Tests in reactor
A comparison between Zymomonas mobilis NRRL 806 and Saccharomyces cerevisiae LPB1 behaviors for ethanol production and sugar uptake was made. A bench scale batch reactor (BE Marubishi, MDL) with volume of 6 L (utile volume of 5 L) was used. The operation conditions were maintained constant: 7.3 rad s-1 (only to homogenize medium, not to supply oxygen) and 30 °C (automatic control). The soybean molasses concentration was set in 150 g L-1 of soluble solids and the pH in 6.0 for Zymomonas mobilis and 5.0 for Saccharomyces cerevisiae (optimum values for each strain). The initial number of cells (CFU) for both tests was approximately equal 2.0 × 107 mL-1. Erlenmeyer static tests with Zymomonas mobilis in soybean molasses at 150 and 200 g L-1 of soluble solids were also carried out in order to compare the results.