) from A. terreus NIH2624 was secreted as a functional protein into the extracellular medium. At 60°C, the purified A. terreus enzyme generated the same pattern of oligosaccharides as Pectinex Ultra, but at lower temperatures it also produced oligomers with up to seven units. We achieved activities of up to 986.4U/mL in high-level expression experiments, which is better than previous reports of optimised Aspergillus spp. fermentations.

Production of Protein Complexes in Non-methylotrophic and Methylotrophic Yeasts : Nonmethylotrophic and Methylotrophic Yeasts

Protein complexes can be produced in multimilligram quantities using nonmethylotrophic and methylotrophic yeasts such as Saccharomyces cerevisiae and Komagataella (Pichia) pastoris. Yeasts have distinct advantages as hosts for recombinant protein production owing to their cost efficiency, ease of cultivation and genetic manipulation, fast growth rates, capacity to introduce post-translational modifications, and high protein productivity (yield) of correctly folded protein products. Despite those advantages, yeasts have surprisingly lagged behind other eukaryotic hosts in their use for the production of multisubunit complexes. As our knowledge of the metabolic and genomic bottlenecks that yeast microorganisms face when overexpressing foreign proteins expands, new possibilities emerge for successfully engineering yeasts as superb expression hosts. In this chapter, we describe the current state of the art and discuss future possibilities for the development of yeast-based systems for the production of protein complexes.

A scalable low-cost cGMP process for clinical grade production of the HIV inhibitor 5P12-RANTES in Pichia pastoris

In the continued absence of an effective anti-HIV vaccine, approximately 2 million new HIV infections occur every year, with over 95% of these in developing countries. Calls have been made for the development of anti-HIV drugs that can be formulated for topical use to prevent HIV transmission during sexual intercourse. Because these drugs are principally destined for use in low-resource regions, achieving production costs that are as low as possible is an absolute requirement. 5P12-RANTES, an analog of the human chemokine protein RANTES/CCL5, is a highly potent HIV entry inhibitor which acts by achieving potent blockade of the principal HIV coreceptor, CCR5. Here we describe the development and optimization of a scalable low-cost production process for 5P12-RANTES based on expression in Pichia pastoris. At pilot (150 L) scale, this cGMP compliant process yielded 30 g of clinical grade 5P12-RANTES. As well as providing sufficient material for the first stage of clinical development, this process represents an important step towards achieving production of 5P12-RANTES at a cost and scale appropriate to meet needs for topical HIV prevention worldwide.

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New medicines are required to prevent the spread of HIV/AIDS in low-resource regions.

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5P12-RANTES, a chemokine analog, is a promising new candidate drug.

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We describe a process for producing clinical grade cGMP 5P12-RANTES in Pichia pastoris.

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This is a key step to achieving production at cost and scale appropriate for use worldwide.