Next-generation Biofuels Research Articles

Comparative research on acetone-butanol-ethanol (ABE) and butanol (Bu) as next-generation biofuels in compression ignition engine

Increasing global energy demand, along with economic and environmental issues, have necessitated substituting fossil fuels with biofuels. ABE (acetone-butanol-ethanol mixture), an intermediate product of biobutanol fermentation characterized by low-cost production, has recently emerged as a promising renewable fuel to replace biobutanol (Bu) for engine applications. This study compares ABE and Bu to determine which fuel is superior. To this end, their effects on engine operation and pollutant emissions were investigated. Each biofuel was tested on a research engine under varied loading conditions after being blended with diesel fuel at concentrations of 5, 10, 20, and 30% by volume. The results revealed that the diesel (D)-ABE and diesel-biobutanol (D-Bu) blends experienced dominant premixed combustion; however, deteriorated engine performance somewhat. ABE30 and Bu30 presented the highest increases in fuel consumption (11.67% and 7.89%, respectively), and the highest decreases in thermal efficiency (2.17% and 1.17%, respectively). All fuel blends offered a remarkable concurrent reduction in NO emission and smoke opacity. More specifically, ABE20 provided an average reduction in NO and smoke opacity (41.79% and 49.59%, respectively), as compared to diesel fuel, whereas Bu20 offered a mean reduction in NO and smoke opacity (45.42% and 54.98%, respectively). Collectively, results revealed that Bu20 and its counterpart ABE20 could be the most suitable candidates among the tested fuels. Considering ABE’s lower cost and less energy intensity production process than Bu, ABE20, which is compatible with existing engine technology and improves NOX-PM trade-off with a slight sacrifice in engine performance, emerges as a most promising biofuel.

The Interplay between the Temperature and Pressure on the Reaction Pathways of the Prenol Oxidation by Hydroxyl Radicals.

Despite prenol emerging as a next-generation biofuel, some questions about its mechanism still need to be adequately proposed to rationalize its consumption and evaluate its efficiency in spark-ignition (SI) engines. Here, we present new insights into the reaction mechanism of prenol (3-methyl-2-buten-1-ol) with OH radicals as a function of temperature and pressure. We have determined that the different temperature and pressure conditions control the preferred products. At combustion temperatures and low pressures, OH-addition adducts are suppressed, increasing the formation of α and δ allylic radicals responsible for the auto-ignition.

Engineering the carbon and redox metabolism of Paenibacillus polymyxa for efficient isobutanol production.

Paenibacillus polymyxa is a non-pathogenic, Gram-positive bacterium endowed with a rich and versatile metabolism. However interesting, this bacterium has been seldom used for bioproduction thus far. In this study, we engineered P. polymyxa for isobutanol production, a relevant bulk chemical and next-generation biofuel. A CRISPR-Cas9-based genome editing tool facilitated the chromosomal integration of a synthetic operon to establish isobutanol production. The 2,3-butanediol biosynthesis pathway, leading to the main fermentation product of P. polymyxa, was eliminated. A mutant strain harbouring the synthetic isobutanol operon (kdcA from Lactococcus lactis, and the native ilvC, ilvD and adh genes) produced 1 g L-1 isobutanol under microaerobic conditions. Improving NADPH regeneration by overexpression of the malic enzyme subsequently increased the product titre by 50%. Network-wide proteomics provided insights into responses of P. polymyxa to isobutanol and revealed a significant metabolic shift caused by alcohol production. Glucose-6-phosphate 1-dehydrogenase, the key enzyme in the pentose phosphate pathway, was identified as a bottleneck that hindered efficient NADPH regeneration through this pathway. Furthermore, we conducted culture optimization towards cultivating P. polymyxa in a synthetic minimal medium. We identified biotin (B7), pantothenate (B5) and folate (B9) to be mutual essential vitamins for P. polymyxa. Our rational metabolic engineering of P. polymyxa for the production of a heterologous chemical sheds light on the metabolism of this bacterium towards further biotechnological exploitation.

Low-temperature ignition and oxidation mechanisms of tetrahydropyran

Cyclic ethers are relevant as next-generation biofuels and are also combustion intermediates that follow directly from unimolecular decomposition of hydroperoxyalkyl radicals. Accordingly, cyclic ether reactions are crucial to understanding low-temperature oxidation for advanced compression-ignition applications in combustion where peroxy radials are central to degenerate chain-branching pathways. Reaction mechanisms relevant to low-temperature ignition of cyclic ethers contain intrinsic complexities due to competing reactions of carbon-centered radicals formed in the initiation step undergoing either ring-opening or reactions with O2. To gain insight into mechanisms describing tetrahydropyran combustion, ignition delay time and speciation measurements were conducted. The present work integrates measurements below 1000 K of ignition delay times and species profiles in rapid compression machine experiments from 5 – 20 bar, spanning several equivalence ratios, with jet-stirred reactor experiments at 1 bar and stoichiometric conditions. The experiments are complemented with the development of the first chemical kinetics mechanism for tetrahydropyran that includes peroxy radical reactions, including O2-addition to tetrahydropyranyl (Ṙ), HOȮ-elimination from tetrahydropyranylperoxy (ROȮ) and hydroperoxytetrahydropyranyl (Q˙OOH), bi-cyclic ether formation, β-scission of Q˙OOH, and ketohydroperoxide formation.Negative-temperature coefficient (NTC) behavior is exhibited in the experiments and is reflected in the model predictions, which were within experimental uncertainty for several conditions. Disparities between the model predictions and experiments were analyzed via sensitivity analysis to identify contributing factors from elementary reactions. The analyses examine the role of ring-opening products of tetrahydropyranyl and hydroperoxytetrahydropyranyl isomers to identify reaction mechanisms that may contribute to model uncertainties. The detection of 66 species in the JSR experiments indicates that tetrahydropyran undergoes complex reaction networks, which includes interconnected reactions of aldehyde radicals and alkyl radicals. Primary radicals pentanal-5-yl and butanal-4-yl are derived from ring-opening reactions of tetrahydropyran-1-yl and undergo subsequent decarbonylation to form alkyl radicals (1-butyl and 1-propyl) that undergo reaction with O2 and may contribute to chain-branching, in addition to pathways involving tetrahydropyran-derived ketohydroperoxides.

Respiration is essential for aerobic growth of Zymomonas mobilis ZM4.

A key to producing next-generation biofuels is to engineer microbes that efficiently convert non-food materials into drop-in fuels, and to engineer microbes effectively, we must understand their metabolism thoroughly. Zymomonas mobilis is a bacterium that is a promising candidate biofuel producer, but its metabolism remains poorly understood, especially its metabolism when exposed to oxygen. Although Z. mobilis respires with oxygen, its aerobic growth is poor, and disruption of genes related to respiration counterintuitively improves aerobic growth. This unusual result has sparked decades of research and debate regarding the function of respiration in Z. mobilis. Here, we used a new set of mutants to determine that respiration is essential for aerobic growth and likely protects the cells from damage caused by oxygen. We conclude that the respiratory pathway of Z. mobilis should not be deleted from chassis strains for industrial production because this would yield a strain that is intolerant of oxygen, which is more difficult to manage in industrial settings.

Autologous tooth bone graft block compared with advanced platelet-rich fibrin in alveolar ridge preservation: A clinico-radiographic study.

To determine the clinico-radiographic efficiency of partially demineralized dentin matrix block (PDDM block), a mixture of PDDM with advanced-platelet-rich fibrin+ (A-PRF+) and injectable platelet-rich fibrin versus A-PRF+ alone in alveolar socket preservation. Sixteen molar teeth indicated for extraction were randomly assigned into two groups. For the test group, sockets were packed with PDDM block and control group, with A-PRF+ plug alone. Clinical and radiographic cone-beam computed tomography methods were used to assess the horizontal and vertical ridge dimensional changes at baseline and 4 months. Clinically, the mid buccal and palatal crestal height (10.25 ± 0.86 and 9.75 ± 0.28 mm) and alveolar ridge width (11.37 ± 0.25 mm) were significantly higher in the test group as compared to the control group, 4 months after tooth extraction (P < 0.01). Radiographically, there was improved apposition and nonsignificant resorption for the test group in ridge height and width, whereas statistically significant higher resorption was seen in the control group at 4 months. The application of the PDDM block demonstrated efficacy in maintaining the dimensions of the extraction socket when compared to A-PRF+ alone. This autologous and immune-free regenerative biomaterial is widely obtainable, offering a glimpse into the potential of next-generation biofuels for regeneration.

Biogas production potential of aquatic weeds as the next-generation feedstock for bioenergy production: a review.

Aquatic weeds have exceptionally high reproduction rates, are rich in cellulose and hemicellulose, and contain a negligible amount of lignin, making them an ideal crop for the next generation of biofuels. Previously reported studies proposed that water hyacinth, water lettuce, common duckweeds, and water spinach can be managed or utilized using different advanced techniques; from them, anaerobic digestion is one of the feasible and cost-effective techniques to manage these biowastes. The present study was carried out to investigate the potential of utilizing four common aquatic weed species (water hyacinth, water lettuce, common duckweeds, and water spinach) as substrates for anaerobic digestion in order to produce biogas for use in biofuels. The high reproduction rates and high cellulose and hemicellulose content, coupled with low lignin content, of these aquatic weeds make them ideal candidates for this purpose. The study evaluated the feasibility of using anaerobic digestion as a management technique for these aquatic weeds, which are often considered invasive and difficult to control. The results from various studies indicate that these aquatic weeds are productive feedstock options for anaerobic digestion, yielding a high biogas output. Among the aquatic weeds studied, water hyacinth, water lettuce, and common duckweeds exhibit higher methane production compared to water spinach. The study provides an overview of the characteristics and management strategies of these aquatic weeds in relation to biogas production, with possible future developments in the field.

Heterologous expression of a yeast lipid transporter promotes accumulation of storage compounds in Chlamydomonas

Microalgae offer renewable and sustainable sources for the bioindustrial production of next-generation biofuels and biomaterials. In this work, we heterologously expressed a lipid transporter gene (MMF1) from the major facilitator superfamily in the model green microalga Chlamydomonas reinhardtii, under the influence of a strong light and temperature-inducible promoter. The full-length cDNA sequence of MMF1 from Moesziomyces antarcticus T-34 (MaMMF1) encodes for a 542 amino acid polypeptide with transmembrane efflux pump activity. M. antarcticus is a fungus that can produce and secrete large amounts of glycolipid biosurfactants known as mannosylerythritol lipids (MELs) under nitrogen starvation conditions. Heterologous expression of MaMMF1 in C. reinhardtii resulted in a slight increase in cell biomass, with mutants exhibiting on average about 1.8-fold larger cell sizes. Total lipid content almost doubled in cells expressing MaMMF1 relative to the control strain when cultures were grown for two days under nitrogen starvation. Moreover, average starch content was over 2-fold higher in the mutants. Our results showed that algal strains engineered with the MaMMF1 MEL transporter were capable of possibly redirecting the carbon flux, which resulted in improved growth and accumulation of high-value storage compounds.

Temperature -and pressure-dependent branching ratios for 2,6-dimethylheptyl radicals (C9H19) + O2 reaction: An ab initio and RRKM/ME approach on a key component of bisabolane biofuel

Chemical kinetics mechanisms contain elementary reactions and associated Arrhenius rate parameters are necessary to understand the modeling of hydrocarbon autoignition chemistry. The complexity of such mechanisms is increased due to interest in operating next-generation combustion strategies in the low-temperature region (≤1000 K), which is governed by O2-addition to alkyl radicals (R), subsequent radical isomerization and decomposition steps thereafter. In this work, we report theoretically the reaction of molecular oxygen to the four isomers of 2,6-dimethylheptyl radicals (C9H19). The stationary points on potential energy surfaces (PES), rate constants, and branching ratios from C9H19 isomers initiated by O2 has been investigated by a combination of ab initio/density functional theory (CBS-QB3) and advanced statistical rate theory i.e., microcanonical variational transition state theory (μCVTST) and Rice-Ramsperger-Kassel-Marcus (RRKM)/master equation (ME) simulations. The temperature- and pressure-dependent rate constants and branching ratios over temperature range 400 K–1000 K (with an interval of 50 K) and with different pressures 0.001, 0.01, 0.1, 1, 10 and 100 bar were computed. The RRKM/ME calculations reveal for addition of O2 to the primary radical, 2,6-dimethylhept-1-yl + O2 reaction, the formation of 2-iso-butyl-4-methyl-tetrahydrofuran (a five membered cyclic ether) + OH via concerted C–C and O–O bond scission of primary-secondary QOOH and formation of ROO-1 is the kinetically favorable pathway below 600 K. For 2,6-dimethylhept-2-yl + O2, three competitive favorable channels lead to the formation of 5-iso-propyl-2,2-dimethyl-tetrahydrofuran + OH, a five membered cyclic ether formed coincident with OH in a chain-propagating step from decomposition of tertiary-secondary hydroperoxyalkyl (QOOH), formation of a six membered cyclic ether i.e., 2,2,6,6-tetramethylpyran and ROO-2, however at higher temperature (>900 K) and 2–6-dimethyl-2-heptene is contributed equally over other products. For 2,6-dimethylhept-3-yl + O2 reaction, leading to 5-iso-propyl-2,2-dimethyltetrahydrofuran + OH (same products as in ROO-2) from decomposition of secondary–tertiary hydroperoxyalkyl (QOOH). For 2,6-dimethylhept-4-yl + O2 reaction, it reveals the formation of chain-propagation channels leading to iso-butene + methyl-isobutanal + OH. The results of this study reveals the importance of temperature- and pressure-dependent branching ratios, which is necessary to understand the low temperature internal combustion mechanism. The unimolecular rate constants were also compared with the previously reported values for 2,6-dimethylheptyl radical + O2 and similar reaction system i.e., 2,5-dimethylhexyl radical + O2. The updated rate constants and branching ratios may also serve as general prototypes for low-temperature oxidation of branched alkanes of next-generation biofuels with similar structural motifs, such as bisabolane and farnesane.

Case study of autocatalysis reactions on tetra hybrid binary nanofluid flow via Riga wedge: Biofuel thermal application

Ethanol and biodiesel, which both belong to the first generation of biofuel technology, are the two most popular forms of biofuels now in use. In order to create next-generation biofuels using waste, cellulosic biomass, and algae-based resources, the Bioenergy Technologies Office (BETO) is working with business. The present article is designed to study the effect of tetra hybrid nanoparticles with the utilization of the novel Hamilton and Crosser model and catalytic reaction on binary fluid with the consideration of ethanol biofuel as a base fluid. Ethanol comprising tetra hybrid nanoparticles and heterogeneous catalytic reaction amplifies thermal conductivity and significantly increases brake thermal efficiency and reduces brake-specific fuel consumption in diesel engines. Therefore, the aim of this article is a theoretical checkup that is related to heat and mass transport of biofuel flow considering binary fluid accompanied with autocatalysis reaction and novel tetra hybrid nanoparticles on biofluid flow subjected to a Riga wedge. Transportation of heat via nonuniform heat source/sink, thermal radiation, and thermal conductivity are in our consideration. The mathematics of the assumed problem generates the system of non-linear partial differential equations from basic equations of momentum, energy, and mass. The usage of non-dimensional variables gave a system of non-linear ODEs with boundary conditions which are further dealt with in the Lobatto111A scheme. The results are obtained for stretching/shrinking wedge with several parameters. From obtained results, it is observed that the velocity field diminishes owing to magnification in Weissenberg number and Casson fluid parameter. The temperature field diminishes by amplifying heat generation, thermal radiation, and variable thermal conductivity parameter. Concentration distribution escalates by rising homogeneous reaction parameters.

High production of furfural by flash pyrolysis of C6 sugars and lignocellulose by Pd-PdO/ZnSO4 catalyst

Furfural (C5H4O2) is an important platform chemical for the synthesis of next-generation bio-fuels. Herein, we report a novel and reusable heterogeneous catalyst, Pd-PdO/ZnSO4 with 1.1 mol% palladium (Pd), for the production of furfural by flash pyrolysis of lignocelluloses at 400 °C. For both dry and wet C6 cellulose and its monomers, the furfural yields reach 74–82 mol%, relative to 96 mol% from C5 xylan and 23–33 wt% from sugarcane bagasse and corncob. The catalyst has a well-defined structure and bifunctional property, comprising a ZnSO4 support for the dehydration and isomerization of glucose, and a local core-shell configuration for metallic Pd0 encapsulated by an oxide (PdO) layer. The PdO layer is active for the Grob fragmentation of formaldehyde (HCHO) from glucose, which is subsequently in-situ steam reformed into syn-gas (i.e. H2 and CO), whereas the Pd0 core is active in promoting the last dehydration step for the formation of furfural.

Integrating Carbohydrate and C1 Utilization for Chemicals Production.

In the face of increasing mobility and energy demand, as well as the mitigation of climate change, the development of sustainable and environmentally friendly alternatives to fossil fuels will be one of the most important tasks facing humankind in the coming years. In order to initiate the transition from a petroleum-based economy to a new, greener future, biofuels and synthetic fuels have great potential as they can be adapted to already common processes. Thereby, especially synthetic fuels from CO2 and renewable energies are seen as the next big step for a sustainable and ecological life. In our study, we directly address the sustainable production of the most common biofuel, ethanol, and the highly interesting next-generation biofuel, isobutanol, from methanol and xylose, which are directly derivable from CO2 and lignocellulosic waste streams, respectively, such integrating synthetic fuel and biofuel production. After enzyme and reaction optimization, we succeeded in producing either 3 g L-1 ethanol or 2 g L-1 isobutanol from 7.5 g L-1 xylose and 1.6 g L-1 methanol. In our cell-free enzyme system, C1-compounds are efficiently combined and fixed by the key enzyme transketolase and converted to the intermediate pyruvate. This opens the way for a hybrid production of biofuels, platform chemicals and fine chemicals from CO2 and lignocellulosic waste streams as alternative to conventional routes depending solely either on CO2 or sugars.

The Key to A Sustainable Future- Algal Biofuel

The depletion of fossil fuel reserves is posing a significant challenge in meeting the increasing energy demands. In response to concerns related to pollution, global warming, and rising oil costs, the exploration for alternative energy sources has gained momentum. Among these alternatives, macroalgae has emerged as a promising renewable energy option. Furthermore, various alternative fuels, such as hydrogen, natural gas, propane, ethanol, methanol, butanol, vegetable and waste-derived oils, and electricity, can be utilized either in a standalone fuel system or in combination with conventional fuels like gasoline, diesel, and petrol within hybrid-electric or flexible fuel systems. A particularly noteworthy advancement in next-generation biofuels is the production of biofuels derived from microalgae. Although further research is required to optimize algae production methods, equal attention must be given to downstream processing, particularly the generation of biofuels. In the face of the severe global consequences associated with the fossil fuel energy crisis, biofuels are progressively establishing themselves as a potent and sustainable source of renewable energy.

Development of a stable semi-continuous lipid production system of an oleaginous Chlamydomonas sp. mutant using multi-omics profiling

BackgroundMicroalgal lipid production has attracted global attention in next-generation biofuel research. Nitrogen starvation, which drastically suppresses cell growth, is a common and strong trigger for lipid accumulation in microalgae. We previously developed a mutant Chlamydomonas sp. KAC1801, which can accumulate lipids irrespective of the presence or absence of nitrates. This study aimed to develop a feasible strategy for stable and continuous lipid production through semi-continuous culture of KAC1801.ResultsKAC1801 continuously accumulated > 20% lipid throughout the subculture (five generations) when inoculated with a dry cell weight of 0.8–0.9 g L−1 and cultured in a medium containing 18.7 mM nitrate, whereas the parent strain KOR1 accumulated only 9% lipid. Under these conditions, KAC1801 continuously produced biomass and consumed nitrates. Lipid productivity of 116.9 mg L−1 day−1 was achieved by semi-continuous cultivation of KAC1801, which was 2.3-fold higher than that of KOR1 (50.5 mg L−1 day−1). Metabolome and transcriptome analyses revealed a depression in photosynthesis and activation of nitrogen assimilation in KAC1801, which are the typical phenotypes of microalgae under nitrogen starvation.ConclusionsBy optimizing nitrate supply and cell density, a one-step cultivation system for Chlamydomonas sp. KAC1801 under nitrate-replete conditions was successfully developed. KAC1801 achieved a lipid productivity comparable to previously reported levels under nitrogen-limiting conditions. In the culture system of this study, metabolome and transcriptome analyses revealed a nitrogen starvation-like response in KAC1801.

Prenol as a Next-Generation Biofuel or Additive: A Comprehension of the Hydrogen Abstraction Reactions by a H Atom.

Thermal rate coefficients for the hydrogen abstraction reactions of prenol (3-methyl-2-butenol) by a hydrogen atom were calculated with the multipath canonical variational theory with small-curvature tunneling (MP-CVT/SCT). The conformational search was performed with a dual-level approach, and the multistructural torsional anharmonicity effects were corrected through the rovibrational partition function calculated with the multistructural method based on a coupled torsional potential (MS-T(C)). This methodology allows us to estimate the thermal rate constants in the temperature range of 200-2500 K and fit them into two analytical expressions. Differences between the number of conformations on the torsional potential energy surfaces for prenol and the transition state decrease the thermal rate constants for the H-abstraction at the α carbon. An opposite behavior was detected for the abstractions on the δ site. The product branching ratios were calculated using single-structure and multipath approaches. The product distributions from the former are shown to be inadequate for studying the mechanism under combustion conditions. The values estimated from MP-CVT/SCT rate coefficients indicated that the radicals from (Rα) and (Rδ)/(Rδ') are formed in considerable amounts. These species are fundamental in comprehending the inhibition and promotion of the autoignition phenomena.

Critical Assessment of Reaction Pathways for Next-Generation Biofuels from Renewable Resources: 5-Ethoxymethylfurfural

Critical Assessment of Reaction Pathways for Next-Generation Biofuels from Renewable Resources: 5-Ethoxymethylfurfural

Performance and Emission Analysis of Watermelon Seed Oil Methyl Ester and n-Butanol Blends Fueled Diesel Engine

The impact of n-butanol, a next-generation biofuel, with watermelon methyl ester in a constant-speed diesel engine was analyzed. Methyl ester from watermelon seed oil is considered to be a promising alternative source to the standard diesel due to similar characterization. The n-butanol additive was added in small proportions as an oxygenated fuel for reducing emissions, improving thermal efficiency, and accelerating the combustion process. N-Butanol is blended with watermelon methyl ester in the form of emulsions in two different proportions (5% and 10% volume basis). Experiments were conducted with three different emulsions fuels, WME20, W20Bu5D75, and W20Bu10D70, and compared vis-à-vis standard diesel. Investigations revealed that the addition of n-butanol as an enhancer with WME20 improved characteristics owing to its inherent nature of oxygen content. The blending of WME with n-butanol improves brake thermal efficiency when compared to WME20 and slightly matches with standard diesel. The max BTE was recorded 32.79% for WME20Bu10D70 at the crest load. The peak BSFC was 0.26 kg/kWh for W20Bu10D70 at the crest load. The emissions such as CO, smoke opacity, and HC were significantly reduced, vis-à-vis diesel, and the oxides of nitrogen (NOX) and carbon dioxide (CO2) were decreased, relative to WME20. The maximum EGT was 354.98°C for W20Bu10D70 at the crest load. The peak CO emissions were 0.078% for W20Bu5D75 at the crest load. The blending of n-butanol with WME20 reduces the ignition delay while the combustion duration increases with an increase at full load conditions. The emulsion fuels tested in an unmodified engine did no negative impact on the engine stability.

Production of 4-Deoxy-L-erythro-5-Hexoseulose Uronic Acid Using Two Free and Immobilized Alginate Lyases from Falsirhodobacter sp. Alg1.

Falsirhodobacter sp. alg1 expresses two alginate lyases, AlyFRA and AlyFRB, to produce the linear monosaccharide 4-deoxy-L-erythro-5-hexoseulose uronic acid (DEH) from alginate, metabolizing it to pyruvate. In this study, we prepared recombinant AlyFRA and AlyFRB and their immobilized enzymes and investigated DEH production. Purified AlyFRA and AlyFRB reacted with sodium alginate and yielded approximately 96.8% DEH. Immobilized AlyFRA and AlyFRB were prepared using each crude enzyme solution and κ-carrageenan, and immobilized enzyme reuse in batch reactions and DEH yield were examined. Thus, DEH was produced in a relatively high yield of 79.6%, even after the immobilized enzyme was reused seven times. This method can produce DEH efficiently and at a low cost and can be used to mass produce the next generation of biofuels using brown algae.

A Comprehensive Review of Feedstocks as Sustainable Substrates for Next-Generation Biofuels

A Comprehensive Review of Feedstocks as Sustainable Substrates for Next-Generation Biofuels

Comparative functional genomics identifies an iron-limited bottleneck in a Saccharomyces cerevisiae strain with a cytosolic-localized isobutanol pathway

Metabolic engineering strategies have been successfully implemented to improve the production of isobutanol, a next-generation biofuel, in Saccharomyces cerevisiae. Here, we explore how two of these strategies, pathway re-localization and redox cofactor-balancing, affect the performance and physiology of isobutanol producing strains. We equipped yeast with isobutanol cassettes which had either a mitochondrial or cytosolic localized isobutanol pathway and used either a redox-imbalanced (NADPH-dependent) or redox-balanced (NADH-dependent) ketol-acid reductoisomerase enzyme. We then conducted transcriptomic, proteomic and metabolomic analyses to elucidate molecular differences between the engineered strains. Pathway localization had a large effect on isobutanol production with the strain expressing the mitochondrial-localized enzymes producing 3.8-fold more isobutanol than strains expressing the cytosolic enzymes. Cofactor-balancing did not improve isobutanol titers and instead the strain with the redox-imbalanced pathway produced 1.5-fold more isobutanol than the balanced version, albeit at low overall pathway flux. Functional genomic analyses suggested that the poor performances of the cytosolic pathway strains were in part due to a shortage in cytosolic Fe–S clusters, which are required cofactors for the dihydroxyacid dehydratase enzyme. We then demonstrated that this cofactor limitation may be partially recovered by disrupting iron homeostasis with a fra2 mutation, thereby increasing cellular iron levels. The resulting isobutanol titer of the fra2 null strain harboring a cytosolic-localized isobutanol pathway outperformed the strain with the mitochondrial-localized pathway by 1.3-fold, demonstrating that both localizations can support flux to isobutanol.