Maximum Butanol Concentration Research Articles

The Effect of Technological Conditions on ABE Fermentation and Butanol Production of Rye Straw and the Composition of Volatile Compounds.

The objective of this study was to evaluate the effect of pretreatment and different technological conditions on the course of ABE fermentation of rye straw (RS) and the composition of volatile compounds in the distillates obtained. The highest concentration of ABE and butanol was obtained from the fermentation of pretreated rye straw by alkaline hydrolysis followed by detoxification and enzymatic hydrolysis. After 72 h of fermentation, the maximum butanol concentration, productivity, and yield from RS were 16.11 g/L, 0.224 g/L/h, and 0.402 g/g, respectively. Three different methods to produce butanol were tested: the two-step process (SHF), the simultaneous process (SSF), and simultaneous saccharification with ABE fermentation (consolidation SHF/SSF). The SHF/SSF process observed that ABE concentration (21.28 g/L) was higher than in the SSF (20.03 g/L) and lower compared with the SHF (22.21 g/L). The effect of the detoxification process and various ABE fermentation technologies on the composition of volatile compounds formed during fermentation and distillation were analyzed.

Biohydrogen Gas/Acetone-Butanol-Ethanol Production from Agave Guishe Juice as a Low-Cost Growing Medium

Different strategies have been assessed for the revalorization of guishe to obtain biomolecules. The juice obtained after the mechanical extraction of guishe is rich in phytochemicals and sugars which can be converted to other products. The objective of the present study was to evaluate the production of hydrogen and butanol at different guishe juice concentrations (and therefore, different sugar concentrations) via fermentation in batch mode using Clostridium acetobutylicum ATCC 824. Fermentation assays were performed in triplicate under anaerobic conditions at 35 °C for 142 h. Guishe juice was supplemented with all components of synthetic medium (salts, vitamins and reducing agents), except glucose, and diluted at different concentrations: 20%, 40%, 60%, 80% and 100%. For comparison purposes, a control was carried out in a synthetic medium using glucose as carbon source. Results showed a maximum butanol concentration of 5.39 g/L using 80% guishe juice, corresponding to a productivity and yield of 0.04 g/L h−1 and 0.24 g/g, respectively. Meanwhile, the highest productivity (1.16 L H2/L d−1; 1.99 mmol H2/L h−1) and yield (18.4 L/kg) of hydrogen were obtained with 40% guishe juice. This study demonstrates the potential of guishe juice to be used as a low-cost substrate for hydrogen and butanol production.

Waste-to-energy: biobutanol production from cellulosic residue of sweet potato by Clostridia acetobutylicum

Biobutanol has been emerging as a renewable replacement to overcome fossil fuel limit due to its attractive qualities. The waste resources utilization is an economically feasible and eco-friendly way to produce biobutanol. In this work, the potential of butanol fermentation with sweet potato residue (SPR) obtained from ethanol fermentation was evaluated. To assist sugar release for butanol production by Clostridia acetobutylicum, a pretreatment approach with dilute sulfuric acid was established via response surface methodology. The maximum butanol concentration of 3.77 g/L was obtained at the optimal conditions of pretreatment at 1% (v/v) dilute sulfuric acid, and 115℃ for 30 min. Detoxifying the hydrolysate with XAD-4 resin significantly enhanced butanol fermentation performance, while adding nutritional supplements had no significant influence. The stability of the fermentation process was verified by the 2 L-scale of fermentation, resulting in 7.96 g/L of butanol, 13.42 g/L h of Acetone-Butanol-Ethanol (ABE), and 0.34 g/g of ABE yield, respectively. This study demonstrates a bio-refinery strategy of conversion from waste biomass to energy, confirms the feasibility of utilizing the cost saving SPR as feedstock to produce butanol through fermentation, and provides a novel approach for minimization of environmental pollution.

Fed-batch simultaneous saccharification and fermentation including in-situ recovery for enhanced butanol production from rice straw

This paper describes a study of fed-batch SSFR (simultaneous saccharification, fermentation and recovery) for butanol production from alkaline-pretreated rice straw (RS) in a 2-L stirred tank reactor. The initial solid (9.2% w/v) and enzyme (19.9 FPU g-dw-1) loadings were previously optimized by 50-mL batch SSF assays. Maximum butanol concentration of 24.80 g L-1 was obtained after three biomass feedings that doubled the RS load (18.4% w/v). Butanol productivity (0.344 g L-1h−1) also increased two-fold in comparison with batch SSF without recovery (0.170 g L-1h−1). Although fed-batch SSFR was able to operate with a single initial enzyme dosage, an extra dosage of nutrients was required with the biomass additions to achieve this high productivity. The study showed that SSFR can efficiently improve butanol production from a lignocellulosic biomass accompanied by the efficient use of the enzyme.

Applying Odor Preconcentrator for Enhancing Human Olfaction: Feasibility Study

Introduction The human sense of smell plays important roles in various scenes in everyday life although we are unconscious of its importance in most cases. For example, olfaction provides alerts that lets us notice dangers or risks such as a fire and rotten food. Savory food smells and comfort flower fragrances make our lives richer. However, it is known that the human olfaction deteriorates with our age [1]. There is no device that can improve the deteriorated olfaction whereas impaired vision can be improved using eyeglasses and a hearing aids can improve our audition. The aim of this research project is to develop an olfactory amplifier for humans [2,3]. In chemical analysis, preconcentrators are frequently used to analyze faint chemical substances [4]. We propose to apply this technique to enhance the sensitivity of human olfaction. In the proposed olfactory amplifier system, airborne odor molecules are collected into adsorbent, as in the preconcentrator. When a sufficient amount of odor molecules are collected, the adsorbent is heated to a high temperature to thermally desorb the collected molecules in a short time. The concentrated odors are thus generated. Here we report our new device made with a monolithic silica adsorbent. Results of an odor concentration experiment and a sensory test are presented to show that the device can generate a clearly perceivable smell from a faint smell sample. Method The schematic diagram of our new device that uses a disc-shaped monolithic silica (MonoTrap DSC18, GL Science) as an adsorbent is shown in Figure 1. The cross section of the device is shown in Figure 2. The diameter and thickness of the monolithic silica disk are 10 mm and 1 mm, respectively. This adsorbent is housed in a flow cell which was made by putting a rubber sheet with a hole in the middle between an acrylic plate and a printed circuit board. A meander heater made on the printed circuit board is used for thermally desorbing the collected odor molecules from the monolithic silica disk. Five stainless-steel tubes are attached to the flow cell. Air is sent into the flow cell through the center tube, and is exhausted from the four outer tubes.In the odor concentration experiment, 1.2 ppm 1-butanol vapor packed in a sampling bag was sent into the flow cell at a flow rate of 0.8 L/min for 10 min. The collected butanol molecules were desorbed by heating up the monolithic silica to 200 degrees centigrade. Clean air was sent to the flow cell at a flow rate of 20 mL/min to take the concentrated odor vapor out from the flow cell. The concentration of the butanol vapor presented from the device was measured using a semiconductor gas sensor (TGS2620, Figaro Engineering). In the sensory test, we prepared liquid apple flavor consisting of nine components. The flavor was diluted by 100 times using liquid paraffin. Eight subjects participated in the sensory test. Each subject was asked to sniff the diluted apple flavor and compare its smell with the smell of the concentrated vapor presented from the odor amplifier device. Results and Discussions Figure 3 shows the response curves of the gas sensor which was exposed to the vapor coming out from the odor amplifier device. The sensor response is defined as the ratio of the sensor resistance in gas to that in air. Its value decreases with the gas concentration. At 20 s from the start of recording the sensor response, the heater was turned on. The pump was activated after 4 s delay from the activation of the heater. The concentration factor calculated from the maximum butanol concentration detected by the gas sensor was 13.1. When the delay was reduced to 0 s, the concentration factor was slightly decreased. Table 1 shows the result of the sensory test. All subjects answered that the vapor presented from the amplifier device had a stronger smell and that the difference in the smell intensity was significant. Seven out of eight subjects even told us that they perceived no smell from the diluted liquid apple flavor. Most subjects told us that the original and concentrated smells were different because they were unable to perceive the original smell. These results show that a sufficient odor amplification effect can be obtained by a concentration factor of approximately 10. Future work will be addressed to enable quicker presentation of concentrated odors. This work was supported in part by JSPS KAKENHI Grant Numbers 19K14947 and 19H02103, and Research Grant from the Okawa Foundation for Information and Telecommunications.

Applying Odor Preconcentrator for Enhancing Human Olfaction: Feasibility Study

Introduction The human sense of smell plays important roles in various scenes in everyday life although we are unconscious of the importance in most cases. For example, olfaction provides an alert that lets us notice dangers or risks such as a fire and rotten food. Savory food smells and comfort flower fragrances make our lives richer. However, it is known that the human olfaction deteriorates with our age [1]. There is no device that can improve the deteriorated olfaction whereas impaired vision can be improved using eyeglasses and a hearing aids can improve our audition. The aim of this research project is to develop an olfactory amplifier for humans [2,3]. In chemical analysis, preconcentrators are frequently used to analyze faint chemical substances [4]. We propose to apply this technique to enhance the sensitivity of human olfaction. In the proposed olfactory amplifier system, airborne odor molecules are collected into adsorbent, as in the preconcentrator. When a sufficient amount of odor molecules are collected, the adsorbent is heated to a high temperature to thermally desorb the collected molecules in a short time. The concentrated odors are thus generated. Here we report our new device made with a monolithic silica adsorbent. Results of odor concentration experiments and a sensory test are presented to show that the device can generate a concentrated smell from a faint smell. Method The schematic diagram of our new device that uses a disc-shaped monolithic silica (MonoTrap DSC18, GL Science) as an adsorbent is shown in Figure 1. The cross section of the device is shown in Figure 2. The diameter and thickness of the monolithic silica disk are 10 mm and 1 mm, respectively. This adsorbent is housed in a flow cell which was made by putting a rubber sheet with a hole in the middle between an acrylic plate and a printed circuit board. A meander heater made on the printed circuit board is used for thermally desorbing the collected odor molecules from the monolithic silica disk. Five stainless tubes are attached to the flow cell. Air is sent into the flow cell through the center tube, and is exhausted from the four outer tubes.In the odor concentration experiment, 1.2 ppm 1-butanol vapor packed in a sampling bag was sent into the flow cell at a flow rate of 0.8 L/min for 10 min. The collected gas was desorbed by heating up the monolithic silica to 200 degrees centigrade. Clean air was sent to the flow cell at a flow rate of 20 mL/min to take the concentrated gas out from the flow cell. The concentration of the butanol gas presented from the device was measured using a semiconductor gas sensor (TGS2620, Figaro Engineering) In the sensory test, we prepared liquid apple flavor consisting of nine components. The flavor was diluted by 100 times using liquid paraffin. Eight subjects participated in the sensory test. Each subject was asked to sniff the diluted apple flavor and compare the smell with the smell of the concentrated vapor presented from the odor amplifier device. Results and Discussions Figure 3 shows the response curve of the gas sensor which was exposed to the vapor coming out from the odor amplifier device. The sensor response is defined as the ratio of the sensor resistance in gas to that in air. Its value decreases with the gas concentration. At 20 s from the start of recording the sensor response, the heating was turned on. The pump was activated after 4 s delay from the activation of the heater. The concentration factor calculated from the maximum butanol concentration detected by the gas sensor was 13.1. When the delay was reduced to 0 s, the concentration factor was slightly decreased. Table 1 shows the result of the sensory test. All subjects answered that the vapor presented from the amplifier device had a stronger smell and that the difference in the smell intensity was significant. Seven out of eight subjects even told us that they perceived no smell from the diluted liquid apple flavor. This resulted in their answers to the third question: most subjects told us that the original and concentrated smells were different because they were unable to perceive the original smell. These results show that a sufficient odor amplification effect can be obtained by a concentration factor of approximately 10. Future work will be addressed to enable quicker presentation of concentrated odors. This work was supported in part by JSPS KAKENHI Grant Numbers 19K14947 and 19H02103, and Research Grant from the Okawa Foundation for Information and Telecommunications.

Impacts of Initial Sugar, Nitrogen and Calcium Carbonate on Butanol Fermentation from Sugarcane Molasses by Clostridium beijerinckii

Low-cost nitrogen sources, i.e., dried spent yeast (DSY), rice bran (RB), soybean meal (SM), urea and ammonium sulfate were used for batch butanol fermentation from sugarcane molasses by Clostridium beijerinckii TISTR 1461 under anaerobic conditions. Among these five low-cost nitrogen sources, DSY at 1.53 g/L (nitrogen content equal to that of 1 g/L of yeast extract) was found to be the most suitable. At an initial sugar level of 60 g/L, the maximum butanol concentration (PB), productivity (QB) and yield (YB/S) were 11.19 g/L, 0.23 g/L·h and 0.31 g/g, respectively. To improve the butanol production, the concentrations of initial sugar, DSY and calcium carbonate were varied using response surface methodology (RSM) based on Box–Behnken design. It was found that the optimal conditions for high butanol production were initial sugar, 50 g/L; DSY, 6 g/L and calcium carbonate, 6.6 g/L. Under these conditions, the highest experimental PB, QB and YB/S values were 11.38 g/L, 0.32 g/L·h and 0.40 g/g, respectively with 50% sugar consumption (SC). The PB with neither DSY nor CaCO3 was only 8.53 g/L. When an in situ gas stripping system was connected to the fermenter to remove butanol produced during the fermentation, the PB was increased to 15.33 g/L, whereas the YB/S (0.39 g/g) was not changed. However, the QB was decreased to 0.21 g/L·h with 75% SC.

Clostridium strain selection for co-culture with Bacillus subtilis for butanol production from agave hydrolysates

In this work, three Clostridium strains were tested for butanol production from Agave lechuguilla hydrolysates to select one for co-culturing. The agave hydrolysates medium was supplemented with nutrients and reducing agents to promote anaerobiosis. Clostridium acetobutylicum ATCC 824 had the highest butanol production (6.04 g/L) and was selected for further analyses. In the co-culture process, Bacillus subtilis CDBB 555 was used to deplete oxygen and achieve anaerobic conditions required for butanol production. The co-culture was prepared with C. acetobutylicum and B. subtilis without anaerobic pretreatment. Butanol production in co-culture from agave hydrolysates was compared with experiments using synthetic medium with glucose and a pure culture of C. acetobutylicum. The maximum butanol concentration obtained was 8.28 g/L in the co-cultured hydrolysate medium. Results obtained in the present work demonstrated that agave hydrolysates have the potential for butanol production using a co-culture of B. subtilis and C. acetobutylicum without anaerobic pretreatment.

Methylimidazolium-based ionic liquids influence the biobutanol production by solvent-producing Clostridium

Ionic liquids (ILs) used to pretreat lignocellulosic biomass could stimulate or be detrimental to the subsequent fermentation process when the ILs retained in the biomass hydrolysate. This study aimed to investigate if the presence of the ILs including 1-allyl-3-methylimidazolium chloride ([AMIM][Cl]), 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]), 1-ethyl-3-methylimidazolium chloride ([EMIM][Cl]), 1-ethyl-3-methylimidazolium acetate ([EMIM][Ac]), and1-ethyl-3-methylimidazolium diethyl phosphate ([EMIM][DEP]) either enhanced or inhibited biobutanol production by Clostridium saccharoperbutylacetonicum N1-4. Results show that the presence of the five ILs at low concentration increased the butanol productions. The maximum butanol concentrations were obtained at 1 g L−1 for [AMIM][Cl], [BMIM][Cl], [EMIM][Cl], and [EMIM][DEP], and at 0.5 g L−1 for [EMIM][Ac]. The increase in the butanol concentrations was advantageous to the butanol and total solvent (acetone, butanol and ethanol) yields. Conversely, the butanol production rates were generally reduced by the ILs except for the observed hormesis at 0.5 and 1.0 g L−1 of both [BMIM][Cl] and [EMIM][Cl]. It was also observed that high levels of ILs impeded the speed of cell growth and thus decelerated the butanol production. Overall, the acetone-butanol-ethanol (ABE) fermentation was stimulated at low IL concentrations whereas was hindered at high concentrations.

Optimization of Key Factors Affecting Butanol Production from Sugarcane Juice by Clostridium beijerinckii TISTR 1461

Optimization of key factors affecting butanol production from sugarcane juice by Clostridium beijerinckii TISTR 1461 using the response surface methodology (RSM) with central composite design (CCD) was investigated. The effects of three key factors i.e. butyric acid, yeast extract and ammonium acetate were evaluated individually and interactively. The optimum conditions of butanol fermentation were predicted to be 6.85 g/L butyric acid, 3.0 g/L yeast extract, and 2.3 g/L ammonium acetate, under which a maximum butanol concentration of 11.06 g/L was estimated. The optimum conditions were applied in a batch fermentation using a 2-L fermenter with agitation rate of 100 rpm at 37ºC. The butanol produced was 11.77 g/L which was close to the predicted value. The process showed the promising alternative for butanol production from agricultural product using Clostridium beijerinckii TISTR 1461.

Novel kinetic model for the simulation analysis of the butanol productivity of Clostridium acetobutylicum ATCC 824 under different reactor configurations

Abstract Acetone–butanol–ethanol (ABE) fermentation process can be exploited for the generation of butanol as biofuel, however it does need to overcome its low volumetric solvent productivity before it can commercially compete with fossil fuel technologies. In this regard, mathematical modelling and simulation analysis are tools that can serve as the base for process engineering development of biological systems. In this work, a novel phenomenological kinetic model of Clostridium acetobutylicum ATCC 824 was considered as a benchmark system to evaluate the behaviour of an ABE fermentation under different process configurations using both free and immobilized cells: single stage batch operation, fed-batch, single stage Continuous Stirred Tank Reactor (CSTR) and multistage CSTRs with and without biomass recirculation. The proposed model achieved a linear correlation index r 2 = 0.9952 and r 2 = 0.9710 over experimental data for free and immobilized cells respectively. The predicted maximum butanol concentration and productivity obtained were 13.08 g·L − 1 and 1.9620 g·L − 1 ·h − 1 respectively, which represents an increase of 1.01% and 990% versus the currently developed industrial scale process reported currently into the literature. These results provide a reliable platform for the design and optimization of the ABE fermentation system and showcase the adequate predictive nature of the proposed model.

Impact of pH and butyric acid on butanol production during batch fermentation using a new local isolate of Clostridium acetobutylicum YM1.

The effect of pH and butyric acid supplementation on the production of butanol by a new local isolate of Clostridium acetobutylicum YM1 during batch culture fermentation was investigated. The results showed that pH had a significant effect on bacterial growth and butanol yield and productivity. The optimal initial pH that maximized butanol production was pH 6.0 ± 0.2. Controlled pH was found to be unsuitable for butanol production in strain YM1, while the uncontrolled pH condition with an initial pH of 6.0 ± 0.2 was suitable for bacterial growth, butanol yield and productivity. The maximum butanol concentration of 13.5 ± 1.42 g/L was obtained from cultures grown under the uncontrolled pH condition, resulting in a butanol yield (YP/S) and productivity of 0.27 g/g and 0.188 g/L h, respectively. Supplementation of the pH-controlled cultures with 4.0 g/L butyric acid did not improve butanol production; however, supplementation of the uncontrolled pH cultures resulted in high butanol concentrations, yield and productivity (16.50 ± 0.8 g/L, 0.345 g/g and 0.163 g/L h, respectively). pH influenced the activity of NADH-dependent butanol dehydrogenase, with the highest activity obtained under the uncontrolled pH condition. This study revealed that pH is a very important factor in butanol fermentation by C. acetobutylicum YM1.

Selective Water Removal by Sorption from Butanol–Water Vapor Mixtures: Analyses of Key Operating Parameters and Site Energy Distribution

In the present paper, selective water removal from butanol–water vapor mixture was carried out in a pressure swing adsorption (PSA) system using canola meal (CM) biosorbent. Five operating parameters (temperature, pressure, feed butanol concentration, feed flow rate, and CM particle size) were studied by the orthogonal array design method and range analysis to obtain the favorable process conditions for butanol drying. The performance of butanol dehydration was evaluated using five indices: water uptake, butanol uptake, water selectivity, butanol recovery, and maximum butanol concentration in the effluent. The obtained favorable dehydration conditions resulted in the maximum effluent butanol concentration of >99 v/v %, water uptake of 0.48 g/g-ads, water separation factor of 5.4, and butanol recovery of 90%. The Dubinin–Polanyi model for large pores fit the water adsorption isotherms reasonably well. Furthermore, site energy distribution of water adsorption was also estimated. Average site energy (3.33 kJ...

Direct fermentation of sweet sorghum juice by Clostridium acetobutylicum and Clostridium tetanomorphum to produce bio-butanol and organic acids

Article history: Single- and co-culture clostridial fermentation was conducted to obtain organic alcohols and acids from sweet sorghum juice as a low cost feedstock. Different inoculum concentrations of single cultures (3, 5, 10 v/v %) as well as different ratios of C. acetobutylicum to C. tetanomorphum (3:10, 10:3, 6.5:6.5, 3:3, and 10:10 v/v %, respectively) were utilized for the fermentation. The maximum butanol concentration of 6.49 g/L was obtained after 96 h fermentation with 10 % v/v C. acetobutylicum as a single culture. The fermentation with 10% v/v C. tetanomorphum resulted in more than 5 g/l butyric acid production. Major organic acid concentration (lactic acid) of 2.7 g/L was produced when an inoculum ratio of 6.5: 6.5 %v/v C. acetobutylicum to C. tetanomorphum was used.

Immobilization of Clostridium acetobutylicum DSM 792 as macroporous aggregates through cryogelation for butanol production

In this study, a new cell immobilization technique is presented. Cells of Clostridium acetobutylicum DSM 792 form a macroporous aggregate through cryogelation with concomitant crosslinking together with activated polyethyleneimine (PEI) and poly(vinyl alcohol) (PVA). The cell based cryogel presents a highly porous, elastic structure with walls consisting of densely packed crosslinked cells. The immobilization process maintained the viability of cells as new bacterial cells were observed when gel-plugs were incubated in liquid medium, glucose was consumed and solvent production was observed. Solvent production was improved 2.7-fold in immobilized cells in comparison to free cells. It was possible to reuse the gel-plugs 3–5 times in partial or completely fresh medium, reaching a maximum butanol concentration in the broth of 18.2g/l and yield of 0.41 (g/g) in one of the cycles. The use of cells based cryogels can be a good alternative for improvement of acetone-butanol-ethanol (ABE) process as cells are immobilized in a macroporous structure with low limitations for mass transfer with potential for high yield production.

Enhancing butanol production with Clostridium pasteurianum CH4 using sequential glucose–glycerol addition and simultaneous dual-substrate cultivation strategies

Adding butyrate significantly enhanced butanol production from glycerol with Clostridium pasteurianum CH4, which predominantly produces butyrate (instead of butanol) when grown on glucose. Hence, the butyrate produced from assimilating glucose can be used to stimulate butanol production from glycerol under dual-substrate cultivation with glucose and glycerol. This proposed butanol production process was conducted by employing sequential or simultaneous addition of the two substrates. The latter approach exhibited better carbon source utilization and butanol production efficiencies. Under the optimal glucose to glycerol ratio (20gL−1 to 60gL−1), the simultaneous dual-substrate strategy obtained maximum butanol titer, productivity and yield of 13.3gL−1, 0.28gL−1h−1, and 0.38mol butanol/mol glycerol, respectively. Moreover, bagasse and crude glycerol as dual-substrates were also converted into butanol efficiently with a maximum butanol concentration, productivity and yield of 11.8gL−1, 0.14gL−1h−1, and 0.33mol butanol/mol glycerol, respectively.

Biobutanol production from agricultural waste by an acclimated mixed bacterial microflora

Biobutanol production from cellulosic feedstock is considered promising and economically feasible. A highly efficient butanol-producing bacterial microflora (containing mainly Clostridial species) was obtained from hydrogen-producing sewage sludge. In this work, two types of agricultural waste (i.e. rice straw and sugarcane bagasse) were alkaline pretreated and then hydrolyzed using a cocktail of cellulases originating from Pseudomonas sp. CL3 and Clostridium sp. TCW1. The hydrolysates were used to produce biobutanol by the isolated mixture culture using either separate hydrolysis and fermentation (SHF) or a combination of SHF with simultaneous saccharification and fermentation (SHF–SSF) processes. In the SHF process, the maximum butanol concentration, productivity, yield and ABE (acetone–butanol–ethanol) ratio from bagasse were 2.29g/L, 1.00g/Ld, 0.52mol butanol/mol reducing sugar and 0.12:1:0.06, respectively, and for rice straw were 2.92g/L, 1.41g/Ld, 0.51mol butanol/mol reducing sugar and 0.19:1:0.1, respectively. In the SHF–SSF process, the maximum butanol concentration, productivity, and yield for bagasse were 1.95g/L, 0.61g/Ld and 0.37mol butanol/mol reducing sugar, respectively, and for rice straw were 2.93g/L, 0.86g/Ld and 0.49mol butanol/mol reducing sugar, respectively. This work demonstrated a novel and feasible approach of converting agricultural waste into a valuable biofuel (i.e. butanol).

Butanol production from the effluent of hydrogen fermentation

The purpose of the study was to recover butanol from the effluent of the hydrogen-producing bioreactor containing acetate, butyrate, and carbohydrate. The butanol production by Clostridium beijerinckii NRRL B592 was evaluated under both unsterilized and sterilized conditions for examining the potential of butanol production for the practical application. Sucrose of 10 g/L and butyrate of 2 g/L coupled with acetate buffer were used to mimic the effluent. Sucrose was completely consumed in the both unsterilized and sterilized conditions during acetone-butanol-ethanol (ABE) fermentation. However, the results illustrate that the carbohydrate consumption rate in the unsterilized condition was higher than that in the sterilized condition. The maximum butanol concentrations of 3,500 and 3,750 mg/L were achieved in the sterilized and unsterilized conditions, respectively. Meanwhile, it was found that the acetate and the butyrate concentrations of 600 and 1,500 mg/L, and 300 and 1,000 mg/L were ingested to yield butanol in the sterilized condition and in the unsterilized condition, respectively. The results concluded that high levels of acetate and butyrate could eliminate the interference of other microbial populations, resulting in the enrichment of C. beijerinckii NRRL B592 in the fermentor. The butanol production by C. beijerinckii NRRL B592 could be, therefore, produced from the effluent of the hydrogen-producing bioreactor. It promised that the microbial butanol production is one of attractive bioprocesses to recover energy from wastes.

Production of Acetone–Butanol–Ethanol (ABE) in Direct Fermentation of Cassava by Clostridium saccharoperbutylacetonicum N1-4

In this work, acetone-butanol-ethanol (ABE) fermentation characteristics of cassava starch and cassava chips when using Clostridium saccharoperbutylacetonicum N1-4 was presented. The obtained results in batch mode using a 1-L fermenter showed that C. saccharoperbutylacetonicum N1-4 was a hyperamylolytic strain and capable of producing solvents efficiently from cassava starch and cassava chips, which was comparable to when glucose was used. Batch fermentation of cassava starch and cassava chips resulted in 21.0 and 19.4 g/L of total solvent as compared with 24.2 g/L of total solvent when using glucose. Solvent productivity in fermentation of cassava starch was from 42% to 63% higher than that obtained in fermentation using corn and sago starches in the same condition. In fermentation of cassava starch and cassava chips, maximum butanol concentration was 16.9 and 15.5 g/L, respectively. Solvent yield and butanol yield (based on potential glucose) was 0.33 and 0.41, respectively, for fermentation of cassava starch and 0.30 and 0.38, respectively for fermentation using cassava chips.