Novel Capsular Polysaccharide from Lobochlamys segnis

Michael J Allen,Gino Schiano Di Visconte,Andrew Spicer

doi:10.3390/polysaccharides2010009

Michael J Allen, Gino Schiano Di Visconte + Show 1 more

Open Access

https://doi.org/10.3390/polysaccharides2010009

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Abstract

In recent years there has been a significant effort from food, nutraceutical, cosmeceutical, pharmaceutical, and biomedical industries to discover and develop new natural ingredients. Microalgae have been recognised as potential sources of high value chemicals, with most attention focused upon antioxidants, pigments, and specialty oils. An under-exploited group of biochemicals produced by microalgae are extracellular polymeric substances (EPS). Lobochlamys segnis (formerly called Chlamydomonas segnis) was previously reported to produce a large amount of capsular polysaccharide (CPS) closely related to hyaluronan (HA) under stress conditions. In this work, the purified CPS was characterised and shown to have an average molecular mass (Mn) of about 3.7 MDa, and displayed a highly branched random coil structure unlike the simple repeating linear HA polysaccharide. Chemical analysis showed the presence of galactose, glucuronic acid, and glucose sugars confirming that the product has a different composition to that of HA. Mixotrophic growth and stress conditions were identified and improved upon with a pH control system using acetic acid solution to induce efficient production of CPS. Extraction and purification conditions were also identified exploiting the high Mn of the product. The CPS showed thickening properties and both significant antioxidant capacity and reducing power, which could have commercial applications. This is the first report on the characterization of this novel polysaccharide with non-Newtonian properties similar to HA.

Highlights

Polysaccharides (PS) are long chains of linear or branched sugar monomers linked through glycosidic bonds
Lobochlamys segnis is a microalga that is closely related to Chlamydomonas [5] and has been reported to produce an HA-like capsule under stress conditions [7]
The only other report of HA being produced within the plant kingdom, and within another green microalga, occurs when Chlorella variabilis or close relatives are infected by Chlorella viruses carrying a viral HA synthase gene [22]

Summary

Introduction

Polysaccharides (PS) are long chains of linear or branched sugar monomers linked through glycosidic bonds. Some PS possess biological activities such as antiviral, anticoagulant, immunomodulating, and antitumoral activities [2]. Due to these characteristics, PS can be used in a variety of different commercial applications, including biomedical devices, pharmaceuticals, cosmetics, adhesives, detergents, food additives, textiles, brewing, and wastewater treatments [1]. Hyaluronan (HA) is a linear, polydisperse, high molecular weight (MW) glycosaminoglycan (GAG), composed of alternating repeats of β-1,4-D-glucuronic acid and β-1,3-Nacetyl-D-glucosamine units [3]. In addition to being highly biocompatible and biodegradable, the basic physicochemical properties of HA that are of relevance to biomedical applications are related to viscosity, elasticity, lubrication, and its high capacity for water retention [4]

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