Combined strategies for improving the heterologous expression of a novel xylanase from Fusarium oxysporum Fo47 in Pichia pastoris

Xylanase, an enzyme capable of hydrolyzing non-starch polysaccharides found in grain structures like wheat, has been found to improve the organizational structure of dough and thus increase its volume. In our past work, one promising xylanase FXYL derived from Fusarium oxysporum Fo47 and first expressed 779.64 U/mL activity in P. pastoris. It has shown significant potential in improving the quality of whole wheat bread, making it become a candidate for development as a new flour improver. After optimization of expression elements and gene dose, the xylanase activity of FXYL strain carrying three-copies reached 4240.92 U/mL in P. pastoris. In addition, 12 factors associated with the three stages of protein expression pathway were co-expressed individually in order in three-copies strain, and the translation factor Pab1 co-expression increased FXYL activity to 8893.53 U/mL. Nevertheless, combining the most effective or synergistic factors from three stages did not exhibit better results than co-expressing them alone. To further evaluate the industrial potential, the xylanase activity and protein concentration reached 81184.51 U/mL and 11.8 g/L in a 5 L fed-batch fermenter. These engineering strategies improved the expression of xylanase FXYL by more than 104-fold, providing valuable insights for the cost-effective industrial application of FXYL in the baking field.

The superposition anti-viral activity of porcine tri-subtype interferon expressed by Saccharomyces cerevisiae

Interferon (IFN)-mediated antiviral responses are central to host defense against viral infection. Porcine viral infection has emerged as a serious hazard for the pig industry. The construction of an engineered Saccharomyces cerevisiae strain that efficiently produces porcine IFN has demonstrated several advantages. It can be easily fed to pigs, which helps in reducing antibiotic residues in pork and improve meat quality. In this study, the stable expression of several porcine IFN molecules (pIFN-α1, pIFN-β, pIFN-λ1, pIFN-λ1-β, pIFN-λ1-β-α1) were determined using an engineered S. cerevisiae system. With the YeastFab assembly method, the complete transcriptional units containing promoter (GPD), secretory peptide (α-mating factor), target gene (IFN) and terminator (ADH1) were successfully constructed using the characteristics of type II restriction endonuclease, and then integrated into the chromosomes Ⅳ and XVI of ST1814 yeast host strain, respectively. The expression kinetics of recombinant pIFNs were further analyzed. Synergism in the expression level of IFN receptor, antiviral protein, and viral loading was observed in viral-cell infection model treated with different porcine IFN subtypes. The porcine reproductive and respiratory syndrome viral load and antibody titer in serum decreased significantly after oral administration of IFN expression yeast fermentation broth. These findings indicate the potential efficacy of multi-valent pIFNs expressing S. cerevisiae as a potent feed material to prevent viral infections of pigs.

Secreted expression of truncated capsid protein from porcine circovirus type 2 in Pichia pastoris

OBJECTIVE

To achieve secreted expression of the truncated capsid protein from porcine circovirus type 2 (PCV2) in Pichia pastoris.

RESULTS

A truncated cap gene (tcap) with a deleted N-terminal nuclear localization signal was optimized and synthesized. Effective secreted expression was achieved in P. pastoris GS115. The high-productive recombinant strain for tCap was grown in a 5 l bioreactor and the productivity of tCap in supernatant reached 250 μg/ml. Furthermore, serum antibody test demonstrated that adjuvant-assisting tCap induced a significant increase of specific PCV2-Cap antibody over time in mice and a similar antibody level in pigs compared with a commercial Cap-based subunit vaccine.

CONCLUSION

This work establishes a secreted expression strategy in P. pastoris for the production of PCV2 Cap with superior bioactivity, and this strategy might provide potential uses in developing Cap-based subunit vaccine in the future.