2,182 research outputs found
Special Issue on “Bioreactor System: Design, Modeling and Continuous Production Process”
No full textBiochemical engineering deals with the processing of biological or chemical materials using enzymes or living cells as biological catalysts [...
Special Issue on “Advances in Bioprocess Technology”
No full textThis Special Issue, “Advances in Bioprocess Technology”, focuses on the latest advancements in sustainable bioprocess technologies [...
MFA of Clostridium acetobutylicum pathway: the role of glucose and xylose on the acid formation/uptake
No full textThe concerns regarding energy and environmental issues have revalued the interest in the use of biomass as a renewable energy source. According to this scenario, studies have bloomed in the scientific literature regarding the production of energy vectors from a wide spectrum of biomass. Solvent-producing clostridia could produce acetone, butanol, and ethanol (ABE) from several biomasses such as palm oil waste (Lee et al., 1995), agro-industrial waste(water)s (Raganati et al., 2013), and agricultural crops (Qureshi et al., 2001). The remarkable features of the butanol – e.g. hydrophobicity, high energy density, storage and transportation consistent with current structures – make this alcohol a potential substitute and/or supplement of gasoline (Table 1) (Cascone, 2008; Masiero et al., 2011)
Techno-economic analysis of a Butanol recovery process based on gas stripping technique
No full textAcetone-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
Biosuccinic Acid from Lignocellulosic-Based Hexoses and Pentoses by Actinobacillus succinogenes: Characterization of the Conversion Process
No full textSuccinic acid (SA) is a well-established chemical building block. Actinobacillus succinogenes fermentation is by far the most investigated route due to very promising high SA yield and titer on several sugars. This study contributes to include the SA production within the concept of biorefinery of lignocellulose biomass. The study was focused on the SA production by A. succinogenes DSM 22257 using sugars representative from lignocellulose hydrolysis— glucose, mannose, arabinose, and xylose—as carbon source. Single sugar batch fermentation tests and mixture sugar fermentation tests were carried out. All the sugars investigated were converted in succinic acid by A. succinogenes. The best fermentation performances were measured in tests with glucose as carbon source. The bacterial growth kinetics was characterized by glucose inhibition. No inhibition phenomena were observed with the other sugar investigated. The sugar mixture fermentation tests highlighted the synergic effects of the copresence of the four sugars. Under the operating conditions tested, the final concentration of succinic acid in the sugar mixture test was larger (27 g/L) than that expected (25.5 g/L) by combining the fermentation of the single sugar. Moreover, the concentration of acetic and formic acid was lower, consequently obtaining an increment in the succinic acid specificity
Improving Microalgae Feasibility Cultivation: Preliminary Results on Exhausted Medium Reuse Strategy
No full textAlthough microalgae exploitation is very promising, process sustainability is undermined by biomass production and harvesting. Among the various bottlenecks of the production process, particular attention should be paid to the water footprint. Indeed, a huge volume of water is required in microalgae production. Water reuse can support both the water footprint and medium cost reduction, saving water and unconverted substrates. The present study reports preliminary results regarding the utilization of a water reuse strategy for two Chlorophyta microalgae under batch conditions. Growth parameters and chlorophyll content are monitored and the optimal amount of reused medium is assessed. The results show that 70% of the medium can be reused with no loss of specific growth rate and chlorophyll fraction for Pseudococcomyxa simplex in three consecutive batch cultivations. By contrast, a significant decline in Chlorella vulgaris growth was observed after the first cultivation in reused medium, across all tested conditions
Butanol production from hexoses and pentoses by fermentation of Clostridium acetobutylicum
No full textThe present paper reports the characterization of ABE (acetone-butanol-ethanol) production by Clostridium acetobutylicum DSM 792 for sugars representative of hydrolysed lignocellulosic biomass (glucose, mannose, arabinose, xylose). The attention was focused on: the selection of an optimal medium for the simultaneous conversion of the investigated sugars; the assessment of interference-synergistic effects during the fermentation of mixtures of the investigated sugars. The synthetic medium was optimised in terms of nutritional factors: the KH2PO4-K2HPO4 concentration was increased up to 5 g/L; the MgSO4 concentration was increased up to 2 g/L; the MnSO4 concentration was increased up to 0.1 g/L; the FeSO4 concentration ranged between 0.002 and 0.01 g/L); the CaCO3 concentration was increased up to 10 g/L. The optimal concentration of the investigated factors was assessed and it varied from one sugar to another. The batch fermentations of a mixture of the four sugars highlighted their synergistic effects. Once set the initial concentration of the sugars (60 g/L), the butanol and solvent concentration increased up to 14.6 and 20.6 g/L, respectively, when the four sugars were present
Production of Alcohols from C1-waste Gas Fermentation by Clostridium carboxidivorans in a Continuous Gas Fed Bioreactor
No full textSyngas – a gas mixture of CO, CO2, and H2 – can be produced by gasification of C-based streams (e.g. biomass, plastics). It is as a cost-effective substrate for the production of numerous valuable products. Some microorganisms can thrive using CO or syngas as carbon and energy source, and just a few strains are able to converting CO/syngas into biofuels. Clostridium carboxidivorans is a microorganism known for its ability to produce short- and long-chain acids and alcohols, including acetic acid, butyric acid, hexanoic acid, ethanol, butanol and hexanol. This contribution focuses on characterizing CO fermentation by C. carboxidivorans in a continuous gas-fed bioreactor. The bioreactor was continuously supplied with a 100% CO stream at a flow rate of 0.6 L/h. Fermentation tests were carried out at constant temperature with an without pH control. The fermentation process was characterized in terms of metabolites and cell production, CO conversion, specific rate of cells/metabolite production and yields. Ethanol was the primary solvent produced and a shift towards longer-chain alcohols was observed under constant pH. The maximum cell concentration was 0.56 gDM/L with and without pH control. The highest solvent concentrations was 1820 mg/L of ethanol without pH control, and 330 mg/L of butanol and 20 mg/L of hexanol with pH control. The study highlithed the role of the substrate composition and the operating conditions on syngas. The reported results provides a first guidline for syngas fermentation for the production of biofuels and chemicals
Clostridium acetobutylicum Fermentation on Lignocellulosic-based Hexoses and Pentoses for Butanol Production
No full textThe 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
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