Raw Glycerol as an Alternative Carbon Source for Cultivation of Exopolysaccharide-Producing Bacteria

Abstract

<p>The large-scale use of biodiesel has shown significant environmental benefits as regards the reduction of global warming impacts. The increased generation of glycerol, the main byproduct of the reaction, makes necessary to propose alternatives to its use. In this context, the aim of this study was to evaluate raw glycerol (RG), a byproduct from biodiesel synthesis, as a carbon source for the cultivation of bacteria recognized as exopolysaccharides (EPSs) producers, compared with sucrose (S) and with a mixture of both components in a ratio of 1:1 w:w (SRG). The bacteria used were: <em>Xanthomonas campestris </em>pv. <em>mangiferaeindicae</em> IBSBF 1230, <em>Pseudomonas oleovorans</em> NRRL B-14683, <em>Sphingomonas capsulata</em> NRRL B-4261 and <em>Zymomonas mobilis</em> NRRL B-4286. All bacteria were capable of growing and producing EPSs using RG as the sole carbon source. For <em>X</em>. <em>campestris</em>, EPSs concentration of around 4.00 g L<sup>-1</sup> was found for the different carbon sources tested. For <em>P. oleovorans</em>, only the medium composed by S (0.85 g L<sup>-1</sup>) differed from the other media, with better results being found using RG and SRG. <em>S. capsulata</em> showed higher concentration in the medium containing S and SRG, around 3.40 g L<sup>-1</sup>, and in the medium containing RG this value decreased to 1.70 g L<sup>-1</sup>. <em>Z. mobilis</em>, on the other hand, showed a better result using SRG (1.41 g L<sup>-1</sup>), and in the medium containing S and RG, these values were lower, reaching 0.27 and 0.77 g L<sup>-1</sup>, respectively.</p>

Screening of Local Wild Xanthomonas Species for Xanthan Production on Crude Glycerol-based Medium

“…One of economically and environmentally acceptable solution is potential use of crude glycerol as a raw material in biotechnological production [5,6]. Several studies indicate that certain strains of bacteria of the genus Xanthomonas possess the ability to biosynthesize xanthan on a medium containing crude glycerol as the only carbon source [7][8][9].…”

“…This indicates that there is a need for isolation of new Xanthomonas strains able to metabolize glycerol and produce xanthan. Due to this reason, other Xanthomonas strains, rather than reference strain, were used in previous studies focused on xanthan production on glycerol-based media [8,9,15,16].…”

The effect of cultivation time on xanthan production by Xanthomonas spp. on glycerol containing medium

“…Several studies suggest that certain strains of bacteria of the genus Xanthomonas possess the ability to biosynthesize xanthan on a medium with glycerol as a sole carbon source (15,16). Research related to the xanthan biosynthesis on glycerol containing media is still in initial stages, probably by reason of impaired metabolic activity of the applied producing strains (17).…”

Carbon Sources for Biomass, Food, Fossils, Biofuels and Biotechnology - Review Article

“…Fungus Thamnidium elegans grown on raw glycerol and autotrophic microalga Nannochloropsis salina produce polyunsaturated fatty lipids with antimicrobial activity, offering an alternative solution to increased microbial resistance to traditional antibiotic drugs (Sayegh et al, 2015). Trindade et al, (2015) reported about the production of exopolysaccharides (used in food, chemical and pharmaceutical industry, among others) by various bacteria including Xanthomonas campestris pv. mangiferaeindicae IBSBF 1230, Pseudomonas oleovorans NRRL B-14683, Sphingomonas capsulata NRRL B-4261 and Zymomonas mobilis NRRL B-4286 from raw glycerol, a byproduct from biodiesel synthesis, instead of commonly used glucose, directly impacting production costs and limiting market potential.…”