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• Four different molasses were tested as alternative carbon sources. • Corn steep liquor (CSL) was tested as an alternative nitrogen sources. • Molasses and CSL serves as a cost-effective medium for ABE fermentation. • Hydrolyzed black soldier fly larval meals were feasible for ABE fermentation. Biobutanol, produced through acetone-butanol-ethanol (ABE) fermentation, has been proposed for use as a transportation fuel and for the development of butanol-based materials. However, the economic viability of ABE fermentation is heavily dependent on the cost of raw materials. This study assesses various carbon and nitrogen sources for ABE fermentation. Carbon sources examined include local molasses (M1), Thai molasses (M2), Taiwan sugar agricultural molasses (M3), and Taiwan sugar edible molasses (M4). Nitrogen sources considered are corn steep liquor (CSL), acid-hydrolyzed black soldier fly larval meal (IA), and enzyme-hydrolyzed black soldier fly larval meal (IE). Our findings reveal that M2CSL, a combination of Thai molasses and corn steep liquor, serves as a cost-effective and efficient medium for ABE fermentation, resulting in a butanol concentration of 7.4 ± 3.5 g/L. Furthermore, our research identifies variations in molasses and their impact on sucrose consumption inhibition. Notably, this study underscores the potential of insect peptone derived from enzyme-hydrolyzed black soldier fly larval meal (IE) as an alternative nitrogen source, while cautioning against the use of insect peptone obtained from acid-hydrolyzed black soldier fly larval meal (IA) due to its inhibitory properties. [ABSTRACT FROM AUTHOR]

In this study, the integrated in situ extraction-gas stripping process was coupled with continuous ABE fermentation using immobilized Clostridium acetobutylicum. At the same time, oleyl alcohol was cocurrently flowed into the packed bed reactor with the fresh medium and then recycled back to the packed bed reactor after removing butanol in the stripper. A high glucose consumption of 52 g/L and a high butanol productivity of 11 g/L/h were achieved, resulting in a high butanol yield of 0.21 g-butanol/g-glucose. This can be attributed to both the high bacterial activity for solvent production as well as a threefold increase in the bacterial density inside the packed bed reactor. Also reported is that 64 % of the butanol produced can be recovered by the integrated in situ extraction-gas stripping process. A high butanol productivity and a high glucose consumption were simultaneously achieved. [ABSTRACT FROM AUTHOR]

A novel integrated in situ extraction-gas stripping process (Process 3 in this study) is proposed for running batch Acetone–Butanol–Ethanol (ABE) fermentation. The process involves two butanol separation processes in which butanol is first extracted by oleyl alcohol during ABE fermentation and gas stripping is carried out on butanol in the oleyl alcohol phase at the same time. The butanol productivity and yield of Process 3 is 0.28 ± 0.01 g/L/h and 0.226 ± 0.001 g-butanol/g-glucose. The ABE productivity and yield are 0.46 ± 0.01 g/L/h and 0.374 ± 0.002 g-ABE/g-glucose. Glucose utilization was 97% and initial glucose consumption was 121 ± 2 g/L. Butanol and ABE concentrations of 93–113 and 166–204 g/L in the condensate can be achieved. This study demonstrates that Process 3 as described here enhances ABE fermentation and also results in the production of high purity solvents. [ABSTRACT FROM AUTHOR]

Abstract: Batch, fed-batch, and continuous A–B–E fermentations were conducted and compared with pH controlled at 4.5, the optimal range for solvent production. While the batch mode provides the highest solvent yield, the continuous mode was preferred in terms of butanol yield and productivity. The highest butanol yield and productivity found in the continuous fermentation at dilution rate of 0.1h−1 were 0.21g-butanol/g-glucose and 0.81g/L/h, respectively. In the continuous and fed-batch fermentation, the time needed for passing acidogenesis to solventogenesis was an intrinsic hindrance to higher butanol productivity. Therefore, a low dilution rate is suggested for the continuous A–B–E fermentation, while the fed-batch mode is not suggested for solvent production. While 3:6:1 ratio of acetone, butanol, and ethanol is commonly observed from A–B–E batch fermentation by Clostridium acetobutylicum when the pH is uncontrolled, up to 94% of the produced solvent was butanol in the chemostat with pH controlled at 4.5. [Copyright &y& Elsevier]

Abstract: A novel tri-layer composite membrane consisting of the active layer polydimethylsiloxane (PDMS, Sylgard® 184) and dual support layers of high porosity polyethylene (PE) and high mechanical stiffness perforated metal was investigated for the separation of 1-butanol from aqueous solution by means of pervaporation. The experimental data show that total flux and separation factor are both increased by placing a layer of hydrophobic PE between the PDMS and the metal support. The enhancement is especially obvious at low temperatures. With the feed solution of 2% 1-butanol at 37°C, the PDMS/PE/Brass support composite membrane confers a total flux of 132g/h/m2 and a separation factor of 32. With the increase of the PDMS thickness, the separation factor increases as the total flux declines. It is suggested that while the water flux remains stable, the 1-butanol flux has linear relationship with respect to the feed concentration of 1-butanol. The overall mass transfer coefficient for butanol was determined to be 6.9E−7m/s using the resistance-in-series model. Using a semi-empirical Sherwood number correlation, the mass transfer coefficient of 1-butanol through the liquid side boundary layer was estimated to be 25.5E−7m/s. This is more than 3 times higher than the overall mass transfer coefficient, indicating that the membrane dominates the mass transfer of the pervaporation process. [Copyright &y& Elsevier]

Napier grass is a potential feedstock for biofuel production because of its strong adaptability and wide availability. Compositional analysis has been done on Napier grass which was collected from a local area of Taiwan. By comparing acid- and alkali-pretreatment, it was found that the alkali-pretreatment process is favorable for Napier grass. An overall glucose yield of 0.82 g/g-glucose total can be obtained with the combination of alkali-pretreatment (2.5 wt% NaOH, 8 wt% sample loading, 121 °C, and a reaction time of 40 min) and enzymatic hydrolysis (40 FPU/g-substrate). Semi-simultaneous saccharification fermentation (sSSF) was carried out, where enzymatic hydrolysis and ABE fermentation were operated in the same batch. It was found that after 24-h hydrolysis, followed by 96-h fermentation, the butanol and acetone concentrations reached 9.45 and 4.85 g/L, respectively. The butanol yield reached 0.22 g/g-sugar glucose+xylose . Finally, the efficiency of butanol production from Napier grass was calculated at 31%. [ABSTRACT FROM AUTHOR]

In this study, effects of the agitation speed, the flow rate, and type of non-polar gases on the performance of gas stripping was systematically investigated. Macroscopically, the stripping rate of butanol is linearly proportional to the concentration of butanol in the feed solution. Nevertheless, a decrease in butanol selectivity was observed with the increasing butanol concentrations up to 0.01 g/cm 3 . This can be attributed to the thermodynamics reason that with increasing butanol concentrations in the feed, more stripping gas will dissolve in the feed solution that decrease the activity of butanol for mass transfer from liquids to gas bubbles. This can be supported by the use of highly soluble gas of carbon dioxide as the stripping gas where the K s a dropped 48% compared to the nitrogen stripping. By the parameter sensitivity analysis, it has been shown that the dominant variable is the flow rate. The best strategy of maximizing the performance of 1-butanol gas stripping at a given flow rate is to bubble the gases at a high superficial velocity, which leads to a less resistance on the liquid side for mass transfer. [ABSTRACT FROM AUTHOR]

• ABE fermentation integrated extraction-gas stripping was performed in a 5-L PBR. • The inoculation in the PBR should be specifically executed. • Butanol productivity of 2.5 g L-1 h−1 was achieved with a dilution rate of 0.5 h−1. • Inhomogeneous bacterial growth in PBR was the critical issue at the 5-L scale. A 5-L pilot-scale packed-bed bioreactor with integrated in situ extraction/gas-stripping was designed and manufactured for automated acetone-butanol-ethanol (ABE) fermentation using immobilized Clostridium acetobutylicum. A continuous run of 770-h demonstrated the robustness of the bioreactor. Optimal inoculation protocols were developed to prevent mass transfer hindrance and improve butanol productivity and bacterial growth. At a dilution rate of 0.1 h−1, an improvement of 0.44 g L−1 h−1 in butanol productivity was observed with the continuous process coupled with extraction/gas-stripping. However, it was found that the bacterial formation within the packed bed was inhomogeneous, with dense bacterial growth observed only at the bottom. Therefore, inhomogeneous bacterial growth cannot be simply overcome with the in situ extraction/gas-stripping process. This highlights the need to address the issue of inhomogeneous bacterial growth in pilot-scale packed-bed reactors to improve their efficiency. [ABSTRACT FROM AUTHOR]

Abstract: In this study, engineered butanologenic Escherichia coli T5 constructed by the OGAB method was used for 1-butanol production. The results showed the feasibility of the artificial butanologenic operon, (Promoter Pr)-thil-crt-bcd-etfB-etfA-hbd-adhe1-adhe, where the 1-butanol titer, specific BuOH yield, and BuOH yield were 4.50mg/L, 4.50mg-BuOH/g cell, and 0.35mg-BuOH/g-glucose, respectively. Fermentation conditions of anaerobic, low initial concentrations of carbon sources, low oxidation state of carbon source, pH of 6, addition of glutathione and citrate, had been shown for efficiently improving the 1-butanol production. The premise behind these fermentation approaches can be categorized into two lines of reasoning, either elevated the availability of acetyl-CoA or lowered the intracellular redox state. By comparing the fermentation conditions tested in this study, pH has been shown to be the most efficiency strategies for 1-butanol production while the replacement of glucose with glycerol provides the highest improvement in butanol yield. [Copyright &y& Elsevier]