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<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^-1 was found for the different carbon sources tested. For <em>P. oleovorans</em>, only the medium composed by S (0.85 g L^-1) 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^-1, and in the medium containing RG this value decreased to 1.70 g L^-1. <em>Z. mobilis</em>, on the other hand, showed a better result using SRG (1.41 g L^-1), and in the medium containing S and RG, these values were lower, reaching 0.27 and 0.77 g L^-1, respectively.</p>

The main goal of this study was to investigate the immobilization of commercial ß-galactosidase from Kluyveromyces lactis (Lactozym®) on Eupergit® C. A Plackett-Burman design was proposed. The ionic strength and pH were the variables that presented significant effect (p<0.1) on immobilization. The increase in the ionic strength from 0.1 to 1.5 M and the increase in pH from 6.6 to 7.4 represented an increase of 28.56% and a reduction of 18.19% in the immobilization yield, respectively. At 25°C, pH 6.6, ionic strength of 1.5 M, immobilization for 8 h, 1 mM of divalent magnesium ion and 0.4 mL of enzyme added, reached 85% immobilization yield. The free and immobilized enzymes were characterized. pH and temperature profiles showed maximum activity at pH 6.6 and 45°C, for both free and immobilized enzymes. There was a gain in thermal stability with enzyme immobilization and there was an increase of about four times in the half-life of the immobilized derivative at 45°C (from 0.43 h to 1.78 h). This greater thermal stability was also made clear through the calculation of thermodynamic parameters (ΔH, ΔG and ΔS). Km values, 30.33 mM and 104.00 mM for free and immobilized enzymes, respectively, represented a reduction in substrate affinity after immobilization, possibly owing to stereo-conformational factors. In a batch reactor for lactose hydrolysis from cheese whey, an increase in lactose conversion with immobilization was observed at 40°C and 45°C (90.43% and 65.36%, respectively) in relation to the free enzyme (84.17% and 39.58%, respectively).

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*Letras minúsculas diferentes para um mesmo óleo indicam que há diferença significativa entre as gomas a 95% de confiança (p<0,05). Letras maiúsculas diferentes para uma mesma goma indicam que há diferença significativa entre os óleos a 95% de confiança (p<0,05).