Efficient production of N-terminally truncated biologically active human interleukin-6 by Bacillus brevis

Microbial protein cell factories fight back?

The biopharmaceutical market is growing faster than ever, with two production systems competing for market dominance: mammalian cells and microorganisms. In recent years, based on the rise of antibody-based therapies, new biotherapeutic approvals have favored mammalian hosts. However, not only has extensive research elevated our understanding of microbes to new levels, but emerging therapeutic molecules also facilitate their use; thus, is it time for microbes to fight back? In this review, we answer this timely question by cross-comparing four microbial production hosts and examining the innovations made to both their secretion and post-translational modification (PTM) capabilities. Furthermore, we discuss the impact of tools, such as omics and systems biology, as well as alternative production systems and emerging biotherapeutics.

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.

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.

A Bacillus subtilis fusion protein system to produce soybean Bowman–Birk protease inhibitor

A fusion protein based expression system was developed in the Gram-positive bacterium Bacillus subtilis to produce the soybean Bowman-Birk protease inhibitor (sBBI). The N-terminus of the mature sBBI was fused to the C-terminus of the 1st cellulose binding domain linker (CBD linker) of the BCE103 cellulase (from an alkalophilic Bacillus sp.). The strong aprE promoter was used to drive the transcription of the fusion gene and the AprE signal sequence was fused to the mature BCE103 cellulase for efficient secretion of the fusion protein into the culture medium. It was necessary to use a B. subtilis strain deficient in nine protease genes in order to reduce the proteolytic degradation of the fusion protein during growth. The fusion protein was produced in shake flasks at concentrations >1g/L. After growth, the sBBI was activated by treatment with 2-mercaptoethanol to allow the disulfide bonds to form correctly. An economical and scalable purification process was developed to purify sBBI based on acid precipitation of the fusion protein followed by acid/heat cleavage of the fusion protein at labile Asp-Pro bonds in the CBD linker. If necessary, non-native amino acids at the N- and C-termini were trimmed off using glutamyl endopeptidase I. After purification, an average of 72 mg of active sBBI were obtained from 1L of culture broth representing an overall yield of 21% based on the amount of sBBI activated before purification.

Overview of bacterial expression systems for heterologous protein production: from molecular and biochemical fundamentals to commercial systems

During the proteomics period, the growth in the use of recombinant proteins has increased greatly in the recent years. Bacterial systems remain most attractive due to low cost, high productivity, and rapid use. However, the rational choice of the adequate promoter system and host for a specific protein of interest remains difficult. This review gives an overview of the most commonly used systems: As hosts, Bacillus brevis, Bacillus megaterium, Bacillus subtilis, Caulobacter crescentus, other strains, and, most importantly, Escherichia coli BL21 and E. coli K12 and their derivatives are presented. On the promoter side, the main features of the l-arabinose inducible araBAD promoter (PBAD), the lac promoter, the l-rhamnose inducible rhaP BAD promoter, the T7 RNA polymerase promoter, the trc and tac promoter, the lambda phage promoter p L , and the anhydrotetracycline-inducible tetA promoter/operator are summarized.