Sequential Mixed Cultures : From Syngas to Malic Acid

Synthesis gas (syngas) fermentation using acetogenic bacteria is an approach for production of bulk chemicals like acetate, ethanol, butanol, or 2,3-butandiol avoiding the fuel vs. food debate by using carbon monoxide, carbon dioxide, and hydrogen from gasification of biomass or industrial waste gases. Suffering from energetic limitations, yields of C₄-molecules produced by syngas fermentation are quite low compared with ABE fermentation using sugars as a substrate. On the other hand, fungal production of malic acid has high yields of product per gram metabolized substrate but is currently limited to sugar containing substrates. In this study, it was possible to show that Aspergilus oryzae is able to produce malic acid using acetate as sole carbon source which is a main product of acetogenic syngas fermentation. Bioreactor cultivations were conducted in 2.5 L stirred tank reactors. During the syngas fermentation part of the sequential mixed culture, Clostridium ljungdahlii was grown in modified Tanner medium and sparged with 20 mL/min of artificial syngas mimicking a composition of clean syngas from entrained bed gasification of straw (32.5 vol-% CO, 32.5 vol-% H₂, 16 vol-% CO₂, and 19 vol-% N₂) using a microsparger. Syngas consumption was monitored via automated gas chromatographic measurement of the off-gas. For the fungal fermentation part gas sparging was switched to 0.6 L/min of air and a standard sparger. Ammonia content of medium for syngas fermentation was reduced to 0.33 g/L NH₄Cl to meet the requirements for fungal production of dicarboxylic acids. Malic acid production performance of A. oryzae in organic acid production medium and syngas medium with acetate as sole carbon source was verified and gave YP∕S values of 0.28 g/g and 0.37 g/g respectively. Growth and acetate formation of C. ljungdahlii during syngas fermentation were not affected by the reduced ammonia content and 66 % of the consumed syngas was converted to acetate. The overall conversion of CO and H₂ into malic acid was calculated to be 3.5 g malic acid per mol of consumed syngas or 0.22 g malic acid per gram of syngas

Hydrogen-rich syngas fermentation for bioethanol production using Sacharomyces cerevisiea

Bioethanol is an eco-friendly biofuel due to its merit that makes it a top-tier fuel. The present study emphasized on bioethanol production from hydrogen-rich syngas through fermentation using Sacharomyces cerevisiea. Syngas fermentation was performed in a tar free fermenter using a syngas mixture of 13.05% H2, 22.92% CO, 7.9% CO2, and 1.13% CH4, by volume. In the fermentation process, effects of various parameters including syngas impurity, temperature, pH, colony forming unit, total organic carbon and syngas composition were investigated. The yield of bioethanol was identified by Gas chromatography-Mass spectrometry analysis and further, it was confirmed by Nuclear magnetic resonance (1H) analysis. From GC-MS results, it is revealed that the concentration of bioethanol using Saccharomyces cerevisiae was 30.56 mmol from 1 L of syngas. Thus, hydrogen-rich syngas is suited for bioethanol production through syngas fermentation using Saccharomyces cerevisiae. This research may contribute to affordable and environment-friendly bioethanol-based energy to decrease the dependency on fossil fuels. © 2019 Hydrogen Energy Publications LL

A Systematic Review of Syngas Bioconversion to Value-Added Products from 2012 to 2022

ABSTRACT: Synthesis gas (syngas) fermentation is a biological carbon fixation process through which carboxydotrophic acetogenic bacteria convert CO, CO2, and H-2 into platform chemicals. To obtain an accurate overview of the syngas fermentation research and innovation from 2012 to 2022, a systematic search was performed on Web of Science and The Lens, focusing on academic publications and patents that were published or granted during this period. Overall, the research focus was centered on process optimization, the genetic manipulation of microorganisms, and bioreactor design, in order to increase the plethora of fermentation products and expand their possible applications. Most of the published research was initially funded and developed in the United States of America. However, over the years, European countries have become the major contributors to syngas fermentation research, followed by China. Syngas fermentation seems to be developing at "two-speeds", with a small number of companies controlling the technology that is needed for large-scale applications, while academia still focuses on low technology readiness level (TRL) research. This systematic review also showed that the fermentation of raw syngas, the effects of syngas impurities on acetogen viability and product distribution, and the process integration of gasification and fermentation are currently underdeveloped research topics, in which an investment is needed to achieve technological breakthroughs.info:eu-repo/semantics/publishedVersio

The Future of Biorefining Agricultural Biomass

Resource /Energy Economics and Policy,

Evaluation of some renewable energy technologies

Purpose. The study aims to outline and compare various renewable energy alternatives in view of the global warming crisis and depletion of fossil fuels which cause emissions of carbon dioxide. Carbon dioxide is a major source of pollution and is an absorbent for radiation. Methods. Literature surveys and analysis of benefits and drawbacks of the competing technologies should include the capital costs, running costs and carbon footprint. Liquid fuels have high energy to weight ratio compare to say solar panels or thermal absorbers, but what is neglected is the large refinery and other processing machinery behind the liquid fuel which is adding to the carbon footprint. Findings. Producer gas and bacterial engines are suggested as possible pollution reducing and cost effective methods for power generation. Coal, biomass, geothermal and hydroelectric have the lowest running cost, but carbon footprint cost is neglected. Solar chimneys, with low mechanical efficiency have low running costs, and no pollution. Modification of internal combustion engines to use producer gas and alcohol may reduce overall carbon footprint. Originality. Many researches focus on energy and mechanical efficiency. Bacterial engines have yet to be fully developed, and these are wonderful chemical factories but not understood in terms of classical thermodynamics. For all technologies, return on investment is more appropriate since capital costs are also included, which are neglected in mechanical efficiency calculations. Practical implications. Depletion of forest cover which acts as a greenhouse gas sink contributes to global warming. Worldwide, million of cars with internal combustion engines consuming petroleum, if converted to alternative fuels, can help in reducing the carbon gas emissions and ultimately to a slowdown in the global warming rate.Мета. Надати і порівняти різні види відновлюваної енергії з урахуванням енергетичної кризи, пов'язаної з глобальним потеплінням і виснаженням викопних джерел палива, що призводить до викидів вуглекислого газу, який є головним джерелом забруднення атмосфери й поглинання радіації. Методика. При огляді літературних джерел та аналізі переваг і недоліків конкуруючих технологій необхідно враховувати капітальні й експлуатаційні витрати, а також вуглецевий слід. Рідкі види палива відрізняються більш високою питомою енергією по масі в порівнянні з сонячними панелями або термокомпенсаторами. Не можна недооцінювати той факт, що виробництво рідкого палива передбачає наявність громіздкого очисного й переробного обладнання, робота якого збільшує вуглецевий слід. Результати. Генераторний газ і бактеріальні двигуни пропонуються в якості способу зменшення забруднення та економічного отримання електричної енергії. Отримання електроенергії на геотермальних і гідроелектростанціях, а також на станціях, що працюють на вугіллі чи біомасі, передбачає низькі витрати на експлуатацію. Однак, при цьому не враховуються витрати на боротьбу з вуглецевими викидами. Сонячні електростанції аеродинамічного типу при малому механічному ККД відрізняються низькими експлуатаційними витратами і практично не забруднюють навколишнє середовище. Модифіковані двигуни внутрішнього згоряння, що дозволяють отримувати генераторний газ і спирт, можуть сприяти зменшенню вуглецевих викидів. Наукова новизна. Багато вчених розглядають проблеми отримання енергії й підвищення механічного ККД. Необхідно вдосконалювати бактеріальні двигуни, свого роду хімічні фабрики, робота яких ще не до кінця зрозуміла з точки зору класичної термодинаміки. Оцінюючи різні технології, слід виходити з окупності інвестицій, оскільки вона включає капітальні витрати, які зазвичай не враховуються при розрахунках механічного ККД. Практична значимість. Скорочення лісового покриву планети, який є поглиначем парникових газів, призводить до глобального потепління. Якщо двигуни мільйонів машин по всьому світу перевести з бензину на альтернативні види палива, скоротяться парникові викиди й сповільняться темпи глобального потепління.Цель. Представить и сравнить различные виды возобновляемой энергии с учетом энергетического кризиса, связанного с глобальным потеплением и истощением ископаемых источников топлива, что приводит к выбросам углекислого газа, который является главным источником загрязнения атмосферы и поглощения радиации. Методика. При обзоре литературных источников и анализе преимуществ и недостатков конкурирующих технологий необходимо учитывать капитальные и эксплуатационные затраты, а также углеродный след. Жидкие виды топлива отличаются более высокой удельной энергией по массе по сравнению с солнечными панелями или термокомпенсаторами. Нельзя недооценивать тот факт, что производство жидкого топлива предполагает наличие громоздкого очистного и перерабатывающего оборудования, работа которого увеличивает углеродный след. Результаты. Генераторный газ и бактериальные двигатели предлагаются в качестве способа уменьшения загрязнения и экономичного получения электрической энергии. Получение электроэнергии на геотермальных и гидроэлектростанциях, а также на станциях, работающих на угле или биомассе, предполагает низкие расходы на эксплуатацию. Однако, при этом не учитываются расходы на борьбу с углеродистыми выбросами. Солнечные электростанции аэродинамического типа при малом механическом КПД отличаются низкими эксплуатационными расходами и практически не загрязняют окружающую среду. Модифицированные двигатели внутреннего сгорания, позволяющие получать генераторный газ и спирт, могут способствовать уменьшению углеродистых выбросов. Научная новизна. Многие ученые рассматривают проблемы получения энергии и повышения механического КПД. Необходимо совершенствовать бактериальные двигатели, своего рода химические фабрики, работа которых еще не до конца понятна с точки зрения классической термодинамики. Оценивая различные технологии, следует исходить из окупаемости инвестиций, поскольку она включает капитальные затраты, которые обычно не учитываются при расчетах механического КПД. Практическая значимость. Сокращение лесного покрова планеты, который является поглотителем парниковых газов, приводит к глобальному потеплению. Если двигатели миллионов машин по всему миру перевести с бензина на альтернативные виды топлива, сократятся парниковые выбросы и замедлятся темпы глобального потепления.This work was presented at the International Conference on Environmental Design and Innovation, Amman Jordan in May 2016. The author thanks the organizers and Al-Zaytoona University for local hospitality

Microbial Communities Involved in Carbon Monoxide and Syngas Conversion to Biofuels and Chemicals

abstract: On average, our society generates ~0.5 ton of municipal solid waste per person annually. Biomass waste can be gasified to generate synthesis gas (syngas), a gas mixture consisting predominantly of CO, CO2, and H2. Syngas, rich in carbon and electrons, can fuel the metabolism of carboxidotrophs, anaerobic microorganisms that metabolize CO (a toxic pollutant) and produce biofuels (H2, ethanol) and commodity chemicals (acetate and other fatty acids). Despite the attempts for commercialization of syngas fermentation by several companies, the metabolic processes involved in CO and syngas metabolism are not well understood. This dissertation aims to contribute to the understanding of CO and syngas fermentation by uncovering key microorganisms and understanding their metabolism. For this, microbiology and molecular biology techniques were combined with analytical chemistry analyses and deep sequencing techniques. First, environments where CO is commonly detected, including the seafloor, volcanic sand, and sewage sludge, were explored to identify potential carboxidotrophs. Since carboxidotrophs from sludge consumed CO 1000 faster than those in nature, mesophilic sludge was used as inoculum to enrich for CO- and syngas- metabolizing microbes. Two carboxidotrophs were isolated from this culture: an acetate/ethanol-producer 99% phylogenetically similar to Acetobacterium wieringae and a novel H2-producer, Pleomorphomonas carboxidotrophicus sp. nov. Comparison of CO and syngas fermentation by the CO-enriched culture and the isolates suggested mixed-culture syngas fermentation as a better alternative to ferment CO-rich gases. Advantages of mixed cultures included complete consumption of H2 and CO2 (along with CO), flexibility under different syngas compositions, functional redundancy (for acetate production) and high ethanol production after providing a continuous supply of electrons. Lastly, dilute ethanol solutions, typical of syngas fermentation processes, were upgraded to medium-chain fatty acids (MCFA), biofuel precursors, through the continuous addition of CO. In these bioreactors, methanogens were inhibited and Peptostreptococcaceae and Lachnospiraceae spp. most likely partnered with carboxidotrophs for MCFA production. These results reveal novel microorganisms capable of effectively consuming an atmospheric pollutant, shed light on the interplay between syngas components, microbial communities, and metabolites produced, and support mixed-culture syngas fermentation for the production of a wide variety of biofuels and commodity chemicals.Dissertation/ThesisDoctoral Dissertation Civil, Environmental and Sustainable Engineering 201

Advanced biofuel technologies : status and barriers

Large-scale production of crop based (first generation) biofuels may not be feasible without adversely affecting global food supply or encroaching on other important land uses. Because alternatives to liquid fossil fuels are important to develop in order to address greenhouse gas mitigation and other energy policy objectives, the potential for increased use of advanced (non-crop, second generation) biofuel production technologies has significant policy relevance. This study reviews the current status ofseveral advanced biofuel technologies. Technically, it would be possible to produce a large portion of transportation fuels using advanced biofuel technologies, specifically those that can be grown using a small portion of the world's land area (for example, microalgae), or those grown on arable lands without affecting food supply (for example, agricultural residues). However, serious technical barriers limit the near-term commercial application of advanced biofuels technologies. Key technical barriers include low conversion efficiency from biomass to fuel, limits on supply of key enzymes used in conversion, large energy requirements for operation, and dependence in many cases on commercially unproven technology. Despite a large future potential, large-scale expansion of advanced biofuels technologies is unlikely unless and until further research and development lead to lowering these barriers.Energy Production and Transportation,Climate Change Mitigation and Green House Gases,Renewable Energy,Crops&Crop Management Systems,Sanitation and Sewerage

Carbon roadmap from syngas to polyhydroxyalkanoates in Rhodospirillum rubrum

The gasification of organic waste materials to synthesis gas (syngas), followed by microbial fermentation provides a significant resource for generating bioproducts such as polyhydroxyalkanoates (PHA). The anaerobic photosynthetic bacterium, Rhodospirillum rubrum, is an organism particularly attractive for the bioconversion of syngas into PHAs. In this study, a quantitative physiological analysis of R. rubrum was carried out by implementing GC-MS and HPLC techniques to unravel the metabolic pathway operating during syngas fermentation that leads to PHA production. Further, detailed investigations of the central carbon metabolites using 13C-labeled substrate showed significant CO2 assimilation (of 40 %) into cell material and PHA from syngas carbon fraction. By a combination of quantitative gene expression and enzyme activity analyses, the main role of carboxylases from the central carbon metabolism in CO2 assimilation was shown, where the Calvin Benson-Bassham Cycle (CBB) played a minor role. This knowledge sheds light about the biochemical pathways that contribute to synthesis of PHA during syngas fermentation being valuable information to further optimize the fermentation process.This work has been funded by the EU project SYNPOL (grant agreement n° 311815) under the European Union’s Seventh Framework Programme.Peer reviewe

Life Cycle Assessment of Sweet Sorghum as Feedstock for Second-generation Biofuel Production

There exist few life cycle assessments (LCAs) in the literature that focus on the second-generation biofuel production from sweet sorghum, a non-food-source feedstock that offers several advantages in terms of farming requirements compared to corn or sugarcane. The objective of this LCA study was to evaluate biofuels produced from sweet sorghum to determine the potential environmental benefits of producing sweet sorghum biofuel compared to conventional fossil fuels. The biofuel production process used for this study differed from other LCAs in that, in parallel to stalk juice extraction and fermentation, residual bagasse and vinasse was pyrolyzed and upgraded to a diesel equivalent as opposed to being fermented or combusted for a source of heat or electricity production. The life cycle inventory included data available in the literature regarding mass and energy input requirements for farming, juice extraction, fermenting, pre-treatment, pyrolysis, and steam reforming steps. Experimental data for bio-oil upgrading was obtained from a pilot plant in Huntsville, AR, including hydrogen gas requirements for hydrotreatment and diesel, biochar, and non-condensable gas yields. The functional unit used for this study was the total kilometers driven by standard passenger vehicles using ethanol, gasoline and diesel produced from 1 ha of harvested sweet sorghum (76 wet tons). Total biofuel yields resulting from this basis were 5,122 L of bioethanol, 2,708 L of gasoline and 780 L of diesel. With these yields, distances of 58,500 km, 21,500 km, and 12,070 km were chosen as the functional unit for the combustion of E85, E10, and diesel, respectively based on vehicle fuel efficiencies from the GREET model. Compared to conventional gasoline, this production process resulted in nearly 50% reduction of GHGs and 46% reduction in fossil fuel depletion, in addition to reductions in eutrophication, ecotoxicity, and carcinogenics. However, fossil fuels were lower by 25%, 45%, and 12% in the categories of non-carcinogenics, respiratory effects, and smog, respectively. These lower impacts for fossil fuels are driven by heavy-metal uptake from corn production and the fact that less electricity is used in the supply chain compared to biofuel production. A Monte Carlo simulation showed the comparative impact assessment results were not sensitive to uncertainty in the life cycle inventory. While the impact assessment showed benefits in producing sweet sorghum biofuel compared to fossil fuels, further research must be conducted on land use and water use. A detailed process simulation, coupled with continued experimental studies of the pyrolysis and upgrading processes, is recommended for further process optimization and heat integration, as well as composition analyses of the various co-products resulting from the process. Further studies will provide valuable information in choosing between feedstocks, specifically those which can be used to produce second-generation biofuels