Perspectives for Glyco-Engineering of Recombinant Biopharmaceuticals from Microalgae

Abstract

Microalgae exhibit great potential for recombinant therapeutic protein production, due to lower production costs, immunity to human pathogens, and advanced genetic toolkits. However, a fundamental aspect to consider for recombinant biopharmaceutical production is the presence of correct post-translational modifications. Multiple recent studies focusing on glycosylation in microalgae have revealed unique species-specific patterns absent in humans. Glycosylation is particularly important for protein function and is directly responsible for recombinant biopharmaceutical immunogenicity. Therefore, it is necessary to fully characterise this key feature in microalgae before these organisms can be established as industrially relevant microbial biofactories. Here, we review the work done to date on production of recombinant biopharmaceuticals in microalgae, experimental and computational evidence for N- and O-glycosylation in diverse microalgal groups, established approaches for glyco-engineering, and perspectives for their application in microalgal systems. The insights from this review may be applied to future glyco-engineering attempts to humanize recombinant therapeutic proteins and to potentially obtain cheaper, fully functional biopharmaceuticals from microalgae.

N- and O-Glycosylation Pathways in the Microalgae Polyphyletic Group

“…In most eukaryotes including humans, O-glycans do not present a common structure or a consensus sequence. For example, O-glycans in yeasts are composed of multiple Man residues attached to a Ser or a Thr (Schoberer and Strasser, 2018;Barolo et al, 2020). In mammals, most of O-glycans were found on mucins.…”

“…Currently, DNA recombinant technology and transgenesis have been successfully implemented in some microalgae. In this context, microalgae have been investigated as emerging industrial platforms for the production of high value-added biopharmaceuticals (Barolo et al, 2020;Dehghani et al, 2020;Rosales-Mendoza et al, 2020). Indeed, microalgae are easy and fast to grow, safe and cheap making them attractive expression systems for the production of therapeutic proteins (Hempel and Maier, 2016;Rosales-Mendoza et al, 2020).…”

The Potential of Algal Biotechnology to Produce Antiviral Compounds and Biopharmaceuticals

“…It is well known that glycosylation influences the safety and efficacy of antigens and antibodies. It is interesting to note that recent experimental and computational evidences for N- and O-glycosylation have led to the design of glyco-engineering approaches in algae [ 217 ].…”

“…All this knowledge offers the perspectives to achieve the production of bioproducts with specific glycan patterns that could ultimately optimize their functionality [ 217 ]. In regard to antibodies production, although chloroplast has proven capacity to produce full-length antibodies making it the first line of action; exploring nuclear expression is an opportunity to obtain a product that is glycosylated and exported to the culture medium for simplified purification.…”

Cell-Free Synthetic Glycobiology: Designing and Engineering Glycomolecules Outside of Living Cells

“…This cell-based library of human glycan structures should become a valuable resource for dissecting glycan biosynthesis and glycomolecule interactions within a native physiological context (Narimatsu et al, 2019 ). It should also be pointed out that advances in cell-based glycoengineering have extended beyond mammalian cells, with significant progress toward producing homogeneous glycoforms in other eukaryotes including yeast (Hamilton et al, 2003 ; Wildt and Gerngross, 2005 ), microalgae (Barolo et al, 2020 ), insect cells (Toth et al, 2014 ), and plant cell cultures (Montero-Morales and Steinkellner, 2018 ; Hurtado et al, 2020 ). Comprehensive reviews of the glycoengineering approaches developed in these eukaryotic systems have been published elsewhere (Hamilton and Zha, 2015 ; Heffner et al, 2018 ).…”