Expression of Aspergillus niger glucose oxidase in yeast Pichia pastoris SMD1168

Hypersecretory production of glucose oxidase in Pichia pastoris through combinatorial engineering of protein properties, synthesis, and secretion

Glucose oxidase (EC 1.1.3.4, GOD) is a widely used industrial enzyme. To construct a GOD-hyperproducing Pichia pastoris strain, combinatorial strategies have been applied to improve GOD activity, synthesis, and secretion. First, wild-type GOD was subjected to saturation mutagenesis to obtain an improved variant, MGOD1 (V20W/T30S), with 1.7-fold higher kcat /KM . Subsequently, efficient signal peptides were screened, and the copy number of MGOD1 was optimized to generate a high-producing strain, 8GM1, containing eight copies of AOX1 promoter-GAS1 signal peptide-MGOD1 expression cassette. Finally, the vesicle trafficking of 8GM1 was engineered to obtain the hyperproducing strain G1EeSe co-expressing the trafficking components EES and SEC. 22, and the EES gene (PAS_chr3_0685) was found to facilitate both protein secretion and production for the first time. Using these strategies, GOD secretion was enhanced 65.2-fold. In the 5-L bioreactor, conventional fed-batch fermentation without any process optimization resulted in up to 7223.0 U/mL extracellular GOD activity (3.3-fold higher than the highest level reported to date), with almost only GOD in the fermentation supernatant at a protein concentration of 30.7 g/L. Therefore, a GOD hyperproducing strain for industrial applications was developed, and this successful case can provide a valuable reference for the construction of high-producing strains for other industrial enzymes.

The potential of cold-shock promoters for the expression of recombinant proteins in microbes and mammalian cells

BACKGROUND

Low-temperature expression of recombinant proteins may be advantageous to support their proper folding and preserve bioactivity. The generation of expression vectors regulated under cold conditions can improve the expression of some target proteins that are difficult to express in different expression systems. The cspA encodes the major cold-shock protein from Escherichia coli (CspA). The promoter of cspA has been widely used to develop cold shock-inducible expression platforms in E. coli. Moreover, it is often necessary to employ expression systems other than bacteria, particularly when recombinant proteins require complex post-translational modifications. Currently, there are no commercial platforms available for expressing target genes by cold shock in eukaryotic cells. Consequently, genetic elements that respond to cold shock offer the possibility of developing novel cold-inducible expression platforms, particularly suitable for yeasts, and mammalian cells.

CONCLUSIONS

This review covers the importance of the cellular response to low temperatures and the prospective use of cold-sensitive promoters to direct the expression of recombinant proteins. This concept may contribute to renewing interest in applying white technologies to produce recombinant proteins that are difficult to express.

Glucose Oxidase, an Enzyme “Ferrari”: Its Structure, Function, Production and Properties in the Light of Various Industrial and Biotechnological Applications

Glucose oxidase (GOx) is an important oxidoreductase enzyme with many important roles in biological processes. It is considered an “ideal enzyme” and is often called an oxidase “Ferrari” because of its fast mechanism of action, high stability and specificity. Glucose oxidase catalyzes the oxidation of β-d-glucose to d-glucono-δ-lactone and hydrogen peroxide in the presence of molecular oxygen. d-glucono-δ-lactone is sequentially hydrolyzed by lactonase to d-gluconic acid, and the resulting hydrogen peroxide is hydrolyzed by catalase to oxygen and water. GOx is presently known to be produced only by fungi and insects. The current main industrial producers of glucose oxidase are Aspergillus and Penicillium. An important property of GOx is its antimicrobial effect against various pathogens and its use in many industrial and medical areas. The aim of this review is to summarize the structure, function, production strains and biophysical and biochemical properties of GOx in light of its various industrial, biotechnological and medical applications.

Enhanced in vitro anticancer activity of yeast expressed recombinant glucose oxidase versus commercial enzyme

Cancer treatments continue to have many disadvantages. Reactive oxygen species, such as H₂O₂, in high concentrations, can cause cytotoxicity to cells, being even greater in cancer cells. One of the H₂O₂-producing enzymes is glucose oxidase; its application in cancer treatment should be explored. In this work, the extracellular expression of the mutated recombinant enzyme glucose oxidase was carried out in the eukaryotic expression system Pichia pastoris SMD1168, through the modification and optimization of the gox gene of Aspergillus niger to improve its expression in yeast and its purification. Also, the secretion signal of the alpha-mating factor from Saccharomyces cerevisiae was added to the gene for extracellular expression, and it was inserted into the expression vector pPIC3.5k. The extracellular expression of the enzyme facilitated purification by anion exchange chromatography; the purification was corroborated by SDS-PAGE, with a molecular weight of its subunit between 63 kDa and 100 kDa. The mutated recombinant enzyme glucose oxidase showed greater anticancer activity compared to the commercial glucose oxidase and could have potential for cancer treatment. KEY POINTS: • Pichia pastoris is an excellent eukaryotic expression system for proteins that need post-translational modifications. • Extracellular expression facilitates protein purification. • Glucose oxidase has potential application in cancer treatment.

Expression of Aspergillus niger glucose oxidase in Pichia pastoris and its antimicrobial activity against Agrobacterium and Escherichia coli

The gene encoding glucose oxidase from Aspergillus niger ZM-8 was cloned and transferred to Pichia pastoris GS115, a transgenic strain P. pastoris GS115-His-GOD constructed. The growth curve of P. pastoris GS115-His-GOD was consistent with that of Pichia pastoris GS115-pPIC9K under non-induced culture conditions. Under methanol induction conditions, the growth of the GOD-transgenic strain was significantly lowered than P. pastoris GS115-pPIC9K with the induced-culture time increase, and the optical densities of GOD-transgenic strain reached one-third of that of the P. pastoris GS115-pPIC9K at 51 h. The activity of glucose oxidase in the cell-free supernatant, the supernatant of cell lysate, and the precipitation of cell lysate was 14.3 U/mL, 18.2 U/mL and 0.48 U/mL, respectively. The specific activity of glucose oxidase was 8.3 U/mg, 6.52 U/mg and 0.73 U/mg, respectively. The concentration of hydrogen peroxide formed by glucose oxidase from supernatant of the fermentation medium, the supernatant of the cell lysate, and the precipitation of cell lysate catalyzing 0.2 M glucose was 14.3 μg/mL, 18.2 μg/mL, 0.48 μg/mL, respectively. The combination of different concentrations of glucose oxidase and glucose could significantly inhibit the growth of Agrobacterium and Escherichia coli in logarithmic phase. The filter article containing supernatant of the fermentation medium, supernatant of the cell lysate, and precipitation of cell lysate had no inhibitory effect on Agrobacterium and E. coli. The minimum inhibitory concentration of hydrogen peroxide on the plate culture of Agrobacterium and E. coli was 5.6 × 10³ μg/mL and 6.0 × 10³ μg/mL, respectively.

Improvement Strategies, Cost Effective Production, and Potential Applications of Fungal Glucose Oxidase (GOD): Current Updates

Fungal glucose oxidase (GOD) is widely employed in the different sectors of food industries for use in baking products, dry egg powder, beverages, and gluconic acid production. GOD also has several other novel applications in chemical, pharmaceutical, textile, and other biotechnological industries. The electrochemical suitability of GOD catalyzed reactions has enabled its successful use in bioelectronic devices, particularly biofuel cells, and biosensors. Other crucial aspects of GOD such as improved feeding efficiency in response to GOD supplemental diet, roles in antimicrobial activities, and enhancing pathogen defense response, thereby providing induced resistance in plants have also been reported. Moreover, the medical science, another emerging branch where GOD was recently reported to induce several apoptosis characteristics as well as cellular senescence by downregulating Klotho gene expression. These widespread applications of GOD have led to increased demand for more extensive research to improve its production, characterization, and enhanced stability to enable long term usages. Currently, GOD is mainly produced and purified from Aspergillus niger and Penicillium species, but the yield is relatively low and the purification process is troublesome. It is practical to build an excellent GOD-producing strain. Therefore, the present review describes innovative methods of enhancing fungal GOD production by using genetic and non-genetic approaches in-depth along with purification techniques. The review also highlights current research progress in the cost effective production of GOD, including key advances, potential applications and limitations. Therefore, there is an extensive need to commercialize these processes by developing and optimizing novel strategies for cost effective GOD production.