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Continuous production of acetone, n-butanol, and ethanol (ABE) was carried out using immobilized cells of Clostridium acetobutylicum DSM 792 using glucose and sugar mixture as a substrate. Among various lignocellulosic materials screened as a support matrix, coconut fibers and wood pulp fibers were found to be promising in batch experiments. With a motive of promoting wood-based bio-refinery concept, wood pulp was used as a cell holding material. Glucose and sugar mixture (glucose, mannose, galactose, arabinose, and xylose) comparable to lignocellulose hydrolysate was used as a substrate for continuous production of ABE. We report the best solvent productivity among wild-type strains using column reactor. The maximum total solvent concentration of 14.32 g L was obtained at a dilution rate of 0.22 h with glucose as a substrate compared to 12.64 g L at 0.5 h dilution rate with sugar mixture. The maximum solvent productivity (13.66 g L h) was obtained at a dilution rate of 1.9 h with glucose as a substrate whereas solvent productivity (12.14 g L h) was obtained at a dilution rate of 1.5 h with sugar mixture. The immobilized column reactor with wood pulp can become an efficient technology to be integrated with existing pulp mills to convert them into wood-based bio-refineries. [ABSTRACT FROM AUTHOR]

The biomass obtained after the extraction of forskolin from the roots of Coleus forskohlii was evaluated as a substrate for the production of acetone-butanol-ethanol (ABE). The spent biomass constituting more than 90% of the raw material showed 50–70% carbohydrates with starch and cellulose being the major constituents. This study was undertaken to optimize enzymatic hydrolysis of C. forskohlii roots for maximum release of fermentable sugars and subsequent fermentation to ABE. The root biomass was hydrolyzed using the Stargen ® 002 and Accellerase ® 1500. Cocktail of both enzymes (16U Stargen ® 002 and 60 FPU Accellerase ® 1500) could produce 41.2 g/l of total reducing sugars (glucose equivalent to 32.33 g/l). The production of ABE was optimized in a batch fermentation using Clostridium acetobutylicum NCIM 2877. The maximum ABE production using the root hydrolysates was 0.55 g/l. Pretreatment with lime and Amberlite XAD-4 increased the production of total solvent to 5.33 g/l. [ABSTRACT FROM AUTHOR]

Acetone being a non-fuel solvent produced during the traditional acetone-butanol-ethanol (ABE) fermentation by Clostridium acetobutylicum ; reduces the overall fuel alcohol yield. However, the conversion of acetone into isopropanol has been recommended to improve the process economy. The present study aims to develop an engineered C. acetobutylicum DSM 792 strain to convert acetone into isopropanol by introducing the secondary alcohol dehydrogenase gene from Clostridium beijerinckii NRRL B593 using the allele-coupled exchange approach. Batch and continuous fermentation experiments were carried out with a modified strain C. acetobutylicum DSM 792-ADH to improve the isopropanol yield and titer. The growth and production behavior of the modified strain in stationary flask culture and controlled batch culture was studied. Almost 50% of acetone was converted into isopropanol with highest total solvent yield to be 0.39 g g −1 glucose. The modified strain also utilized sugar mixture and SO 2 –ethanol–water spent liquor as a substrate to produce the solvents. [ABSTRACT FROM AUTHOR]

Highlights: [•] Advanced and economical production of biobutanol. [•] Continuous two stage fermentation with integrated liquid–liquid recovery technique. [•] Utilization of lignocellulosic sugar mixture (pentoses and hexoses). [•] Long run system operation with high solvent productivity (10.85g/Lh) and yield. [•] Can be integrated to the wood based biorefinery to make it industrially feasible. [ABSTRACT FROM AUTHOR]

Abstract: The present study proposes the use of market rejected and waste vegetables as a supplement for improved acetone–ethanol–butanol (ABE) solvent production. In the present study, three different perishable vegetables were evaluated as supplements for ABE fermentation. These vegetables were found to stimulate the solvent production at as low as 1% (w/v) concentration. The supplementation showed improved production of solvents using 4-fold diluted SO2–ethanol–water (SEW) spent liquor supplemented with 25g/l glucose as a substrate. The maximum total solvent production obtained with 5% (w/v) supplementation of carrot, cabbage and tomato was 9.96g/l, 10.49g/l and 10.65g/l, respectively as compared to the control value of 7.43g/l. The applicability of vegetables was successfully evaluated as a complex medium for solvent production. [Copyright &y& Elsevier]

Abstract: The objective of this study was to optimize continuous acetone–butanol–ethanol (ABE) fermentation using a two stage chemostat system integrated with liquid–liquid extraction of solvents produced in the first stage. This minimized end product inhibition by butanol and subsequently enhanced glucose utilization and solvent production in continuous cultures of Clostridium acetobutylicum B 5313. During continuous two-stage ABE fermentation, sugarcane bagasse was used as the cell holding material for the both stages and liquid–liquid extraction was performed using an oleyl alcohol and decanol mixture. An overall solvent production of 25.32g/L (acetone 5.93g/L, butanol 16.90g/L and ethanol 2.48g/L) was observed as compared to 15.98g/L in the single stage chemostat with highest solvent productivity and solvent yield of 2.5g/Lh and of 0.35g/g, respectively. Maximum glucose utilization (83.21%) at a dilution rate of 0.051/h was observed as compared to 54.38% in the single stage chemostat. [Copyright &y& Elsevier]

Abstract: SO2–ethanol–water (SEW) spent liquor from spruce chips was successfully used for batch and continuous production of acetone, butanol and ethanol (ABE). Initially, batch experiments were performed using spent liquor to check the suitability for production of ABE. Maximum concentration of total ABE was found to be 8.79g/l using 4-fold diluted SEW liquor supplemented with 35g/l of glucose. The effect of dilution rate on solvent production, productivity and yield was studied in column reactor consisting of immobilized Clostridium acetobutylicum DSM 792 on wood pulp. Total solvent concentration of 12g/l was obtained at a dilution rate of 0.21h−1. The maximum solvent productivity (4.86g/lh) with yield of 0.27g/g was obtained at dilution rate of 0.64h−1. Further, to increase the solvent yield, the unutilized sugars were subjected to batch fermentation. [Copyright &y& Elsevier]

The objective of this study is to develop a process for conditioning spent liquor produced by SO2-ethanol-water (SEW) fractionation of spruce wood chips for fermentation to butanol, ethanol and acetone/isopropanol, i.e., by means of the so called acetone-butanol-ethanol (ABE) process using Clostridia bacteria. This study serves as part of an overall project aiming at the development of economic processes for producing chemicals and biofuels from mixed forest biomass via SEW fractionation and ABE fermentation technologies. [ABSTRACT FROM AUTHOR]