Biological conversion of carbon monoxide to ethanol: Effect of pH, gas pressure, reducing agent and yeast extract

A two-level full factorial design was carried out in order to investigate the effect of four factors on the bioconversion of carbon monoxide to ethanol and acetic acid by Clostridium autoethanogenum: initial pH (4.75–5.75), initial total pressure (0.8–1.6 bar), cysteine–HCl•H2O concentration (0.5–1.2 g/L) and yeast extract concentration (0.6–1.6 g/L). The maximum ethanol production was enhanced up to 200% when lowering the pH and amount yeast extract from 5.75 to 4.75 g/L and 1.6 to 0.6 g/L, respectively. The regression coefficient, regression model and analysis of variance (ANOVA) were obtained using MINITAB 16 software for ethanol, acetic acid and biomass. For ethanol, it was observed that all the main effects and the interaction effects were found statistically significant (p < 0.05). The comparison between the experimental and the predicted values was found to be very satisfactory, indicating the suitability of the predicted model

Carbon monoxide fermentation to ethanol by Clostridium autoethanogenum in a bioreactor with no accumulation of acetic acid

[Abstract] Fermentation of CO or syngas offers an attractive route to produce bioethanol. However, during the bioconversion, one of the challenges to overcome is to reduce the production of acetic acid in order to minimize recovery costs. Different experiments were done with Clostridium autoethanogenum. With the addition of 0.75 μM tungsten, ethanol production from carbon monoxide increased by about 128% compared to the control, without such addition, in batch mode. In bioreactors with continuous carbon monoxide supply, the maximum biomass concentration reached at pH 6.0 was 109% higher than the maximum achieved at pH 4.75 but, interestingly, at pH 4.75, no acetic acid was produced and the ethanol titer reached a maximum of 867 mg/L with minor amounts of 2,3-butanediol (46 mg/L). At the higher pH studied (pH 6.0) in the continuous gas-fed bioreactor, almost equal amounts of ethanol and acetic acid were formed, reaching 907.72 mg/L and 910.69 mg/L respectively.Ministerio de Ciencia e Innovación; CTM2010-15796-TECNOMinisterio de Ciencia e Innovación; CTQ2013-45581-

Ethanol and Acetic Acid Production from Carbon Monoxide in a Clostridium Strain in Batch and Continuous Gas-Fed Bioreactors

The effect of different sources of nitrogen as well as their concentrations on the bioconversion of carbon monoxide to metabolic products such as acetic acid and ethanol by Clostridium autoethanogenum was studied. In a first set of assays, under batch conditions, either NH4Cl, trypticase soy broth or yeast extract (YE) were used as sources of nitrogen. The use of YE was found statistically significant (p < 0.05) on the product spectrum in such batch assays. In another set of experiments, three bioreactors were operated with continuous CO supply, in order to estimate the effect of running conditions on products and biomass formation. The bioreactors were operated under different conditions, i.e., EXP1 (pH = 5.75, YE 1g/L), EXP2 (pH = 4.75, YE 1 g/L) and EXP3 (pH = 5.75, YE 0.2 g/L). When compared to EXP2 and EXP3, it was found that EXP1 yielded the maximum biomass accumulation (302.4 mg/L) and products concentrations, i.e., acetic acid (2147.1 mg/L) and ethanol (352.6 mg/L). This can be attributed to the fact that the higher pH and higher YE concentration used in EXP1 stimulated cell growth and did, consequently, also enhance metabolite production. However, when ethanol is the desired end-product, as a biofuel, the lower pH used in EXP2 was more favourable for solventogenesis and yielded the highest ethanol/acetic acid ratio, reaching a value of 0.54.Ministerio de Ciencia e Innovación; CTM2010-15796-TECN

Bioconversion of carbon monoxide-related volatile compounds into ethanol in bioreactors

[Resumen]Los problemas ambientales asociados al uso de combustibles fósiles, así como su esperada escasez en un futuro próximo, exigen la búsqueda de nuevos combustibles alternativos, como el bioetanol obtenido a partir de residuos o fuentes renovables. El uso de tecnologías de gasificación y de fermentación, la denominada “tecnología híbrida”, representa un enfoque más versátil para la producción de etanol. Este último se considera una energía de bajo coste que se obtiene a partir de una gran variedad de materias primas, que utiliza el potencial de los microorganismos anaerobios para catalizar la conversión de compuestos de un único carbono (C1) a una variedad de productos químicos y combustibles mediante el uso de la vía metabólica reductora del acetil-CoA. Además de utilizar gas de síntesis como materia prima, los efluentes gaseosos que contienen monóxido de carbono y liberados en procesos industriales, también pueden ser utilizados de manera eficiente en la producción de etanol como combustible. El principal objetivo de esta investigación doctoral es la optimización del medio de fermentación y los parámetros de operación para la conversión de monóxido de carbono en etanol.[Resumo]Os problemas ambientais asociados ao uso de combustibles fósiles, así como a súa esperada insuficiencia nun futuro próximo, esixen a procura de novos combustibles alternativos como o bioetanol, obtido a partir de residuos, ou fontes renovables. O uso de tecnoloxías de gasificación e de fermentación, a denominada “tecnoloxía híbrida”, representa un enfoque máis versátil para a produción de etanol. Este último considérase unha enerxía de baixo custo que se pode obter a partir dunha gran variedade de materias primas e que utiliza o potencial dos microorganismos anaerobios para catalizar a conversión de compostos dun único carbono (C1) a unha variedade de produtos químicos e combustibles mediante o uso da vía metabólica redutora do acetil-CoA. Ademais de utilizar gas de síntese como materia prima, os efluentes gaseosos que conteñen monóxido de carbono e liberados en procesos industriais, tamén poden ser utilizados de maneira eficiente na produción de etanol como combustible. O principal obxectivo desta investigación doutoral é a optimización do medio de fermentación e os parámetros de operación para a conversión de monóxido de carbono en etanol

Reactor designs and configurations for biological and bioelectrochemical C1 gas conversion: a review

Microbial C1 gas conversion technologies have developed into a potentially promising technology for converting waste gases (CO2, CO) into chemicals, fuels, and other materials. However, the mass transfer constraint of these poorly soluble substrates to microorganisms is an important challenge to maximize the efficiencies of the processes. These technologies have attracted significant scientific interest in recent years, and many reactor designs have been explored. Syngas fermentation and hydrogenotrophic methanation use molecular hydrogen as an electron donor. Furthermore, the sequestration of CO2 and the generation of valuable chemicals through the application of a biocathode in bioelectrochemical cells have been evaluated for their great potential to contribute to sustainability. Through a process termed microbial chain elongation, the product portfolio from C1 gas conversion may be expanded further by carefully driving microorganisms to perform acetogenesis, solventogenesis, and reverse -oxidation. The purpose of this review is to provide an overview of the various kinds of bioreactors that are employed in these microbial C1 conversion processes.This study was conducted in collaboration with researchers from four different institu tions (Dokuz Eylul University, Turkey; University of Minho, Portugal; Izmir Democracy University, Turkey, and University of A Coruña, Spain), who were supported by the following funding bodies: A.A. [Dokuz Eylul University, Scientific Research Foundation (DEU-BAP) (#2011.KB.FEN.046) and TUBİTAK (#119R029)]; L.P. [Portuguese Foundation for Science and Technology (FCT) (UIDB/04469/2020), and FCT and European Social Fund (POPH-QREN) (POCI-01-0145-FEDER 031377)]; T.K. [TUBİTAK-CAYDAG (118Y305)]; and H.N.A. [Xunta de Galicia (ED431C 2021/55)].A.A. acknowledges the support by Dokuz Eylul University, Scientific Research Foundation (DEU-BAP), Turkey, for the award on (#2011.KB.FEN.046) “Direct Electricity Generation from Treatment Plant Sludges by using MFCs” research project. A.A. acknowledges TUBİTAK for the support on #119R029 “Sustainable Energy Recovery from Treatment plant sludge, green waste and olive pomace via gasification process: Investigation of beneficial usage alternatives of gasification by-products”. L.P. acknowledges the Portuguese Foundation for Science and Technol ogy (FCT) under the scope of the strategic funding of UIDB/04469/2020 unit. Also, the financial sup port from Portuguese Foundation for Science and Technology (FCT) and European Social Fund (POPH-QREN) through the project INNOVsyn - Innovative strategies for syngas fermentation (POCI-01-0145-FEDER-031377) are gratefully acknowledged. T.K. acknowledges the support from The Scientific and Technological Research Council of Turkey (TUBITAK-CAYDAG) (project no: 118Y305). H.N.A. thanks the Xunta de Galicia (Spain) for his postdoctoral fellowship (ED481D 2019/033). H.N.A., belonging to the BIOENGIN group of the UDC, also acknowledges Xunta de Galicia for recognizing the group as a competitive Reference Research Group (GRC) (ED431C 2021/55).info:eu-repo/semantics/publishedVersio

Design of Low-Cost Ethanol Production Medium From Syngas: An Optimization of Trace Metals for Clostridium Ljungdahlii

[Abstract] Syngas fermentation via the Wood-Ljungdahl (WL) pathway is a promising approach for converting gaseous pollutants (CO and CO2) into high-value commodities. Because the WL involves several enzymes with trace metal components, it requires an adequate supply of micronutrients in the fermentation medium for targeted bioprocessing such as bioethanol production. Plackett-Burman statistical analysis was performed to examine the most efficient trace elements (Ni, Mg, Ca, Mn, Co, Cu, B, W, Zn, Fe, and Mo) and their concentrations for Clostridium ljungdahlii on ethanol production. Overall, 1.5 to 2.5 fold improvement in ethanol production could be achieved with designed trace element concentrations. The effects of tungsten and copper on ethanol and biomass production were determined to be the most significant, respectively. The model developed was statistically significant and has the potential to significantly decrease the cost of trace element solutions by 18–22%. This research demonstrates the critical importance of optimizing the medium for syngas fermentation in terms of product distribution and economic feasibility.Turquía. Scientific and Technological Research Council of Turkey; 118Y305Turquía. Ege University; FDK-2020-22039Xunta de Galicia; ED481D 2019/03

Fischer–Tropsch Chemistry at Room Temperature?

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87158/1/7984_ftp.pd

Metabolic shift induced by synthetic co-cultivation promotes high yield of chain elongated acids from syngas

Bio-catalytic processes for sustainable production of chemicals and fuels receive increased attention within the concept of circular economy. Strategies to improve these production processes include genetic engineering of bio-catalysts or process technological optimization. Alternatively, synthetic microbial co-cultures can be used to enhance production of chemicals of interest. It remains often unclear however how microbe to microbe interactions affect the overall production process and how this can be further exploited for application. In the present study we explored the microbial interaction in a synthetic co-culture of Clostridium autoethanogenum and Clostridium kluyveri, producing chain elongated products from carbon monoxide. Monocultures of C. autoethanogenum converted CO to acetate and traces of ethanol, while during co-cultivation with C. kluyveri, it shifted its metabolism significantly towards solventogenesis. In C. autoethanogenum, expression of the genes involved in the central carbon- and energy-metabolism remained unchanged during co-cultivation compared to monoculture condition. Therefore the shift in the metabolic flux of C. autoethanogenum appears to be regulated by thermodynamics, and results from the continuous removal of ethanol by C. kluyveri. This trait could be further exploited, driving the metabolism of C. autoethanogenum to solely ethanol formation during co-cultivation, resulting in a high yield of chain elongated products from CO-derived electrons. This research highlights the important role of thermodynamic interactions in (synthetic) mixed microbial communities and shows that this can be exploited to promote desired conversions.The research leading to these results has received funding from the Netherlands Ministry of Education, Culture and Science and from the Netherlands Science Foundation (NWO) under the Gravitation Grant nr. 024.002.002 and Programme ‘Closed Cycles’ with Project nr. ALWGK.2016.029.info:eu-repo/semantics/publishedVersio

A Review of the Sustainable Utilization of Rice Residues for Bioenergy Conversion Using Different Valorization Techniques, Their Challenges, and Techno-Economic Assessment

[Abstract] The impetus to predicting future biomass consumption focuses on sustainable energy, which concerns the non-renewable nature of fossil fuels and the environmental challenges associated with fossil fuel burning. However, the production of rice residue in the form of rice husk (RH) and rice straw (RS) has brought an array of benefits, including its utilization as biofuel to augment or replace fossil fuel. Rice residue characterization, valorization, and techno-economic analysis require a comprehensive review to maximize its inherent energy conversion potential. Therefore, the focus of this review is on the assessment of rice residue characterization, valorization approaches, pre-treatment limitations, and techno–economic analyses that yield a better biofuel to adapt to current and future energy demand. The pre-treatment methods are also discussed through torrefaction, briquetting, pelletization and hydrothermal carbonization. The review also covers the limitations of rice residue utilization, as well as the phase structure of thermochemical and biochemical processes. The paper concludes that rice residue is a preferable sustainable biomass option for both economic and environmental growth.S.K. would like to thank J.P. for providing guidance and funding for the research study through J510050002—IC—6— BOLDREFRESH2025—CENTRE OF EXCELLENCE from the iRMC of Universiti Tenaga Nasional, Malaysia. H.N.A. thanks the Xunta de Galicia (Spain) for the postdoctoral fellowship (ED 481B-2016/195-0, ED481D 2019/033). E.R.R. thanks the IHE Delft Institute for Water Education for providing staff, time, and support under the project “Support to Society”, to collaborate with researchers from Malaysia, Nigeria and SpainMalasia. Universiti Tenaga Nasional; J510050002–IC–6 BOLDREFRESH2025-CENTER OF EXCELLENCEXunta de Galicia; ED 481B-2016/195-0Xunta de Galicia; ED481D 2019/03

A review of the sustainable utilization of rice residues for bioenergy conversion using different valorization techniques, their challenges, and techno-economic assessment.

The impetus to predicting future biomass consumption focuses on sustainable energy, which concerns the non-renewable nature of fossil fuels and the environmental challenges associated with fossil fuel burning. However, the production of rice residue in the form of rice husk (RH) and rice straw (RS) has brought an array of benefits, including its utilization as biofuel to augment or replace fossil fuel. Rice residue characterization, valorization, and techno-economic analysis require a comprehensive review to maximize its inherent energy conversion potential. Therefore, the focus of this review is on the assessment of rice residue characterization, valorization approaches, pre-treatment limitations, and techno–economic analyses that yield a better biofuel to adapt to current and future energy demand. The pre-treatment methods are also discussed through torrefaction, briquetting, pelletization and hydrothermal carbonization. The review also covers the limitations of rice residue utilization, as well as the phase structure of thermochemical and biochemical processes. The paper concludes that rice residue is a preferable sustainable biomass option for both economic and environmental growth