Recombinant production of a peroxidase-protein G fusion protein in Pichia pastoris

Improvement of the recombinant phytase expression by intermittent feeding of glucose during the induction phase of methylotrophic yeast Pichia pastoris

PURPOSE

For growth of methylotrophic yeast, glycerol is usually used as a carbon source. Glucose is used in some cases, but not widely consumed due to strong repressive effect on AOX1 promoter. However, glucose is still considered as a carbon source of choice since it has low production cost and guarantees growth rate comparable to glycerol.

RESULTS

In flask cultivation of the recombinant yeast, Pichia pastoris GS115(pPIC9K-appA38M), while methanol induction point(OD600) and methanol concentration significantly affected the phytase expression, glucose addition in induction phase could enhance phytase expression. The optimal flask cultivation conditions illustrated by Response Surface Methodology were 10.37 OD600 induction point, 2.02 h before methanol feeding, 1.16% methanol concentration and 40.36μL glucose feeding amount(for 20 mL culture volume) in which the expressed phytase activity was 613.4 ± 10.2U/mL, the highest activity in flask cultivation. In bioreactor fermentation, the intermittent glucose feeding showed several advantageous results such as 68 h longer activity increment, 149.2% higher cell density and 200.1% higher activity compared to the sole methanol feeding method. These results implied that remaining glucose at induction point might exhibit a positive effect on the phytase expression.

CONCLUSION

Glucose intermittent feeding could be exploited for economic phytase production and the other recombinant protein expression by P. pastoris GS115.

Improving the diagnosis of bovine tuberculosis using gold nanoparticles conjugated with purified protein derivative: special regard to staphylococcal protein A and streptococcal protein G

Different ancillary immunodiagnostic tests were traditionally-established for diagnosis of bovine tuberculosis (BTB) either cellular or humoral as tuberculin skin test (TST), gamma interferon (INF-γ), and indirect enzyme-linked immunosorbent assay (iELISA). These tests had been consumed more time and expensive, and needed sophisticated equipment. To dissolve these problems, serological diagnosis depending on humoral immunity is the aim of this work. Herein, slide-based agglutination test was chosen as a rapid and simple field test based on purified protein derivative (PPD) antigen in addition to some supplementation materials such as Staphylococcal protein A (SPA) and Streptococcal protein G (SPG) to improve detection of BTB antibody in serum samples. Gold nanoparticles (Au NPs) were synthesized by gamma ray, and after complete characterization, the synthesized Au NPs were spherical, small-sized, and stable without any impurities. Addition of such supplementation reagents for serodiagnosis of tuberculosis is of paramount important for the detection of serum antibodies against tuberculosis (TB) and it was considered an easily simple and possible way for improving TB diagnosis. In this work, 70 animals tested positive for TST as well as 20 animals tested negative for TST were used for the diagnosis of BTB depending on humoral immune response based on PPD slide agglutination test using reporter regents (SPA and/or SPG) either native or recombinant. The agglutination density was recorded and read in 4 degrees of positivity with scores ranging from negative (-) to very strong reaction (++++) occurred in different times of agglutination. Groups showed 100% positive reactivates employed in Exp. 1, 2, and 3 with differentiation of slide agglutination test density and was rated from moderate positivity (2+) to very strong (4+), with predominant positivity in density of (3+). Pink-colored intensity is associated with the strengthened reactions between PPD-conjugated Au NPs and serum antibody of each tested samples, which allows for visual rapid, simple, and effective attractive diagnosis of BTB. The specificity and sensitivity of the serological tests were characterized. TST offers the highest sensitivity (83.6%) among the other immunoassays, while the lowest specificity was recorded in TST (57.4%). SPA/SPG offers the best performance in term of combined sensitivity and specificity (performance index) of 175.4. Therefore, the development and uses of detection reagent (such as SPA and/or SPG) slide co-agglutination test (COAT), either native or recombinant (rSPA/SPG) for the detection of TB antibodies based on PPD antigen, as well as the uses of Au NPs rSPA/SPG as detection conjugate based on the same antigen, were also performed as a simple, rapid, sensitive, specific, eco-friendly, and low cost, which shows a great potential in field and lab diagnosis of BTB. So, high reduction in reagents that yields reactions similarly as traditional techniques was needed.

Strategies for Making Multimeric and Polymeric Bifunctional Protein Conjugates and Their Applications as Bioanalytical Tools

Enzymes play a central role in the detection of target molecules in biotechnological fields. Most probes used in detection are bifunctional proteins comprising enzymes and binding proteins conjugated by chemical reactions. To create a highly sensitive detection probe, it is essential to increase the enzyme-to-binding protein ratio in the probe. However, if the chemical reactions required to prepare the probe are insufficiently site-specific, the detection probe may lose functionality. Genetic modifications and enzyme-mediated post-translational modifications (PTMs) can ensure the site-specific conjugation of proteins. They are therefore promising strategies for the production of detection probes with high enzyme contents, i.e., polymeric bifunctional proteins. Herein, we review recent advances in the preparation of bifunctional protein conjugates and polymeric bifunctional protein conjugates for detection. We have summarized research on genetically fused proteins and enzymatically prepared polymeric bifunctional proteins, and will discuss the potential use of protein polymers in various detection applications.

A novel fluorescence immunochromatographic assay strip for the diagnosis of schistosomiasis japonica

Background

Schistosomiasis japonica is a severe zoonosis. Domestic animals are the primary source of infection and play an important role in disease transmission. Surveillance and diagnosis play key roles in schistosomiasis control; however, current techniques for the surveillance and diagnosis of the disease have limitations. In this study, we developed a novel fluorescence immunochromatographic assay (FICA) strip to detect anti-Schistosoma japonicum antibodies in host serum.

Methods

A FICA strip was developed for the diagnosis of Schistosoma japonicum in domestic animals. Streptococcus protein G (SPG) and soluble egg antigen (SEA) were transferred onto a nitrocellulose (NC) membrane to form the control line (C) and the test line (T), respectively. With fluorescence activity as well as binding activity to multispecies IgG, the recombinant protein rSPG-RFP was expressed and employed as an antibody indicator in the FICA strips.

Results

The dual gene fusion plasmid was verified by PCR and restriction enzyme digestion. The expressed recombinant protein was 39.72 kDa in size, which was consistent with the predicted molecular weight. The western blot results showed binding activity between rSPG-RFP and IgGs from different hosts. Fluorescence microscopy also showed the fluorescence activity of the protein present. The affinity constant (Ka) values of rSPG-RFP with rabbit, donkey, mouse and goat IgG were 1.9 × 10⁵, 4.1 × 10⁵, 1.7 × 10⁵ and 5.4 × 10⁵, respectively. Moreover, based on the recombinant protein, the test strip for detecting S. japonicum in buffaloes could distinguish positive from negative serum. The lower limit of detection of the FICA strip was 1:10,000. Compared with ELISA, the FICA strips exhibited similar results in the diagnosis of infection in clinical bovine serum samples, with a kappa value of 0.9660 and P < 0.01. The cross-reactivities of the FICA strips with Haemonchus contortus and Schistosoma turkestanicum (30.15% and 91.66%, respectively) were higher than those of ELISA (26.98% and 87.5%, respectively).

Conclusions

Based on the rSPG-RFP protein that we developed, strip detection can be completed within 15 min. Heightened sensitivity allows the strip to accurately identify schistosome antibodies in serum. In conclusion, this method is convenient, feasible, rapid and effective for detecting S. japonicum.

Linear Polymerization of Protein by Sterically Controlled Enzymatic Cross-Linking with a Tyrosine-Containing Peptide Loop

The structure of a protein complex needs to be controlled appropriately to maximize its functions. Herein, we report the linear polymerization of bacterial alkaline phosphatase (BAP) through the site-specific cross-linking reaction catalyzed by Trametes sp. laccase (TL). We introduced a peptide loop containing a tyrosine (Y-Loop) to BAP, and the Y-Looped BAP was treated with TL. The Y-Looped BAP formed linear polymers, whereas BAP fused with a C-terminal peptide containing a tyrosine (Y-tag) showed an irregular shape after TL treatment. The sterically confined structure of the Y-Loop could be responsible for the formation of linear BAP polymers. TL-catalyzed copolymerization of Y-Looped BAP and a Y-tagged chimeric antibody-binding protein, pG₂pA-Y, resulted in the formation of linear bifunctional protein copolymers that could be employed as protein probes in an enzyme-linked immunosorbent assay (ELISA). Copolymers comprising Y-Looped BAP and pG₂pA-Y at a molar ratio of 100:1 exhibited the highest signal in the ELISA with 26- and 20-fold higher than a genetically fused chimeric protein, BAP-pG₂pA-Y, and its polymeric form, respectively. This result revealed that the morphology of the copolymers was the most critical feature to improve the functionality of the protein polymers as detection probes, not only for immunoassays but also for other diagnostic applications.

Expression and Activation of Horseradish Peroxidase-Protein A/G Fusion Protein in Silkworm Larvae for Diagnostic Purposes

Recombinant protein production can create artificial proteins with desired functions by introducing genetic modifications to the target proteins. Horseradish peroxidase (HRP) has been used extensively as a reporter enzyme in biotechnological applications; however, recombinant production of HRP has not been very successful, hampering the utilization of HRP with genetic modifications. A fusion protein comprising an antibody binding protein and HRP will be an ideal bio-probe for high-quality HRP-based diagnostic systems. A HRP-protein A/G fusion protein (HRP-pAG) is designed and its production in silkworm (Bombyx mori) is evaluated for the first time. HRP-pAG is expressed in a soluble apo form, and is activated successfully by incubating with hemin. The activated HRP-pAG is used directly for ELISA experiments and retains its activity over 20 days at 4 °C. Moreover, HRP-pAG is modified with biotin by the microbial transglutaminase (MTG) reaction. The biotinylated HRP-pAG is conjugated with streptavidin to form a HRP-pAG multimer and the multimeric HRP-pAG produced higher signals in the ELISA system than monomeric HRP-pAG. The successful production of recombinant HRP in silkworm will contribute to creating novel HRP-based bioconjugates as well as further functionalization of HRP by applying enzymatic post-translational modifications.

High Expression of Human Cathepsin S by Recombinant Pichia pastoris with Cod Skin as an Organic Co-Nitrogen Source

Human cathepsin S production by recombinant Pichia pastoris using cod skin as the co-nitrogen source was investigated in this study. The addition of carbon sources of glycerol in the fed-batch phase and of methanol in the induction stage was also investigated. A new approach to the highly expression of human cathepsin S was developed using 90 g/L of cod skin (wet weight). After 24 h of the initial fermentation, 4% glycerol (v/v, glycerol/culture) was added once to enhance the cell density (OD600) in the cultivation. Then, adding and maintaining methanol at 0.5% (v/v, methanol/cultivation) after about 48 h of fermentation achieved a high expression of human cathepsin S in a 5-L bioreactor. The results demonstrate that the maximum activity of human cathepsin S in the fermentation supernatant reached 7,152 U/L after 96 h of methanol induction. The methylotrophic yeast P. pastoris grown in the medium containing cod skin (90 g/L) as the co-nitrogen source provided a 21% higher cell density (OD600) and 18.3% higher human cathepsin S yield than P. pastoris grown in BMGY medium. For the first time, human cathepsin S was successfully expressed by P. pastoris with cod skin as the co-nitrogen source. The glycerol fed-batch controlling strategy and method of maintaining methanol at a constant concentration of 0.5% (v/v, methanol/cultivation) in the induction stage was efficient for P. pastoris growth and the expression of human cathepsin S.

Development of NanoLuc bridging immunoassay for detection of anti-drug antibodies

Anti-drug antibodies (ADAs) are generated in-vivo as an immune response to therapeutic antibody drugs and can significantly affect the efficacy and safety of the drugs. Hence, detection of ADAs is recommended by regulatory agencies during drug development process. A widely accepted method for measuring ADAs is "bridging" immunoassay and is frequently performed using enzyme-linked immunosorbent assay (ELISA) or electrochemiluminescence (ECL) platform developed by Meso Scale Discovery (MSD). ELISA is preferable due to widely available reagents and instruments and broad familiarity with the technology; however, MSD platform has gained wide acceptability due to a simpler workflow, higher sensitivity, and a broad dynamic range but requires proprietary reagents and instruments. We describe the development of a new bridging immunoassay where a small (19kDa) but ultra-bright NanoLuc luciferase enzyme is used as an antibody label and signal is luminescence. The method combines the convenience of ELISA format with assay performance similar to that of the MSD platform. Advantages of the NanoLuc bridging immunoassay are highlighted by using Trastuzumab and Cetuximab as model drugs and developing assays for detection of anti-Trastuzumab antibodies (ATA) and anti-Cetuximab antibodies (ACA). During development of the assay several aspects of the method were optimized including: (a) two different approaches for labeling drugs with NanoLuc; (b) sensitivity and dynamic range; and (c) compatibility with the acid dissociation step for improved drug tolerance. Assays showed high sensitivity of at least 1.0ng/mL, dynamic range of greater than four log orders, and drug tolerance of >500.

Cultivation of Pichia pastoris carrying the scFv anti LDL (-) antibody fragment. Effect of preculture carbon source

Antibodies and antibody fragments are nowadays among the most important biotechnological products, and Pichia pastoris is one of the most important vectors to produce them as well as other recombinant proteins. The conditions to effectively cultivate a P. pastoris strain previously genetically modified to produce the single-chain variable fragment anti low density lipoprotein (−) under the control of the alcohol oxidase promoter have been investigated in this study. In particular, it was evaluated if, and eventually how, the carbon source (glucose or glycerol) used in the preculture preceding cryopreservation in 20% glycerol influences both cell and antibody fragment productions either in flasks or in bioreactor. Although in flasks the volumetric productivity of the antibody fragment secreted by cells precultured, cryopreserved and reactivated in glycerol was 42.9% higher compared with cells precultured in glucose, the use of glycerol in bioreactor led to a remarkable shortening of the lag phase, thereby increasing it by no less than thrice compared to flasks. These results are quite promising in comparison with those reported in the literature for possible future industrial applications of this cultivation, taking into account that the overall process time was reduced by around 8 h.

Biotechnological advances towards an enhanced peroxidase production in Pichia pastoris

Horseradish peroxidase (HRP) is a high-demand enzyme for applications in diagnostics, bioremediation, biocatalysis and medicine. Current HRP preparations are isolated from horseradish roots as mixtures of biochemically diverse isoenzymes. Thus, there is a strong need for a recombinant production process enabling a steady supply with enzyme preparations of consistent high quality. However, most current recombinant production systems are limited at titers in the low mg/L range. In this study, we used the well-known yeast Pichia pastoris as host for recombinant HRP production. To enhance recombinant enzyme titers we systematically evaluated engineering approaches on the secretion process, coproduction of helper proteins, and compared expression from the strong methanol-inducible PAOX1 promoter, the strong constitutive PGAP promoter, and a novel bidirectional promoter PHTX1. Ultimately, coproduction of HRP and active Hac1 under PHTX1 control yielded a recombinant HRP titer of 132mg/L after 56h of cultivation in a methanol-independent and easy-to-do bioreactor cultivation process. With regard to the many versatile applications for HRP, the establishment of a microbial host system suitable for efficient recombinant HRP production was highly overdue. The novel HRP production platform in P. pastoris presented in this study sets a new benchmark for this medically relevant enzyme.