Purification and biochemical characterization of recombinant hirudin produced by Saccharomyces cerevisiae

Recombinant hirudin was produced by the yeast Saccharomyces cerevisiae using the alpha-pheromone prepro sequence to direct its secretion into the culture medium. The secreted hirudin was isolated to greater than or equal to 95% purity as measured by 205-nm absorbance integration from a reverse-phase chromatogram. One major activity peak corresponding to the complete, correctly processed molecule and two minor activity peaks corresponding to C-terminally truncated forms were identified. The primary structure of the major peak, determined by N-terminal sequencing of tryptic peptides, was that predicted from the cDNA sequence, and the molecular mass analyzed by fast atom bombardment mass spectrometry (FAB-MS) was 6892.6 (calculated 6892.5). UV spectral analysis suggested that, in contrast to the natural molecule, recombinant hirudin produced by S. cerevisiae is not sulfated.     

Enhanced production of anticoagulant hirudin in recombinant Saccharomyces cerevisiae by chromosomal delta-integration

Recombinant Saccharomyces cerevisiae strains were developed to overproduce an anticoagulant hirudin. The delta-sequences of the yeast retrotransposon Ty1 and URA3 were used as target sites for a hirudin expression cassette. High copy-number transformants were successfully selected using a dominant selection antibiotic, G418. The copy numbers of the hirudin expression cassette integrated into delta-sequences of the yeast chromosome ranged from five to ten copies per cell. Production of hirudin in the delta-integrated recombinant S. cerevisiae system increased over two-fold compared with the YEp-based episomal hirudin expression system. A linear relationship between the copy number of the hirudin expression cassette and hirudin expression level was observed up to 10 copies. The hirudin expression cassettes integrated into the yeast chromosome were stably maintained in non-selective culture conditions.     

Coexpression of BiP increased antithrombotic hirudin production in recombinant Saccharomyces cerevisiae

In order to increase a production level of antithrombotic hirudin, BiP was simultaneously expressed in recombinant Saccharomyces cerevisiae strains carrying ten and 15 copies of the hirudin expression cassette integrated in the chromosome. Coexpression of BiP greatly enhanced both cell growth and hirudin production in recombinant S. cerevisiae. Maximum hirudin concentration of 36 mg l(-1) was obtained from batch culture of the ten copy-number transformant concomitantly harboring an episomal copy of the BiP gene under the control of the GAL1 promoter, which is corresponding to a 2.5-fold increase compared with the control strain carrying the genomic BiP gene only. The mean size of the recombinant yeast cells expressing the BiP gene remained at a relatively constant level compared with the control strains of which size increased after the onset of hirudin expression by the GAL10 promoter.     

Effects of medium composition on hirudin production in recombinant Saccharomyces cerevisiae

Summary The enriched medium based on yeast nitrogen basc(YNB)increased hirudin synthesis and secretion in rccombinant Saccharomyces cerevisiae in batch and fed-batch cultures. Fed-batch fermentation with the defined medium yielded 342mg hirudin/l but supplementation of yeast extract increased the final hirudin concentration to 461mg hirudin/l. The defined medium, however, produced the product protein with higher purity of 21% and hence will allow easy separation of secreted hirudin from other contaminated polypeptides present in the growth medium. In a continuous culuture, the defined medium yielded higher concentrations of cell mass and hirudin than the complex medium.     

Production of recombinant hirudin in galactokinase-deficientSaccharomyces cerevisiae by fed-batch fermentation with continuous glucose feeding

The artificial gene coding for anticoagulant hirudin was placed under the control of theGAL10 promoter and expressed in the galactokinase-deficient strain (Δgal1) ofSaccharomyces cereivisiae, which uses galactose only as a gratuitous inducer in order to avoid its consumption. For efficient production of recombinant hirudin, a carbon source other than galactose should be provided in the medium to support growth of the Δgal1 strain. Here we demonstrate the successful use of glucose in the fed-batch fermentation of the Δgal1 strain to achieve efficient production of recombinant hirudin, with a yield of up to 400 mg hirudin/L.     

Production of ethanol from starch by respiration-deficient recombinant Saccharomyces cerevisiae

A 100%-respiration-deficient nuclear petite amylolytic Saccharomyces cerevisiae NPB-G strain was generated, and its employment for direct fermentation of starch into ethanol was investigated. In a comparison of ethanol fermentation performances with the parental respiration-sufficient WTPB-G strain, the NPB-G strain showed an increase of ca. 48% in both ethanol yield and ethanol productivity.     

Scale-up of recombinant hirudin production fromSaccharomyces cerevisiae

Scale-up of hirudin production fromSaccharomyces cerevisiae from bench-scale to pilot-scale was carried out based on constant volumetric oxygen transfer coefficient (K _L a). Fed-batch mode of cultivation using step-wise feeding strategy of galactose was employed for the production of hirudin in a 30-L and a 300-L pilot-scale fermentor. The final hirudin concentrations were achieved 390 mg/L and 286.1 mg/L, and the volumetric productivities were 80.4% and 90.7% with the 30-L and 300-L fermentors, respectively, compared to the productivity of the 5-L bench-scale fermentor.     

Production of recombinant human serum albumin from Saccharomyces cerevisiae

Human serum albumin has been constitutively expressed in a Saccharomyces cerevisiae brewing yeast. After cell growth and disruption the product was associated with the insoluble fraction and represented approximately 1% of total cell protein. After the cell debris was extensively washed, the albumin was solubilized with 8 M urea and 28 mM 2-mercaptoethanol in 50 mM sodium carbonate buffer, pH 10. The denatured albumin was refolded by dialysis and further purified by anion exchange and gel filtration chromatography. Losses of renatured material could be reduced, or higher protein concentrations used during refolding, if the denatured product was purified by cation-exchange chromatography in urea prior to refolding. Apart from an additional N-terminal N-acetyl methionine, the refolded product proved identical to human serum albumin derived from plasma when compared by a variety of physical, chemical, and biological analytical methods.     

Production of human caseinomacropeptide in recombinant Saccharomyces cerevisiae and Pichia pastoris

Caseinomacropeptide is a polypeptide of 64 amino acid residues (106–169) derived from the C-terminal part of the mammalian milk k-casein. This macropeptide has various biological activities and is used as a functional food ingredient as well as a pharmaceutical compound. The gene encoding the human caseinomacropeptide (hCMP) was synthesized and expressed with an α-factor secretion signal in the two yeast strains, Saccharomyces cerevisiae and Pichia pastoris. The complete polypeptide of the recombinant hCMP was produced and secreted in a culture medium by both the strains, but the highest production was observed in S. cerevisiae with a galactose-inducible promoter. In a fed-batch bioreactor culture, 2.5 g/l of the recombinant hCMP was obtained from the S. cerevisiae at 97 h.     

Effect of galactose feeding on the improved production of hirudin in fed-batch cultures of recombinant Saccharomyces cerevisiae

Different feeding strategies of galactose were employed to improve the production of anticoagulant, hirudin, by fed-batch mode of cultivation from recombinant Saccharomyces cerevisiae. The structural gene coding for hirudin was harboured with GAL10 promoter for controlled expression of hirudin and the MFα 1 signal sequence for secretion into the growth medium. A step-wise feeding of galactose was found as more suitable feeding strategy of galactose which resulted in the final hirudin volumetric productivity of 6,840?μg/l?·?h, than intermittent, continuous and ethanol controlled feeding of galactose. The final volumetric productivity of hirudin obtained by step-wise feeding of galactose was 3.88 fold higher compared with simple batch fermentation.     

Suppression of proteolytic degradation of recombinant hirudin from Saccharomyces cerevisiae using the O2-enriched air

A novel process using O2-enriched air supply was used to suppress the C-terminal proteolytic degradation of recombinant hirudin (r-hirudin) from Saccharomyces cerevisiae. When dissolved O2 was controlled above 20% saturation level using normal air, inactive forms of C-terminally truncated hirudin were observed in culture broth from 48 h of fermentation. The use of O2-enriched air giving above 40% saturation of dissolved O2 suppressed the proteolytic degradation and hence the formation of truncated forms of inactive r-hirudin until 60 h of fermentation.     

Production of wild-type and peptide fusion cutinases by recombinant Saccharomyces cerevisiae MM01 strains

This study focused on the growth of Saccha-romyces cerevisiae MM01 recombinant strains and the respective production of three extracellular heterologous cutinases: a wild-type cutinase and two cutinases in which the primary structure was fused with the peptides (WP)(2) and (WP)(4), respectively. Different cultivation and strategies were tested in a 2-L shake flask and a 5-L bioreactor, and the respective cell growth and cutinase production were analyzed and compared for the three yeast strains. The highest cutinase productions and productivities were obtained in the fed-batch culture, where wild-type cutinase was secreted up to a level of cutinase activity per dry cell weight (specific cell activity) of 4.1 Umg(-1) with activity per protein broth (specific activity) of 266 Umg(-1), whereas cutinase-(WP)(2) was secreted with a specific cell activity of 2.1 Umg(-1) with a specific activity of 200 Umg(-1), and cutinase-(WP)(4) with a specific cell activity of 0.7 Umg(-1) with a specific activity of 15 Umg(-1). The results indicate that the fusion of hydrophobic peptides to cutinase that changes the physical properties of the fused protein limits cutinase secretion and subsequently leads to a lower plasmid stability and lower yeast cell growth. These effects were observed under different cultivation conditions (shake flask and bioreactor) and cultivation strategies (batch culture versus fed-batch culture).     

Production of Extracellular lipases by Saccharomyces cerevisiae

Seven strains of Saccharomyces cerevisiae all produced lipase when grown in shake flask culture. The best strain, DSM 1848, produced 4.0U of lipase in the medium containing olive oil and yeast extract. Production of the lipase was growth-associated.     

Plasmid stability in recombinant Saccharomyces cerevisiae

Because of many advantages, the yeast Saccharomyces cerevisiae is increasingly being employed for expression of recombinant proteins. Usually, hybrid plasmids (shuttle vectors) are employed as carriers to introduce the foreign DNA into the yeast host. Unfortunately, the transformed host often suffers from some kind of instability, tending to lose or alter the foreign plasmid. Construction of stable plasmids, and maintenance of stable expression during extended culture, are some of the major challenges facing commercial production of recombinant proteins. This review examines the factors that affect plasmid stability at the gene, cell, and engineering levels. Strategies for overcoming plasmid loss, and the models for predicting plasmid instability, are discussed. The focus is on S. cerevisiae, but where relevant, examples from the better studied Escherichia coli system are discussed. Compared to free suspension culture, immobilization of cells is particularly effective in improving plasmid retention, hence, immobilized systems are examined in some detail. Immobilized cell systems combine high cell concentrations with enhanced productivity of the recombinant product, thereby offering a potentially attractive production method, particularly when nonselective media are used. Understanding of the stabilizing mechanisms is a prerequisite to any substantial commercial exploitation and improvement of immobilized cell systems.     

Xylitol production by immobilized recombinant Saccharomyces cerevisiae in a continuous packed-bed bioreactor

Continuous xylitol production with two different immobilized recombinant Saccharomyces cerevisiae strains (H475 and S641), expressing low and high xylose reductase (XR) activities, was investigated in a lab-scale packed-bed bioreactor. The effect of hydraulic residence time (HRT; 1.3-11.3 h), substrate/cosubstrate ratio (0.5 and 1), recycling ratio (0, 5, and 10), and aeration (anaerobic and oxygen limited conditions) were studied. The cells were immobilized by gel entrapment using Ca-alginate as support and the beads were treated with Al(3+) to improve their mechanical strength. Xylose was converted to xylitol using glucose as cosubstrate for regeneration of NAD(P)H required in xylitol formation and for generation of maintenance energy. The stability of the recombinant strains after 15 days of continuous operation was evaluated by XR activity and plasmid retention analyses. Under anaerobic conditions the volumetric xylitol productivity increased with decreasing HRT with both strains. With a recycling ratio of 10, volumetric productivities as high as 3.44 and 5.80 g/L . h were obtained with the low XR strain at HRT 1.3 h and with the high XR strain at HRT 2.6 h, respectively. However, the highest overall xylitol yields on xylose and on cosubstrate were reached at higher HRTs. Lowering the xylose/cosubstrate ratio from 1 to 0.5 increased the overall yield of xylitol on xylose, but the productivity and the xylitol yield on cosubstrate decreased. Under oxygen limited conditions the effect of the recycling ratio on production parameters was masked by other factors, such as an accumulation of free cells in the bioreactor and severe genetic instability of the high XR strain. Under anaerobic conditions the instability was less severe, causing a decrease in XR activity from 0.15 to 0.10 and from 3.18 to 1.49 U/mg with the low and high XR strains, respectively. At the end of the fermentation, the fraction of plasmid bearing cells in the beads was close to 100% for the low XR strain; however, it was significantly lower for the high XR strain, particularly for cells from the interior of the beads. (c) 1996 John Wiley & Sons, Inc.     

Characterization of recombinant antistasin secreted by Saccharomyces cerevisiae.

Secretion from recombinant yeast was used as a potential source of large quantities of the leech protein antistasin (ATS), a potent and highly specific inhibitor of the serine protease coagulation factor Xa. Mature recombinant ATS (r-ATS) is obtained after intracellular cleavage by the yscF protease of the mating factor alpha-1 pre-proleader from the fusion protein at the Lys-Arg sequence junction. Production levels are relatively low (ca. 1 mg/liter). Purification of the secreted product from a complex growth medium involved cell removal by microfiltration and diafiltration, cation-exchange capture and concentration on S-Sepharose Fast Flow, C-4 reverse-phase high-performance liquid chromatography (RP-HPLC), and HPLC cation-exchange chromatography step, and RP-HPLC concentration and desalting. The process was scaled up from the 16- to the 250-liter level with a corresponding increase in amount of r-ATS. From the 250-liter fermentation two major forms, r-ATS-I and r-ATS-II, distributed approximately 60:40, and a minor form, r-ATS-minor (ca. 1% of the purified r-ATS), were characterized. Limited N-terminal sequence analysis by Edman degradation indicated that r-ATS-I has the predicted mature N-terminus starting with Gln, that r-ATS-II is N-terminally blocked with pyroglutamate, and that r-ATS-minor is an incompletely processed form. RP-HPLC, hydrophilic-interaction HPLC, cation-exchange HPLC analysis, and electrophoresis results are consistent with the differences observed by sequencing. Preliminary in vitro characterization by intrinsic Ki determination for factor Xa inhibition indicated that the yeast r-ATS forms are indistinguishable from each other as well as from r-ATS expressed by the insect baculovirus host-vector system. Nevertheless, r-ATS-I and r-ATS-II appear less potent than insect-derived r-ATS in the activated partial thromboplastin time clotting assay. Further characterization indicated that C-terminal cleavage at Pro-116 had occurred in r-ATS-I and r-ATS-II as well as oxidation of methionine residues to methionine sulfoxide. The possible role of the C-terminus in inhibition of the prothrombinase complex is discussed.     

Metabolic engineering of recombinant protein secretion by Saccharomyces cerevisiae

The yeast Saccharomyces cerevisiae is a widely used cell factory for the production of fuels and chemicals, and it is also provides a platform for the production of many heterologous proteins of medical or industrial interest. Therefore, many studies have focused on metabolic engineering S. cerevisiae to improve the recombinant protein production, and with the development of systems biology, it is interesting to see how this approach can be applied both to gain further insight into protein production and secretion and to further engineer the cell for improved production of valuable proteins. In this review, the protein post-translational modification such as folding, trafficking, and secretion, steps that are traditionally studied in isolation will here be described in the context of the whole system of protein secretion. Furthermore, examples of engineering secretion pathways, high-throughput screening and systems biology applications of studying protein production and secretion are also given to show how the protein production can be improved by different approaches. The objective of the review is to describe individual biological processes in the context of the larger, complex protein synthesis network.     

Production of glutathione in extracellular form by Saccharomyces cerevisiae

The present research was aimed at inducing, in a post fermentative procedure (biotransformation) and by modifying cell permeability, glutathione (GSH) accumulation and subsequent release from cells of Saccharomyces cerevisiae. With the aim of limiting process costs, research considered the possibility of employing baker's yeasts (S. cerevisiae), inexpensive cells source available on the market, in comparison with a collection strain. The tested yeasts showed different sensitivity to the chemical/physical treatments performed to alter cell permeability. Modest effects were evidenced with Triton, active only on Zeus yeast samples (1.7 g GSH/l, near 60% of which in extracellular form). Lauroyl sarcosine showed an interesting action on GB Italy sample (2.8 g GSH/l, near 80% extracellular). Lyophilization evidenced good performance with Lievitalia yeast strain (2.9 g GSH/l, 90% extracellular). The possibility of obtaining GSH directly in extracellular form represents an interesting opportunity of reducing GSH production cost and furthering the range of application of this molecule.     

Purification and characterization of human caseinomacropeptide produced by a recombinant Saccharomyces cerevisiae

Caseinomacropeptide (CMP) is a biologically active polypeptide derived from the C-terminal of milk kappa-casein. CMP is heterogeneous since it is modified differently by glycosylation and phosphorylation after translation. Recently, recombinant human CMP (hCMP) has been produced as a secretory product in yeast. The present study aimed at the purification and characterization of recombinant hCMP. By sequential molecular cut-off ultrafiltration and anion-exchange chromatography, the recombinant hCMP in the culture broth could be purified to an HPLC purity over 94%. The authenticity of the purified hCMP was confirmed by sequence analysis of N-terminal amino acids. The recombinant hCMP was estimated to be 7.0kDa by SDS-PAGE, and showed a lower glycosylation than the natural bovine CMP.