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>