Disruption of KEX1 gene reduces the proteolytic degradation of secreted two-chain Insulin glargine in Pichia pastoris

Validation of Lon Gene Disruption using Linear DNA Cassette by Crelox Mechanism in E. coli Strains: To Achieve Better Solubility of Putrescine Monooxygenase

Numerous expression systems, engineered strains, and cultivation systems have been developed globally but producing recombinant proteins in the soluble form continues to remain a challenge.  Escherichia coli, a preferred host for the recombinant production of biopharmaceuticals and other proteins. Up to 75% of human proteins expressed in E. coli have only 25% in an active soluble form. The proteolytic activity of Lon encoded protease triggers the inclusion bodies leading to heterogenous secreted proteins thereby hampering downstream processing and isolation. Putrescine monooxygenases are versatile with applications in iron acquisition, pathogen control, biotransformation, bio-remediation and redox reaction are still isolated from plant and microbial sources at low yields. As a prerequisite to developing protease knockout E. coli strains, using the Cre-loxP recombination strategy we have built a full-length Lon disruption cassette (5'lon-lox66-cre-KanR-lox71-3'lon) (3368 bp) consisting of upstream and downstream regions of Lon, loxP sites, and Cre gene driven by T7 promoter to the expression of Cre recombinase and a selectable kanamycin resistance gene. Here, after the integration of the knock-out cassette into the host genome, we show the production of homogeneous protein species of recombinant Putrescine monooxygenase by using an E. coli platform strain in which Lon gene is deleted. This Lon knock-out strain secreted more homogeneous protein at a volumetric yield of 60% of the wild-type strain.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-023-01056-x.

Heterologous expression of Ts8, a neurotoxin from Tityus serrulatus venom, evidences its antifungal activity

In this study we expressed the Ts8, a neurotoxin from Tityus serrulatus scorpion venom, in Pichia pastoris yeast. We evaluated the peptide expression in different conditions, such as pH, temperature, and addition of casamino acids supplement. Analyses of expressed products by mass spectrometry and Edman degradation showed that rTs8 has sites that allow its cleavage by yeast proteases released into the culture medium. The casamino acids addition was favourable for toxin expression, however, was not sufficient to minimize proteolytic degradation. Functional assays with recombinant toxin fragments and native toxins have demonstrated the release of cytokines such as TNF-α and IL-1β in some peptides tested. In addition, the toxins were shown to inhibit the Pichia pastoris growth in antifungal test and were not toxic to alveolar macrophages cells at the concentrations analyzed The electrophysiological screening, by voltage clamp technique, showed that the rTs8 fragment with the highest molecular weight inhibited the Kv1.3 channel, whereas the N-terminal fragment had no activity on the ion channels tested.

Strains and Molecular Tools for Recombinant Protein Production in Pichia pastoris

Within the last two decades, the methylotrophic yeast Pichia pastoris (Komagataella phaffii) has become an important alternative to E. coli or mammalian cell lines for the production of recombinant proteins. Easy handling, strong promoters, and high cell density cultivations as well as the capability of posttranslational modifications are some of the major benefits of this yeast. The high secretion capacity and low level of endogenously secreted proteins further promoted the rapid development of a versatile Pichia pastoris toolbox. This chapter reviews common and new "Pichia tools" and their specific features. Special focus is given to expression strains, such as different methanol utilization, protease-deficient or glycoengineered strains, combined with application highlights. Different promoters and signal sequences are also discussed.

Reduced methanol input induces increased protein output by AOX1 promoter in a trans-acting elements engineered Pichia pastoris

High oxygen consumption and heat release caused by methanol catabolism usually bring difficulties to industrial scale-up and cost for protein expression driven by methanol-induced AOX1 promoter in Pichia pastoris. Here, reduced methanol feeding levels were investigated for expression of insulin precursor in a trans-acting elements engineered P. pastoris strain MF1-IP. Insulin precursor expression level reached 6.69 g/(L supernatant) at the methanol feeding rate of 6.67 mL/(h·L broth), which was 59% higher than that in the wild-type strain WT-IP at the methanol feeding rate of 12 mL/(h·L broth). Correspondingly, the insulin precursor expression level in fermentation broth and maximum specific insulin precursor production rate was 137 and 77% higher than the WT-IP, respectively. However, oxygen consumption and heat evolution were reduced, and the highest oxygen consumption rate and heat evolution rate of the MF1-IP were 18.0 and 37.7% lower than the WT-IP, respectively.

Methanol-Independent Protein Expression by AOX1 Promoter with trans-Acting Elements Engineering and Glucose-Glycerol-Shift Induction in Pichia pastoris

The alcohol oxidase 1 promoter (P_AOX1) of Pichia pastoris is commonly used for high level expression of recombinant proteins. While the safety risk of methanol and tough process control for methanol induction usually cause problems especially in large-scale fermentation. By testing the functions of trans-acting elements of P_AOX1 and combinatorially engineering of them, we successfully constructed a methanol-free P_AOX1 start-up strain, in which, three transcription repressors were identified and deleted and, one transcription activator were overexpressed. The strain expressed 77% GFP levels in glycerol compared to the wide-type in methanol. Then, insulin precursor (IP) was expressed, taking which as a model, we developed a novel glucose-glycerol-shift induced P_AOX1 start-up for this methanol-free strain. A batch phase with glucose of 40 g/L followed by controlling residual glucose not lower than 20 g/L was compatible for supporting cell growth and suppressing P_AOX1. Then, glycerol induction was started after glucose used up. Accordingly, an optimal bioprocess was further determined, generating a high IP production of 2.46 g/L in a 5-L bioreactor with dramatical decrease of oxygen consumption and heat evolution comparing with the wild-type in methanol. This mutant and bioprocess represent a safe and efficient alternative to the traditional glycerol-repressed/methanol-induced P_AOX1 system.