Acetone butanol ethanol (ABE) production from concentrated substrate: reduction in substrate inhibition by fed-batch technique and product inhibition by gas stripping

Abstract

Acetone butanol ethanol (ABE) was produced in an integrated fed-batch fermentation-gas stripping product-recovery system using Clostridium beijerinckii BA101, with H(2) and CO(2) as the carrier gases. This technique was applied in order to eliminate the substrate and product inhibition that normally restricts ABE production and sugar utilization to less than 20 g l(-1) and 60 g l(-1), respectively. In the integrated fed-batch fermentation and product recovery system, solvent productivities were improved to 400% of the control batch fermentation productivities. In a control batch reactor, the culture used 45.4 g glucose l(-1) and produced 17.6 g total solvents l(-1) (yield 0.39 g g(-1), productivity 0.29 g l(-1) h(-1)). Using the integrated fermentation-gas stripping product-recovery system with CO(2) and H(2) as carrier gases, we carried out fed-batch fermentation experiments and measured various characteristics of the fermentation, including ABE production, selectivity, yield and productivity. The fed-batch reactor was operated for 201 h. At the end of the fermentation, an unusually high concentration of total acids (8.5 g l(-1)) was observed. A total of 500 g glucose was used to produce 232.8 g solvents (77.7 g acetone, 151.7 g butanol, 3.4 g ethanol) in 1 l culture broth. The average solvent yield and productivity were 0.47 g g(-1) and 1.16 g l(-1) h(-1), respectively.

Influence of fermentation by-products on the purification of ethanol from water using pervaporation

“…Moreover, energy requirements increase exponentially when ethanol concentration in the feed solution fall below 5 wt.% (Madson and Lococo, 2000). Hence, a lot of research was carried out in finding energetically more attractive separation techniques, such as gas/steam stripping (Ezeji et al, 2004), liquidliquid extraction (Bothun et al, 2002), adsorption (Carton et al, 1998) and pervaporation (Bowen et al, 2007;Fadeev et al, 2003;Ikegami et al, 2003;Nomura et al, 2002). These separation technologies for producing fuel grade ethanol from fermentation broths have been extensively reviewed by Vane and compared to the classical distillation process (Vane, 2008).…”

Life-cycle assessment of corn-based butanol as a potential transportation fuel.

“…Experimental and pilot-scale ABE fermentation processes by this organism resulted in up to 95.1% glucose utilization in fermentation. Using in-situ gas stripping for solvent removal from fermentor minimizes product inhibition and enables higher feed concentration -up to 500g/L of glucose (Ezeji et al 2004). Solvent production in this process in a fed-batch mode reached 65:35:1 of butanol:acetone:ethanol by weight, which is a significant increase in butanol production from 6:3:1 in conventional ABE process.…”

“…ABE production typically starts with a lag phase and gradually increases its rate until the ABE concentration reaches a plateau before it finally decreases (Ezeji et al 2004). A gas mixture of carbon dioxide (CO 2 ) and hydrogen (H 2 ) is also generated from the fermentation.…”

“…The information in this section is based on the research results from Qureshi and Blaschek (2000;2001a, b), Ezeji et al (2004), and Ezeji et al (2005).…”

“…Liu (2003) presents an exhaustive survey of major research findings on ABE downstream processing. Recent studies have focused on integration of fermentation and product removal through in-situ gas stripping and fermentation gas recirculation (Qureshi and Blaschek 2000;Qureshi and Blaschek 2001a;Qureshi and Blaschek 2001b;Ezeji et al 2004;and Ezeji et al 2005). The latest development includes a DuPont patent (2007) describing a strain that produces butanol from biological feedstocks while minimizing acetone production.…”