The moderately halophilic bacterium Nesterenkonia sp. strain F, which was isolated from Aran-Bidgol Lake (Iran), has the ability to produce acetone, butanol, and ethanol (ABE) as well as acetic and butyric acids under aerobic and anaerobic conditions. This result is the first report of ABE production with a wild microorganism from a family other than Clostridia and also the first halophilic species shown to produce butanol under aerobic cultivation. The cultivation of Nesterenkonia sp. strain F under anaerobic conditions with 50 g/l of glucose for 72 h resulted in the production of 105 mg/l of butanol, 122 mg/l of acetone, 0.2 g/l of acetic acid, and 2.5 g/l of butyric acid. Furthermore, the strain was cultivated on media with different glucose concentrations (20, 50, and 80 g/l) under aerobic and anaerobic conditions. Through fermentation with a 50 g/l initial glucose concentration under aerobic conditions, 66 mg/l of butanol, 125 mg/l of acetone, 291 mg/l of ethanol, 5.9 g/l of acetic acid, and 1.2 g/l of butyric acid were produced. The enzymes pertaining to the fermentation pathway in the strain were compared with the enzymes of Clostridium spp., and the metabolic pathway of fermentation used by Nesterenkonia sp. strain F was investigated.
Development of efficient and cost effective pretreatment prior to hydrolysis is essential for the economical production of biobutanol from lignocelluloses. In this study, acetone pretreatment with a number of advantages over the other pretreatments was used to improve enzymatic hydrolysis and fermentation with Clostridium acetobutylicum for acetone-butanol-ethanol (ABE) production from sweet sorghum bagasse (SSB). Using the pretreatment at 180 °C for 60 min, the yield of enzymatic hydrolysis of SSB was improved to 94.2%, leading to a hydrolysate with 36.3 g/l total sugar, which was subsequently fermented to 11.4 g/l ABE. This process resulted in the production of 78 g butanol, 35 g acetone, 12 g ethanol, 28 g acetic acid, and 6 g butyric acid from each kg of SSB. Through the pretreatment, 143 g lignin per kg of SSB was dissolved into the solvent having the potential to be recovered as unaltered pure lignin. Furthermore, the co-production of acetone by the ABE fermentation alleviated the concern of unavoidable solvent loss in the pretreatment, i.e., 24 g acetone/kg SSB, using an integrated process for biobutanol production from SSB. The energy equivalent obtained in the form of butanol and ethanol (72 g gasoline equivalent/kg SSB) was higher than that obtainable via ethanolic fermentation (less than 70 g/kg SSB).
Acetone–butanol–ethanol (ABE) was produced from rice straw using a process containing ethanol organosolv pretreatment, enzymatic hydrolysis, and fermentation by Clostridium acetobutylicum bacterium. Pretreatment of the straw with 75% (v/v) aqueous ethanol containing 1% w/w sulfuric acid at 150 °C for 60 min resulted in the highest total sugar concentration of 31 g/L in the enzymatic hydrolysis. However, the highest ABE concentration and productivity (10.5 g/L and 0.20 g/L h, respectively) were obtained from the straw pretreated at 180 °C for 30 min. Enzymatic hydrolysis of the straw pretreated at 180 °C for 30 min with 5% solid loading resulted in glucose yield of 46.2%, which was then fermented to 80.3 g butanol, 21.1 g acetone, and 22.5 g ethanol, the highest overall yield of ABE production. Thus, the organosolv pretreatment can be applied for efficient production of the solvents from rice straw.
Acetone, butanol, and ethanol (ABE) were produced from softwood pine and hardwood elm using autohydrolysis pretreatment, enzymatic hydrolysis, and fermentation by Clostridium acetobutylicum. The solid residue obtained by autohydrolysis, mainly containing cellulose, was hydrolyzed using a mixture of two commercially available cellulases leading to production of 250 g sugar from each kg pine and 460 g sugar from each kg elm. The fermentation of cellulosic hydrolysates resulted in the production of 79.3 and 117.6 g ABE from each kg of pine and elm, respectively. Through the autohydrolysis, more than 192 g carbohydrate was also released from each kg of the materials in the form of sugars and oligomers into autohydrolysates. Enzymatic hydrolysis of pretreated solid residue in the autohydrolysate liquor resulted in overall hydrolysates with total sugar concentration of more than 21 g/l. In this process, more than 50% of the oligomers of pine autohydrolysate were converted to monomeric sugars and subsequently used for ABE production. Therefore, the fermentation of the overall hydrolysates resulted in the production of 104.5 and 43.4 g ABE from each kg of pine and elm, respectively.
A suitable pretreatment is a prerequisite of efficient acetone-butanol-ethanol (ABE) production from wood by Clostridia. In this study, organosolv fractionation, an effective pretreatment with ability to separate lignin as a co-product, was evaluated for ABE production from softwood pine and hardwood elm. ABE production from untreated woods was limited to the yield of 80 g ABE/kg wood and concentration of 5.5 g ABE/L. Thus, the woods were pretreated with aqueous ethanol at elevated temperatures before hydrolysis and fermentation to ABE by Clostridium acetobutylicum. Hydrolysis of pine and elm pretreated at 180 °C for 60 min resulted in the highest sugar concentrations of 16.8 and 23.2 g/L, respectively. The hydrolysate obtained from elm was fermented to ABE with the highest yield of 121.1 g/kg and concentration of 11.6 g/L. The maximum yield of 87.9 g/kg was obtained from pine pretreated for 30 min at 150 °C. Moreover, structural modifications in the woods were investigated and related to the improvements. The woody biomasses are suitable feedstocks for ABE production after the organosolv pretreatment. Effects of the pretreatment conditions on ABE production might be related to the reduced cellulose crystallinity, reduced lignin and hemicellulose content, and lower total phenolic compounds in the hydrolysates.
Pretreatment with N-methylmorpholine-N-oxide (NMMO), phosphoric acid, and sodium hydroxide was evaluated for improvement of dilute-acid hydrolysis of cotton fiber, the most difficult to break down cellulose. The pretreatments improved the yield of glucose formation by acid hydrolysis. Compared to the other methods, phosphoric acid pretreatment resulted in higher glucose yields and minimal byproduct formations by hydrolysis under milder conditions. Furthermore, the solid residue of the hydrolysis was subjected to enzymatic hydrolysis in order to convert the remaining cellulose to glucose. Different combinations of parameters in dilute-acid and enzymatic hydrolysis were considered for obtaining a high glucose yield with minimal enzyme loading. A process involving phosphoric acid pretreatment, dilute-acid hydrolysis, and enzymatic hydrolysis using only 5 FPU/g cellulase and 10 IU/g β-glucosidase resulted in total glucose yield of 95.4%, and fermentation of the hydrolysates resulted in a yield of 458 g of ethanol/kg of initial cellulose (0.47 g ethanol/g glucose).
Rice straw was hydrolyzed and fermented to acetone, butanol, and ethanol by Clostridium acetobutylicum bacterium. Concentrated phosphoric acid and alkaline treatment with NaOH were used for pretreatment of the straw prior to enzymatic hydrolysis using commercial cellulase and b-glucosidase. The enzymatic hydrolysates were then anaerobically fermented by C. acetobutylicum. Hydrolysis of the alkaline pretreated straw resulted in production of 163.5 g glucose from each kg of untreated rice straw which was then fermented to 45.2 g butanol, 17.7 g acetone, and 1.2 g ethanol. Additionally, concentrated phosphoric acid pretreatment and subsequent hydrolysis resulted in production of 192.3 g glucose from each kg straw from which 44.2 g butanol, 18.2 g acetone, and 0.6 g ethanol were produced after 72 h fermentation. Increasing the produced ABE from less than 10 g to higher than 62 g from each kg straw by the treatments suggested the alkaline and phosphoric acid pretreatments as promising processes for efficient production of ABE from rice straw.
5-Hydroxymethylfurfural (HMF) and furfural, both of which can be derived from renewable sources, are key components for the production of different chemicals and fuels. In this study, rice straw, a cheap, abundant, and mainly unused agricultural waste, is converted to furans by a dilute acid hydrolysis process. The highest yield of HMF in a single-phase hydrolysis was 15.3 g/kg straw, attained at 180 °C during 3 h with 0.5% sulfuric acid, while the maximum yield of furfural, 59 g/kg straw, was obtained at 150 °C during 5 h. Different extracting solvents, including 2-PrOH, 1-BuOH, methyl isobutyl ketone (MIBK), and acetone at 180 °C for 3 h as well as tetrahydrofuran (THF) at 150 °C for 5 h were examined in biphasic systems. Use of the solvents generally improved the production of HMF compared to the single aqueous phase process. The best results of HMF production, more than 59 g/kg straw, were obtained in the systems containing either 2-PrOH or 1-BuOH. Using THF as an extracting solvent, a relatively high furfural yield, 118.2 g/kg straw, was obtained, and 96% of furfural produced in this system was extracted into THF during the process.
Organosolv pretreatment was used to improve solid-state anaerobic digestion (SSAD) form ethane production from three different lignocellulosic substrates (hardwood elm, softwood pine, and agricultural waste rice straw). Pretreatments were conducted at 150 and 180∘C for 30 and 60 min using 75% ethanol solution as an organic solvent with addition of sulfuric acid as a catalyst. The statistical analyses showed that pretreatment temperature was the significant factor affecting methane production. Optimum temperature was 180∘C for elm wood while it was 150∘C for both pinewood and rice straw. Maximum methane production was 152.7, 93.7, and 71.4 liter per kg carbohydrates (CH), which showed up to 32, 73, and 84% enhancement for rice straw, elm wood, and pinewood, respectively, compared to those from the untreated substrates. An inverse relationship between the total methane yield and the lignin content of the substrates was observed. Kinetic analysis of the methane production showed that the process followed a first-order model for all untreated and pretreated lignocelluloses.
The perceived inability to economically provide conventional petroleum to meet the growing energy demands is facing a diverse and broad set of challenges. The major technical and commercial drawbacks of the existing biofuels (bioethanol or biodiesel) have prompted the continuing development of more advanced biofuels such as biobutanol. Acetone–butanol–ethanol (ABE) fermentation is an old process which recently attracted new interests for the production of butanol as an advanced biofuel. Efficient use of low cost lignocellulosic wastes as a carbon source for ABE fermentation can be a proper approach for the economical production of biobutanol. This chapter focuses on the utilization of lignocellulosic materials in ABE fermentation process. It explains the ABE fermentation process especially the processes that were economically used in the Soviet Union, China, and South Africa in the twentieth century. It also summarizes different technologies that have been suggested for the utilization of lignocelluloses for biobutanol production.
Conversion of cellulosic resources to fermentable sugars is a key step in producing renewable fuel and chemicals. In the current study, regeneration of high crystalline cellulose was evaluated as a pretreatment for dilute-acid hydrolysis. The cellulose solvents of N-Methylmorpholine-N-oxide, concentrated phosphoric acid, and Sodium hydroxide were employed for pretreatment of high crystalline cellulose. The regenerated cellulose was consequently considered for dilute-acid hydrolysis. In comparison with other regeneration methods, phosphoric acid pretreatment prior to dilute-acid hydrolysis resulted in higher glucose yields at milder conditions in which least amount of initial cellulose was converted to byproducts.
Dilute acid dehydration of hexoses is a widely applied process for production of 5-Hydroxymethylfurfural (HMF). Fructose dehydration to HMF has higher reaction rates and better selectivity when compared to using glucose. On the othe hand glucose is the preferred feed source for the production of HMF, as it is more abundant and readily available. The efficient production of HMF requires the minimization of unwanted side reactions involving the reactant, the reaction intermediates, and the product. Biphasic systems, in which a waterimmiscible organic solvent is added to extract continuously the HMF from the aqueous phase, offer an important advantage in that the product is separated from the reactant and reaction intermediates and is thereby protected against degradation reactions. In this study, production of HMF from glucose in single and biphasic systems was modeled. Different biphasic systems for dehydration of glucose with 30g/l initial concentration at 180°C, which was catalyzed by 0.5wt% sulfuric acid was compared. Partition coefficent of HMF in organic solvent remarkably affected the yeild of HMF production. Organic solvents with higher HMF partition coefficent resulted in higher HMF concentration in both phase. HMF yeild in the single phase system was 3.3% which was promoted in biphasic systems.
The worldwide dependency on fossil fuels especially on crude oil is increasing; however, being in limited supply, this source of energy and chemicals is leading to a world crisis. Today over 85% of energy and 95% of organic chemicals are supplied from these fossil resources. Moreover, consumption of fossil fuels is responsible for the majority of global warming through emission of carbon dioxide. Cellulose is a sustainable bioresource that can provide renewable fuels and materials. Cellulose is a natural polymer consisting of glucose units. It is abundantly available on earth, and its annual production is estimated at 2×109 tons. Cellulose may be converted to interesting bulk chemicals by acid-catalyzed hydrolysis reaction. During hydrolysis, the β-(1-4)- glycosidic bonds of cellulose are cleaved to give glucose, that can be converted further to various organic (bulk) chemicals. One of these chemicals is 5-Hydroxymethylfurfural (HMF) which is a key component in production of a variety of chemicals and fuels. Dilute acid dehydration of hexoses is a widely applied process for production of HMF. Despite the potential for HMF-based fuels and chemicals, most efforts toward HMF production have used edible starting materials, primarily fructose and glucose. On the other hand an efficient production of HMF directly from cellulose could be more advantageous, that contains some obstacles. Early degradation of HMF in reaction conditions is one of them. HMF can rehydrate, and levulinic and formic acid can be produced. The efficient production of HMF requires the minimization of unwanted side reactions involving the reactant, the reaction intermediates, and the product. Simultaneous extraction of HMF from aqueous phase into an organic phase suggested for conservation of the product. Biphasic systems, in which a water immiscible organic solvent is added to extract continuously the HMF from the aqueous phase, offer an important advantage in that the product is separated from the reactant and reaction intermediates and is thereby protected against degradation reactions. In this study, production of HMF from cellulose in single and biphasic systems was modelled. Different biphasic systems for dehydration of cellulose, which was catalyzed by 0.5wt% sulfuric acid was compared. Effects of different parameters like temperature, retention time and partition coefficient of HMF in organic solvent on the yield of HMF production was investigated. Organic solvents with higher HMF partition coefficient resulted in higher HMF concentration in both phase. Depending on partition coefficient of solvent maximum HMF production in aqueous phase was found at different times. Levulinic acid concentration profile varied by partition coefficient of organic solvent and for solvents with higher partition coefficients lower levulinic acid was produced so lower HMF was degraded in aqueous phase.
The dilute acid hydrolysis of lignocellulosic material is an important part of producing valuable chemicals from lignocellulosis. Penetration of acid into solid phase could be a rate determining step in this process that depends on type and size of lignocellulose, concentration of acid and operating conditions. In this paper we modeled this penetration in four more common lignocellulosis consisting of bagasse, corn stover, rice straw and yellow Poplar. The comparative concentration profile as a function of not only temperature, time and acid concentration but also type and size of lignocellulosic materials was found. Rate of diffusion increases by rising temperature and the rate of diffusion varied with biomass in the order of yellow poplar < bagasse < corn stover < rice straw. In each condition we found critical sizes. For materials coarser than the critical size, diffusion is the rate determining step.
The dilute acid hydrolysis of lignocellulosic material is an important part of producing valuable chemicals from such substrates. Penetration of acid into solid phase could be rate determining step in this process that depends on type and size of substrate, concentration of acid and operating conditions. In this paper we modeled this penetration in four more common substrates consisting of bagasse,corn stover , rice straw and yellow Poplar. In each condition we found critical sizes that for materials with smaller sizes diffusion is the rate determining step.
Lignocellulosic materials are abundant and renewable feedstocks of bioenergy which has recently been used for production of the so-called second-generation biofuels. Pretreatment process is an essential stage to improve the digestibility of lignocellulosic substrates. In this paper, an organosolv process was used to improve the methane yield by solid-state anaerobic digestion (SSAD) of three lignocellulosic substrates (elm, pine wood, and rice straw). To our knowledge, there is no publication on using organosolv pretreatment prior to SSAD. The unique advantage of the organosolv pretreatment is to separate lignin as a value added by product. The Organosolv pretreatment was conducted in four different conditions (at 150 and 180 °C for 30 and 60 min) using 75% ethanol solution on the lignocellulosic materials and the methane production yield through the SSAD was investigated. The results showed that the total methane yield of the pretreated elm, pine, and rice straw was enhanced by 90, 83, and 36%, respectively. The effects of the pretreatment temperature and time on methane yield were also investigated. Statistical analyses showed that the pretreatment temperature was the most influencing factor in the SSAD, while the effect of pretreatment time on methane production from elm, pine, and rice straw was not significant. Almost all of the substrates produced biogases with methane contents between 40% and 50% between day 14 and day 55.
Distillation is the most widely used but the most energy consuming separation process in the chemical industries. In this study distillation unit of LAB production plant was considered. As an idea for reduction of energy consumption, it will be demonstrated theoretically, and shown by simulation means, that if, before entering the unit, the feed is split into two streams, and only one of them is preheated, further savings of energy can be achieved. For observing the effect of feed splitting, the unit was simulated by Hysys. Consequently, Genetic algorithm was applied for minimizing energy consumption. According to the results of this study, 26 percent energy saving was achieved by splitting and preheating feeds of both columns
Hydrodesulfurization (HDS) is a vital process used in producing a clean engine fuels. Dibenzothiophene(DBT) is one of the most refractory sulfur compound in petroleum. There are many researches which are conducted on removal or decreasing this compound. For improving the performance of HDS of DBT, many studies have been performed on different catalyst. HDS of DBT consists of two parallel routes which results in production of Biphenyl (BP) along one route and Cyclohexylbenzene (CHB) along the other. Selectivity in this process is defined based on BP production. In this paper, a mathematical model was applied for HDS of DBT over Co-Mo supported on commercial alumina. The idea of partial separation of BP after using a half-length reactor and consequently performing catalytic reactions in another half-length reactor was investigated by the model. 70% separation of BP resulted in maximum selectivity of 75%, which was 64% without separation. This method also showed increase of 13% in production of BP.
5-Hydroxymethylfurfural (HMF) that is obtained from renewable sources is a key component in production of a variety of chemicals and fuels. HMF could be produced from glucose by dehydration reaction. Unfortunately in the reaction conditions in presence of dilute acid HMF rehydrate and levulinic and formic acid are produced. Simultaneous extraction of HMF from aqueous phase into an organic phase could conserve this valuable product. In this study, production of HMF from glucose in single and biphasic systems was modeled. Different biphasic systems for dehydration of glucose with 30g/l initial concentration at 180°C catalyzed by 0.5wt% sulfuric acid was compared. Partition coefficient of HMF in organic solvent remarkably affected yield of HMF production. Total HMF production respect to partition coefficient of the extracting solvent was found. As an example a solvent with HMF partition coefficient of 7 (e.g. THF) resulted in total HMF yield of 36% which was 3.3% in single phase process.