scholarly journals Recombinant protein secretion by Bacillus subtilis and Lactococcus lactis: pathways, applications, and innovation potential

2021 ◽  
Author(s):  
Jolanda Neef ◽  
Jan Maarten van Dijl ◽  
Girbe Buist

Abstract Secreted recombinant proteins are of great significance for industry, healthcare and a sustainable bio-based economy. Consequently, there is an ever-increasing need for efficient production platforms to deliver such proteins in high amounts and high quality. Gram-positive bacteria, particularly bacilli such as Bacillus subtilis, are favored for the production of secreted industrial enzymes. Nevertheless, recombinant protein production in the B. subtilis cell factory can be very challenging due to bottlenecks in the general (Sec) secretion pathway as well as this bacterium’s intrinsic capability to secrete a cocktail of highly potent proteases. This has placed another Gram-positive bacterium, Lactococcus lactis, in the focus of attention as an alternative, non-proteolytic, cell factory for secreted proteins. Here we review our current understanding of the secretion pathways exploited in B. subtilis and L. lactis to deliver proteins from their site of synthesis, the cytoplasm, into the fermentation broth. An advantage of this cell factory comparison is that it identifies opportunities for protein secretion pathway engineering to remove or bypass current production bottlenecks. Noteworthy new developments in cell factory engineering are the mini-Bacillus concept, highlighting potential advantages of massive genome minimization, and the application of thus far untapped ‘non-classical’ protein secretion routes. Altogether, it is foreseen that engineered lactococci will find future applications in the production of high-quality proteins at the relatively small pilot scale, while engineered bacilli will remain a favored choice for protein production in bulk.

2020 ◽  
Vol 11 (1) ◽  
pp. 295-318 ◽  
Author(s):  
Kang Zhang ◽  
Lingqia Su ◽  
Jing Wu

Bacillus subtilis has become a widely used microbial cell factory for the production of recombinant proteins, especially those associated with foods and food processing. Recent advances in genetic manipulation and proteomic analysis have been used to greatly improve protein production in B. subtilis. This review begins with a discussion of genome-editing technologies and application of the CRISPR–Cas9 system to B. subtilis. A summary of the characteristics of crucial legacy strains is followed by suggestions regarding the choice of origin strain for genetic manipulation. Finally, the review analyzes the genes and operons of B. subtilis that are important for the production of secretory proteins and provides suggestions and examples of how they can be altered to improve protein production. This review is intended to promote the engineering of this valuable microbial cell factory for better recombinant protein production.


2007 ◽  
Vol 14 (1-3) ◽  
pp. 48-58 ◽  
Author(s):  
E. Morello ◽  
L.G. Bermúdez-Humarán ◽  
D. Llull ◽  
V. Solé ◽  
N. Miraglio ◽  
...  

2020 ◽  
Vol 11 ◽  
pp. e00141
Author(s):  
Yanfeng Liu ◽  
Anqi Su ◽  
Rongzhen Tian ◽  
Jianghua Li ◽  
Long Liu ◽  
...  

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Patrick Lenz ◽  
Fabienne Hilgers ◽  
Alina Burmeister ◽  
Leonie Zimmermann ◽  
Kristina Volkenborn ◽  
...  

Abstract Background Bacillus subtilis is one of the most important microorganisms for recombinant protein production. It possesses the GRAS (generally recognized as safe) status and a potent protein secretion capacity. Secretory protein production greatly facilitates downstream processing and thus significantly reduces costs. However, not all heterologous proteins are secreted and intracellular production poses difficulties for quantification. To tackle this problem, we have established a so-called intracellular split GFP (iSplit GFP) assay in B. subtilis as a tool for the in vivo protein detection during expression in batch cultures and at a single-cell level. For the iSplit GFP assay, the eleventh β-sheet of sfGFP is fused to a target protein and can complement a detector protein consisting of the respective truncated sfGFP (GFP1-10) to form fluorescent holo-GFP. Results As proof of concept, the GFP11-tag was fused C-terminally to the E. coli β-glucuronidase GUS, resulting in fusion protein GUS11. Variable GUS and GUS11 production levels in B. subtilis were achieved by varying the ribosome binding site via spacers of increasing lengths (4–12 nucleotides) for the GUS-encoding gene. Differences in intracellular enzyme accumulation were determined by measuring the GUS11 enzymatic activity and subsequently by adding the detector protein to respective cell extracts. Moreover, the detector protein was co-produced with the GUS11 using a two-plasmid system, which enabled the in vivo detection and online monitoring of glucuronidase production. Using this system in combination with flow cytometry and microfluidics, we were able to monitor protein production at a single-cell level thus yielding information about intracellular protein distribution and culture heterogeneity. Conclusion Our results demonstrate that the iSplit GFP assay is suitable for the detection, quantification and online monitoring of recombinant protein production in B. subtilis during cultivation as well as for analyzing production heterogeneity and intracellular localization at a single-cell level. Graphic abstract


2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Javier Garrigós-Martínez ◽  
Kiira Vuoristo ◽  
Miguel Angel Nieto-Taype ◽  
Juha Tähtiharju ◽  
Jaana Uusitalo ◽  
...  

Abstract Background Pichia pastoris is a powerful and broadly used host for recombinant protein production (RPP), where past bioprocess performance has often been directed with the methanol regulated AOX1 promoter (PAOX1), and the constitutive GAP promoter (PGAP). Since promoters play a crucial role in an expression system and the bioprocess efficiency, innovative alternatives are constantly developed and implemented. Here, a thorough comparative kinetic characterization of two expression systems based on the commercial PDF and UPP promoters (PPDF, PUPP) was first conducted in chemostat cultures. Most promising conditions were subsequently tested in fed-batch cultivations. These new alternatives were compared with the classical strong promoter PGAP, using the Candida antarctica lipase B (CalB) as model protein for expression system performance. Results Both the PPDF and PUPP-based expression systems outperformed similar PGAP-based expression in chemostat cultivations, reaching ninefold higher specific production rates (qp). CALB transcription levels were drastically higher when employing the novel expression systems. This higher expression was also correlated with a marked upregulation of unfolded protein response (UPR) related genes, likely from an increased protein burden in the endoplasmic reticulum (ER). Based on the chemostat results obtained, best culture strategies for both PPDF and PUPP expression systems were also successfully implemented in 15 L fed-batch cultivations where qp and product to biomass yield (YP/X*) values were similar than those obtained in chemostat cultivations. Conclusions As an outcome of the macrokinetic characterization presented, the novel PPDF and PUPP were observed to offer much higher efficiency for CalB production than the widely used PGAP-based methanol-free alternative. Thus, both systems arise as highly productive alternatives for P. pastoris-based RPP bioprocesses. Furthermore, the different expression regulation patterns observed indicate the level of gene expression can be adjusted, or tuned, which is interesting when using Pichia pastoris as a cell factory for different products of interest.


2020 ◽  
Author(s):  
Rasool Saghaleyni ◽  
Magdalena Malm ◽  
Jan Zrimec ◽  
Ronia Razavi ◽  
Num Wistbacka ◽  
...  

SummaryHigher eukaryotic cell lines like HEK293 are the preferred hosts for production of therapeutic proteins requiring human post translational processing. However, recombinant protein production can result in severe stress on the cellular machinery, resulting in limited titre and product quality. To investigate the cellular and metabolic characteristics associated with these limitations, we compared erythropoietin (secretory) and GFP (non-secretory) protein producer HEK293 cell-lines using transcriptomics analysis. Despite the high demand for ATP in all protein producer clones, a significantly higher capacity for ATP production was observed with erythropoietin producers as evidenced by the enrichment of upregulated genes in the oxidative phosphorylation pathway. In addition, ribosomal genes exhibited specific patterns of expression depending on the recombinant protein and the production rate. In a clone displaying a dramatically increased erythropoietin secretion, we detected higher ER stress, including upregulation of the ATF6B gene. Our results are significant in recognizing key pathways for recombinant protein production and identifying potential target genes for further development of secretory power in mammalian cell factories.In BriefAlthough the protein secretion process has been widely studied, the complexity of it leaves many questions with regards to defining bottlenecks for successful protein secretion to be answered. By investigating the transcriptomic profiles of different HEK293 clones with varying translational rates producing either the secreted protein erythropoietin or the intracellular GFP, we reveal that high ATP production and improved capacity of specific post-translational pathways are key factors associated with boosting erythropoietin production.HighlightsTranscriptomics analysis of a panel of HEK293 stable cell lines expressing GFP or erythropoietin (EPO) at varying translational ratesExpression of mitochondrial ribosomal genes is positively correlated with EPO secretionExpression of different cytosolic ribosomal genes are correlated with productivity in a recombinant-protein specific mannerHigh EPO producing clones have significant upregulation of ATF6B, potentially enabling a beneficial ER stress response to cope with high protein secretionGraphical Abstract


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