Butanol production by clostridium acetobutylicum in a series of packed biofilm bed reactors

The reactor design plays a key role in the fermentative production of biobutanol. The high cell concentration that may be reached in confined – biofilm, membrane, recycling - cell reactors offers high conversion rates. To the authors knowledge, the concentration of solvents in the broth from biofilm reactors reported in literature is not particularly high and it negatively affects the successive stages for butanol recovery. The low concentration of solvents in the produced stream is typically due to the inhibitory effect of solvents on the fermentation. Therefore, the butanol bioreactor productivity is as low as the bioreactor behaviour approaches the CSTR limit. The aim of this contribution is to report recent results on the design of a continuous biofilm reactor to optimize the process performances. Clostridium acetobutylicum DSM 792 was adopted for the fermentation process. The conversion was carried out in 4 packed bed reactors (PBRs) connected in series: the first reactor of the series was kept under acidogenesis and the successive reactors were kept under solventogenesis. Tests were carried out feeding the reactor system with solutions bearing glucose. Please click Additional Files below to see the full abstract

Biobutanol production from high sugar content wastewaters

Over the last decade, the depletion of oil resources and concerns regarding both economic and environmental issues associated with petroleum-based fuels have renewed interests in biofuel production from renewable resources . Industrial and academic researches have paid attention to the development of (bio)sustainable processes and to the produce biofuels by conversion of renewable feedstoks. The spectrum of biofuels includes the butanol, a simple four carbon alcohol characterized by interesting features. A biotechnological route to produce butanol is based on the fermentation of clostridia: saccharolytic butyric acid-producing bacteria able to produce acetone-butanol-ethanol (ABE) by fermentation adopting a wide spectrum of carbohydrates, typically present in renewable unexpensive feedstocks. This contribution reports about a study on the feasibility of bio-butanol production by fermentation of high-sugar content beverages (HSCBs). The anaerobic solventogenic bacterium Clostridium acetobutylicum DSM 792 was adopted for the fermentation process. Commercial pineapple juice, lemon syrup and tonic water were tested as substrate for the fermentation. Preliminary tests pointed out that: i) the microorganism did not grow on any of the HSBCs investigated without complex medium supplementation; ii) the conversion degree of sucrose was quite low. Therefore, tests were carried out with broth made of the complex medium and HSCB pre-idrolized (sucrose idrolized to glucose and fructose)

Special Issue on “Bioreactor System: Design, Modeling and Continuous Production Process”

Biochemical engineering deals with the processing of biological or chemical materials using enzymes or living cells as biological catalysts. At a central position in a biotechnolog- ical process is the bioreactor. The term bioreactor refers to a device, or system that contains substrates and enzymes or cells as biocatalysts and provides an environment in which the biocatalysts can perform their functions. The characteristics of enzyme biocatalysts resemble more or less those of chemical catalysts in that their activities degrade with time, whereas cells are self-multiplying living systems. Both types of biocatalysts have undergone successful developments in producing various product

BUTANOL PRODUCTION BY FERMENTATION OF RENEWABLE FEEDSTOCKS

The study carried out during the present Ph.D. program aimed at investigating the Acetone-Butanol-Ethanol (ABE) production process by fermentation. The work was carried out at the Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale of the University of Naples ‘Federico II’. The activities were articulated according to three paths: i) the characterization of the ABE fermentation process as regards kinetics and yields using different renewable resources (lignocellulosic biomass, high sugar content beverges and cheese whey); ii) the characterization of the ABE fermentation process according to the metabolic flux analaysis (MFA) and to the dynamic kinetic models; iii) the development of innovative continuous biofilm reactor for the ABE production. A commercial clostridia strain was investigated. Clostridium acetobutylicum DSM 792 was selected for its ability to produce ABE with satisfactory selectivity towards the butanol. The ABE fermentation process by adopting renewable resources. Characterization in terms of kinetics and yields. The study was aimed at the assessment of both the kinetics and the yields of cell growth and metabolites produced during the fermentation of: • sugars representative of hydrolized lignocellulosic biomass fermentation (glucose, mannose, arabinose and xylose); • sugars representative of high sugar content beverages (glucose, fructose and sucrose); • High sugar content beverages. Batch cultures of free C.acetobutyicum cells were inveastigated. Tests were focused on the preliminary characterization of the fermentation with the aim of highlighting the relevant features of the process. The fermentation was characterized in terms of kinetics and yields under a wide interval of operating conditions (substrate concentration, nutrient concentrations, ...). Characterization of the ABE fermentation process. MFA and dynamic kinetic models. The MFA and the kinetic dynamic methodology were adopted to characterize the ABE fermentation. Selected batch fermentation tests were carried out with the aim to charcaterize the time-evolution of the concentration of substrate, cells and metabolities. Tests were carried out at initial sugar concentration 60 g/L. The time- series of concentration were processed according the MFA and the kinetic model methodology. In particular: • the MFA was adopted to investigate the role of the main reaction steps of the Clostridium acetobutylicum metabolic pathway to convert reference sugars (glucose and xylose) of hydrolyzed lignocellulosic biomass into butanol. Results of batch fermentation tests carried out using glucose and xylose as carbon source were adopted for the flux assessment. The stoichiometric matrix of the model was characterized by a singularity that prevented the assessment of a unique set of fluxes of the primary metabolic activity. The non linear constrain proposed by Desai et al. (1999) relating the acetate and butyrate uptake fluxes was adopted to solve the model equation set. The MFA was proposed with reference to glucose and xylose as carbon source. The comparison of the assessed fluxes suggested the role of each reaction step as a function of the carbon source investigated. 5 • A kinetic dynamic model of acetone–butanol–ethanol (ABE) production by Clostridium acetobutylicum DSM 792 was proposed using the biochemical networks simulator COPASI. Effects of substrate were studied implementing the model with different sugars: glucose, mannose, fructose, sucrose, lactose, xylose and arabinose. If necessary, the metabolic pathway was modified according to the specific sugar. In particular, the Embden-Meyerhof-Parnas (EMP) pathway equations were used for hexose and disaccharide sugars while the pentose phosphate (PP) pathway equations were used for pentose sugars. Development of innovative continuous biofilm reactor for the ABE production. The study was aimed at the assessment of the butanol production in a C. acetobutylicum biofilm reactor. The activity aimed at the butanol production regarded the design, set-up and operation of a biofilm fixed bed reactor. Unsupplemented cheese whey was adopted as renewable feedstock. Operating conditions of the continuous tests were selected to maximize the butanol production and butanol selectivity. In particular, main activities were: § The selection of a pre-treatment process of the cheese-whey coupled with fermentation tests carried out under batch conditions to assess effects of the pre-treatment on fermentation performances; § Tests with the pre-treated cheese whey to characterize the fermentation process in terms of butanol production and butanol selectivity; § Design, set-up, and optimization of a fixed bed biofilm reactor for cheese whey conversion; § Tests with the biofilm reactor under continuous conditions. The success of operation of the Packed Bed Reactor (PBR) has fuelled the development of an innovative continuous biofilm reactor configuration: “carosello” of packed bed biofilm reactors connected in series. The reactor system has been equipped with a device to switch the feeding at the reactor according to a pre-set sequence. A mathematical model to support the bioreactor system design was developed

Special Issue on “Bioreactor System: Design, Modeling and Continuous Production Process”

Biochemical engineering deals with the processing of biological or chemical materials using enzymes or living cells as biological catalysts [...

Clostridium acetobutylicum Fermentation on Lignocellulosic-based Hexoses and Pentoses for Butanol Production

The Acetone-Butanol-Ethanol (ABE) fermentation is receiving renewed interest as a way to upgrade renewable resources into valuable base chemicals and liquid fuels. Abundance and un-competitiveness with food sources are desired features of a potential substrate, and they are met by lignocellulosic biomass. Lignocellulosic biomass may be fermented provided that the hydrolysis in simple sugars – hexoses and pentoses - is carried out (Qureshi, Biopr Biosyst Eng, 2007, 30, 419). Although some reports on ability of Clostridium strains are available in scientific literature, no systematic investigation has been carried out. This contribution is about the characterization of the ABE fermentation by C. acetobutylicum DSM 792 using sugars representative for hydrolysis products of lignocellulosic biomass: hexoses (glucose and mannose) and pentoses (arabinose and xylose). Batch fermentations of single sugars were carried out. The conversion process was characterized as a function of time in terms of biomass, acids and solvents concentrations, pH, and total organic compounds. Effects of CaCO3 supplement to the fermentation broth were investigated. The fermentation performance of the investigated sugars decreases in the order glucose, mannose, arabinose, and xylose. The poor performance when using xylose can be explained on a metabolic level by various hypotheses: additional energy demand from H+ dependent symport of xylose into cells; inhibition or operon repression by other substrates or products (sugars/acids/solvents) (Ounine et al., Appl Environ Microbiol 1985, 49, 874); metabolic bottleneck in regeneration within the sugar conversion pathway by glyceraldehyde-3-P, which is a substrate for many other, competing reactions; metabolic bottleneck in availability of transketolase, this enzyme catalyzes two reactions. The CaCO3 supplementation improves the fermentation performance in terms of both the conversion degree of the substrate and the final solvent concentration

Bioreactors for succinic acid production processes

Succinic acid (SA) has been recognized as one of the most important bio-based building block chemicals due to its numerous potential applications. Fermentation SA production from renewable carbohydrate feedstocks can have the economic and sustainability potential to replace petroleum-based production in the future, not only for existing markets, but also for new larger volume markets. Design and operation of bio-reactors play a key role. During the last 20 years, many different fermentation strategies for SA production have been described in literature, including utilization of immobilized biocatalysts, integrated fermentation and separation systems and batch, fed-batch, and continuous operation modes. This review is an overview of different fermentation process design developed over the past decade and provides a perspective on remaining challenges for an economically feasible succinate production processes. The analysis stresses the idea of improving the efficiency of the fermentation stage by improving bioreactor design and by increasing bioreactor performance.</p

Butanol production by clostridium acetobutylicum in a continuous packed bed reactor fed with cheese whey

This research work reports on the feasibility of bio-butanol production by fermentation of cheese whey in a continuous packed bed reactor (PBR). The anaerobic solventogenic bacterium Clostridium acetobutylicum DSM 792 was adopted for the fermentation processes and commercial cheese whey powder was adopted as substrate. The fermentation plant consisted of a PBR, liquid pumps, a thermostatic unit, and a pH control unit. The PBR was a 4 cm ID, 16 cm high glass tube with a 8 cm bed of 3 mm Tygon rings, as carriers. The pH ranged between 4.5 and 5.5, the dilution rate (D) between 0.4 h-1 and 0.64 h-1. The PBR feedstock was a solution of deproteinized cheese whey powder. Results show that the best performance (butanol productivity 2.66 g/Lh, butanol concentration 4.93 g/L, butanol yield 0.26 g/g, butanol selectivity of the overall solvents production 82%w) was at D=0.54 h-1. Copyright �� 2013, AIDIC Servizi S.r.l

Techno-economic analysis of a Butanol recovery process based on gas stripping technique

Acetone-Butanol-Ethanol (ABE) industrial production by fermentation is strongly affected by the low concentration of solvent (<25 g/L) that affects the cost of the recovery process. To decrease the overall cost of the butanol production, alternative routes for the recovery have proposed in literature. This paper presents a techno-economic analysis of an innovative butanol recovery process from ABE fermentation broth based on gas stripping technique. The comparison with a recovery process based on conventional distillation is also presented. The investigated recovery line included gas stripping, absorption of butanol in a selected solvent, and distillation to separate the butanol from the selected liquid. The proposed and the conventional processes were modelled by means of the commercial software Aspen Plus to assess energy and material balances. The estimation of the investment cost was carried out by using Aspen Icarus and approximated methodologies typical of the process engineering. Gas stripping flow rate, solvent flow rate, and feed preheating temperature were explored as design variables. The effect of the butanol concentration in the typical fermentation broth was also presented and discussed. From the economic point of view, the proposed process was the most convenient to recover butanol from fermentation broth. The incidence of the recovered section on the assessed butanol production cost by fermentation ranged between 0.33 and 0.92 $/kg, when butanol concentration in the fermentation broth changed in the interval 5-18 g/L