Secretory production of single-chain antibody (scFv) in Brevibacillus choshinensis using novel fusion partner

Enhanced extracellular α-amylase production in Brevibacillus choshinensis by optimizing extracellular degradation and folding environment

A strategy for optimizing the extracellular degradation and folding environment of Brevibacillus choshinensis has been used to enhance the extracellular production of recombinant α-amylase. First, a gene (bcp) encoding an extracellular protease and another encoding an extracellular chaperone (prsC) were identified in the genome of B. choshinensis HPD31-SP3. Then, the effect of extracellular protein degradation on recombinant α-amylase production was investigated by establishing a CRISPR/Cas9n system to knock out bcp. The effect of extracellular folding capacity was investigated separately by coexpressing extracellular chaperones genes from different sources (prsA, prsC, prsL, prsQ) in B. choshinensis. The final recombinant strain (BCPPSQ), which coexpressed prsQ in a genetic background lacking bcp, produced an extracellular α-amylase activity of 6940.9 U/mL during shake-flask cultivation. This was 2.1-fold greater than that of the original strain BCWPS (3367.9 U/mL). Cultivation of BCPPSQ in a 3-L fermenter produced an extracellular α-amylase activity of 17 925.6 U/mL at 72 h, which was 7.6-fold greater than that of BCWPS (2358.1 U/mL). This strategy demonstrates its great potential in enhancing extracellular α-amylase production in B. choshinensis. What's more, this study provides a strategic reference for improving the extracellular production of other recombinant proteins in B. choshinensis.

Current pivotal strategies leading a difficult target protein to a sample suitable for crystallographic analysis

Crystallographic structural analysis is an essential method for the determination of protein structure. However, crystallization of a protein of interest is the most difficult process in the analysis. The process is often hampered during the sample preparation, including expression and purification. Even after a sample has been purified, not all candidate proteins crystallize. In this mini-review, the current methodologies used to overcome obstacles encountered during protein crystallization are sorted. Specifically, the strategy for an effective crystallization is compared with a pipeline where various expression hosts and constructs, purification and crystallization conditions, and crystallization chaperones as target-specific binder proteins are assessed by a precrystallization screening. These methodologies are also developed continuously to improve the process. The described methods are useful for sample preparation in crystallographic analysis and other structure determination techniques, such as cryo-electron microscopy.

Available strategies for improved expression of recombinant proteins in Brevibacillus expression system: a review

Brevibacillus offers great potential as a recombinant protein expression host because of its exceptional abilities to synthesize and excrete proteins and its low extracellular protease activity. Despite these strengths, effective recombinant expression strategies are still the key to achieving high-level expression of recombinant proteins in Brevibacillus due to individual differences among strains and target proteins. Many strategies have been developed to improve recombinant protein expression in Brevibacillus. This review begins by introducing the processes used to establish and apply the Brevibacillus expression system, and then critically discusses the strategies available for improving recombinant protein expression in Brevibacillus, including optimization of the host and the expression vector, co-expression of a fusion partner or foldase, and optimization of the fermentation process. Finally, the prospects for further improvement of recombinant protein expression based on Brevibacillus are also discussed. This review is intended to provide a strategic reference for scientists wanting to improve the expression of a specific recombinant protein in Brevibacillus or other expression systems.

Extracellular production of recombinant sus scrofa trefoil factor 3 by Brevibacillus choshinensis

Trefoil factor 3 (TFF3) is involved in cell adhesion, motility and apoptosis, regulates mucosal immunity and maintains the functional integrity of intestinal epithelia. The upregulation of TFF3 expression in the weaning rat intestine attracted our interest. The present study hypothesized that TFF3 may serve a role in preventing diarrhea in weaning piglets, which is an important consideration in the pig farming industry. Previous recombinant TFF3 protein expression yields obtained from Escherichia coli were too low and the bioactivity of the protein was poor. Hence, this expression system was unsuitable for industrial applications. The present study explored the production of recombinant sus scrofa TFF3 in a Brevibacillus choshinensis (B. choshinensis) expression system, aiming to enhance the expression level of bioactive protein. To achieve this, the sus scrofa TFF3-encoding gene fragment was fused into an E. coli-Brevibacillus shuttle vector pNCMO2. High levels of TFF3 (30 mg/l) were produced and secreted into the B. choshinensis culture medium in soluble form with a molecular mass of 13.6 kDa and high immunoreactivity in western blotting. Thus, Brevibacillus may be used to produce useful mucosal factors for biochemical analyses and mucosal protection, and in industrial applications to produce novel inhibitors of diarrhea.

Functional characterization of unique enzymes in Xanthomonas euvesicatoria related to degradation of arabinofurano-oligosaccharides on hydroxyproline-rich glycoproteins

In this study, we clarified the functions of three uncharacterized enzymes, XCV2724, XCV2728, and XCV2729, in Xanthomonas euvesicatoria, the causal agent of bacterial spot of tomato and pepper. The genes corresponding to the three enzymes are homologs of hypBA1, hypBA2, and hypAA from Bifidobacterium longum and are unique to Xanthomonas spp. among plant pathogenic bacteria. Functional characterization of the recombinant enzymes expressed using microbial systems revealed that they degrade the arabinofurano-oligosaccharides present on hydroxyproline (Hyp)-rich glycoproteins (HRGPs) such as extensin and solanaceous lectins in plant cell walls. These enzymes work coordinately to degrade the oligosaccharides. First, XeHypAA (XCV2728), belonging to the glycoside hydrolase (GH) 43 family, releases L-arabinose from L-arabinofuranose (Araf)-α1,3-Araf-ß1,2-Araf-ß1,2-Araf-ß-Hyp (Ara4-Hyp), cleaving its α1,3 bond; second, XeHypBA2 (XCV2729), belonging to the GH121 family, releases the disaccharide Araf-ß1,2-Araf from Araf-ß1,2-Araf-ß1,2-Araf-ß-Hyp (Ara3-Hyp); finally, XeHypBA1 (XCV2724), belonging to GH family 127, releases L-arabinose from Araf-ß-Hyp (Ara-Hyp). In summary, the main oligosaccharide structure of Ara4-Hyp on the HRGPs is degraded to Ara3-Hyp, then to Ara-Hyp, and finally to Ara monosaccharides by the action of these three enzymes. HRGPs containing oligosaccharide substrates have been reported to contribute to plant defense, and interestingly, the promoter region of the operon (xehypBA2 and xehypAA) contains the plant-inducible promoter box for binding the regulator protein HrpX involved in pathogenicity. We then analyzed the expression level of the operon gene in hrp-inducing medium and in plants and constructed gene-deletion mutants. However, although the operon was evidently upregulated by HrpX, three single-gene deletion mutants (ΔxehypBA1, ΔxehypBA2, ΔxehypAA) and even a triple-gene deletion mutant (ΔxehypBA1-BA2-AA) remained pathogenic, and had no effect on nonhost resistance, either, indicating that these three enzymes are not involved in either pathogenicity or nonhost resistance reactions. This is the first report of enzymes in plant pathogenic bacteria that catalyze the degradation of Hyp-linked-L-arabinofuranosides in plant cell walls.

Improved scFv Anti-LOX-1 Binding Activity by Fusion with LOX-1-Binding Peptides

The oxidized low-density lipoprotein receptor-1 (LOX-1) targeted single-chain variable fragment (scFvs) is a promising molecule for the targeted delivery of imaging and therapeutic molecules of atherosclerotic diseases; however, its applications are limited by the inherent low antigen affinity. In this study, the three-dimensional (3D) model of the anti-LOX-1 scFv was constructed and its docking with the LOX-1 protein was developed. To improve the LOX-1-binding activity, the anti-LOX-1 scFv was designed to fuse with one of three LOX-1-binding heptapeptides, LTPATAI, FQTPPQL, and LSIPPKA, at its N-terminus and C-terminus and in the linker region, which have different LOX-1-binding interfaces with the anti-LOX-1 scFv analyzed by an array of computational approaches. These scFv/peptide fusions were constructed, successfully expressed in Brevibacillus choshinensis hosts, and purified by a two-step column purification process. The antigen binding activity, structural characteristics, thermal stability, and stability in serum of these fusion proteins were examined. Results showed that the scFv with N-terminal fusing peptides proteins demonstrated increased LOX-1-binding activity without decrease in stability. These findings will help increase the application efficacy of LOX-1 targeting scFv in LOX-1-based therapy.

Mini review: Recombinant production of tailored bio-pharmaceuticals in different Bacillus strains and future perspectives

Bio-pharmaceuticals like antibodies, hormones and growth factors represent about one-fifth of commercial pharmaceuticals. Host candidates of growing interest for recombinant production of these proteins are strains of the genus Bacillus, long being established for biotechnological production of homologous and heterologous proteins. Bacillus strains benefit from development of efficient expression systems in the last decades and emerge as major industrial workhorses for recombinant proteins due to easy cultivation, non-pathogenicity and their ability to secrete recombinant proteins directly into extracellular medium allowing cost-effective downstream processing. Their broad product portfolio of pharmaceutically relevant recombinant proteins described in research include antibody fragments, growth factors, interferons and interleukins, insulin, penicillin G acylase, streptavidin and different kinases produced in various cultivation systems like microtiter plates, shake flasks and bioreactor systems in batch, fed-batch and continuous mode. To further improve production and secretion performance of Bacillus, bottlenecks and limiting factors concerning proteases, chaperones, secretion machinery or feedback mechanisms can be identified on different cell levels from genomics and transcriptomics via proteomics to metabolomics and fluxomics. For systematical identification of recurring patterns characteristic of given regulatory systems and key genetic targets, systems biology and omics-technology provide suitable and promising approaches, pushing Bacillus further towards industrial application for recombinant pharmaceutical protein production.

Efficient extracellular expression of Bacillus deramificans pullulanase in Brevibacillus choshinensis

In this study, the pullulanase gene from Bacillus deramificans was efficiently expressed in Brevibacillus choshinensis. The optimal medium for protein expression was determined through a combination of single-factor experiments and response surface methodology. The initial pH of the medium and the culture temperature were optimized. The pullulanase yield increased 10.8-fold through medium and condition optimization at the shake-flask level. From the results of these experiments, the dissolved oxygen level was optimized in a 3-L fermentor. Under these optimized conditions, the pullulanase activity and the specific pullulanase productivity reached 1005.8 U/mL and 110.5 × 103 U/g dry cell weight, respectively, with negligible intracellular expression. The Brevibacillus choshinensis expression system has proven to be valuable for the extracellular production of pullulanase.

Recombinant antibody production evolves into multiple options aimed at yielding reagents suitable for application-specific needs

BACKGROUND

Antibodies have been a pillar of basic research, while their relevance in clinical diagnostics and therapy is constantly growing. Consequently, the production of both conventional and fragment antibodies constantly faces more demanding challenges for the improvement of their quantity and quality. The answer to such an increasing need has been the development of a wide array of formats and alternative production platforms. This review offers a critical comparison and evaluation of the different options to help the researchers interested in expressing recombinant antibodies in their choice.

RESULTS

Rather than the compilation of an exhaustive list of the recent publications in the field, this review intendeds to analyze the development of the most innovative or fast-growing strategies. These have been illustrated with some significant examples and, when possible, compared with the existing alternatives. Space has also been given to those solutions that might represent interesting opportunities or that investigate critical aspects of the production optimization but for which the available data as yet do not allow for a definitive judgment.

CONCLUSIONS

The take-home message is that there is a clear process of progressive diversification concerning the antibody expression platforms and an effort to yield directly application-adapted immune-reagents rather than generic naked antibodies that need further in vitro modification steps before becoming usable.