Production of gellan gum, an exopolysaccharide, from biodiesel-derived waste glycerol by Sphingomonas spp.

In the present study, biodiesel-derived waste glycerol (WG) was used for the isolation and production of gellan, an exopolysaccharide, on media containing WG as the main carbon source. Two bacterial isolates showed gellan producing potential which were identified as Sphingomonas pseudosanguinis (Accession No. GI:724472387) and Sphingomonas yabuuchiae (GI:724472388) by 16S rRNA gene sequencing. To maximize gellan production by S. pseudosanguinis and S. yabuuchiae, media optimization was performed at different pHs and glycerol concentrations. Morphological observations through microscopic images showed the production of gellan from these isolates. Simple linear regression showed better utilization of WG by S. pseudosanguinis than S. yabuuchiae at pH 6 and pH 7. Though, both the strains showed reverse trend at pH 8. Both the strains were able to produce high amounts of gellan gum (51.6 and 52.6 g/l, respectively) using WG (80 g/l) as the sole carbon source, in a minimal medium. This is the first report on the efficient degradation of WG and low-cost production of gellan. Owing to these characteristics, S. pseudosanguinis and S. yabuuchiae demonstrate great potential for use in the commercial production of gellan and in the bioremediation of WG.