Cell surface display of functionally active lipases from Yarrowia lipolytica in Pichia pastoris

Biofilm-Based Biocatalysis for Galactooligosaccharides Production by the Surface Display of β-Galactosidase in Pichia pastoris

Galactooligosaccharides (GOS) are one of the most important functional oligosaccharide prebiotics. The surface display of enzymes was considered one of the most excellent strategies to obtain these products. However, a rough industrial environment would affect the biocatalytic process. The catalytic process could be efficiently improved using biofilm-based fermentation with high resistance and activity. Therefore, the combination of the surface display of β-galactosidase and biofilm formation in Pichia pastoris was constructed. The results showed that the catalytic conversion rate of GOS was up to 50.3% with the maximum enzyme activity of 5125 U/g by screening the anchorin, and the number of the continuous catalysis batches was up to 23 times. Thus, surface display based on biofilm-immobilized fermentation integrated catalysis and growth was a co-culture system, such that a dynamic equilibrium in the consolidated integrative process was achieved. This study provides the basis for developing biofilm-based surface display methods in P. pastoris during biochemical production processes.

Saccharomyces cerevisiae cell surface display technology: Strategies for improvement and applications

Microbial cell surface display technology provides a powerful platform for engineering proteins/peptides with enhanced properties. Compared to the classical intracellular and extracellular expression (secretion) systems, this technology avoids enzyme purification, substrate transport processes, and is an effective solution to enzyme instability. Saccharomyces cerevisiae is well suited to cell surface display as a common cell factory for the production of various fuels and chemicals, with the advantages of large cell size, being a Generally Regarded As Safe (GRAS) organism, and post-translational processing of secreted proteins. In this review, we describe various strategies for constructing modified S. cerevisiae using cell surface display technology and outline various applications of this technology in industrial processes, such as biofuels and chemical products, environmental pollution treatment, and immunization processes. The approaches for enhancing the efficiency of cell surface display are also discussed.

Characterization of yeast cell surface displayed Lentinula edodes xylanase and its effects on the hydrolysis of wheat

The current study displayed a xylanase from Lentinula edodes on the surface of Pichia pastoris (sdLeXyn) and investigated its properties and effects on the wheat hydrolysis. Fluorescence microscope results showed that sdLeXyn was successfully anchored and displayed on the surface of P. pastoris X-33 cells. The highest activity of sdLeXyn was obtained at pH 3.0 and 50 °C. The sdLeXyn exhibited anti-high temperature property and showed broad temperature adaptability (>55% of the highest activity at 20-80 °C). The sdLeXyn was very stable at room temperature and could remain functionally stable at 50 °C for 3 h. The K_m value was greater in sdLeXyn than that in free recombinant L. edodes xylanase. The sdLeXyn exhibited well resistance to Mn²⁺, Zn²⁺, Ca²⁺, Na⁺, Cu²⁺, Mg²⁺, K⁺, Ni²⁺ (1 mM and 5 mM) except Cu²⁺, which reduced the sdLeXyn activity by 54.5% at 5 mM dosage. The activity of sdLeXyn was increased by 42.6% by 5 mM Mn²⁺, 5 mM DTT, Trition X-100, and Tween 20 did not affect the activity of sdLeXyn, but SDS and EDTA slightly reduced it by 12.8% and 14.6%, respectively. The sdLeXyn could resist the degradation of pepsin, efficiently hydrolyzed wheat and reduced the viscosity of wheat hydrolysate. Current data indicate that the sdLeXyn has a potential as a feed additive to improve the utilization of wheat in poultry production.

Cell surface display of proteins on filamentous fungi

Protein display approaches have been useful to endow the cell surface of yeasts with new catalytic activities so that they can act as enhanced whole-cell biocatalysts. Despite their biotechnological potential, protein display technologies remain poorly developed for filamentous fungi. The lignocellulolytic character of some of them coupled to the cell surface biosynthesis of valuable molecules by a single or a cascade of several displayed enzymes is an appealing prospect. Cell surface protein display consists in the co-translational fusion of a functional protein (passenger) to an anchor one, usually a cell-wall-resident protein. The abundance, spacing, and local environment of the displayed enzymes-determined by the relationship of the anchor protein with the structure and dynamics of the engineered cell wall-are factors that influence the performance of display-based biocatalysts. The development of protein display strategies in filamentous fungi could be based on the field advances in yeasts; however, the unique composition, structure, and biology of filamentous fungi cell walls require the customization of the approach to those microorganisms. In this prospective review, the cellular bases, the design principles, and the available tools to foster the development of cell surface protein display technologies in filamentous fungi are discussed.

Surface-Displayed Thermostable Candida rugosa Lipase 1 for Docosahexaenoic Acid Enrichment

Yeast surface display has emerged as a viable approach for self-immobilization enzyme as whole-cell catalysts. Herein, we displayed Candida rugosa lipase 1 (CRL LIP1) on the cell wall of Pichia pastoris for docosahexaenoic acid (DHA) enrichment in algae oil. After a 96-h culture, the displayed CRL LIP1 achieved the highest activity (380 ± 2.8 U/g) for hydrolyzing olive oil under optimal pH (7.5) and temperature (45 °C) conditions. Additionally, we improved the thermal stability of displayed LIP1, enabling retention of 50% of its initial bioactivity following 6 h of incubation at 45 °C. Furthermore, the content of DHA enhanced from 40.61% in original algae oil to 50.44% in glyceride, resulting in a 1.24-fold increase in yield. The displayed CRL LIP1 exhibited an improved thermal stability and a high degree of bioactivity toward its native macromolecule substrates algae oil and olive oil, thereby expanding its potential for industrial applications in fields of food and pharmaceutical. These results suggested that surface display provides an effective strategy for simultaneous convenient expression and target protein immobilization.

Yeast arming systems: pros and cons of different protein anchors and other elements required for display

Yeast display is a powerful strategy that consists in exposing peptides or proteins of interest on the cell surface of this microorganism. Ever since initial experiments with this methodology were carried out, its scope has extended and many applications have been successfully developed in different science and technology fields. Several yeast display systems have been designed, which all involve introducting into yeast cells the gene fusions that contain the coding regions of a signal peptide, an anchor protein, to properly attach the target to the cell surface, and the protein of interest to be exposed, all of which are controlled by a strong promoter. In this work, we report the description of such elements for the alternative systems introduced by focusing particularly on anchor proteins. The comparisons made between them are included whenever possible, and the main advantages and inconveniences of each one are discussed. Despite the huge number of publications on yeast surface display and the revisions published to date, this topic has not yet been widely considered. Finally, given the growing interest in developing systems for non-Saccharomyces yeasts, the main strategies reported for some are also summarized.

Establishment of cell surface engineering and its development

Cell surface display of proteins/peptides has been established based on mechanisms of localizing proteins to the cell surface. In contrast to conventional intracellular and extracellular (secretion) expression systems, this method, generally called an arming technology, is particularly effective when using yeasts as a host, because the control of protein folding that is often required for the preparation of proteins can be natural. This technology can be employed for basic and applied research purposes. In this review, I describe various strategies for the construction of engineered yeasts and provide an outline of the diverse applications of this technology to industrial processes such as the production of biofuels and chemicals, as well as bioremediation and health-related processes. Furthermore, this technology is suitable for novel protein engineering and directed evolution through high-throughput screening, because proteins/peptides displayed on the cell surface can be directly analyzed using intact cells without concentration and purification. Functional proteins/peptides with improved or novel functions can be created using this beneficial, powerful, and promising technique.

Engineering Novel and Improved Biocatalysts by Cell Surface Display

Biocatalysts, especially enzymes, have the ability to catalyze reactions with high product selectivity, utilize a broad range of substrates, and maintain activity at low temperature and pressure. Therefore, they represent a renewable, environmentally friendly alternative to conventional catalysts. Most current industrial-scale chemical production processes using biocatalysts employ soluble enzymes or whole cells expressing intracellular enzymes. Cell surface display systems differ by presenting heterologous enzymes extracellularly, overcoming some of the limitations associated with enzyme purification and substrate transport. Additionally, coupled with directed evolution, cell surface display is a powerful platform for engineering enzymes with enhanced properties. In this review, we will introduce the molecular and cellular principles of cell surface display and discuss how it has been applied to engineer enzymes with improved properties as well as to develop surface-engineered microbes as whole-cell biocatalysts.

High-yield phosphatidylserine production via yeast surface display of phospholipase D from Streptomyces chromofuscus on Pichia pastoris

The gene encoding phospholipase D (PLD) from Streptomyces chromofuscus was displayed on the cell surface of Pichia pastoris GS115/pKFS-pldh using a Flo1p anchor attachment signal sequence (FS anchor). The displayed PLD (dPLD) showed maximum enzymatic activity at pH 6.0 and 55 °C and was stable within a broad range of temperatures (20-65 °C) and pHs (pH 4.0-11.0). In addition, the thermostability, acid stability and organic solvent tolerance of the dPLD were significantly enhanced compared with the secreted PLD (sPLD) from S. chromofuscus. Use of dPLD for conversion of phosphatidylcholine (PC) and l-serine to phosphatidylserine (PS) showed that 67.5% of PC was converted into PS at the optimum conditions. Moreover, the conversion rate of PS remained above 50% after 7 repeated batch cycles. Thus, P. pastoris GS115/pKFS-pldh shows the potential for viable industrial production of PS.

Arming Technology in Yeast-Novel Strategy for Whole-cell Biocatalyst and Protein Engineering

Cell surface display of proteins/peptides, in contrast to the conventional intracellular expression, has many attractive features. This arming technology is especially effective when yeasts are used as a host, because eukaryotic modifications that are often required for functional use can be added to the surface-displayed proteins/peptides. A part of various cell wall or plasma membrane proteins can be genetically fused to the proteins/peptides of interest to be displayed. This technology, leading to the generation of so-called "arming technology", can be employed for basic and applied research purposes. In this article, we describe various strategies for the construction of arming yeasts, and outline the diverse applications of this technology to industrial processes such as biofuel and chemical productions, pollutant removal, and health-related processes, including oral vaccines. In addition, arming technology is suitable for protein engineering and directed evolution through high-throughput screening that is made possible by the feature that proteins/peptides displayed on cell surface can be directly analyzed using intact cells without concentration and purification. Actually, novel proteins/peptides with improved or developed functions have been created, and development of diagnostic/therapeutic antibodies are likely to benefit from this powerful approach.

Cell-surface expression of Aspergillus saitoi-derived functional α-1,2-mannosidase on Yarrowia lipolytica for glycan remodeling

Expression of proteins on the surface of yeast has a wide range of applications, such as development of live vaccines, screening of antibody libraries, and use as whole-cell biocatalysts. The hemiascomycetes yeast Yarrowia lipolytica has been raised as a potential host for heterologous expression of recombinant proteins. In this study, we report the expression of Aspergillus saitoi α-1,2-mannosidase, encoded by the msdS gene, on the cell surface of Y. lipolytica. As the first step to achieve the secretory expression of msdS protein, four different signal sequences-derived from the endogenous Y. lipolytica Lip2 and Xpr2 prepro regions and the heterologous A. niger α-amylase and rice α-amylase signal sequences-were analyzed for their secretion efficiency. It was shown that the YlLip2 prepro sequence was most efficient in directing the secretory expression of msdS in fully N-glycosylated forms. The surface display of msdS was subsequently directed by fusing GPI anchoring motifs derived from Y. lipolytica cell wall proteins, YlCwp1p and YlYwp1p, respectively, to the C-terminus of the Lip2 prepro-msdS protein. The expression of actively functional msdS protein on the cell surface was confirmed by western blot, flow cytometry analysis, along with the α-1,2-mannosidase activity assay using intact Y. lipolytica cells as the enzyme source. Furthermore, the glycoengineered Y. lipolytica Δoch1Δmpo1 strains displaying α-1,2-mannosidase were able to convert Man8GlcNAc2 to Man5GlcNAc2 efficiently on their cell-wall mannoproteins, demonstrating its potential used for glycoengineering in vitro or in vivo.

Efficient display of active Geotrichum sp. lipase on Pichia pastoris cell wall and its application as a whole-cell biocatalyst to enrich EPA and DHA in fish oil

Geotrichum sp. lipase (GSL) was first displayed on the cell wall of Pichia pastoris on the basis of the a-agglutinin anchor system developed in Saccharomyces cerevisiae . Surface display levels were monitored using Western blotting, immunofluorescence miscroscopy, and fluorescence-activated cell sorting analysis. Lipase activity of the yeast whole cells reached a maximum at 273 ± 2.4 U/g of dry cells toward olive oil after 96 h of culture at 30 °C, with optimal pH and temperature at 7.5 and 45 °C, respectively. Displayed GSL exhibited relatively high stability between pH 6.0 and 8.0 and retained >70% of the maximum activity. The surface-displayed lipase retained 80% of its original activity after incubation at 45 °C for 4 h. Moreover, the GSL-displaying yeast whole cells were then used as a biocatalyst to enrich eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil on the basis of selective hydrolysis. As a result, EPA and DHA increased from 1.53 and 24.1% in the original fish oil to 1.85 and 30.86%, which were increases of 1.21- and 1.29-fold, respectively. The total yield of EPA and DHA reached 46.62%.

Development of a novel rDNA based plasmid for enhanced cell surface display on Yarrowia lipolytica

In this study, a novel rDNA based plasmid was developed for display of heterologous proteins on the cell surface of Yarrowia lipolytica using the C-terminal end of the glycosylphosphatidylinositol (GPI) anchored Y. lipolytica cell wall protein 1 (YlCWP1). mCherry was used as a model protein to assess the efficiency of the constructed plasmid. Y. lipolytica transformants harbouring the expression cassettes showed a purple colour phenotype on selective YNB-casamino plates as compared to control cells indicating that mCherry was displayed on the cells. Expression of mCherry on cells of Y. lipolytica was confirmed by both fluorescent microscopy and flow cytometry. Furthermore, SDS-PAGE analysis and matrix-assisted laser desorption/ionization (MALDI)-time-of (TOF)-mass spectrometry (MS) peptide mass fingerprinting (PMF) confirmed that the protein cleaved from the yeast cells using enterokinase was mCherry. Efficient cleavage of mCherry reported in this work offers an alternative purification method for displayed heterologous proteins on Y. lipolytica cells using the plasmid constructed in this study. The developed displaying system offers great potential for industrial production and purification of heterologous proteins at low cost.

Display of Candida antarctica lipase B on Pichia pastoris and its application to flavor ester synthesis

Two alternative cell-surface display systems were developed in Pichia pastoris using the alpha-agglutinin and Flo1p (FS) anchor systems, respectively. Both the anchor cell wall proteins were obtained originally from Saccharomyces cerevisiae. Candida antarctica lipase B (CALB) was displayed functionally on the cell surface of P. pastoris using the anchor proteins alpha-agglutinin and FS. The activity of CALB displayed on P. pastoris was tenfold higher than that of S. cerevisiae. The hydrolytic and synthetic activities of CALB fused with alpha-agglutinin and FS anchored on P. pastoris were investigated. The hydrolytic activities of both lipases displayed on yeast cells surface were more than 200 U/g dry cell after 120 h of culture (200 and 270 U/g dry cell, respectively). However, the synthetic activity of CALB fused with alpha-agglutinin on P. pastoris was threefold higher than that of the FS fusion protein when applied to the synthesis of ethyl caproate. Similarly, the CALB displayed on P. pastoris using alpha-agglutinin had a higher catalytic efficiency with respect to the synthesis of other short-chain flavor esters than that displayed using the FS anchor. Interestingly, for some short-chain esters, the synthetic activity of displaying CALB fused with alpha-agglutinin on P. pastoris was even higher than that of the commercial CALB Novozyme 435.

Cell-surface display of the active mannanase in Yarrowia lipolytica with a novel surface-display system

A novel surface-display system was constructed using the cell-wall anchor protein Flo1p from Saccharomyces cerevisiae, the mannanase (man1) from Bacillus subtilis fused with the C-terminus of Flo1p and the 6xHis tag was inserted between Flo1p and man1. The fusion protein was displayed on the cell surface of Yarrowia lipolytica successfully, and it was confirmed by immunofluorescence. In succession, the surface-displayed mannanase was characterized. The optimum catalytic conditions for the recombinant mannanase were 55 degrees C at pH 6.0, and it exhibited high stability against pH variation. The highest activity of the recombinant mannanase reached 62.3 IU/g (dry cell weight) after the recombinant was cultivated for 96 h in YPD medium [1% (w/v) yeast extract/2% (w/v) peptone/2% (w/v) glucose]. To our knowledge, the present paper is the first to report that high-activity mannanase is displayed on the cell surface of Y. lipolytica with Flo1p.

Pichia surface display: display of proteins on the surface of glycoengineered Pichia pastoris strains

Expression of proteins on the surface of yeasts has a wide range of applications in biotechnology, such as directed evolution of proteins for increased affinity and thermal stability, screening of antibody libraries, epitope mapping, and use as whole-cell biocatalysts. However, hyperglycosylation can interfere with overall protein accessibility on the surface. Therefore, the less elaborate hyperglycosylation in wild type Pichia pastoris and the availability of glycoengineered strains make this yeast an excellent alternative for surface display of glycoproteins. Here, we report the implementation of the well-established a-agglutinin-based yeast surface display technology in P. pastoris. Four heterologous proteins were expressed on the surface of a wild type and a glycoengineered strain. Surface display levels were monitored by Western blot, immunofluorescence microscopy, and FACS analysis. The availability of glycoengineered strains makes P. pastoris an excellent alternative for surface display of glycoproteins and paves the way for new applications.