Engineering Biology to Construct Microbial Chassis for the Production of Difficult-to-Express Proteins

Abstract

A large proportion of the recombinant proteins manufactured today rely on microbe-based expression systems owing to their relatively simple and cost-effective production schemes. However, several issues in microbial protein expression, including formation of insoluble aggregates, low protein yield, and cell death are still highly recursive and tricky to optimize. These obstacles are usually rooted in the metabolic capacity of the expression host, limitation of cellular translational machineries, or genetic instability. To this end, several microbial strains having precisely designed genomes have been suggested as a way around the recurrent problems in recombinant protein expression. Already, a growing number of prokaryotic chassis strains have been genome-streamlined to attain superior cellular fitness, recombinant protein yield, and stability of the exogenous expression pathways. In this review, we outline challenges associated with heterologous protein expression, some examples of microbial chassis engineered for the production of recombinant proteins, and emerging tools to optimize the expression of heterologous proteins. In particular, we discuss the synthetic biology approaches to design and build and test genome-reduced microbial chassis that carry desirable characteristics for heterologous protein expression.

Streptomycetes: Attractive Hosts for Recombinant Protein Production

“…As reported in Table 1, only in the case of a chitinase (Nguyen-Thi and Doucet, 2016), the protein productivity was more than 1 g/L. These results point out the crucial need to overcome intrinsic bottlenecks in protein productivity in streptomycetes, by redesigning their regulatory networks and secretion pathways by system biology, as recently proposed by Kim et al (2020).…”

“…In post-genomic era, a further ambitious goal is applying synthetic biology approaches for building a Streptomyces ‘super host’ with metabolic networks rewired to facilitate heterologous protein expression. Synergic application of genome minimization strategies (i.e., systematic removal of those elements – as secondary metabolites or proteases – that can hamper protein production) and engineering of translation and transcription machineries, might help reaching this goal ( Kim et al, 2020 ). To this end, it is encouraging considering that performing Streptomyces ‘super hosts’ have been already constructed for the heterologous production of antibiotics ( Gomez-Escribano and Bibb, 2011 ; Myronovskyi et al, 2018 ).…”

Characterization of efficient xylanases from industrial-scale pulp and paper wastewater treatment microbiota

“…Herein, 14 genes with xylanase activities were identified by expressing a total of 40 xylanase genes in E. coli , showing that the heterologous expression system of xylanase genes in E. coli cannot express all recovered genes. Therefore, the future development of novel efficient microbial chassis systems for functional environmental gene expression might improve the understanding of functional genes and their respective catalytic mechanisms in natural microbiota (de Paula et al 2019 ; Kim et al 2020 ). Nowadays, the progressive engineering of expression systems in microbial hosts, such as Saccharomyces cerevisiae , might lead to an efficient microbial cell factory for lignocellulose degradation (Tang et al 2017 ).…”

Conversion of l-arabinose to l-ribose by genetically engineered Candida tropicalis

“…This makes the production process more complicated and expensive. Besides, bacterial endotoxins and the use of antibiotics can cause health problems [25][26][27]. In this study, to overcome these limitations, the l-ribose-producing yeast strain was constructed with expressing l-arabinose isomerase and l-ribose isomerase under the control of the GAPDH promoter.…”