H‐B‐E (hexanol‐butanol‐ethanol) fermentation for the production of higher alcohols from syngas/waste gas

CO, H₂, and CO₂ are major components of syngas and some industrial CO‐rich waste gases (e.g. waste gases from steel industries), besides some additional minor compounds. It was recently shown that those gases can be bioconverted, by acetogenic/solventogenic bacteria, into ethanol and higher alcohols such as butanol, but also hexanol, through the so‐called HBE fermentation. That process presents some advantages over existing chemical conversion processes. This paper reviews HBE fermentation from C1‐gases after briefly describing the more conventional ABE (acetone‐butanol‐ethanol) fermentation from carbohydrates by Clostridium acetobutylicum, in order to allow for comparison of both processes. Although acetone may appear in carbohydrate fermentation, alcohols are the only major end‐metabolites in the HBE process with Clostridium carboxidivorans. The few acetogenic bacteria known to metabolize C1‐gases and produce butanol or higher alcohols are described. Clostridium carboxidivorans has been used in most cases. Bioconversion of the gaseous substrates takes place in two stages, namely acidogenesis (production of acids) followed by solventogenesis (production of alcohols), characterized by different optimal fermentation conditions. Major parameters affecting each bioconversion stage as well as the overall fermentation process are analyzed. Although it has been claimed that acidification is required in ABE fermentation to initiate the solventogenic stage, strong acidification seems to some extent not to be a prerequisite for solventogenesis in the HBE process. Bioreactors potentially suitable for this type of bioconversion process are described as well. © 2017 Society of Chemical Industry     

Purified Butanol from Lignocellulose – Solvent-Impregnated Resins for an Integrated Selective Removal

In traditional microbial biobutanol production, the solvent must be recovered during fermentation process for a sufficient space-time yield. Thermal separation is not feasible due to the boiling point of n-butanol. As an integrated and selective solid-liquid separation alternative, solvent impregnated resins (SIRs) were applied. Two polymeric resins were evaluated and an extractant screening was conducted. Vacuum application with vapor collection in fixed-bed column as bioreactor bypass was successfully implemented as butanol desorption step. In course of further increasing process economics, fermentation with renewable lignocellulosic substrates was conducted using Clostridium acetobutylicum. Utilization of SIR was shown to be a potential strategy for solvent removal from fermentation broth, while application of a bypass column allows for product removal and recovery at once.     

Effects of carbon source and metabolic engineering on butyrate production in <Emphasis Type="Italic">Escherichia coli</Emphasis>

Butyrate was produced in recombinant Escherichia coli strains by applying metabolic engineering strategies. The genes for producing butyrate were cloned from Clostridium acetobutylicum and then expressed in E. coli. To study important factors for improving the productivity of butyrate, we deleted pta and ptsG genes in E. coli and compared the effects of these gene deletions in E. coli B and K strains. The effect of carbon sources, glucose and glycerol, was also compared. A significant improvement of butyrate production was made when glycerol was used as a carbon source, resulting in 0.56 g/l of butyrate in LB medium with 1% (v/v) glycerol.     

Isolation,Screening, and Characterization of Naphthalene-Degrading Bacteria from Zarand Mine,Iran

ABSTRACT

PAHs are aromatic hydrocarbons with two or more fused benzene rings. They are formed during the thermal breakdown of organic molecules and their succeeding recombination. Naphthalene is the simplest (PAHs) that is carcinogenic. Bioremediation method is considered as an economical and safe approach for the elimination of aromatic compounds from environment. The bacteria were capable to grow on various hydrocarbons like naphthalene. The aim of this research is to isolate and identify naphthalene-degrading bacteria from the coal mine of Zarand. Four samples of water and sludge from various sites of the mine were collected. These sites include the following: Main coal vacate site (MC), Inoculum Sump site (IB), Sludge aggregate site (SA), and Near sludge aggregate site (NF). In this study, 12 bacterial strains that utilize naphthalene at initial concentration 200 mg/L (ppm) as carbon and energy sources for growth were isolated from the Zarand mine in Iran. In addition, bacterial cell density was assayed by measuring the OD₆₀₀. In addition, total naphthalene-degrading bacteria were quantified with the most probable number (MPN) procedure using microtiter plates and the colony-forming unit (CFU) method. The results had shown that most of the naphthalene degrader bacteria aggregated in (SA) site. Six bacteria, isolated from wastewater and oil-contaminated soil showed great potential as naphthalene degraders up to 400 (ppm) and selected for biochemical characteristics. Naphthalene tolerance of the strains in various concentrations of naphthalene indicates that the strain 38 N can grow best at 600 (ppm) naphthalene. This strain was identified based on 16S rRNA gene analysis that showed belonging to Sphingobacterium multivorum AHB38N.     

Improvement of mono and diacylglycerol production via enzymatic glycerolysis in tert‐butanol system

In this work we report experimental data regarding the glycerolysis of olive oil using Novozym 435 in tert‐butanol organic system aiming at the production of monoacylglycerols (MAG) and diacylglycerols (DAG). Experiments were performed in batch mode, recording the reaction kinetics and evaluating the effects of temperature, enzyme concentration, tert‐butanol:oil/glycerol volume ratio and using solvent to substrates ratio of 1:1 and 5:1 v/v. Experimental results showed that lipase‐catalyzed glycerolysis in tert‐butanol might be a potential route for the production of high contents of MAG and DAG. The results also showed that it is possible to maximize the production of MAG and/or DAG, depending on the glycerol to oil molar ratio employed in the reactional system. Higher contents of MAG (53 wt%) and DAG (50 wt%) were achieved using glycerol to oil molar ratio of 3:1/6:1 and 0.5:1.5, respectively, both in 8 h of reaction at 70°C, 600 rpm and enzyme concentration of 10 wt%.     

Assessment of in situ butanol recovery by vacuum during acetone butanol ethanol (ABE) fermentation

BACKGROUND: Butanol fermentation is product limiting owing to butanol toxicity to microbial cells. Butanol (boiling point: 118 °C) boils at a higher temperature than water (boiling point: 100 °C) and application of vacuum technology to integrated acetone–butanol–ethanol (ABE) fermentation and recovery may have been ignored because of direct comparison of boiling points of water and butanol. This research investigated simultaneous ABE fermentation using Clostridium beijerinckii 8052 and in situ butanol recovery by vacuum. To facilitate ABE mass transfer and recovery at fermentation temperature, batch fermentation was conducted in triplicate at 35 °C in a 14 L bioreactor connected in series with a condensation system and vacuum pump. RESULTS: Concentration of ABE in the recovered stream was greater than that in the fermentation broth (from 15.7 g L^?1 up to 33 g L^?1). Integration of the vacuum with the bioreactor resulted in enhanced ABE productivity by 100% and complete utilization of glucose as opposed to a significant amount of residual glucose in the control batch fermentation. CONCLUSION: This research demonstrated that vacuum fermentation technology can be used for in situ butanol recovery during ABE fermentation and that C. beijerinckii 8052 can tolerate vacuum conditions, with no negative effect on cell growth and ABE production. Copyright © 2011 Society of Chemical Industry     

Membrane Vesicles of Pectobacterium as an Effective Protein Secretion System

Bacteria of genus Pectobacterium are Gram-negative rods of the family Pectobacteriaceae. They are the causative agent of soft rot diseases of crops and ornamental plants. However, their virulence mechanisms are not yet fully elucidated. Membrane vesicles (MVs) are universally released by bacteria and are believed to play an important role in the pathogenicity and survival of bacteria in the environment. Our study investigates the role of MVs in the virulence of Pectobacterium. The results indicate that the morphology and MVs production depend on growth medium composition. In polygalacturonic acid (PGA) supplemented media, Pectobacterium produces large MVs (100–300 nm) and small vesicles below 100 nm. Proteomic analyses revealed the presence of pectate degrading enzymes in the MVs. The pectate plate test and enzymatic assay proved that those enzymes are active and able to degrade pectates. What is more, the pathogenicity test indicated that the MVs derived from Pectobacterium were able to induce maceration of Zantedeschia sp. leaves. We also show that the MVs of β-lactamase producing strains were able to suppress ampicillin activity and permit the growth of susceptible bacteria. Those findings indicate that the MVs of Pectobacterium play an important role in host-pathogen interactions and niche competition with other bacteria. Our research also sheds some light on the mechanism of MVs production. We demonstrate that the MVs production in Pectobacterium strains, which overexpress a green fluorescence protein (GFP), is higher than in wild-type strains. Moreover, proteomic analysis revealed that the GFP was present in the MVs. Therefore, it is possible that protein sequestration into MVs might not be strictly limited to periplasmic proteins. Our research highlights the importance of MVs production as a mechanism of cargo delivery in Pectobacterium and an effective secretion system.     

Uptake of organic acids byClostridium acetobutylicum B18 under controlled pH and reduced butanol inhibition

Uptake of organic acids byClostridium acetobutylicum B18 was studied at controlled pH and under reduced butanol inhibition conditions. A pervaporative membrane module was placed in the fermentor to remove butanol from the fermentation broth. Uptake of added butyric acid followed zero order kinetics at pH 4.75 and first order kinetics at pH 5.75. At pH 5.25 the kinetic order shifted from zero to first order as the butyric acid was taken up. At the point of order shift undissociated butyric acid (UBA) concentration was approximately 0.5 g/L. Unlike butyric acid, uptake of acetic acid followed first order kinetics regardless of pH. The difference in acid uptake kinetics could be explained by the combined effect of acid diffusion across the cell membrane and intracellular enzymatic reaction. The acid concentration for kinetic order shift seemed to be dependent upon pH and the kind of the acid used. Glucose was consumed simultaneously with added acids. Both butyric and acetic acids were taken up simultaneously but the rate was faster for butyric acid. Added butyric acid was completely assimilated whereas acetic acid uptake was incomplete.     

Effects of Organic and N Fertilizers on Methane Production Potential in a Chinese Rice Soil and its Microbiological Aspect

An incubation experiment to determine the effects of organic and chemical N fertilizers on methane (CH₄) production potential in a Chinese flooded rice soil was conducted. Organic matter, added as rice straw and organic manure, increased CH₄ production rate significantly. Chemical N fertilizers such as ammonium bicarbonate (AB), modified ammonium bicarbonate (MAB), and urea (U) did not show a clear effect when they were applied with rice straw. Field results may be very different because of the involvement of rice plants. Organic manure showed different promoting effects on CH₄ production rate. Pig manure stimulated the production rate most, followed by chicken and cattle manure. This difference in organic manure was not related to either total C added to the system or to C/N. The study on bacteria groups related to CH₄ production indicated that the different effects of organic matter may be closely related to content of easily decomposable organic matter. A significant linear relationship between CH₄ production and the logarithm of the number of zymogenic bacteria was found with an r value of 0.96. This finding suggests that the number of zymogenic bacteria may be used as an index to predict CH₄ production potential in flooded rice fields and other wetlands.     

Adsorption of butanol from aqueous solution onto a new type of macroporous adsorption resin: Studies of adsorption isotherms and kinetics simulation

BACKGROUND: Owing to the rapid depletion of petroleum fuel, the production of bio‐butanol has attracted much attention. However, low butanol productivity severely limits its potential industrial application. It is important to establish an approach for recovering low‐concentration butanol from fermentation broth. Experiments were conducted using batch adsorption mode under different conditions of initial butanol concentration and temperature. Batch adsorption data were fitted to Langmuir and Freundlich isotherms and the macropore diffusion, pseudo‐first‐ and second‐order models for kinetic study. RESULTS: The maximum adsorption capacity of butanol onto KA‐I resin increase with increasing temperature, ranged from 139.836 to 304.397 mg g^?1. The equilibrium adsorption data were well fitted by the Langmuir isotherm. The adsorption kinetics was more accurately represented by the macropore diffusion model, which also clearly predicted the intraparticle distribution of the concentration. The effective pore diffusivity (D_p) was dependent upon temperature, but independent of initial butanol concentration, and was 0.251 × 10^?10, 0.73 × 10^?10, 1.32 × 10^?10 and 4.31 × 10^?10 m² s^?1 at 283.13, 293.13, 303.13 and 310.13 K, respectively. CONCLUSION: This work demonstrates that KA‐I resin is an efficient adsorbent for the removal of butanol from aqueous solutions and available for practical applications for future in situ product recovery of butanol from ABE fermentation broth. Copyright © 2012 Society of Chemical Industry     

Experimental Investigation and Thermodynamic Modeling of Glycerin/Methanol/Organic Solvent Systems

Glycerin is an important by‐product in biodiesel production. To increase its quality to be suitable for use it in other operations, e.g., the pharmaceutical industry, it needs to be purified. Therefore, the purification of glycerin by liquid‐liquid extraction of methanol using different solvents was investigated. It was shown that, in terms of separation, petroleum ether was more effective than toluene and toluene was more effective than n‐butanol. In addition to the experimental investigations, the NRTL and UNIQUAC thermodynamic models were used to predict the compositions of ternary mixtures of glycerin + methanol + organic solvent in glycerin‐rich and organic solvent‐rich phases. The results showed the high accuracy of the presented models and their consistency with the measured data.     

Pervaporation of organic compounds from aqueous mixtures using polydimethylsiloxane‐containing block copolymer membranes

Pervaporation of aqueous mixtures of ethanol, acetone, butanol, isobutanol, and furfural through polystyrene‐b‐polydimethylsiloxane‐b‐polystyrene (SDS) triblock copolymer membranes is reported. These mixtures are important for biofuel production from lignocellulosic feedstocks. Feedstock depolymerization results in the formation of furfural which must be removed before fermentation. Ethanol, butanol, isobutanol, and acetone are important fermentation biofuels. The membrane selectivity of SDS is about unity over a wide range of concentrations of aqueous ethanol mixtures, similar to the membrane selectivity of crosslinked polydimethylsiloxane (PDMS). The permeabilities of butanol, isobutanol, and furfural are larger than those of ethanol and acetone. The volatile organic compound permeability through SDS is similar to or higher than that through PDMS across a broad range of temperatures and feed concentrations is found. More selective and permeable membranes are needed to lower the cost of biofuel purification. The SDS membranes developed are but one step toward improved membranes. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2789–2794, 2015     

Evaluation of the performance of catalytic oxidation of VOCs by a mixed oxide at a semi‐pilot scale†

Volatile organic compounds (VOCs) are one of the main contributors to air pollution. To reduce anthropogenic emissions, it is necessary to improve existing techniques such as catalytic oxidation through the development of new cost‐effective catalysts. Although many studies deal with the development and testing of new materials, most are performed at laboratory scale, of which only a few study mixtures of VOCs. To assess their viability for industrial applications, further tests are required, namely, mixture tests at intermediate scale in relevant environment and extrapolated on an industrial scale. In this work, the catalytic performance of a new mixed oxide Co‐Al‐Ce was investigated towards the oxidation of the n‐butanol and toluene on a semi‐pilot scale (TRL 4). Single component and mixture experiments were performed for several concentrations at a fixed flow rate. A commercial catalyst Pd/γ‐Al₂O₃ was used as the benchmark to evaluate the performance of the mixed oxide. The Co‐Al‐Ce catalyst enables complete oxidation of n‐butanol at the same temperature as the reference catalyst. Moreover, it provides a better selectivity for n‐butanol, while providing an equivalent one for the oxidation of toluene. In mixtures, the presence of n‐butanol promotes the oxidation of toluene for both catalysts but more significantly for the Co‐Al‐Ce catalyst. The presence of toluene inhibits the oxidation of n‐butanol for the Co‐Al‐Ce and promotes it for high conversions of n‐butanol for the Pd/γ‐Al₂O₃ catalyst.     

The role of butanol in the development of sustainable fuel technologies

OVERVIEW: The development of innovative methods to efficiently convert biomass to fuels and industrial chemicals is one of the grand challenges of the current age. n‐Butanol is a versatile and sustainable platform chemical that can be produced from a variety of waste biomass sources. The emergence of new technologies for the production of fuels and chemicals from butanol will allow it to be a significant component of a necessarily dynamic and multifaceted solution to the current global energy crisis. IMPACT: The production of butanol from biomass and its utilization as a precursor to a diverse set of fuel products has the potential to reduce petroleum use worldwide. In concert with other emerging renewable technologies, significant reductions in greenhouse gas emissions may be realized. The rapid incorporation of renewables into the world fuel supply may also help to offset predicted increases in transportation fuel prices as the supply of oil declines. APPLICATIONS: Recent work has shown that butanol is a potential gasoline replacement that can also be blended in significant quantities with conventional diesel fuel. These efforts have transitioned to research focused on the development of viable methods for the production of an array of oxygenated and fully saturated jet and diesel fuels from butanol. The technologies discussed in this paper will help drive the commercialization and utilization of a spectrum of butanol based sustainable fuels that can supplement and partially displace conventional petroleum derived fuels. Published 2010 by John Wiley and Sons, Ltd.     

Reaction Kinetics of Steam Reforming of n‐Butanol over a Ni/Hydrotalcite Catalyst

Pyrolytic lignin can be transformed to liquid transportation fuels by hydrotreatment, which requires hydrogen (H₂). Bio‐oil is a suitable renewable feedstock for H₂ production. Here, n‐butanol was chosen as a model compound representing alcohols in the bio‐oil aqueous fraction. H₂ production from steam reforming of n‐butanol was investigated in a fixed‐bed reactor using a commercial Ni/hydrotalcite catalyst. A plausible reaction pathway in the presence of Ni was discussed. An increase in reforming temperature, space time, and steam/carbon ratio in the feed enhanced the n‐butanol conversion and H₂ yield. Reaction kinetics was studied in the defined chemical control regime. The reaction order with respect to n‐butanol (one) and the activation energy were determined.     

Exploring the potential of recovering 1‐butanol from aqueous solutions by liquid demixing upon addition of carbohydrates or salts

BACKGROUND: Fermentative production of 1‐butanol yields dilute aqueous solutions. Recovery of the butanol from these solutions is most commonly performed by energy‐intensive distillation. This work investigated the liquid‐liquid (L‐L) phase behavior of mixtures of butanol and water to explore the potential of using L‐L phase separation as a recovery possibility for 1‐butanol. The phase behavior is preferably influenced by compounds already present in the fermentation, such as carbohydrates and salts. RESULTS: The L‐L phase equilibria of butanol and water were determined in the presence of glucose, fructose, sucrose, NaCl, LiCl and CaCl₂. The aqueous and organic phase split is more pronounced in the presence of salts than in the presence of carbohydrates. Demixing is achieved with about 0.3 kg salt kg^?1 aqueous phase containing 40 g of butanol. CONCLUSION: Operation of L‐L based recovery using salts or carbohydrates requires extreme concentrations of those compounds. For feed material containing 40 g kg^?1 butanol, the tested carbohydrates do not influence the phase equilibria sufficiently to allow butanol separation. Fermentative butanol concentrations up to 70 g kg^?1 are required to create an effective L‐L phase split. The remaining residual aqueous carbohydrate solution might be used as feed for a following fermentation. Copyright © 2011 Society of Chemical Industry     

Deoxycholic acid formation in gnotobiotic mice associated with human intestinal bacteria

In humans and animals, intestinal flora is indispensable for bile acid transformation. The goal of our study was to establish gnotobiotic mice with intestinal bacteria of human origin in order to examine the role of intestinal bacteria in the transformation of bile acids in vivo using the technique of gnotobiology. Eight strains of bile acid-deconjugating bacteria were isolated from ex-germ-free mice inoculated with a human fecal dilution of 10⁻⁶, and five strains of 7α-dehydroxylating bacteria were isolated from the intestine of limited human flora mice inoculated only with clostridia. The results of biochemical tests and 16S rDNA sequence analysis showed that seven out of eight bile acid-deconjugating strains belong to a bacteroides cluster (Bacteroides vulgatus, B. distasonis, and B. uniformis), and one strain had high similarity with Bilophila wadsworthia. All five strains that converted cholic acid to deoxycholic acid had greatest similarity with Clostridium hylemonae. A combination of 10 isolated strains converted taurocholic acid into deoxycholic acid both in vitro and in the mouse intestine. These results indicate that the predominant bacteria, mainly Bacteroides, in human feces comprise one of the main bacterial groups for the deconjugation of bile acids, and clostridia may play an important role in 7α-dehydroxylation of free-form primary bile acids in the intestine although these strains are not predominant. The gnotobiotic mouse with bacteria of human origin could be a useful model in studies of bile acid metabolism by human intestinal bacteria in vivo.     

新型生物能源丁醇的研究进展和市场现状

对生物丁醇的理化性质和应用领域、国内外市场现状、生产技术现状和发展限制因素进行了总结分析,并提出了改良菌种,提高丁醇耐受性和产丁醇比例;开发高效的发酵工艺;开发高效低能耗的分离工艺;拓展原料品种,开发纤维素丁醇生产工艺等技术改进和发展方向的建议,以期能促进生物丁醇行业的产业化和可持续发展。     

Rapid differentiation of new isolates with MALDI-TOF mass spectrometry via discriminant function analysis based on principal components

Discriminant function analysis based on principal components was applied to the spectral outputs of whole cell suspensions of nine isolates from matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. First, based on the salt tolerance and whole cell proteins, the similarity of the isolates to moderate halophiles was established. Intact microorganisms were then inferentially clustered by MALDI-TOF mass spectroscopy taking four type strains as precursors. Two of these type strains were moderate halophilic bacteria (Halomonas salina and Halomonas halophila), one was a mesophilic bacteria (Escherichia coli), and one was a halophilic archaea (Haloarcula vallismortis). Results showed that the isolates were significantly similar to halophiles but were different from a mesophile. This investigation demonstrates the feasibility of using whole cell suspensions for rapid differentiation prior to extensive experimentation.     

Application of lipase immobilized on nylon‐6 for the synthesis of butyl acetate by transesterification reaction in n‐heptane

A purified alkaline thermotolerant bacterial lipase from Bacillus coagulans BTS‐3 was immobilized on nylon‐6 matrix activated by glutaraldehyde. The matrix showed ～ 70% binding efficiency for lipase. The bound lipase was used to perform transesterification in n‐heptane. The reaction studied was conversion of vinyl acetate and butanol to butyl acetate and vinyl alcohol. Synthesis of butyl acetate was used as a parameter to study the transesterification reaction. The immobilized enzyme achieved ～ 75% conversion of vinyl acetate and butanol (100 mmol/L each) into butyl acetate in n‐heptane at 55°C in 12 h. When alkane of C‐chain lower or higher than n‐heptane was used as an organic solvent, the conversion of vinyl acetate and butanol to butyl acetate decreased. During the repetitive transesterification under optimal conditions, the nylon bound lipase produced 77.6 mmol/L of butyl acetate after third cycle of reuse. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007