High Butanol Production Research Articles

AI-based screening of Clostridium acetobutylicum with high furfural tolerance and butanol production

Advances in strain breeding for butanol biosynthesis were quite limited because of physiological complexity of solventogenic Clostridia. Using AI, this study developed a high-throughput screening method for Clostridium acetobutylicum to find strains with inhibitor tolerance and high butanol production. A mutant library was generated from C. acetobutylicum ATCC 824 through ARTP mutagenesis and physiological traits were digitized using color indicators. The classification performance of Machine learning algorithms (PCA, PLS, SVM, ANN) were compared for different butanol-producing strains. Among 2000 strains screened, C. acetobutylicum Tust-f3 was identified, which could tolerate 4.5 g/L furfural and yield 10.5 g/L butanol from undetoxified lignocellulosic hydrolysate. Proteome analysis reveals that 38 proteins may play a crucial role. Subsequently, seven universal detoxification components for furfural were identified via heterologous expression in E. coli Genes CA_RS19590 and CA_RS08810 showed significant growth improvement (14.44 and 14.28-fold, respectively, compared to control). This study highlights the potential of machine learning in strain selection and breeding.

Novel Batch and Repeated-Batch Butanol Fermentation from Sweet Sorghum Stem Juice by Co-Culture of Arthrobacter and Immobilized Clostridium in Scaled-Up Bioreactors

This research aims to study butanol fermentation from sweet sorghum stem juice (SSJ) by immobilized Clostridium beijerinckii TISTR 1461 cells on bamboo chopsticks using Arthrobacter sp. as an efficient bacterium for creating anaerobic conditions in scaled-up bioreactors. For batch culture in a 1-L screw-capped bottle, a butanol concentration (PB), butanol productivity (QB), and butanol yield (YB/S) were 12.09 g/L, 0.26 g/L·h and 0.28 g/g, respectively. These values were ~8 to 14% higher than those of a single culture using oxygen-free nitrogen (OFN) gas to generate anaerobic conditions. When butanol fermentation by the co-culture was scaled-up to 5-L and 30-L stirred-tank fermenters, the butanol production efficiency was not different from that using the 1-L bottles. Additionally, repeated-batch butanol fermentation in the 1-L bottles by the co-culture was successfully operated for four successive cycles with high butanol production. All results clearly indicate that Arthrobacter sp. is promising for creation of anaerobic conditions for butanol production by immobilized Clostridium in large scale bioreactors.

Acetone-Butanol-Ethanol as the Next Green Biofuel - A Review

The development of diesel engines faces challenging targets to satisfy stringent emissions regulation. To address this issue, the use of alcohol biofuels such as methanol and ethanol has attracted numerous attention due to their physicochemical properties and the possibility to be produced from renewable sources and agricultural waste material. Compared to ethanol, longer carbon alcohol such as butanol has higher energy density and lower latent heat, hygroscopicity, aggressivity, and toxicity. It can also be produced from biomass. Yet, despite its noticeable advantages, the use of butanol in the internal combustion engine is hindered by its low production efficiency. If Acetone-Butanol-Ethanol (ABE) is further distilled and purified, pure butanol and ethanol can be acquired, but this involves an energy-intensive process, thus increasing the production cost of butanol. To solve this problem, the direct use of ABE as a biofuel is considered a promising strategy. The idea of using ABE directly in internal combustion engines is then proposed to solve the economic issue of high butanol production costs. A scoping literature review was performed to screen and filter previously published papers on ABE by identifying knowledge gaps instead of discussing what is already known. Therefore, repeated and almost identical studies were eliminated, thus reporting only the most significant and impactful published papers. In terms of the objective, this article aims to review the progress of ABE as a promising biofuel in regard to the engine performance, combustion, and emission characteristics. Focus is also given to ABE’s physicochemical properties. Despite their considerable importance, the fuel properties of ABE are rarely discussed. Therefore, this review article intends to analytically discuss the physicochemical properties of ABE in terms of their calorific value, density, kinematic viscosity, and distillation. In general, it is concluded that engine emissions such as NOx and Particulate Matter (PM) could be reduced considerably with the use of ABE. Yet, the BSFC was found to increase due to the relatively lower calorific value and density of ABE blends as opposed to gasoline or diesel fuel, thereby increasing its fuel consumption. In terms of ABE’s fuel properties, in general, ABE can be used due to its satisfying physicochemical properties. However, it should be noted that the ABE-gasoline/diesel blends are greatly influenced by each of its component ratios (acetone, butanol, ethanol).

Enhanced butanol production in Clostridium acetobutylicum by manipulating metabolic pathway genes

Biobutanol is naturally produced by solventogenic clostridia during acetone-butanol-ethanol (ABE) fermentation, which is hampered by low butanol titer, yield and productivity. Here, Clostridium acetobutylicum ATCC 55025 and its robust mutant HKKO with histidine kinase genes cac3319/cac0323 knockout were metabolically engineered to eliminate acetone formation and improve butanol production. By knocking out acetoacetate decarboxylase gene adc in ATCC 55025 and HKKO, the acetone titer decreased to 0.1 g/L and the butanol/ABE ratio increased by 39.0 % and 40.9 %, respectively. However, the butanol production was limited to ∼11 g/L. To improve butanol production, an alternative strategy was used by overexpressing acetaldehyde/alcohol dehydrogenase gene adhE2 in HKKO, and the mutant produced butanol of 19.7 g/L than that of 18.2 g/L from HKKO with high butanol productivity of 0.41 g/L/h and yield of 0.26 g/g. This study provides novel insights into the roles of adc and adhE2 on butanol biosynthesis and generates a hyper-butanol-producing strain.

High butanol production from galactose riched red seaweed Gracilaria lemaneiformis by solventogenic Clostridium sp. strain NJ4

Butanol can be biosynthesized by solventogenic clostridia from starchy based materials; however, the high substrate costs hinder its further commercial production. Red seaweed, an abundant and renewable bioresource has attracted more attention owing to its fast-growth, high carbohydrates and low lignin contents, such as Gracilaria lemaneiformis. The newly isolated Clostridium sp. strain NJ4 possesses relatively high utilization capacities of various mono-sugars including glucose, xylose and galactose. Furthermore, 17.77 g/L of butanol was produced from the mixed sugar of glucose, galactose and xylose fermentation by using strain NJ4, indicating the promising potential for butanol production from red seaweed by using strain NJ4. After concentration and detoxification of G. lemaneiformis hydrolysate, 43.18 g/L and 47.37 g/L of glucose and galactose were achieved. And 12.56 and 19.86 g/L of butanol and acetone-butanol-ethanol were finally produced by using Clostridium sp. strain NJ4, representing the highest butanol production from G. lemaneiformis hydrolysate.

Comparison of acetone–butanol–ethanol fermentation and ethanol catalytic upgrading as pathways for butanol production: A techno-economic and environmental assessment

Butanol is an important compound used as a building block for producing value-added products and an energy carrier. The main butanol production pathways are conventional acetone–butanol–ethanol (ABE) fermentation and catalytic upgrading of ethanol. On the other hand, the application of biomass as a promising substrate for biofuel production has been widely considered recently. However, few studies have compared different butanol production pathways using biomass as raw material. In light of that, the present work aims (i) to provide a short review of the catalytic ethanol upgrading and (ii) to compare conventional ABE fermentation and catalytic ethanol upgrading processes from the economic and environmental perspectives. Aspen Plus v9.0 was used to simulate both processes. The economic and environmental assessments were carried out considering the Colombian economic context, a gate-to-gate approach, and single impact categories. Considering a processing scale of 1000 ton/d, the conventional ABE fermentation process presented a more favorable technical, economic, and environmental performance for butanol production from biomass. It also offered lower net energy consumption (i.e., 57.9 GJ/ton of butanol) and higher butanol production (i.e., 2.59 ton/h). Nevertheless, the proposed processing scale was insufficient to reach economic feasibility for both processes. To overcome this challenge, the minimum processing scale had to be higher than 1584 ton/d and 1920 ton/d for conventional ABE fermentation and catalytic ethanol upgrading, respectively. Another critical factor in enhancing the economic feasibility of both butanol production pathways was the minimum selling price of butanol. More specifically, prices higher than 1.56 USD/kg and 1.80 USD/kg would be required for conventional ABE fermentation and catalytic ethanol upgrading, respectively. From the environmental impact point of view, the conventional ABE fermentation process led to a lower potential environmental impact than catalytic ethanol upgrading (0.12 PEI/kg vs. 0.18 PEI/kg, respectively).

Quantitative proteomic analysis to reveal expression differences for butanol production from glycerol and glucose by Clostridium sp. strain CT7

Clostridium sp. strain CT7 is a new emerging microbial cell factory with high butanol production ratio owing to its non-traditional butanol fermentation mode with uncoupled acetone and 1,3-propanediol formation. Significant changes of metabolic products profile were shown in glycerol- and glucose-fed strain CT7, especially higher butanol and lower volatile fatty acids (VFAs) production occurred from glycerol-fed one. However, the mechanism of this interesting phenomenon was still unclear. To better elaborate the bacterial response towards glycerol and glucose, the quantitative proteomic analysis through iTRAQ strategy was performed to reveal the regulated proteomic expression levels under different substrates. Proteomics data showed that proteomic expression levels related with carbon metabolism and solvent generation under glycerol media were highly increased. In addition, the up-regulation of hydrogenases, ferredoxins and electron-transferring proteins may attribute to the internal redox balance, while the earlier triggered sporulation response in glycerol-fed media may be associated with the higher butanol production. This study will pave the way for metabolic engineering of other industrial microorganisms to obtain efficient butanol production from glycerol.

Consolidated bioprocessing performance of a two-species microbial consortium for butanol production from lignocellulosic biomass.

Consolidated bioprocessing (CBP) by using microbial consortium was considered as a promising approach to achieve direct biofuel production from lignocellulose. In this study, the interaction mechanism of microbial consortium consisting of Thermoanaerobacterium thermosaccharolyticum M5 and Clostridium acetobutylicum NJ4 was analyzed, which could achieve efficient butanol production from xylan through CBP. Strain M5 possesses efficient xylan degradation capability, as 19.73 g/L of xylose was accumulated within 50 hr. The efficient xylose utilization capability of partner strain NJ4 could relieve the substrate inhibition to hydrolytic enzymes of xylanase and xylosidase secreted by strain M5. In addition, the earlier solventogenesis of strain NJ4 was observed due to the existence of butyrate generated by strain M5. The mutual interaction of these two strains finally gave 13.28 g/L of butanol from 70 g/L of xylan after process optimization, representing a relatively high butanol production from hemicellulose. Moreover, 7.61 g/L of butanol was generated from untreated corncob via CBP. This successfully constructed microbial consortium exhibits efficient cooperation performance on butanol production from lignocellulose, which could provide a platform for the emerging butanol production from lignocellulose.

Synergetic Engineering of Central Carbon, Energy, and Redox Metabolisms for High Butanol Production and Productivity by Clostridium acetobutylicum

Biobutanol, as an advanced biofuel substitute, is reviving via microbial acetone-butanol-ethanol (ABE) fermentation. However, this biochemical process compromises low butanol production and product...

Thermostable, Solvent, Surfactant, Reducing Agent and Chelator Resistant α-Amylase from Bacillus Strain IBT108: A Suitable Candidate Enables One-Step Fermentation of Waste Potato for High Butanol and Hydrogen Production

α-Amylase is the major biocatalyst involved in saccharification process of starch-based biofuel production. Most of the α-amylases reported in literature are not stable and catalytically active in presence of metabolites (biosolvents, and bioacids), and other media components such as salts and reducing agents, hence starch-based biofuels are produced by two-step process of separate hydrolysis by α-amylase, and later the fermentation of biofuel production. Finding new α-amylase with special properties can assist to integrate the process of saccharification and biofuel fermentation. We report a new α-amylase produced from wild type Bacillus strain IBT108. This α-amylase (10.5 U/ml) can be produced from wheat bran (5%) based medium. It can be purified by diethylaminoethyl weak anion exchange-based fast protein liquid chromatography. Purified α-amylase has molecular mass of 68 kDa with a high specific activity (734.8 U/mg), and significant Vmax (1428.6 U/mg) and Km (2.8 mg/ml). Protein fingerprinting analysis reveals that it is a unique member of super-families of AmyAc and MaltAmyC which can act on both α-1,4 and α-1,6-glycosidic linkages of starch. It shows optimal activity at pH 7 and 70 °C, retains 72–92% of its activity in acidic pH range between 4 and 6.5, and stable at 60 °C for 2 h. Notably, it is resistant to 5 mM concentration of urea, dithiothreitol, β-mercaptoethanol, surfactants and EDTA, also shows > 70% of its activity in presence of 1 M solvents. Consequently, adding this α-amylase (2.5–3 U/ml) assists Clostridia to effectively utilize 375 g/l waste potato, and produce high concentration of butanol (20.41–23.74 g/l) and hydrogen (3.20–4.38 l/l).

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.

High butanol production from glycerol by using Clostridium sp. strain CT7 integrated with membrane assisted pervaporation

In this study, a unique butanol-ethanol fermentation process from glycerol integrated with pervaporation by using Clostridium sp. strain CT7 was investigated. 20.4 g/L of butanol and 0.3 g/L of ethanol were produced from 51.3 g/L of glycerol in the PV coupled batch fermentation process with butanol productivity of 0.15 g/L/h and yield of 0.40 g/g due to the reduced butanol inhibition by butanol removal. Subsequently, 41.9 g/L of butanol and 0.4 g/L of ethanol were obtained from 103.3 g/L of glycerol, with butanol productivity of 0.21 g/L/h and yield of 0.41 g/g in the PV coupled fed-batch fermentation process. The high butanol production could be attributed to the thin PDMS layer and negligible transportation resistance of the support. These results indicated the PV coupled fermentation process from glycerol using PDMS/ceramic composite membrane by Clostridium sp. strain CT7 might show a great potential for sustainable biobutanol production from low-cost carbon sources.

Nutrient modulation based process engineering strategy for improved butanol production from Clostridium acetobutylicum.

The present study demonstrates a process engineering strategy to achieve high butanol titer and productivity from wild type Clostridium acetobutylicum MTCC 11274. In the first step, two different media were optimized with the objectives of maximizing the biomass and butanol productivity, respectively. In the next step, attributes of these two media compositions were integrated to design a two-stage fed-batch process which resulted in maximal butanol productivity of 0.55 g L-1 h-1 with titer of 13.1 g L-1 . Further, two-stage fed-batch process along with combinatorial use of magnesium limitation and calcium supplementation resulted in the highest butanol titer and productivity of 16.5 g L-1 and 0.59 g L-1 h-1 , respectively. Finally, integration of the process with gas stripping and modulation of feeding duration resulted in a cumulative butanol titer of 54.3 g L-1 and productivity of 0.58 g L-1 h-1 . The strategy opens up possibility of developing a viable butanol bioprocess. © 2019 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2771, 2019.

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.

Characterization and genome analysis of a butanol\u2013isopropanol-producing Clostridium beijerinckii strain BGS1

BackgroundOne of the main challenges of acetone–butanol–ethanol fermentation is to reduce acetone production with high butanol yield. Converting acetone into isopropanol is an alternative pathway to reduce fermentation by-products in the fermentation broth. Here, we aimed to cultivate a wild-type Clostridium strain with high isopropanol and butanol production and reveal its genome information.ResultsClostridium beijerinckii strain BGS1 was found to be capable of producing 10.21 g/L butanol and 3.41 g/L isopropanol, higher than previously known wild-type isopropanol–butanol-producing Clostridium species. Moreover, culture BGS1 exhibited a broad carbon spectrum utilizing diverse sugars such as arabinose, xylose, galactose, cellobiose, and sucrose, with 9.61 g/L butanol and 2.57 g/L isopropanol generated from 60 g/L sucrose and less amount from other sugars. Based on genome analysis, protein-based sequence of strain BGS1 was closer to C. beijerinckii NCIMB 8052, reaching 90.82% similarity, while compared to C. beijerinckii DSM 6423, the similarity was 89.53%. In addition, a unique secondary alcohol dehydrogenase (sAdhE) was revealed in the genome of strain BGS1, which distinguished it from other Clostridium species. Average nucleotide identity analysis identified strain BGS1 belonging to C. beijerinckii. The transcription profile and enzymatic activity of sAdhE proved its function of converting acetone into isopropanol.ConclusionsClostridium beijerinckii strain BGS1 is a potential candidate for industrial isopropanol and butanol production. Its genome provides unique information for genetic engineering of isopropanol–butanol-producing microorganisms.

Modeling Butanol Synthesis in Xylose by Clostridium saccharoperbutylacetonicum

To examine the effect of xylose concentration on butanol synthesis by Clostridium saccharoperbutylacetonicum, a kinetic model of acetone-butanol-ethanol fermentation in the media with various xylose concentrations (40 g/L to 60 g/L) was developed and implemented in COPASI. Batch fermentation experiments were conducted to feed and validate the model, and the highest butanol production was achieved in 45 g/L xylose medium. Strong correlations (R2 > 0.91) between model simulation and experimental results were obtained. The modeling results suggested that the reaction rates in R6 (from acetate to acetyl-CoA), R8 (from acetyl-CoA to acetoacetyl-CoA), R9 (from acetoacetyl-CoA to butyryl-CoA), R10 (from butyryl-CoA to butanol), R14 (from butyrate to butyryl-CoA), and R20 (xylose consumption) were higher in groups with an initial xylose of 45 g/L, 50 g/L, or 55 g/L than those in groups with 40 g/L or 60 g/L xylose. In contrast, the reaction rates in R13 (from butyryl-CoA to butyrate) and R16 (from biomass to inactive cells) were lower in groups with initial xylose of 45 g/L, 50 g/L, or 55 g/L than those in groups with 40 g/L or 60 g/L xylose, which indicated that when initial xylose concentration changed, those reactions were affected, which resulted in different butanol syntheses.

Phosphoric acid-acetone process for cleaner production of acetone, butanol, and ethanol from waste cotton fibers

Abstract To move biobutanol toward a commercialized biofuel, its production process should be developed based on renewable and cost-effective carbon sources. In this study, it was shown that cotton, a commodity that typically ends in landfill sites or incinerators, can be utilized as a feasible source after the phosphoric acid-acetone process. The treatment with phosphoric acid (19 g/g) resulted in 94% cotton dissolution after 60 min, and the addition of acetone (41 g/g) was accompanied by 97% precipitation. Enzymatic hydrolysis of regenerated cellulose (15 filter paper unit per mL (FPU/mL)) followed by fermentation by Clostridium acetobutylicum resulted in 5.4 g/L acetone-butanol-ethanol (ABE). In this process, 208 g acid and 138 FPU cellulase were used for production of each g ABE. Increasing enzyme dosage to 25 FPU/g resulted in 79% higher butanol production (161 g ABE/kg). Through cyclic acid re-concentration, phosphoric acid consumption decreased to 82 g/g ABE. Furthermore, by applying an additional dilute phosphoric acid pretreatment, the enzyme consumption reduced to 113 FPU/g ABE.

Consolidated bioprocessing of butanol production from xylan by a thermophilic and butanologenic Thermoanaerobacterium sp. M5

BackgroundConsolidated bioprocessing (CBP) has attracted increasing attention since it can accomplish hydrolytic enzymes production, lignocellulose degradation and microbial fermentation in one single step. Currently, biobutanol is mainly produced by mesophilic and solventogenic clostridia, such as Clostridium beijerinckii and C. acetobutylicum, which cannot directly utilize lignocellulose, an abundant, renewable and economic feedstock. Hence, metabolic construction or isolation of novel cellulolytic/hemicellulolytic and solventogenic bacteria to achieve direct butanol production from lignocellulose offers a promising alternative.ResultsIn this study, a newly isolated Thermoanaerobacterium sp. M5 could directly produce butanol from xylan through CBP at 55 °C via the butanol–ethanol pathway. Further genomic and proteomic analysis showed that the capabilities of efficient xylan degradation and butanol synthesis were attributed to the efficient expression of xylanase, β-xylosidase and the bifunctional alcohol/aldehyde dehydrogenase (AdhE). Process optimization based on the characteristic of AdhE could further improve the final butanol titer to 1.17 g/L from xylan through CBP. Furthermore, a new co-cultivation system consisting of Thermoanaerobacterium sp. M5 which could release xylose from xylan efficiently and C. acetobutylicum NJ4 which possesses the capacity of high butanol production was established. This microbial co-cultivation system could improve the butanol titer to 8.34 g/L, representing the highest butanol titer from xylan through CBP.ConclusionsA newly thermophilic and butanogenic bacterium Thermoanaerobacterium sp. M5 was isolated and key enzymes responsible for butanol production were characterized in this study. High butanol titer was obtained from xylan through process optimization. In addition, the newly set up microbial co-cultivation system, consisting of Thermoanaerobacterium sp. M5 and C. acetobutylicum NJ4, achieved the highest butanol production from xylan compared with the reported co-cultivation systems.

High biobutanol production integrated with in situ extraction in the presence of Tween 80 by Clostridium acetobutylicum

Abstract This study investigates the improvement of butanol production in the presence – Tween 80 by Clostridium acetobutylicum NJ4. With supplementation of 15% Tween 80 (v/v), the final butanol titer could be significantly enhanced to 18.65 g/L from 70 g/L glucose, which is 38% higher than that in the control batch (13.47 g/L). With further in situ extraction using biodiesel, the butanol titer was finally improved to 33.90 g/L in the fed batch mode. The supplementation of Tween 80 could improve butanol tolerance of strain NJ4 up to 18 g/L compared to 10 g/L of control. Meanwhile, butanol dehydrogenase activity was improved to 3.89 U/mg, which is 80.93% higher than that of the control. These factors may attribute to the high butanol production. The finding of this study thus offers fundamental knowledge for the future development of alternative ABE production strategies.

Dynamic Nonlinear Feedback Control Applied to Improve Butanol Production by Clostridium acetobutylicum

Abstract The goal of this work is to present a closed-loop operational strategy in order to improve the butanol production in an anaerobic continuous bioreactor for the called Acetone-Butanol-Ethanol (ABE) process. The proposed control scheme considers a class of feedback signal which includes a nonlinear bounded function of the regulation error. The control scheme is applied to a phenomenological unstructured kinetic model obtained from an experimental and metabolic study of butanol production by Clostridium acetobutylicum, which allows the proposed structure to predict several operational conditions from batch and continuous regimes. Numerical experiments using the proposed model considering continuous operation were performed in order to find a feasible operating region for maximum butanol production at open-loop regime. The proposed methodology is applied to regulate the product concentration, manipulating the dilution rate to lead to a higher butanol productivity. The closed-loop behaviour of the bioreactor is analysed, finding that the proposed controller minimizes the response time of the system and allows it to achieve a productivity gain of 55 % over open-loop operation. Further numerical experiments show the satisfactory closed-loop performance of the proposed methodology in comparison with a PI controller.