Role of N-linked glycosylation in the secretion and enzymatic properties of Rhizopus chinensis lipase expressed in Pichia pastoris

Optimizing Pichia pastoris protein secretion: Role of N-linked glycosylation on the α-mating factor secretion signal leader

The methylotrophic yeast, Pichia pastoris (P. pastoris; syn. Komagataella spp.), known for its ability to grow to high cell densities, its strong and tightly regulated promoters, and mammalian liked secretion pathway, has been widely used as a robust system to secrete heterologous proteins. The α-mating factor (MF) secretion signal leader from Saccharomyces cerevisiae (S. cerevisiae) is currently the most successfully used secretion signal sequence in the P. pastoris system. In this study, the secretion efficiency mediated by the α-MF secretion signal leaders from Komagataella pastoris (K. pastoris) and Komagataella phaffii (K. phaffii) was assessed using Enhanced Green Fluorescent Protein (EGFP) as a reporter. The results indicated that the secretion efficiency associated with the α-MF secretion signal leaders from K. pastoris and K. phaffii was notably lower in comparison to the α-MF secretion signal leader from S. cerevisiae. Further research indicated that N-linked glycosylation of the α-MF secretion signal leader enhanced the secretion of EGFP. Disruption of calnexin impaired the secretion of EGFP mediated by the N-linked glycosylated α-MF secretion signal leader, without affecting EGFP secretion mediated by the non-N-linked glycosylation α-MF secretion signal leader. The N-linked glycosylated of the α-MF secretion signal leader reduced the unfolded protein response (UPR) in the endoplasmic reticulum (ER). The enhancement of EGFP secretion by the N-linked glycosylated α-MF secretion signal leader might be achieved through the acceleration of proper folding of glycoproteins by the molecular chaperone calnexin. This study enhances the understanding of protein secretion in P. pastoris, specifically highlighting the influence of N-linked glycosylation on secretion efficiency, and could have implications for the production of recombinant proteins in bioengineering and biotechnological applications in P. pastoris.

Highly efficient expression of Rasamsonia emersonii lipase in Pichia pastoris: characterization and gastrointestinal simulated digestion in vitro

BACKGROUND

Acidic lipases with high catalytic activities under acidic conditions have important application values in the food, feed and pharmaceutical industries. However, the availability of acidic lipases is still the main obstacle to their industrial applications. Although a novel acidic lipase Rasamsonia emersonii (LIPR) was heterologously expressed in Escherichia coli, the expression level was unsatisfactory.

RESULTS

To achieve the high-efficiency expression and secretion of LIPR in Pichia pastoris GS115, the combinatorial optimization strategy was adopted including gene codon preference, signal peptide, molecular chaperone co-expression and disruption of vacuolar sorting receptor VPS10. The activity of the combinatorial optimization engineered strain in a shake flask reached 1480 U mL-1, which was 8.13 times greater than the P. pastoris GS115 parental strain. After high-density fermentation in a 5-L bioreactor, the highest enzyme activity reached as high as 11 820 U mL-1. LIPR showed the highest activity at 40 °C and pH 4.0 in the presence of Ca2+ ion. LIPR exhibited strong tolerance to methanol, indicating its potential application in biodiesel biosynthesis. Moreover, the gastrointestinal digestion simulation results demonstrated that LIPR was tolerant to pepsin and trypsin, but its activity was inhibited by sodium taurodeoxycholate.

CONCLUSION

This study provided an effective approach for the high expression of acidic lipase LIPR. LIPR was more appropriate for lipid digestion in the stomach than in intestine according to the gastrointestinal digestion simulation results. © 2024 Society of Chemical Industry.

Glycosylation of cellulase: a novel strategy for improving cellulase

Protein glycosylation is the most complex posttranslational modification process. Most cellulases from filamentous fungi contain N-glycosylation and O-glycosylation. Here, we discuss the potential roles of glycosylation on the characteristics and function of cellulases. The use of certain cultivation, inducer, and alteration of engineering glycosylation pathway can enable the rational control of cellulase glycosylation. Glycosylation does not occur arbitrarily and may tend to modify the 3D structure of cellulases by using specially distributed glycans. Therefore, glycoengineering should be considered comprehensively along with the spatial structure of cellulases. Cellulase glycosylation may be an evolution phenomenon, which has been considered as an economical way for providing different functions from identical proteins. In addition to gene and transcription regulations, glycosylation may be another regulation on the protein expression level. Enhanced understanding of the potential regulatory role of cellulase glycosylation will enable synthetic biology approaches for the development of commercial cellulase.

High-Level Expression and Biochemical Characterization of a Maltotetraose Amylase in Pichia pastoris X-33 for Maltotetraose Production

Maltotetraose amylase, which catalyzes the hydrolysis of amylaceous polysaccharides into maltooligosaccharides with maltotetraose as the main product, is extensively used in the food industry. However, the lack of efficient expression system for maltotetraose amylase has hampered its production and application. In this study, high-level production of a maltotetraose amylase mutant (referred to as Pp-Mta∆CBM) from Pseudomonas saccharophila was achieved in Pichia pastoris X-33. First, the gene of maltotetraose amylase with the carbohydrate-binding module (CBM) removed was codon-optimized and cloned into the pPICZαA vector, followed by transformation into P. pastoris X-33 for expression. Using the promoter PAOX1 and signal peptide α-factor, high-level production of Pp-Mta∆CBM with minimal extracellular impurity proteins was achieved, resulting in an extracellular activity of 367.9 U/mL after 7 days of cultivation in shake flasks. Next, the expressed Pp-Mta∆CBM was purified and characterized. This recombinant enzyme was glycosylated and has maximum activity at 55 ℃ and pH 7.0. Its Km for soluble starch was 4.1 g/L, and its kcat was 3237.6 s-1. Finally, the Pp-Mta∆CBM was found to produce a maximum maltotetraose yield of 57.1% in the presence of 200 g/L of substrate. The findings presented in this study demonstrate the efficient production of Pp-Mta∆CBM in P. pastoris, providing a new expression system for maltotetraose amylase and laying the foundation for its scale-up production and industrial application.

Biochemical analyses of a novel acidophilic GH5 β-mannanase from Trichoderma asperellum ND-1 and its application in mannooligosaccharides production from galactomannans

In this study, an acidophilic GH5 β-mannanase (TaMan5) from Trichoderma asperellum ND-1 was efficiently expressed in Pichia pastoris (a 2.0-fold increase, 67.5 ± 1.95 U/mL). TaMan5 displayed the highest specificity toward locust bean gum (K_m = 1.34 mg/mL, V_max = 749.14 μmol/min/mg) at pH 4.0 and 65°C. Furthermore, TaMan5 displayed remarkable tolerance to acidic environments, retaining over 80% of its original activity at pH 3.0-5.0. The activity of TaMan5 was remarkably decreased by Cu²⁺, Mn²⁺, and SDS, while Fe²⁺/Fe³⁺ improved the enzyme activity. A thin-layer chromatography (TLC) analysis of the action model showed that TaMan5 could rapidly degrade mannan/MOS into mannobiose without mannose via hydrolysis action as well as transglycosylation. Site-directed mutagenesis results suggested that Glu²⁰⁵, Glu³¹³, and Asp³⁵⁷ of TaMan5 are crucial catalytic residues, with Asp¹⁵² playing an auxiliary function. Additionally, TaMan5 and commercial α-galactosidase displayed a remarkable synergistic effect on the degradation of galactomannans. This study provided a novel β-mannanase with ideal characteristics and can be considered a potential candidate for the production of bioactive polysaccharide mannobiose.

Process development for an effective COVID-19 vaccine candidate harboring recombinant SARS-CoV-2 delta plus receptor binding domain produced by Pichia pastoris

Recombinant protein-based SARS-CoV-2 vaccines are needed to fill the vaccine equity gap. Because protein-subunit based vaccines are easier and cheaper to produce and do not require special storage/transportation conditions, they are suitable for low-/middle-income countries. Here, we report our vaccine development studies with the receptor binding domain of the SARS-CoV-2 Delta Plus strain (RBD-DP) which caused increased hospitalizations compared to other variants. First, we expressed RBD-DP in the Pichia pastoris yeast system and upscaled it to a 5-L fermenter for production. After three-step purification, we obtained RBD-DP with > 95% purity from a protein yield of > 1 g/L of supernatant. Several biophysical and biochemical characterizations were performed to confirm its identity, stability, and functionality. Then, it was formulated in different contents with Alum and CpG for mice immunization. After three doses of immunization, IgG titers from sera reached to > 10⁶ and most importantly it showed high T-cell responses which are required for an effective vaccine to prevent severe COVID-19 disease. A live neutralization test was performed with both the Wuhan strain (B.1.1.7) and Delta strain (B.1.617.2) and it showed high neutralization antibody content for both strains. A challenge study with SARS-CoV-2 infected K18-hACE2 transgenic mice showed good immunoprotective activity with no viruses in the lungs and no lung inflammation for all immunized mice.

Recombinant Hemagglutinin protein and DNA-RNA-combined nucleic acid vaccines harbored by Yeast elicit protective immunity against H9N2 Avian Influenza infection

A safe, convenience, and effective vaccine for controlling avian influenza virus infection is crucial in scale poultry production. Yeasts are considered useful vaccine vehicles for the delivery of antigens, which has been used to protect human and animal health. We report here the development of H9N2 strain hemagglutinin (HA)-based recombinant protein vaccines (rH9HA) and DNA-RNA-combined vaccine (rH9-DNA-RNA) in Saccharomyces cerevisiae for the first time. The immunogenicity assay indicated that both rH9HA and rH9-DNA-RNA could induce robust production of serum IgG, mucosal sIgA, and cellular immune responses. The reshape and diversification of gut microbiota and an enriched Lactobacillus, Debaryomyces were observed after oral immunization with rH9HA or rH9-DNA-RNA yeast vaccine, which might contribute to modulate the intestinal mucosal immunity and antiviral process. Oral immunized birds with either rH9HA or rH9-DNA-RNA were effectively protected from H9N2 virus challenge. Our findings suggested that yeast-derived H9N2 HA-based recombinant protein vaccines and DNA-RNA-combined nucleic acid vaccines are feasible and efficacious, opening up a new avenue for rapid and cost-effective production of avian influenza vaccines to achieve good protection effect.

Current advances of Pichia pastoris as cell factories for production of recombinant proteins

Pichia pastoris (syn. Komagataella spp.) has attracted extensive attention as an efficient platform for recombinant protein (RP) production. For obtaining a higher protein titer, many researchers have put lots of effort into different areas and made some progress. Here, we summarized the most recent advances of the last 5 years to get a better understanding of its future direction of development. The appearance of innovative genetic tools and methodologies like the CRISPR/Cas9 gene-editing system eases the manipulation of gene expression systems and greatly improves the efficiency of exploring gene functions. The integration of novel pathways in microorganisms has raised more ideas of metabolic engineering for enhancing RP production. In addition, some new opportunities for the manufacture of proteins have been created by the application of novel mathematical models coupled with high-throughput screening to have a better overview of bottlenecks in the biosynthetic process.

Effect of N-glycosylation on secretion, stability, and biological activity of recombinant human interleukin-3 (hIL-3) in Pichia pastoris

Human interleukin-3 (hIL-3) is a clinically important cytokine used to treat hematological malignancies, bone marrow transplantation, cytopenias, and immunological disorders. The cloning of hIL-3 gene was previously reported by our group, where its expression was optimized under methanol-inducible AOX1 promoter having N-terminal α mating factor signal sequence from Saccharomyces cerevisiae. This study investigated the role of glycosylation pattern on its molecular stability, secretion efficiency, and biological activity using the mutagenesis approach. The two N-linked glycosylation positions at N15th (Asn15) and N70th (Asn70) were sequentially mutated to generate three recombinant hIL-3 variants, i.e., N15A, N70A, and N15/70A. Asparagine at these positions was replaced with non-polar alanine amino acid (Ala, A). The alteration of N-linked glycosylation sites was disadvantageous to its efficient secretion in Pichia pastoris, where a 52.32%, 36.48%, 71.41% lower production was observed in N15A, N70A, and N15/70A mutants, respectively, as compared to native control. The fully glycosylated native hIL-3 protein showed higher thermal stability over its deglycosylated counterparts. The biological activity of native, N15A, N70A, and N15/70A hIL-3 protein was evaluated, where N15/70A mutant showed slightly higher proliferation efficacy than other combinations.

Different N-Glycosylation Sites Reduce the Activity of Recombinant DSPAα2

Bat plasminogen activators α2 (DSPAα2) has extremely high medicinal value as a powerful natural thrombolytic protein. However, wild-type DSPAα2 has two N-glycosylation sites (N185 and N398) and its non-human classes of high-mannose-type N-glycans may cause immune responses in vivo. By mutating the N-glycosylation sites, we aimed to study the effect of its N-glycan chain on plasminogen activation, fibrin sensitivity, and to observe the physicochemical properties of DSPAα2. A logical structure design was performed in this study. Four single mutants and one double mutant were constructed and expressed in Pichia pastoris. When the N398 site was eliminated, the plasminogen activator in the mutants had their activities reduced to ~40%. When the N185 site was inactivated, there was a weak decrease in the plasminogen activation of its mutant, while the fibrin sensitivity significantly decreased by ~10-fold. Neither N-glycosylation nor deglycosylation mutations changed the pH resistance or heat resistance of DSPAα2. This study confirms that N-glycosylation affects the biochemical function of DSPAα2, which provides a reference for subsequent applications of DSPAα2.

The introduction of an N-glycosylation site into prochymosin greatly enhances its production and secretion by Pichia pastoris

BACKGROUND

N-glycosylation is one of the most important post-translational modifications. Many studies have shown that N-glycosylation has a significant effect on the secretion level of heterologous glycoproteins in yeast cells. However, there have been few studies reporting a clear and unified explanation for the intracellular mechanism that N-glycosylation affect the secretion of heterologous glycoproteins so far. Pichia pastoris is an important microbial cell factory producing heterologous protein. It is of great significance to study the effect of N-glycosylation on the secretion level of heterologous protein. Camel chymosin is a glycoprotein with higher application potential in cheese manufacturing industry. We have expressed camel prochymosin in P. pastoris GS115, but the lower secretion level limits its industrial application. This study attempts to increase the secretion level of prochymosin through N-glycosylation, and explore the molecular mechanism of N-glycosylation affecting secretion.

RESULTS

Adding an N-glycosylation site at the 34th amino acid of the propeptide of prochymosin significantly increased its secretion in P. pastoris. N-glycosylation improved the thermostability of prochymosin without affecting the enzymatic activity. Immunoprecipitation coupled to mass spectrometry (IP-MS) analysis showed that compared with the wild prochymosin (chy), the number of proteins interacting with N-glycosylated mutant (chy34) decreased, and all differential interacting proteins (DIPs) were down-regulated in chy34-GS115 cell. The DIPs in endoplasmic reticulum were mainly concentrated in the misfolded protein pathway. Among the five DIPs in this pathway, overexpression of BiP significantly increased the secretion of chy. The knockout of the possible misfolded protein recognition elements, UDP-glycose:glycoprotein glucosyltransferase 1 and 2 (UGGT1/2) had no effect on the growth of yeast cells and the secretion of prochymosin.

CONCLUSIONS

In conclusion, N-glycosylation increased the secretion of prochymosin in P. pastoris trough the adjustment of intracellular interacted proteins. The results of our study may help to elucidate the molecular mechanism of N-glycosylation affecting secretion and provide a new research method to improve the secretion of heterologous glycoprotein in P. pastoris.

Oral immunization of recombinant Saccharomyces cerevisiae expressing fiber-2 of fowl adenovirus serotype 4 induces protective immunity against homologous infection

Hydropericardium-hepatitis syndrome (HHS) caused by fowl adenovirus (FAdV) serotype 4 strains is a highly contagious disease that causes significant economic loss to the global poultry industry. However, subunit vaccine against FAdV-4 infection is not yet commercially available to date. This study aims to explore the potential for oral immunization of recombinant Saccharomyces cerevisiae expressing Fiber-2 of FAdV-4 as a subunit vaccine. Here, we constructed recombinant S. cerevisiae (ST1814G/Fiber-2) expressing recombinant Fiber-2 (rFiber-2), which was displayed on the cell surface. To evaluate the immune response and protective effect of live recombinant S. cerevisiae, chickens were orally immunized with the constructed live ST1814G/Fiber-2, three times at 5-day intervals, and then challenged with FAdV-4. The results showed that oral administration of live ST1814G/Fiber-2 could stimulate the production of humoral immunity, enhance the body's antiviral activity and immune regulation ability, improve the composition of gut microbiota, provide protection against FAdV-4 challenge, reduce viral load in the liver, and alleviate the pathological damage of heart, liver, and spleen for chicken. In addition, we found the synergistic effect in combining the ST1814G/Fiber-2 yeast and inactivated vaccine to trigger stronger humoral immunity and mucosal immunity. Our results suggest that oral live ST1814G/Fiber-2 is a potentially safer auxiliary preparation strategy in controlling FAdV-4 infection.

Producing Natural Flavours from Isoamyl Alcohol and Fusel Oil by Using Immobilised Rhizopus oryzae Lipase

Enzymatic synthesis of short-chain esters (flavours) might enable their labelling as natural, increasing their value. Covalently immobilised Rhizopus oryzae lipase (EO-proROL) was used to synthesise isoamyl butyrate and acetate. In cyclohexane, the best performer reaction solvent, 1.8 times higher yield of isoamyl butyrate (ca. 100%) than isoamyl acetate (ca. 55%) was obtained. Optimum initial acid concentration (410 mM) and acid:alcohol mole ratio (0.5) were established by a central composite rotatable design to maximise isoamyl butyrate single-batch and cumulative production with reused enzyme. These conditions were used to scale up the esterification (150 mL) and to assess yield, initial esterification rate, productivity and enzyme operational stability. Commercial isoamyl alcohol and fusel oil results were found to be similar as regards yield (91% vs. 84%), initial reaction rate (5.4 µM min−1 with both substrates), operational stability (40% activity loss after five runs with both) and productivity (31.09 vs. 28.7 mM h−1). EO-proROL specificity for the structural isomers of isoamyl alcohol was also evaluated. Thus, a successful biocatalyst and product conditions ready to be used for isoamyl ester industrial production are here proposed.

Enhancing the Thermostability of Phytase to Boiling Point by Evolution-Guided Design

The good thermostability of enzymes is an important basis for their wide application in industry. In this study, the phytase APPA from Yersinia intermedia was designed by evolution-guided design. Through the collection of homologous sequences in the NCBI database, we obtained a sequence set composed of 5,569 sequences, counted the number and locations of motif N-X-T/S, and selected the sites with high frequency in evolution as candidate sites for experiments. Based on the principle that N-glycosylation modification sites are located on the protein surface, 13 mutants were designed to optimize the number and location of N-glycosylation sites. Through experimental verification, 7 single mutants with improved thermostability were obtained. The best mutant, M14, with equal catalytic efficiency as the wild-type was obtained through combined mutation. The half-life (t_1/2) value of mutant M14 was improved from 3.32 min at 65°C to 25 min of at 100°C, allowing it to withstand boiling water treatment, retaining approximately 75% initial activity after a 10-min incubation at 100°C. Differential scanning calorimetry analysis revealed that while the mutants' thermodynamic stability was nearly unchanged, their kinetic stability was greatly improved, and the combined mutant exhibited strong refolding ability. The results of a in vitro digestibility test indicated that the application effect of mutant M14 was about 4.5 times that of wild-type APPA, laying a foundation for its industrial application. IMPORTANCE Due to the harsh reaction conditions of industrial production, the relative instability of enzymes limits their application in industrial production, such as for food, pharmaceuticals, and feed. For example, the pelleting process of feed includes a brief high temperature (80 to 85°C), which requires the enzyme to have excellent thermostability. Therefore, a simple and effective method to improve the thermostability of enzymes has important practical value. In this study, we make full use of the existing homologous sequences (5,569) in the database to statistically analyze the existence frequency of N-X-T/S motifs in this large sequence space to design the phytase APPA with improved thermostability and a high hit rate (~50%). We obtained the best combination mutant, M14, that can tolerate boiling water treatment and greatly improved its kinetic stability without damaging its specific activity. Simultaneously, we proved that its performance improvement is due to its enhanced refolding ability, which comes from N-glycan modification rather than amino acid replacement. Our results provide a feasible and effective method for the modification of enzyme thermostability.

Postbiotics as the new frontier in food and pharmaceutical research

Food is the essential need of human life and has nutrients that support growth and health. Gastrointestinal tract microbiota involves valuable microorganisms that develop therapeutic effects and are characterized as probiotics. The investigations on appropriate probiotic strains have led to the characterization of specific metabolic byproducts of probiotics named postbiotics. The probiotics must maintain their survival against inappropriate lethal conditions of the processing, storage, distribution, preparation, and digestion system so that they can exhibit their most health effects. Conversely, probiotic metabolites (postbiotics) have successfully overcome these unfavorable conditions and may be an appropriate alternative to probiotics. Due to their specific chemical structure, safe profile, long shelf-life, and the fact that they contain various signaling molecules, postbiotics may have anti-inflammatory, immunomodulatory, antihypertensive properties, inhibiting abnormal cell proliferation and antioxidative activities. Consequently, present scientific literature approves that postbiotics can mimic the fundamental and clinical role of probiotics, and due to their unique characteristics, they can be applied in an oral delivery system (pharmaceutical/functional foods), as a preharvest food safety hurdle, to promote the shelf-life of food products and develop novel functional foods or/and for developing health benefits, and therapeutic aims. This review addresses the latest postbiotic applications with regard to pharmaceutical formulations and commercial food-based products. Potential postbiotic applications in the promotion of host health status, prevention of disease, and complementary treatment are also reviewed.

Influence of codon optimization, promoter, and strain selection on the heterologous production of a β-fructofuranosidase from Aspergillus fijiensis ATCC 20611 in Pichia pastoris

Fructooligosaccharides (FOS) are compounds possessing various health properties and are added to functional foods as prebiotics. The commercial production of FOS is done through the enzymatic transfructolysation of sucrose by β-fructofuranosidases which is found in various organisms of which Aureobasidium pullulans and Aspergillus niger are the most well known. This study overexpressed two differently codon-optimized variations of the Aspergillus fijiensis β-fructofuranosidase-encoding gene (fopA) under the transcriptional control of either the alcohol oxidase (AOX1) or glyceraldehyde-3-phosphate dehydrogenase (GAP) promoters. When cultivated in shake flasks, the two codon-optimized variants displayed similar volumetric enzyme activities when expressed under control of the same promoter with the GAP strains producing 11.7 U/ml and 12.7 U/ml, respectively, and the AOX1 strains 95.8 U/ml and 98.6 U/ml, respectively. However, the highest production levels were achieved for both codon-optimized genes when expressed under control of the AOX1 promoter. The AOX1 promoter was superior to the GAP promoter in bioreactor cultivations for both codon-optimized genes with 13,702 U/ml and 2718 U/ml for the AOX1 promoter for ATUM and GeneArt^®, respectively, and 6057 U/ml and 1790 U/ml for the GAP promoter for ATUM and GeneArt^®, respectively. The ATUM-optimized gene produced higher enzyme activities when compared to the one from GeneArt^®, under the control of both promoters.

Disrupting putative N-glycosylation site N17 in lipase Lip11 of Yarrowia lipolytica yielded a catalytically efficient and thermostable variant accompanying conformational changes

Lip11 gene from oleaginous yeast Yarrowia lipolytica MSR80 was recombinantly expressed in Pichia pastoris X33. Native secretion signal present in its sequence resulted in 92 % expression in comparison to α-secretion factor which resulted to 900 U/L in the extracellular broth. Catalytic triad in Lip11, like most lipases, was formed by serine, histidine, and aspartate residues. While point mutation disrupting putative glycosylation site (N389) present towards the C-terminus ruinously effected its stability and catalytic activity, disruption of the first putative glycosylation site (N17) located towards the N-terminus presented interesting insights. Mutation resulted in a variant N1 exhibiting higher thermal and acid stability; a t_1/2 of 198 min was obtained at 50 °C and it retained almost 80 % activity following incubation at pH 3. Catalytic efficiency was improved by 2.7 fold and a 10 °C rise in temperature optima was accompanied by higher relative activity in acidic range. Thermal stability corresponded to convoying structural modifications in the tertiary structure, findings of fluorescence spectroscopy suggested. Thermal fluorescence studies revealed a Tm of 65 °C for both Lip11 and N1 and λmax of Lip11 exhibited a blue shift upon refolding while no shift in the λmax of N1 was observed. A resilient tertiary structure which could fold back to its native confirmation upon thermal denaturation and increase in surface-exposed hydrophobic residues as revealed by ANS binding assay summed up to thermal stability of N1. Furthermore, circular dichroism data disclosed an alternate ratio of alpha-helices and beta-sheets; respective values changed from 36 % and 8%-27% and 19 %. Following mutation, substrate specificity remained unaffected and similar to native protein, N1 showed activation in presence of organic solvents and most divalent cations.

Trehalose supplementation enhanced the biocontrol efficiency of Sporidiobolus pararoseus Y16 through increased oxidative stress tolerance and altered transcriptome

BACKGROUND

In the process of biological control, the antagonistic yeasts contend with various stresses that negatively influence yeasts' biocontrol efficiency. In the current study, we investigated the effect of trehalose supplementation on the biocontrol efficiency and oxidative stress tolerance of Sporidiobolus pararoseus Y16.

RESULTS

S. pararoseus Y16, an antagonistic yeast cultured in trehalose supplemented medium, exhibited better biocontrol efficiency against Penicillium expansum and Aspergillus tubingensis in table grapes. Trehalose-treated S. pararoseus Y16 cells showed good proliferation efficiency and oxidative stress tolerance than untreated cells. Increased β-1,3-glucanase, catalase, superoxide dismutase activity, and low protein carbonylation were observed in trehalose-amended S. pararoseus Y16 upon H₂ O₂ exposure. The RNA sequencing results indicated that trehalose significantly altered the transcriptome of S. pararoseus Y16. The GO, KEGG, and COG annotations revealed that the differentially regulated genes corresponded to the various biological process of the yeast.

CONCLUSION

Our findings suggested that trehalose use could enhance the biocontrol efficiency and oxidative stress tolerance of S. pararoseus Y16. Trehalose supplementation altered the transcriptome of S. pararoseus Y16, particularly the genes that correspond to amino acid metabolism, nucleotide metabolism, and protein modification. Thereby the oxidative stress tolerance and biological control efficiency of S. pararoseus Y16 was enhanced by trehalose. © 2021 Society of Chemical Industry.

Native Structural and Functional Proteoform Characterization of the Prolyl-Alanyl-Specific Endoprotease EndoPro from Aspergillus niger

The prolyl-alanyl-specific endoprotease (EndoPro) is an industrial enzyme produced in Aspergillus niger. EndoPro is mainly used for food applications but also as a protease in proteomics. In-depth characterization of this enzyme is essential to understand its structural features and functionality. However, there is a lack of analytical methods capable of maintaining both the structural and functional integrity of separated proteoforms. In this study, we developed an anion exchange (AEX) method coupled to native mass spectrometry (MS) for profiling EndoPro proteoforms. Moreover, we investigated purified EndoPro proteoforms with complementary MS-based approaches, including released N-glycan and glycopeptide analysis, to obtain a comprehensive overview of the structural heterogeneity. We showed that EndoPro has at least three sequence variants and seven N-glycosylation sites occupied by high-mannose glycans that can be phosphorylated. Each glycosylation site showed high microheterogeneity with ∼20 glycans per site. The functional characterization of fractionated proteoforms revealed that EndoPro proteoforms remained active after AEX-separation and the specificity of these proteoforms did not depend on N-glycan phosphorylation. Nevertheless, our data confirmed a strong pH dependence of EndoPro cleavage activity. Altogether, our study demonstrates that AEX-MS is an excellent tool to characterize complex industrial enzymes under native conditions.

Generation of phytase chimeras with low sequence identities and improved thermal stability

Being able to recombine more than two genes with four or more crossover points in a sequence independent manner is still a challenge in protein engineering and limits our capabilities in tailoring enzymes for industrial applications. By computational analysis employing multiple sequence alignments and homology modeling, five fragments of six phytase genes (sequence identities 31-64 %) were identified and efficiently recombined through phosphorothioate-based cloning using the PTRec method. By combinatorial recombination, functional phytase chimeras containing fragments of up to four phytases were obtained. Two variants (PTRec 74 and PTRec 77) with up to 32 % improved residual activity (90 °C, 60 min) and retained specific activities of > 1100 U/mg were identified. Both variants are composed of fragments from the phytases of Citrobacter braakii, Hafnia alvei and Yersinia mollaretii. They exhibit sequence identities of ≤ 80 % to their parental enzymes, highlighting the great potential of DNA recombination strategies to generate new enzymes with low sequences identities that offer opportunities for property right claims.

Propeptide in Rhizopus chinensis Lipase: New Insights into Its Mechanism of Activity and Substrate Selectivity by Computational Design

Most fungal lipases contain a propeptide, which is very important for their function and substrate selectivity. In the present study, Rhizopus chinensis lipase (RCL) was used as a research model to explore the mechanism of the propeptide of the lipase. Conventional molecular dynamics (MD) and metadynamics simulations were used to explore the mechanism by which the propeptide affects the activity of the lipase, which was subsequently verified by mutation experiments. MD simulations indicated that the propeptide had an inhibitory effect on the lid movement of RCL and found a key region (Val5-Thr10) on the propeptide. Subsequently, site-directed mutations were created in this region. The mutations enhanced the lipase catalytic efficiency to 700% and showed the potential for the propeptide to shift the substrate specificity of RCL. The specificity and activity of RCL mutants also had similar trends to wild-type RCL toward triglycerides with varying chain lengths. The mutual corroboration of simulation and site-directed mutagenesis results revealed the vital role of the key propeptide region in the catalytic activity and substrate specificity of the lipase.

Comparison of Three Glycoproteomic Methods for the Analysis of the Secretome of CHO Cells Treated with 1,3,4-O-Bu3ManNAc

Comprehensive analysis of the glycoproteome is critical due to the importance of glycosylation to many aspects of protein function. The tremendous complexity of this post-translational modification, however, makes it difficult to adequately characterize the glycoproteome using any single method. To overcome this pitfall, in this report we compared three glycoproteomic analysis methods; first the recently developed N-linked glycans and glycosite-containing peptides (NGAG) chemoenzymatic method, second, solid-phase extraction of N-linked glycoproteins (SPEG), and third, hydrophilic interaction liquid chromatography (HILIC) by characterizing N-linked glycosites in the secretome of Chinese hamster ovary (CHO) cells. Interestingly, the glycosites identified by SPEG and HILIC overlapped considerably whereas NGAG identified many glycosites not observed in the other two methods. Further, utilizing enhanced intact glycopeptide identification afforded by the NGAG workflow, we found that the sugar analog 1,3,4-O-Bu₃ManNAc, a "high flux" metabolic precursor for sialic acid biosynthesis, increased sialylation of secreted proteins including recombinant human erythropoietin (rhEPO).

Rhizopus oryzae Lipase, a Promising Industrial Enzyme: Biochemical Characteristics, Production and Biocatalytic Applications

Lipases are biocatalysts with a significant potential to enable a shift from current pollutant manufacturing processes to environmentally sustainable approaches. The main reason of this prospect is their catalytic versatility as they carry out several industrially relevant reactions as hydrolysis of fats in water/lipid interface and synthesis reactions in solvent-free or non-aqueous media such as transesterification, interesterification and esterification. Because of the outstanding traits of Rhizopus oryzae lipase (ROL), 1,3-specificity, high enantioselectivity and stability in organic media, its application in energy, food and pharmaceutical industrial sector has been widely studied. Significant advances have been made in the biochemical characterisation of ROL particularly in how its activity and stability are affected by the presence of its prosequence. In addition, native and heterologous production of ROL, the latter in cell factories like Escherichia coli, Saccharomyces cerevisiae and Komagataella phaffii (Pichia pastoris), have been thoroughly described. Therefore, in this review, we summarise the current knowledge about R. oryzae lipase (i) biochemical characteristics, (ii) production strategies and (iii) potential industrial applications.

Co-expression of Pseudomonas alcaligenes lipase and its specific foldase in Pichia pastoris by a dual expression cassette strategy

Lipomax is a commercialized foldase-dependent Pseudomonas lipase that was previously expressed only in Pseudomonas strains. Here, using Pichia pastoris as the host, we report a new co-expression method that leads to the successful production of Lipomax. The active Lipomax is extracellularly co-expressed with its cognate foldase (LIM); and the purified enzyme mix has the optimum pH at pH 8.0 and an optimal temperature around 40 °C. N-glycosylation was observed for Pichia produced Lipomax, and its reduction was shown to increase the lipolytic activity. With different p-nitrophenyl esters as the substrates, the substrate profiling analyses further indicate that Lipomax prefers esters with middle-long chain fatty acids, showing the highest specific activity to p-nitrophenyl caprylate (C8). The extracellular co-expression of Lipomax and LIM in Pichia will not only increase our ability to investigate additional eukaryotic hosts for lipase expression, but also be of considerable value in analyzing other foldase-dependent lipases.

Improved Protocol for the Production of the Low-Expression Eukaryotic Membrane Protein Human Aquaporin 2 in Pichia pastoris for Solid-State NMR

Solid-state nuclear magnetic resonance (SSNMR) is a powerful biophysical technique for studies of membrane proteins; it requires the incorporation of isotopic labels into the sample. This is usually accomplished through over-expression of the protein of interest in a prokaryotic or eukaryotic host in minimal media, wherein all (or some) carbon and nitrogen sources are isotopically labeled. In order to obtain multi-dimensional NMR spectra with adequate signal-to-noise ratios suitable for in-depth analysis, one requires high yields of homogeneously structured protein. Some membrane proteins, such as human aquaporin 2 (hAQP2), exhibit poor expression, which can make producing a sample for SSNMR in an economic fashion extremely difficult, as growth in minimal media adds additional strain on expression hosts. We have developed an optimized growth protocol for eukaryotic membrane proteins in the methylotrophic yeast Pichia pastoris. Our new growth protocol uses the combination of sorbitol supplementation, higher cell density, and low temperature induction (LT-SEVIN), which increases the yield of full-length, isotopically labeled hAQP2 ten-fold. Combining mass spectrometry and SSNMR, we were able to determine the nature and the extent of post-translational modifications of the protein. The resultant protein can be functionally reconstituted into lipids and yields excellent resolution and spectral coverage when analyzed by two-dimensional SSNMR spectroscopy.

Redesigning N-glycosylation sites in a GH3 β-xylosidase improves the enzymatic efficiency

BACKGROUND

β-Xylosidases are glycoside hydrolases (GHs) that cleave xylooligosaccharides and/or xylobiose into shorter oligosaccharides and xylose. Aspergillus nidulans is an established genetic model and good source of carbohydrate-active enzymes (CAZymes). Most fungal enzymes are N-glycosylated, which influences their secretion, stability, activity, signalization, and protease protection. A greater understanding of the N-glycosylation process would contribute to better address the current bottlenecks in obtaining high secretion yields of fungal proteins for industrial applications.

RESULTS

In this study, BxlB-a highly secreted GH3 β-xylosidase from A. nidulans, presenting high activity and several N-glycosylation sites-was selected for N-glycosylation engineering. Several glycomutants were designed to investigate the influence of N-glycans on BxlB secretion and function. The non-glycosylated mutant (BxlB^non-glyc) showed similar levels of enzyme secretion and activity compared to the wild-type (BxlB^wt), while a partially glycosylated mutant (BxlB^N1;5;7) exhibited increased activity. Additionally, there was no enzyme secretion in the mutant in which the N-glycosylation context was changed by the introduction of four new N-glycosylation sites (BxlB^CC), despite the high transcript levels. BxlB^wt, BxlB^non-glyc, and BxlB^N1;5;7 formed similar secondary structures, though the mutants had lower melting temperatures compared to the wild type. Six additional glycomutants were designed based on BxlB^N1;5;7, to better understand its increased activity. Among them, the two glycomutants which maintained only two N-glycosylation sites each (BxlB^N1;5 and BxlB^N5;7) showed improved catalytic efficiency, whereas the other four mutants' catalytic efficiencies were reduced. The N-glycosylation site N5 is important for improved BxlB catalytic efficiency, but needs to be complemented by N1 and/or N7. Molecular dynamics simulations of BxlB^non-glyc and BxlB^N1;5 reveals that the mobility pattern of structural elements in the vicinity of the catalytic pocket changes upon N1 and N5 N-glycosylation sites, enhancing substrate binding properties which may underlie the observed differences in catalytic efficiency between BxlB^non-glyc and BxlB^N1;5.

CONCLUSIONS

This study demonstrates the influence of N-glycosylation on A. nidulans BxlB production and function, reinforcing that protein glycoengineering is a promising tool for enhancing thermal stability, secretion, and enzymatic activity. Our report may also support biotechnological applications for N-glycosylation modification of other CAZymes.

Unique N-glycosylation of a recombinant exo-inulinase from Kluyveromyces cicerisporus and its effect on enzymatic activity and thermostability

Background

Inulinase can hydrolyze polyfructan into high-fructose syrups and fructoligosaccharides, which are widely used in food, the medical industry and the biorefinery of Jerusalem artichoke. In the present study, a recombinant exo-inulinase (rKcINU1), derived from Kluyveromyces cicerisporus CBS4857, was proven as an N-linked glycoprotein, and the removal of N-linked glycan chains led to reduced activity.

Results

Five N-glycosylation sites with variable high mannose-type oligosaccharides (Man_3–9GlcNAc₂) were confirmed in the rKcINU1. The structural modeling showed that all five glycosylation sites (Asn-362, Asn-370, Asn-399, Asn-467 and Asn-526) were located at the C-terminus β-sandwich domain, which has been proven to be more conducive to the occurrence of glycosylation modification than the N-terminus domain. Single-site N-glycosylation mutants with Asn substituted by Gln were obtained, and the Mut with all five N-glycosylation sites removed was constructed, which resulted in the loss of all enzyme activity. Interestingly, the N362Q led to an 18% increase in the specific activity against inulin, while a significant decrease in thermostability (2.91 °C decrease in T_m) occurred, and other single mutations resulted in the decrease in the specific activity to various extents, among which N467Q demonstrated the lowest enzyme activity.

Conclusion

The increased enzyme activity in N362Q, combined with thermostability testing, 3D modeling, kinetics data and secondary structure analysis, implied that the N-linked glycan chains at the Asn-362 position functioned negatively, mainly as a type of steric hindrance toward its adjacent N-glycans to bring rigidity. Meanwhile, the N-glycosylation at the other four sites positively regulated enzyme activity caused by altered substrate affinity by means of fine-tuning the β-sandwich domain configuration. This may have facilitated the capture and transfer of substrates to the enzyme active cavity, in a manner quite similar to that of carbohydrate binding modules (CBMs), i.e. the chains endowed the β-sandwich domain with the functions of CBM. This study discovered a unique C-terminal sequence which is more favorable to glycosylation, thereby casting a novel view for glycoengineering of enzymes from fungi via redesigning the amino acid sequence at the C-terminal domain, so as to optimize the enzymatic properties.

Design of Glyco-Linkers at Multiple Structural Levels to Modulate Protein Stability

N-glycosylation has critical roles in regulating protein stability, but the molecular basis is poorly understood. In this study, we integrated experimental and computational techniques to investigate the mechanism by which full-length N-glycans modulate protein stability from quaternary structure perspective. We found the two inherent N-glycans of β-glucuronidase expressed in Pichia pastoris function as "glyco-linkers" that hold spatially proximal motifs together to compact the local protein structure. We further designed and placed glyco-linkers in the unusual form of glyco-bridge and glyco-hairpin at the interfaces between domains and monomers with higher structural level, respectively, which conferred dramatically higher kinetic stability and thermodynamic stability than the inherent N-glycans. Our study not only provides unique insight into the interactions between glycans and proteins from a quaternary structure perspective but also facilitates the rational design of N-glycans as general tools that can enhance protein stability.

Effect of N-Linked Glycosylation of Recombinant Windmill Palm Tree Peroxidase on Its Activity and Stability

Plant secretory peroxidases are valuable commercial enzymes. The windmill palm tree Trachycarpus fortunei produces one of the most stable and fastest peroxidases (WPTP) characterized to date; however, an economical source is needed. Pichia pastoris has been used as an expression system for WPTP and other peroxidases. However, yeast and plants synthesize different types of N-linked glycan structures and may differ the level of glycosylation at each site. Such non-native glycosylation can have unwanted consequences. Glycosylation site N256 was under-glycosylated in the wild-type (1.5%) compared to the native enzyme (55%); therefore, we mutated WPTP to promote glycosylation at this site (WPTP E254G). Glycosylation increased four-fold, as measured by liquid chromatography-tandem mass spectrometry. The mutation did not change the substrate specificity and optimal pH- and thermo-stability ranges, but it increased the catalytic activity 2-3-fold. In comparison with wild-type WPTP, WPTP E254G showed a shift of the most stable pH from 7 to 9, making it suitable for applications under alkaline conditions.

Effect of β-mannanase domain from Trichoderma reesei on its biochemical characters and synergistic hydrolysis of sugarcane bagasse

BACKGROUND

β-mannanase is a key enzyme for hydrolyzing mannan, a major constituent of hemicellulose, which is the second most abundant polysaccharide in nature. Different structural domains greatly affect its biochemical characters and catalytic efficiency. However, the effects of linker and carbohydrate-binding module (CBM) on β-mannanase from Trichoderma reesei (Man1) have not yet been fully described. The present study aimed to determine the influence of different domains on the expression efficiency, biochemical characteristics and hemicellulosic deconstruction of Man1.

RESULTS

The expression efficiency was improved after truncating CBM. Activities of Man1 and Man1ΔCBM (CBM) in the culture supernatant after 168 h of induction were 34.5 and 42.9 IU mL^-1 , although a value of only 0.36 IU mL^-1 was detected for Man1ΔLCBM (lacking CBM and linker). Man1 showed higher thermostability than Man1ΔCBM at low temperature, whereas Man1ΔCBM had a higher specificity for galactomannan (K_m  = 2.5 mg mL^-1 ) than Man1 (K_m  = 4.0 mg mL^-1 ). Both Man1 and Man1ΔCBM could synergistically improve the hydrolysis of cellulose, galactomannan and pretreated sugarcane bagasse, with a 10-30% improvement of the reducing sugar yield.

CONCLUSION

Linker and CBM domains were vital for mannanase activity and expression efficiency. CBM affected the thermostability and adsorption ability of Man1. The results obtained in the present study should help guide the rational design and directional modification of Man with respect to improving its catalytic efficiency. © 2017 Society of Chemical Industry.

Structural and functional characterization of a highly secreted α-l-arabinofuranosidase (GH62) from Aspergillus nidulans grown on sugarcane bagasse

Carbohydrate-Active Enzymes are key enzymes for biomass-to-bioproducts conversion. α-l-Arabinofuranosidases that belong to the Glycoside Hydrolase family 62 (GH62) have important applications in biofuel production from plant biomass by hydrolyzing arabinoxylans, found in both the primary and secondary cell walls of plants. In this work, we identified a GH62 α-l-arabinofuranosidase (AnAbf62A_wt) that was highly secreted when Aspergillus nidulans was cultivated on sugarcane bagasse. The gene AN7908 was cloned and transformed in A. nidulans for homologous production of AnAbf62A_wt, and we confirmed that the enzyme is N-glycosylated at asparagine 83 by mass spectrometry analysis. The enzyme was also expressed in Escherichia coli and the studies of circular dichroism showed that the melting temperature and structural profile of AnAbf62A_wt and the non-glycosylated enzyme from E. coli (AnAbf62A_deglyc) were highly similar. In addition, the designed glycomutant AnAbf62A_N83Q presented similar patterns of secretion and activity to the AnAbf62A_wt, indicating that the N-glycan does not influence the properties of this enzyme. The crystallographic structure of AnAbf62A_deglyc was obtained and the 1.7Å resolution model showed a five-bladed β-propeller fold, which is conserved in family GH62. Mutants AnAbf62A_Y312F and AnAbf62A_Y312S showed that Y312 was an important substrate-binding residue. Molecular dynamics simulations indicated that the loop containing Y312 could access different conformations separated by moderately low energy barriers. One of these conformations, comprising a local minimum, is responsible for placing Y312 in the vicinity of the arabinose glycosidic bond, and thus, may be important for catalytic efficiency.

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.

Enzymatic Degradation of Aromatic and Aliphatic Polyesters by P. pastoris Expressed Cutinase 1 from Thermobifida cellulosilytica

To study hydrolysis of aromatic and aliphatic polyesters cutinase 1 from Thermobifida cellulosilytica (Thc_Cut1) was expressed in P. pastoris. No significant differences between the expression of native Thc_Cut1 and of two glycosylation site knock out mutants (Thc_Cut1_koAsn and Thc_Cut1_koST) concerning the total extracellular protein concentration and volumetric activity were observed. Hydrolysis of poly(ethylene terephthalate) (PET) was shown for all three enzymes based on quantification of released products by HPLC and similar concentrations of released terephthalic acid (TPA) and mono(2-hydroxyethyl) terephthalate (MHET) were detected for all enzymes. Both tested aliphatic polyesters poly(butylene succinate) (PBS) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were hydrolyzed by Thc_Cut1 and Thc_Cut1_koST, although PBS was hydrolyzed to significantly higher extent than PHBV. These findings were also confirmed via quartz crystal microbalance (QCM) analysis; for PHBV only a small mass change was observed while the mass of PBS thin films decreased by 93% upon enzymatic hydrolysis with Thc_Cut1. Although both enzymes led to similar concentrations of released products upon hydrolysis of PET and PHBV, Thc_Cut1_koST was found to be significantly more active on PBS than the native Thc_Cut1. Hydrolysis of PBS films by Thc_Cut1 and Thc_Cut1_koST was followed by weight loss and scanning electron microscopy (SEM). Within 96 h of hydrolysis up to 92 and 41% of weight loss were detected with Thc_Cut1_koST and Thc_Cut1, respectively. Furthermore, SEM characterization of PBS films clearly showed that enzyme tretment resulted in morphological changes of the film surface.

Role of N-linked glycosylation in the enzymatic properties of a thermophilic GH 10 xylanase from Aspergillus fumigatus expressed in Pichia pastoris

N-Glycosylation is a posttranslational modification commonly occurred in fungi and plays roles in a variety of enzyme functions. In this study, a xylanase (Af-XYNA) of glycoside hydrolase (GH) family 10 from Aspergillus fumigatus harboring three potential N-glycosylation sites (N87, N124 and N335) was heterologously produced in Pichia pastoris. The N-glycosylated Af-XYNA (WT) exhibited favorable temperature and pH optima (75°C and pH 5.0) and good thermostability (maintaining stable at 60°C). To reveal the role of N-glycosylation on Af-XYNA, the enzyme was deglycosylated by endo-β-N-acetylglucosaminidase H (DE) or modified by site-directed mutagenesis at N124 (N124T). The deglycosylated DE and mutant N124T showed narrower pH adaptation range, lower specific activity, and worse pH and thermal stability. Further thermodynamic analysis revealed that the enzyme with higher N-glycosylation degree was more thermostable. This study demonstrated that the effects of glycosylation at different degrees and sites were diverse, in which the glycan linked to N124 played a key role in pH and thermal stability of Af-XYNA.

Effect of Glycosylation on the Biocatalytic Properties of Hydroxynitrile Lyase from the Passion Fruit, Passiflora edulis: A Comparison of Natural and Recombinant Enzymes

A hydroxynitrile lyase from the passion fruit Passiflora edulis (PeHNL) was isolated from the leaves and showed high stability in biphasic co-organic solvent systems for cyanohydrin synthesis. Cyanohydrins are important building blocks for the production of fine chemicals and pharmaceuticals. Thus, to enhance production yields of PeHNL for industrial applications, we cloned and expressed recombinant PeHNL in Escherichia coli BL21(DE3) and Pichia pastoris GS115 cells without a signal peptide sequence. The aim of this study is to determine the effect of N-glycosylation on enzyme stability and catalytic properties in microbial expression systems. PeHNL from leaves (PeHNL-N) and that expressed in P. pastoris (PeHNL-P) were glycosylated, whereas that expressed in E. coli (PeHNL-E) was not. The enzymes PeHNL-N and PeHNL-P showed much better thermostability, pH stability, and organic solvent tolerance than the deglycosylated enzyme PeHNL-E and the deglycosylated mutant N105Q from P. pastoris (PeHNL-P-N105Q). The glycosylated PeHNL-P also efficiently performed transcyanation of (R)-mandelonitrile with a 98 % enantiomeric excess in a biphasic system with diisopropyl ether. These data demonstrate the efficacy of these methods for improving enzyme expression and stability for industrial application through N-glycosylation.

Overexpressing target helper genes enhances secretion and glycosylation of recombinant proteins in Pichia pastoris under simulated microgravity

In this study, the potential helper genes were identified through the data analysis of transcriptomic and proteomic profiling in recombinant Pichia pastoris cultured under simulated microgravity (SMG). Co-expressing of four genes PRX1, YAP1, AHA1, and YPT6, involved in the oxidative stress response and protein folding, exhibited promising helper factor effects on the recombinant protein yields in engineered P. pastoris, respectively. When two of the above genes were co-expressed simultaneously, β-glucuronidase (PGUS) specific activity was further increased by 30.3-50.6 % comparing with that of single helper gene, particularly when the oxidative stress response and protein folding genes were both present in the combinations. In addition, co-expressing co-chaperone AHA1 and transcription factor YAP1 not only enhanced PGUS secretion, but also affected its glycosylation. Thus, through deep "omics" analysis of SMG effects, our results provided combined impact of new helper factors to improve the efficacy of recombinant protein secretion and glycosylation in engineered P. pastoris.

Δ9-Tetrahydrocannabinolic acid synthase: The application of a plant secondary metabolite enzyme in biocatalytic chemical synthesis

Δ(9)-Tetrahydrocannabinolic acid synthase (THCAS) from the secondary metabolism of Cannabis sativa L. catalyzes the oxidative formation of an intramolecular CC bond in cannabigerolic acid (CBGA) to synthesize Δ(9)-tetrahydrocannabinolic acid (THCA), which is the direct precursor of Δ(9)-tetrahydrocannabinol (Δ(9)-THC). Aiming on a biotechnological production of cannabinoids, we investigated the potential of the heterologously produced plant oxidase in a cell-free system on preparative scale. THCAS was characterized in an aqueous/organic two-liquid phase setup in order to solubilize the hydrophobic substrate and to allow in situ product removal. Compared to the single phase aqueous setup the specific activity decreased by a factor of approximately 2 pointing to a substrate limitation of CBGA in the two-liquid phase system. However, the specific activity remained stable for at least 3h illustrating the benefit of the two-liquid phase setup. In a repeated-batch setup, THCAS showed only a minor loss of specific activity in the third batch pointing to a high intrinsic stability and high solvent tolerance of the enzyme. Maximal space-time-yields of 0.121gL(-1)h(-1) were reached proving the two-liquid phase concept suitable for biotechnological production of cannabinoids.