Enhancement of n-butanol production by in situ butanol removal using permeating–heating–gas stripping in acetone–butanol–ethanol fermentation

Acetone–butanol–ethanol (ABE) fermentation integrated with simplified gas stripping using sweet sorghum bagasse as immobilized carrier

“…However, the concentration of the product in the condensate was stable as it is illustrated in Fig 5b, which indicated that the fluctuant of the ABE in the bioreactor was correlated with gas stripping. Though the solvents concentration were wildly changed during one period of gas stripping, however, averagely, the ABE concentration always remained stable and resulted in the stable output of the production in the condensate (about 45-55 g/L of acetone, 140-175 g/L of butanol, 20-30 g/L of ethanol), which was similar with the phenomenon of previous studies [20,30]. Therefore, concentration of butanol exceed $8% (w/v), the critical concentration of water-oil phase separation, which would significantly simplify the butanol purification process and reduce the energy cost to produce anhydrous butanol product [27,29,30].…”

“…Besides, what particularly intrigued was that the fermentation period gradually shorted with time during the operation. This phenomenon was contrary to the results of other reports in the case of fed-batch fermentation-gas stripping integration [20,29,30]. It might be caused by the facilitation of the simplified process in the current work.…”

“…And the carrier then blocked the gas diffusion. In consideration of the poor mass transfer using the fibrous bed bioreactor or the fluidized bed reactor, a spinner flask, or named stripper, was often used to couple with the bioreactor [8,19,20]. As a result, the integrated processes based on the immobilized technique were much more complex compared with the gas stripping associated with traditional free cells bioreactor [21,22].…”

Applied in situ product recovery in ABE fermentation

“…A major focus of the hybrid separation processes has been improving the efficiency of gas stripping. This has included investigations into multi‐stage gas stripping processes, increasing the temperature at which gas stripping is performed and hybrid gas‐stripping pervaporation processes, with the aim of reducing the energy requirements for further separation of the condensate. Oudshoorn et al .…”

“…estimated the selectivity of gas stripping for butanol to be 4–22, which is low compared to distillation with an estimated selectivity of 72, thereby the recovered solution is not very concentrated. It has been widely noted that to achieve significant decreases in the energy for downstream purification, two‐phase separation needs to be observed in the recovered ABE solution . To achieve this phase separation, it has been suggested that the butanol concentration in the fermenter should be greater than 8 g/L, but concentrations this high start to impact on the fermentation performance …”