The sweet branch of metabolic engineering: cherry-picking the low-hanging sugary fruits

Abstract

In the first science review on the then nascent Metabolic Engineering field in 1991, Dr. James E. Bailey described how improving erythropoietin (EPO) glycosylation can be achieved via metabolic engineering of Chinese hamster ovary (CHO) cells. In the intervening decades, metabolic engineering has brought sweet successes in glycoprotein engineering, including antibodies, vaccines, and other human therapeutics. Today, not only eukaryotes (CHO, plant, insect, yeast) are being used for manufacturing protein therapeutics with human-like glycosylation, newly elucidated bacterial glycosylation systems are enthusiastically embraced as potential breakthrough to revolutionize the biopharmaceutical industry. Notwithstanding these excitement in glycoprotein, the sweet metabolic engineering reaches far beyond glycoproteins. Many different types of oligo- and poly-saccharides are synthesized with metabolically engineered cells. For example, several recombinant hyaluronan bioprocesses are now in commercial production, and the titer of 2′-fucosyllactose, the most abundant fucosylated trisaccharide in human milk, reaches over 20 g/L with engineered E. coli cells. These successes represent only the first low hanging fruits, which have been appreciated scientifically, medically and fortunately, commercially as well. As one of the four building blocks of life, sugar molecules permeate almost all aspects of life. They are also unique in being intimately associated with all major types of biopolymers (including DNA/RNA, proteins, lipids) meanwhile they stand alone as bioactive polysaccharides, or free soluble oligosaccharides. As such, all sugar moieties in biological components, small or big and free or bound, are important targets for metabolic engineering. Opportunities abound at the interface of glycosciences and metabolic engineering. Continued investment and successes in this branch of metabolic engineering will make vastly diverse sugar-containing molecules (a.k.a. glycoconjugates) available for biomedical applications, sustainable technology development, and as invaluable tools for basic scientific research. This short review focuses on the most recent development in the field, with emphasis on the synthesis technology for glycoprotein, polysaccharide, and oligosaccharide.

Bioengineered production of glycosaminoglycans and their analogues

“…Synthetic biology techniques are becoming increasingly important tools for pathway optimization and metabolic engineering [15]. Some GAGs including chondroitin and hyaluronic acid have been prepared using metabolic engineering [45,[51][52][53][54][55][56][57]. Currently, commercial scale production of hyaluronan relies on bacterial expression systems in Streptococci and endotoxin-free microorganisms such as Bacilli.…”

Drug Resistance in Bacteria, Fungi, Malaria, and Cancer

“…One of the famous examples of protein engineering is manufacturing of synthetic glycoproteins. But recent progress in synthetic protein biology has made this arduous task not only possible but also motivating (Chen 2015). Most of these proteins are surface Fig.…”

Engineered heparins as new anticoagulant drugs

“…Increasing safety concerns have led to a movement away from traditional animal‐sourced methods of GAG production, due to the associated drawbacks of high interspecies viral contamination risk and inconsistent product quality and activity . Metabolic engineering plays an important role in the development of strains that use recombinant technologies to synthesize polysaccharides such as heparin, HA, and CS . The sulfated GAGs, heparin and CS, have more intricate chemical compositions than the simple repeating disaccharide unit of HA.…”