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A dual-dimensional CRISPR toolkit enables one-step high-efficiency multiplex genome editing in Komagataella phaffii.

Against the backdrop of green biomanufacturing, engineering methanol-utilizing Komagataella phaffii (K. phaffii) represents an effective strategy to expand the one carbon (C1) product profile and speed up the industrialization of C1-based bioeconomy. To address the technical challenges of low efficiency and cumbersome experimental procedures for multiplex gene editing and precise large-fragment integration during the reconstruction of complex metabolic pathways in K. phaffii, this study established a CRISPR toolkit - Efficient Multi-Gene Editing System 3.0 (EMGES 3.0) - which enabled one-step large-fragment integration coupled with multiplex gene knockout. EMGES 3.0 was constructed through the synergistic optimization of a repair-engineered chassis and an episomal CRISPR vector. For chassis engineering, five DNA repair modules: Δlig4 (DNA Ligase IV, non-homologous end joining end ligation), ppMRE11(The endogenous MRE11 gene from Pichia pastoris) overexpression (The Meiotic Recombination 11, DNA double-strand break end resection), Δrad9 (Radiation-Sensitive 9, DNA damage checkpoint regulation), Δmph1 (Mutator Phenotype Helicase 1, improvement of homologous recombinant strand extension), and PapRecT-PaSSB co-expression (stabilization of recombination intermediates) were integrated to generate the highly recombinogenic strain Y09. For vector engineering, cenARS was replaced by panARS and the endogenous promoter PGAP was employed to drive the double hammerhead ribozyme-single guide RNA-hepatitis delta virus ribozyme (double HH-sgRNA-HDV: dHgH)-mediated sgRNA expression, yielding the optimized vector Nov_pGAP_panARS_pLAT1_Cas9. These two features on K. phaffii together enhanced the EMGES 3.0 to a higher standard of transformation rate and editing efficiency. According to our results, EMGES 3.0 achieved dual-functional gene knockout efficiencies between 76.6% and 100%. For insertion of medium-long fragments (>4.5 kb), the efficiency achieved 93.3%. In addition, the one-step integration of ultra-long fragments (>16 kb) achieved 14.8%, which was reported for the first time. Furthermore, the efficiency of simultaneous long-fragment integration at three neutral loci reached 38.4% (>15 kb). We applied the system for one-step production of free fatty acids (FFAs, yield: 5.82 ∼ 7.30 mg/L/OD600) and resveratrol (yield: 1.14 ∼ 1.28 mg/L) using methanol as the sole carbon source. EMGES 3.0 provides a robust technical foundation for complex compounds biosynthesis and high-yield industrial strains, while also advancing K. phaffii as an industrial synthetic biology chassis for efficient C1 utilization.

CRISPR-Cas Systems

Heterologous expression and optimization of the antimicrobial peptide acidocin 4356 in Komagataella phaffii to target Pseudomonas aeruginosa.

Multidrug-resistant (MDR) pathogens, particularly Pseudomonas aeruginosa, pose a serious global health threat due to their increasing prevalence and limited therapeutic options. Antimicrobial peptides (AMPs) offer promising alternatives to traditional antibiotics, yet their large-scale application remains constrained by high production costs and technical challenges. This research sought to develop a yeast-based system for the cost-efficient synthesis of acidocin 4356 (ACD), an antimicrobial peptide proven effective against P. aeruginosa. A codon-optimized ACD gene was cloned into the pPICZα-A expression vector and integrated into the Komagataella phaffii (formerly Pichia pastoris) GS115 genome. Colony PCR confirmed successful integration, and specific transformants demonstrated expression of the 6 × His-ECS-rACD fusion protein, as verified by SDS-PAGE and dot blot analysis. After Ni-NTA chromatography and enterokinase digestion, rACD was found at ~ 20 kDa instead of 8.3 kDa, suggesting oligomerization or post-translational modifications. Response surface methodology determined the optimal temperature, pH, and methanol concentration for peptide synthesis. Under optimal circumstances (21 °C, pH 6.24, and 1.089% methanol), rACD synthesis increased by 34.12% over baseline conditions (30 °C, pH 6, 1% methanol). AlphaFold structural modeling identified three α-helices in high-confidence regions, implicated in bacterial membrane disruption. Antimicrobial assays demonstrated potent rACD activity against P. aeruginosa, yielding a 58.29% reduction in growth at 150 µg/mL and MIC50 and MIC90 values of 143.04 and 320.64 µg/mL, respectively. These findings underscore K. phaffii as a robust platform for AMP production and highlight rACD's therapeutic potential as an effective agent against MDR P. aeruginosa, warranting further investigation into its clinical and industrial applications. KEY POINTS: • Developing a novel K. phaffii strain for heterologous expression supports efficient rACD peptide production. • Optimized conditions boosted expression yield by 34.12% above the reference fermentation settings. • Recombinant acidocin suppressed Pseudomonas aeruginosa growth by 58%, indicating anti-MDR activity.

Pseudomonas aeruginosa

Inducible flocculation in Komagataella phaffii enables enhanced biomass separation for biopharmaceutical production.

Biomass separation represents a critical bottleneck in Komagataella phaffii-based biopharmaceutical processes, as typically high cell densities of 40 - 50 % create significant operational, technical and economic challenges for harvest operations. Yeast cell aggregation (flocculation) provides a solution to accelerate cell sedimentation by increasing particle size, thus allowing to improve biomass-supernatant separation efficiency during both natural gravity settling and (continuous) centrifugation operations. This study demonstrates successful engineering of K. phaffii strains with an inducible flocculation phenotype using CRISPR/Cas9-based genome editing to integrate the Saccharomyces cerevisiae FLO1 (ScFLO1) gene under control of various regulatory elements, including methanol-inducible and derepressible promoters. Flocculation strength could be enhanced by implementing transcriptional positive feedback circuits based on the methanol-inducible AOX1 promoter. To address methanol-free production requirements, we developed alternative systems to retrofit PAOX1-based ScFLO1 expression and exploited the derepressible PDF promoter, offering broader compatibility with biopharmaceutical manufacturing facilities. Flocculating cells cultivated in a bioreactor demonstrated significantly improved sedimentation behavior, with considerably lower supernatant turbidity after short low-speed centrifugation or gravity sedimentation compared to non-flocculating controls. Crucially, cell flocculation had no negative impact on product amount and quality when expressing a multivalent NANOBODY® VHH molecule with pharmaceutical relevance. Thus, this work establishes the first genetically engineered flocculation system in K. phaffii compatible with recombinant protein production, providing the basis for an innovative approach to streamline harvest operations in biopharmaceutical processes.

Flocculation

Reprogrammed Komagataella phaffii for enhanced secretory expression of human lactoferrin.

Human lactoferrin (hLF) is a multifunctional glycoprotein of the transferrin family derived from milk and mucosal secretions, which exhibits antibacterial, anti-tumor, and immunomodulatory functions, and is an important component of infant formula. Conventional methods for lactoferrin expression are often inefficient, primarily due to inadequate protein synthesis capabilities and poor stability within microbial hosts. Herein, a Komagataella phaffii yeast strain capable of high-level secretory expression of hLF was constructed by reprogramming the endoplasmic reticulum (ER) and vacuole using CRISPR/Cas9 technology. A dual-expression cassette containing the AOX1 promoter, an α-secretion signal peptide, the hLF gene, and a terminator was integrated into three different sites of the K. phaffii genome. The stepwise strategy combining expansion of the ER membrane involved in protein synthesis with knockout of vacuolar proteases further enhanced hLF production. Subsequently, 0.1 g/L FeCl₃ was added to the medium to reduce the toxicity of hLF and improve its stability. After high-density cultivation of K. phaffii through optimization of cultivation conditions in shake flasks and a 5 L bioreactor, the secretory intact hLF titer reached 2214 mg/L, representing a 76.3-fold increase achieved through these engineering strategies. In addition, antibacterial experiments demonstrated that this secretory hLF had a significant inhibitory effect on Escherichia coli, Staphylococcus aureus, and yeast. Overall, the developed K. phaffii protein expression platform enabled efficient production of lactoferrin, demonstrating its potential for expressing other lactoproteins.

Lactoferrin

Enhanced Production of Recombinant Thermophilic Xylanase X11P in Ogataea polymorpha via In-Silico Signal Peptide Discovery and Fed-Batch Fermentation.

Efficient secretion of heterologous proteins is essential for advancing yeast-based bioprocesses, yet signal peptide (SP) optimization in the thermotolerant methylotrophic yeast Ogataea polymorpha remains limited. This study integrates in-silico SP discovery, experimental validation, and bioprocess engineering to enhance secretion of the thermophilic xylanase X11P under sucrose-inducible expression. Genome-wide screening of 5184 O. polymorpha proteins using SignalP, Phobius, DeepLoc, WoLF PSORT, and ProP identified 11 high-confidence SP candidates. Comparative analysis with Komagataella phaffii endogenous proteins guided selection of seven SPs for experimental evaluation. Among these, the novel O. polymorpha α-mating factor-like peptide FUN_005010 exhibited strong secretion-promoting activity, with its prepro-sequence yielding the highest extracellular xylanase levels and outperforming the classical Saccharomyces cerevisiae α-MF. To evaluate industrial applicability, sucrose-based fermentation strategies were systematically optimized in a 5-L bioreactor. Controlled sucrose feeding and balanced C/N ratios were found to be critical for maximizing maltase (MAL) promoter-driven expression. A stepwise increasing sucrose feed combined with induction at 30°C enabled X11P titers up to 770 U/mL, representing a 15-fold improvement over shake-flask cultures. This work demonstrates that the combination of SP evaluation and optimized sucrose-inducible fed-batch operation significantly enhances X11P production in O. polymorpha. The identified FUN_005010-prepro SP and the refined process framework provide valuable tools for developing O. polymorpha as a high-performance industrial expression platform.

Fermentation