Hyaluronic acid (HA), a well-known glycosaminoglycan with a wide range of biomedical applications, has an estimated market of over 10 billion USD and is anticipated to grow at a 7.7% CAGR. Molecular weight (MW) of HA is a critical quality parameter that dictates the rheological and biological properties in determining the end applications. There are a few critical factors that influence the molecular weight during HA synthesis. These factors can be broadly classified into two groups. One is based on the HA synthase, which directly polymerizes the precursors to produce HA, and the other is based on the regulation of the precursor concentrations during syntheses, such as the upregulation of pathway genes, the downregulation of competing metabolites, and specific growth regulators like glucose, temperature, pH and others. However, only a few studies have focused on manipulating these critical factors to produce HA with a specific molecular weight.
Preliminary studies in our laboratory showed that the different streptococcal HA synthases (hasA) in recombinant L. lactis could produce different MWs. Recombinant Lactococcus lactis strains were built with different genetic makeup for the HA synthesis, and the interplay of the genetic and process factors that impact the MW was investigated. Expression of these gene combinations in L. lactis with ldh knockout further enhanced the HA molecular weight. The combinatorial approach employed by us generated HA polymers with different MWs, ranging from 0.2 MDa to 2.6 MDa. These results validate a novel combinatorial approach to modulate the HA MW over a wide range, with significant qualitative importance for different applications.