High-yield production of the human lysozyme by Pichia pastoris SMD1168 using response surface methodology and high-cell-density fermentation

Efficient production of a highly active lysozyme from European flat oyster Ostrea edulis

Lysozyme, an antimicrobial agent, is extensively employed in the food and healthcare sectors to facilitate the breakdown of peptidoglycan. However, the methods to improve its catalytic activity and secretory expression still need to be studied. In the present study, twelve lysozymes from different origins were heterologously expressed using the Komagataella phaffii expression system. Among them, the lysozyme from the European flat oyster Ostrea edulis (oeLYZ) showed the highest activity. Via a semi-rational approach to reduce the structural free energy, the double mutant Y15A/S39R (oeLYZdm) with the catalytic activity 1.8-fold greater than that of the wild type was generated. Subsequently, different N-terminal fusion tags were employed to enhance oeLYZdm expression. The fusion with peptide tag 6×Glu resulted in a remarkable increase in the recombinant oeLYZdm expression, from 2.81 × 103 U mL-1 to 2.11 × 104 U mL-1 in shake flask culture, and eventually reaching 2.05 × 105 U mL-1 in a 3-L fermenter. The work produced the greatest amount of heterologous oeLYZ expression in microbial systems that are known to exist. Reducing the structural free energy and employing the N-terminal fusion tags are effective strategies to improve the catalytic activity and secretory expression of lysozyme.

The molecular modification, expression, and the antibacterial effects studies of human lysozyme

Human lysozyme (hLYZ) has attracted considerable research attention due to its natural and efficient antibacterial abilities and widespread uses. In this study, hLYZ was modified to enhance its enzyme activity and expressed in a Pichia pastoris expression system. A combination mutant HZM(2R-K)-N88D/V110S demonstrated the highest enzyme activity (6213 ± 164 U/mL) in shake flasks, which was 4.07-fold higher when compared with the original strain. Moreover, the recombinant P. pastoris was inducted in a 3 L bioreactor plus methanol/sorbitol co-feeding. After 120 h induction, the antibacterial activity of hLYZ reached 2.23 ± 0.12 × 105 U/mL, with the specific activity increasing to 1.89 × 105 U/mg, which is currently the highest specific activity obtained through recombinant expression of hLYZ. Also, hLYZ supernatants showed 2-fold inhibitory effects toward Staphylococcus aureus and Micrococcus lysodeikticus when compared with HZM(2R-K). Our research generated a hLYZ mutant with high antibacterial capabilities and provided a method for screening of high-quality enzymes.

Highly efficient expression and secretion of human lysozyme using multiple strategies in Pichia pastoris

BACKGROUND

Human lysozyme (hLYZ), an emerging antibacterial agent, has extensive application in the food and pharmaceutical industries. However, the source of hLYZ is particularly limited.

RESULTS

To achieve highly efficient expression and secretion of hLYZ in Pichia pastoris, multiple strategies including G418 sulfate screening, signal sequence optimization, vacuolar sorting receptor VPS10 disruption, and chaperones/transcription factors co-expression were applied. The maximal enzyme activity of extracellular hLYZ in a shaking flask was 81,600 ± 5230 U mL-1 , which was about five times of original strain. To further reduce the cost, the optimal medium RDMY was developed and the highest hLYZ activity reached 352,000 ± 16,696.5 U mL-1 in a 5 L fermenter.

CONCLUSION

This research provides a very useful and cost-effective approach for the hLYZ production in P. pastoris and can also be applied to the production of other recombinant proteins.

Exploring the therapeutic potential of recombinant human lysozyme: a review on wound management system with antibacterial

Lysozyme, a natural antibacterial enzyme protein, possesses the ability to dissolve the cell walls of Gram-positive bacteria, demonstrating broad-spectrum antibacterial activity. Despite its significant potential in treating wound infections and promoting wound healing, its widespread clinical application has yet to be realized. Current research is primarily focused on carrier-based delivery systems for lysozyme. In this review, we discuss four delivery systems that can be employed for lysozyme in wound healing treatment, specifically hydrogels, nanofilms, electrospun fibrous membranes, and modified-lysozyme composite systems. These systems not only enhance the stability of lysozyme but also enable its controlled and sustained release at wound sites, potentially overcoming some of the challenges associated with its direct application. Lastly, we delve into the perspectives and challenges related to the use of these delivery systems, hoping to spur further research and innovation in this promising field.

Controlling Specific Growth Rate for Recombinant Protein Production by Pichia pastoris Under Oxidation Stress in Fed-batch Fermentation

Methanol can be used by Pichia pastoris as the carbon source and inducer to produce recombinant proteins in high-cell-density fermentations. However, methanol oxidation at high specific growth rates can lead to the reactive oxygen species (ROS) accumulation, resulting in cell damage. Here, we study the relationship between methanol feeding and ROS accumulation by controlling specific growth rate during the induction phase. A higher specific growth rate increased the level of ROS accumulation caused by methanol oxidation. While the cell growth rate was proportional to specific growth rate, maximum total protein production and highest enzyme activity were achieved at a specific growth rate of 0.05 1/h as compared to that of 0.065 1/h. Moreover, oxidative damage induced by over-accumulation of ROS in P. pastoris during the methanol induction phase caused cell death and reduced protein expression ability. ROS scavenging system analysis revealed that the higher specific growth rate, especially 0.065 1/h, resulted in increased intracellular catalase activity and decreased glutathione content significantly. Finally, Spearman's correlation analysis further revealed that the reduced glutathione might be beneficial for maintaining cell viability and increasing protein production under oxidative stress caused by ROS toxic accumulation. Our findings suggest an integrated strategy to control the feeding of the essential substrate based on analyzing its response to oxidative stress caused by ROS toxic accumulation, as well as develop a strategy to optimize fed-batch fermentation.

A Combinational Strategy for Effective Heterologous Production of Functional Human Lysozyme in Pichia pastoris

Human lysozyme (hLYZ), known for its bacteriolytic activity, is widely applied in the food and pharmaceutical industries as an antimicrobial agent. However, its extensive application was limited by its low large-scale production efficiency. In this study, a combinational method of integrating codon optimization, multiple gene copies, and ER molecular chaperone co-expression was developed to improve the heterologous production of hLYZ in Pichia pastoris GS115. Our results showed that increasing the copy number of the optimized hLYZ gene in P. pastoris could enhance its secretory production level up to 1.57-fold. The recombinant opt-hLYZ-6C strain that contains six copies of opt-hLYZ gene exhibited the highest mRNA transcription levels, giving the highest production of 0.22 ± 0.02 mg/mL of hLYZ in the medium supernatant with a bacteriolytic activity of 14,680 ± 300 U/mL against Micrococcus lysodeikticus in the shaking flask experiment. Moreover, co-overexpression of ER retention molecular chaperones, such as Pdi1 or Ero1, in the recombinant opt-hLYZ-6C strain both presented positive effects on the secretory production of hLYZ. Our further characterization indicated that tandem co-expression of Ero1 and Pdi1 together presented an added-up effect. The secretory production of hLYZ in the medium supernatant reached 0.34 ± 0.02 mg/mL of the recombinant opt-hLYZ-6C-EP strain in the shaking flask experiment, with a bacteriolytic activity of 21,200 ± 400 U/mL. Compared to the recombinant opt-hLYZ-1C strain, these final improvements were calculated as 2.43-fold and 2.30-fold on secretory protein levels and antibacterial activity, respectively. Finally, the recombinant opt-hLYZ-6C-EP strain was applied for high-density cultivation in 5 L of fermenter, in which the secretory yield of hLYZ reached 2.34 ± 0.02 mg/mL in the medium supernatant, with a bacteriolytic activity of 1.76 ± 0.02 × 10⁵ U/mL against M. lysodeikticus. All these numbers presented the highest heterologous production levels of hLYZ in microbial systems.

Biotransformation of β-hydroxypyruvate and glycolaldehyde to l-erythrulose by Pichia pastoris strain GS115 overexpressing native transketolase

Transketolase is a proven biocatalytic tool for asymmetric carbon-carbon bond formation, both as a purified enzyme and within bacterial whole-cell biocatalysts. The performance of Pichia pastoris as a host for transketolase whole-cell biocatalysis was investigated using a transketolase-overexpressing strain to catalyze formation of l-erythrulose from β-hydroxypyruvic acid and glycolaldehyde substrates. Pichia pastoris transketolase coding sequence from the locus PAS_chr1-4_0150 was subcloned downstream of the methanol-inducible AOX1 promoter in a plasmid for transformation of strain GS115, generating strain TK150. Whole and disrupted TK150 cells from shake flasks achieved 62% and 65% conversion, respectively, under optimal pH and methanol induction conditions. In a 300 μL reaction, TK150 samples from a 1L fed-batch fermentation achieved a maximum l-erythrulose space time yield (STY) of 46.58 g L^-1 h^-1 , specific activity of 155 U gCDW-1, product yield on substrate (Y_p/s ) of 0.52 mol mol^-1 and product yield on catalyst (Y_p/x ) of 2.23g gCDW-1. We have successfully exploited the rapid growth and high biomass characteristics of Pichia pastoris in whole cell biocatalysis. At high cell density, the engineered TK150 Pichia pastoris strain tolerated high concentrations of substrate and product to achieve high STY of the chiral sugar l-erythrulose. © 2017 The Authors Biotechnology Progress published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers Biotechnol. Prog., 34:99-106, 2018.

RSM optimization of HSA/IL1Ra in Pichia pastoris overexpression strain and study of its in vivo activity in reducing hyperglycemia of GK rats

Human serum albumin (HSA) and interleukin-1 receptor antagonist (IL1Ra) fusion protein is a potential long-acting drug in the treatment of type 2 diabetes. Previously, the expression level of HSA/IL1Ra in Pichia pastoris was successfully improved by increasing the gene copy number and coexpression with chaperone (protein disulfide isomerase) in our laboratory. However, the overexpression strain resulted in low production of high- cell-density fermentation. In this study, the culture medium was optimized in both flask and fermenter, and the optimum culture medium notably increased the productivity and stability of HSA/IL1Ra. To further improve the expression, response surface methodology was used to further optimize the culture condition through modeling three selected parameters (induction pH, induction temperature [T], and maximum methanol feed rate [V_m ]). The maximum yield of HSA/IL1Ra reached 1.1 g/L (10-fold higher than original fermentation condition) under the optimized culture condition (pH 7.0, T = 29 ℃ and V_m = 4.82 mL/L/H) in a 5-L fermenter. In addition, the degradation position of HSA/IL1Ra during fermentation was determined to be K571, serving as a potential target for genetic modification strategies to reduce the degradation. Finally, the in vivo activity study showed that HSA/IL1Ra maintained the therapeutic effect of IL1Ra in type 2 diabetes model rats meanwhile reducing the frequency of administration.

Optimization of Recombinant Expression of Synthetic Bacterial Phytase in Pichia pastoris Using Response Surface Methodology

Background:

Escherichia coli phytase is an acidic histidine phytase with great specific activity. Pichia pastoris is a powerful system for the heterologous expression of active and soluble proteins which can express recombinant proteins in high cell density fermenter without loss of product yield and efficiently secrete heterologous proteins into the media. Recombinant protein expression is influenced by expression conditions such as temperature, concentration of inducer, and pH. By optimization, the yield of expressed proteins can be increase. Response surface methodology (RSM) has been widely used for the optimization and studying of different parameters in biotechnological processes.

Objectives:

In this study, the expression of synthetic appA gene in P. pastoris was greatly improved by adjusting the expression condition.

Materials and Methods:

The appA gene with 410 amino acids was synthesized by P. pastoris codon preference and cloned in expression vector pPinkα-HC, under the control of AOX1 promoter, and it was transformed into P. pastoris GS115 by electroporation. Recombinant phytase was expressed in buffered methanol-complex medium (BMMY) and the expression was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and enzymatic assay. To achieve the highest level of expression, methanol concentration, pH and temperature were optimized via RSM. Finally, the optimum pH and temperature for recombinant phytase activity was determined.

Results:

Escherichia coli phytase was expressed in P. pastoris under different cultivation conditions (post-induction temperature, methanol concentration, and post-induction pH). The optimized conditions by RSM using face centered central composite design were 1% (v/v) methanol, pH = 5.8, and 24.5°C. Under the optimized conditions, appA was successfully expressed in P. pastoris and the maximum phytase activity was 237.2 U/mL after 72 hours of expression.

Conclusions:

By optimization of recombinant phytase expression in shake flask culture, we concluded that P. pastoris was a suitable host for high-level expression of phytase and it can possess high potential for industrial applications.