3.3. Batch fermentation integrated with gas stripping
Fig. 3 compared the batch fermentation kinetics with and without gas stripping. As it illustrated in Fig. 3(a), the medium initially contained 59.6 g/L of fermentable sugars (36.2 g/L of sucrose,13.1 g/L of glucose and 10.3 g/L of fructose). And after 80 h of batch fermentation and gas stripping, about 14 g/L of butanol, 8.8 g/L of acetone and 1.2 g/L of ethanol (total ABE: 24 g/L) were determinedin the final fermentation broth. By contrast, similar with the result in Section 3.2, about 13.2 g/L of butanol, 8.4 g/L of acetone and 1.2 g/L of ethanol were generated at the end of fermentation that without gas stripping. Therefore, by applying gas stripping for
in situ ABE recovery, higher concentration of ABE solvents could
be achieved. It was because more sugars were utilized in the inte-
gration process, and the butanol toxicity was decreased by the
effect of product removal at the same time (Xue et al., 2012). Only
about 1 g/L of residual sugars remained at 80 h of fermentation in
the gas stripping integrated process, while there were 3.8 g/L of
total sugar remained in the conventional fermentation broth that
without gas stripping (Fig. 3b). Additionally, after integration, an