Characterisation and Optimisation of Succinoglycan from Garden Grass using Agrobacterium radiobacter NCIM 2443

¹ Department of Biotechnology, IIT Madras, Chennai, India
² Bioprocess Intensification Laboratory, Center for Bioenergy, School of Chemical & Biotechnology, SASTRA Deemed University, Thirumalaisamudram, Thanjavur, India
³ Current Affiliation: Department of Biosystems Engineering, Auburn University, Auburn, Alabama, 36849 USA
⁴ Biorefinery and Process Automation Engineering Center, Department of Chemical and Process Engineering, The Sirindhorn International Thai-German Graduate School of Engineering, King Mongkut’s University of Technology North Bangkok, 10800 Bangkok, Thailand

^* Corresponding author: vponnu@chem.sastra.edu

Abstract

Succinoglycan is an exopolysaccharide that is produced mainly by soil-dwelling microorganisms. It has certain unique structural properties, making it a super viscosifying agent and a thermally stable gel. These properties are contributed by its acidic and water-soluble nature. This heteropolymer is made up of one galactose residue for every seven glucose residues and also includes certain non-carbohydrate residues, namely succinate, acetate and pyruvate. The polymer finds various applications as a thickener and emulsifier for the food industry, fluid loss agent for the cement industry, as a cosmetic additive, etc. Currently, commercial production of succinoglycan is mainly through conventional media. This has a direct effect on the production costs and thus limits the market potential of the biopolymer. This calls for researching low-cost carbon sources. One such carbon source is garden grass, which is being produced and wasted in tons every year. The present study aims to hydrolyze the waste garden grass using chemical methods to recover fermentable sugars and to use these sugars along with nutrient supplementation for succinoglycan production. Initially, we have characterized the garden grass, which had 19.13% extractives. Further, the cellulose content was estimated to be 31.11±2.70 %, and lignin content was estimated to be 16.05 %. The maximum reducing sugar of 0.54 g per g of grass was obtained using 2% H₂SO₄, which was further used for the production of succinoglycan using microbial fermentation with the Agrobacterium radiobacter NCIM 2443 strain. The carbon source, glucose concentration, and C:N ratio were optimized for maximum succinoglycan production. The produced polymer was then characterized using NMR and FT-IR analysis.