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In this work, the acetone-butanol-ethanol (ABE) fermentation was upgraded in order to improve its economy. Fed-batch fermentation was integrated with two-stage gas stripping-pervaporation unit. The permeated ABE condensate was used as substrate for oleates production. Candida sp. 99–125 cells, being rich in lipase activity, were used as full-cell catalyst. Different ABE feeding strategies in the esterification process were compared. As results, 10.1%, 68.6% and 72.5% of butyl oleate were obtained in the one-step added scenario, the stepwise-added scenario, and the simultaneous fed-batch scenario, respectively. The novel hybrid process was energy-saving, environmentally friendly and profitable, showing promise in future industrialization. [ABSTRACT FROM AUTHOR]

In this study, an integrated gas stripping–pervaporation (GS–PV) process was established to enhance the butanol concentration and to reduce the cost of the product separation processes. Batch pervaporation was integrated with in situ gas stripping system of fed-batch acetone–butanol–ethanol (ABE) fermentation. A total 706.68 g/L ABE (54.2 g/L of ethanol, 169.93 g/L of acetone, and 482.55 g/L of butanol) was collected after 11 h of pervaporation separation. The recovery rates of butanol, acetone and ethanol were 98.8%, 99.5% and 82.8% (w/v), respectively. Attractively, the liquor on the permeate side of pervaporation membrane exceeded its azeotropic point which have not been achieved in previous processes basing on individual gas stripping or pervaporation. Furthermore, aiming to construct consolidate commercial guide of biobutanol producing process, GS–PV–distillation process was established and compared with traditional GS–distillation scheme. As a result, 24.83 MJ/kg of butanol was consumed in the novel GS–PV–distillation process. In this scheme, the beer column was deleted from the rectifying column series. Moreover, based on the consolidate GS–PV–distillation integration process, heat recovery network was simulated and designed by Pinch Analysis, and 1.72 MJ/kg of heat could be further saved after heat exchange in the distillation system. And the overall energy demand for butanol production was further decreased to 23.07 MJ/kg, which was only 29.2% of the conventional distillation procedure. [ABSTRACT FROM AUTHOR]

Background: The production of biobutanol from renewable biomass resources is attractive. The energy-intensive separation process and low-titer solvents production are the key constraints on the economy-feasible acetone–butanol–ethanol (ABE) production by fermentation. To decrease energy consumption and increase the solvents concentration, a novel two-stage gas stripping–salting-out system was established for effective ABE separation from the fermentation broth using sweet sorghum bagasse as feedstock. Results: The ABE condensate (143.6 g/L) after gas stripping, the first-stage separation, was recovered and introduced to salting-out process as the second-stage. K4P2O7 and K2HPO4 were used, respectively. The effect of saturated salt solution temperature on final ABE concentration was also investigated. The results showed high ABE recovery (99.32%) and ABE concentration (747.58 g/L) when adding saturated K4P2O7 solution at 323.15 K and 3.0 of salting-out factor. On this condition, the energy requirement of the downstream distillation process was 3.72 MJ/kg of ABE. Conclusions: High-titer cellulosic ABE production was separated from the fermentation broth by the novel two-stage gas stripping–salting-out process. The process was effective, which reduced the downstream process energy requirement significantly. [ABSTRACT FROM AUTHOR]

This paper aimed to use the major part of carbohydrate fractions in enzymatic hydrolysate of sweet sorghum bagasse, acetone-butanol-ethanol (ABE) fermentation was performed following the ethanol fermentation of hexoses. In batch ethanol fermentation stage, 50.8 ± 3.2 g/L of ethanol was produced from 111.5 g/L of glucose in hydrolysate. After ethanol recovery by batch vacuum distillation, 123.6 ± 15.6 g/L of ethanol was obtained in the distillate, while 47.2 ± 2.5 g/L of xylose was remained in the fermentation broth. The ethanol-free broth was further used as the substrate for ABE fermentation. Compared with yeast remaining scenario, the cell-free ethanol fermentation broth showed a better performance in ABE production. 7.37 ± 0.33 g/L of butanol and 10.93 ± 0.54 g/L of ABE solvent were produced after 120 h of batch fermentation. Based on the biorefinery strategy that cascade two-types of fermentation process, the overall solvents yield boosted significantly, about 144.8 g of ethanol, 17.3 g of butanol and 4.8 g of acetone can be produced from 1 kg sweet sorghum bagasse. • High concentration of sugar was obtained by fed-batch enzymatic hydrolysis of the pretreated pulp. • Ethanol was recovered by vacuum distillation after batch fermentation of enzymatic hydrolysate. • The ethanol removal broth was used as the substrate of ABE fermentation. • About 144.8 g of ethanol, 17.3 g of butanol and 4.8 g of acetone per 1 kg of raw material was achieved. [ABSTRACT FROM AUTHOR]

Two-stage pervaporation for ABE recovery from fermentation broth was studied to reduce the energy cost. The permeate after the first stage in situ pervaporation system was further used as the feedstock in the second stage of pervaporation unit using the same PDMS/PVDF membrane. A total 782.5 g/L of ABE (304.56 g/L of acetone, 451.98 g/L of butanol and 25.97 g/L of ethanol) was achieved in the second stage permeate, while the overall acetone, butanol and ethanol separation factors were: 70.7–89.73, 70.48–84.74 and 9.05–13.58, respectively. Furthermore, the theoretical evaporation energy requirement for ABE separation in the consolidate fermentation, which containing two-stage pervaporation and the following distillation process, was estimated less than ∼13.2 MJ/kg-butanol. The required evaporation energy was only 36.7% of the energy content of butanol. The novel two-stage pervaporation process was effective in increasing ABE production and reducing energy consumption of the solvents separation system. [ABSTRACT FROM AUTHOR]

The treatment of high chemical oxygen demand (COD) organic wastewater is one of the major technical bottlenecks for the industrialization of second-generation biobutanol production. An effective strategy to decrease the wastewater discharge in biobutanol fermentation process is broth recycling (BR). Nevertheless, the conventional BR process suffered from server organic-acid by-products inhibition, causing low butanol yield. In this study, to solve the barrier, active carbon (AC) adsorption system was hybrid with the acetone-butanol-ethanol (ABE) fermentation and ex - situ product separation (ESPR) units. After fermentation and pervaporation, organic acids that remaining in the ABE-separated broth were partially adsorbed onto AC so that improve the continuity and efficiency of the BR process. The physicochemical characterizations of different types of commercial ACs and the organic acids adsorption efficiency was evaluated by analyzing the static and dynamic adsorptions kinetics. When adopting the DD-type AC (code C299105), the better adsorbent for organic acids removal, 87.50% of fermentative wastewater can be saved whilst the ABE concentrations were also kept constantly at 15.22 ± 0.45 g L−1 in the following cycles of fermentation, and the ABE productivity was almost no changed (0.21 ± 0.01 g L−1 h−1) after 3 cycles of operation. Therefore, the AC assisted ESPR process is an attractive method for ABE production with low wastewater discharge. [Display omitted] • Active carbon (AC) adsorption was hybrid with ex - situ ABE separation for broth recycling. • The commercial DD-type AC exhibited the high absorbability for acids specific loadings. • The static and dynamic adsorptions kinetics of DD-type AC for organic acids were evaluated. • 87.50% of fermentative wastewater can be saved after recycling the broth for 3 times. [ABSTRACT FROM AUTHOR]

Large amounts of effluent discharge and a costly wastewater treatment hinder the scale-up of the lignocellulosic acetone-butanol-ethanol (ABE) fermentation process. By recycling the broth after solvents removal and using it in the subsequent cycles of biomass hydrolysis and fermentation, the overall amount of effluent can be reduced. However, the ABE production is severely inhibited by the accumulated acids and other toxic by-products when reusing the cycled streams. In this study, a pervaporation assisted sequential fermentation was performed. The ABE liquor recovered after batch fermentation and ex situ pervaporation was used as the buffer for corn stover pulp hydrolysis and the following microbial lipids fermentation. In microbial lipids fermentation stage, toxic acid by-products remained in the liquor can be co-utilized as a substrate. The acids eliminated post-harvested broth was further cycled as the buffer for pulp hydrolysis and ABE fermentation. As a result, ABE yield of 0.349 g/g and concentration of 14.40 g/L were achieved after 3 cycles of operation, which show only 3.86% and 14.98% reduction compared to those of the initial cycle. Remarkably, the effluent discharge was reduced by 92.20% after applying the hybrid two-stage sequential fermentation. Meanwhile, 8.20 g/L of microbial lipids can be co-generated. The novel process offers an environmentally friendly strategy for the co-production of ABE and microbial lipids from lignocelluloses under the concept of biorefinery. Image 1 • ABE fermentation was hybrid with ex situ pervaporation and microbial lipids fermentation. • The effluent wastewater in the hybrid process was reused by a recycled loop. • Acids by-product in the ABE fermentation broth can be used as carbon source for lipids production. • Total 3 cycles of was conducted with 92.20% of ABE wastewater saving rate. • ABE and lipids production were not obvious decreased within 3 cycles of operation. [ABSTRACT FROM AUTHOR]