Optimization of the fermentation and downstream processes for human enterokinase production in Pichia pastoris

High-Yield Preparation of American Oyster Defensin (AOD) via a Small and Acidic Fusion Tag and Its Functional Characterization

The marine peptide, American oyster defensin (AOD), is derived from Crassostrea virginica and exhibits a potent bactericidal effect. However, recombinant preparation has not been achieved due to the high charge and hydrophobicity. Although the traditional fusion tags such as Trx and SUMO shield the effects of target peptides on the host, their large molecular weight (12-20 kDa) leads to the yields lower than 20% of the fusion protein. In this study, a short and acidic fusion tag was employed with a compact structure of only 1 kDa. Following 72 h of induction in a 5 L fermenter, the supernatant exhibited a total protein concentration of 587 mg/L. The recombinant AOD was subsequently purified through affinity chromatography and enterokinase cleavage, resulting in the final yield of 216 mg/L and a purity exceeding 93%. The minimum inhibitory concentrations (MICs) of AOD against Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus galactis ranged from 4 to 8 μg/mL. Moreover, time-killing curves indicated that AOD achieved a bactericidal rate of 99.9% against the clinical strain S. epidermidis G-81 within 0.5 h at concentrations of 2× and 4× MIC. Additionally, the activity of AOD was unchanged after treatment with artificial gastric fluid and intestinal fluid for 4 h. Biocompatibility testing demonstrated that AOD, at a concentration of 128 μg/mL, exhibited a hemolysis rate of less than 0.5% and a cell survival rate of over 83%. Furthermore, AOD's in vivo therapeutic efficacy against mouse subcutaneous abscess revealed its capability to restrain bacterial proliferation and reduce bacterial load, surpassing that of antibiotic lincomycin. These findings indicate AOD's potential for clinical usage.

A simple and efficient method for cytoplasmic production of human enterokinase light chain in E. coli

Human enterokinase light chain (hEKL) cDNA sequence was designed with the help of codon optimization towards Escherichia coli codon preference and ribosome binding site design and artificially synthesized with a thioredoxin fusion tag at the N-terminal and a five his-tag peptide at the C-terminal. The synthetic hEKL gene was cloned into the pET-15 expression vector and transferred into the three different expression strains of E. coli BL21(DE3), NiCo21, and SHuffle T7 Express. Different growth and induction conditions were studied using a statistical response surface methodology (RSM). Recombinant hEKL protein was expressed at high levels in soluble form with 0.71 mM IPTG after 4 h of induction at 25 °C. Autocatalytic process cleaved TRX tag with enterokinase recognition site by the impure hEKL and yielded the mature enzyme. The target protein was then purified to homogeneity (> 95%) by affinity chromatography. The activity of hEKL was comparable to the commercial enzyme. From 1 L culture, 80 mg pure active hEKL was obtained with the specific activity of 6.25 × 10² U/mg. Three main parameters that help us to produce the enzyme in the folded and active form are the type of strain, SHuffle T7 strain, TRX and histidine fusion tags, and growth conditions including the increase of OD of induction and IPTG concentration and the decrease of induction temperature.

Comparison of Periplasmic and Cytoplasmic Expression of Bovine Enterokinase Light Chain in E. coli

Enterokinase enzyme is widely used in production of recombinant proteins. This enzyme is isolated from the intestine and recognizes a specific cleavage site (X↓LYS-ASP₄). Several studies have been performed to produce recombinant active enterokinase. In this study, the coding sequence of bovine enteropeptidase light chain (bEK_L) was isolated from Iranian Sarabi cattle and its expression was investigated in the periplasm and cytoplasm of E. coli by two different expression vectors, pET22 and pET32RH. RNA was extracted from the duodenum part of cattle, cDNA was amplified, the enterokinase light chain coding fragment was cloned and the expression was examined by SDS-PAGE analysis. The higher amounts of soluble enterokinase as a fusion with thioredoxin (Trx) were detected in cytoplasmic expression. The functional enterokinase was purified with a yield of 45 mg per litter by two-steps Ni²⁺ affinity chromatography. The effective activity of the enzyme implies that it can be produced in large scale for biotechnological applications.

A combination strategy of solubility enhancers for effective production of soluble and bioactive human enterokinase

Enterokinase is one of the hydrolases that catalyze hydrolysis to regulate biological processes in intestinal visceral mucosa. Enterokinase plays an essential role in accelerating the process of protein digestion as it converts trypsinogen into active trypsin by accurately recognizing and cleaving a specific peptide sequence, (Asp)4-Lys. Due to its exceptional substrate specificity, enterokinase is widely used as a versatile molecular tool in various bioprocessing, especially in removing fusion tags from recombinant proteins. Despite its biotechnological importance, mass production of soluble enterokinase in bacteria still remains an unsolved challenge. Here, we present an effective production strategy of human enterokinase using tandemly linked solubility enhancers consisting of thioredoxin, phosphoglycerate kinase or maltose-binding protein. The resulting enterokinases exhibited significantly enhanced solubility and bacterial expression level while retaining enzymatic activity, which demonstrates that combinatorial design of fusion proteins has the potential to provide an efficient way to produce recombinant proteins in bacteria.

Recombinant Production of Bovine Enteropeptidase Light Chain in SHuffle® T7 Express and Optimization of Induction Parameters

Enteropeptidase is a duodenum serine protease that triggers the activation of pancreatic enzymes by remarkably specific cleavages after lysine residues of peptidyl substrate (Asp)₄-Lys. This high specific cleavage makes the enzyme a widely used biotechnological tool in laboratory researches and industrial scale. Previous studies both in small and large scales were showed low expression and miss-folding of the expressed protein. In this study, the DNA sequence encoding the light chain (catalytic subunit) of bovine enteropeptidase (EP_L) was subcloned into plasmid pET-32b, downstream to the DNA encoding the fusion partner thioredoxin immediately after the EP_L cleavage site. SHuffle® T7 Express was selected as an expression host due to the ability to promote proper folding and correction of the mis-oxidized bonds. Expression and purification of protein was performed, and the result of biological activity confirmed that the active EP_L was obtained. Optimization of protein expression conditions was accomplished by response surface methodology for significant factors including induction temperature, duration of induction, inducer concentration and OD₆₀₀ of induction. The best conditions were achieved in 1.05 mM IPTG at OD₆₀₀ of 0.6 for seven h incubation at 26.5 °C, and a high level of protein expression was obtained in the optimized condition.

Impact of media components from different suppliers on enterokinase productivity in Pichia pastoris

Background

The aim of this study was to provide an information about the homogeneity on the level of enterokinase productivity in P. pastoris depending on different suppliers of the media components.

Results

In previous studies, we performed the optimisation process for the production of enterokinase by improving the fermentation process. Enterokinase is the ideal enzyme for removing fusion partners from target recombinant proteins. In this study, we focused our optimization efforts on the sources of cultivation media components. YPD media components were chosen as variables for these experiments. Several suppliers for particular components were combined and the optimisation procedure was performed in 24-well plates. Peptone had the highest impact on enterokinase production, where the difference between the best and worst results was threefold. The least effect on the production level was recorded for yeast extract with a 1.5 fold difference. The worst combination of media components had a activity of only 0.15 U/ml and the best combination had the activity of 0.88 U/ml, i.e., a 5.87 fold difference. A substantially higher impact on the production level of enterokinase was observed during fermentation in two selected media combinations, where the difference was almost 21-fold.

Conclusions

Results demonstrated in the present study show that the media components from different suppliers have high impact on enterokinase productivity and also provide the hypothesis that the optimization process should be multidimensional and for achieving best results it is important to perform massive process also in terms of the particular media component supplier .