Clostridium sp. as Bio-Catalyst for Fuels and Chemicals Production in a Biorefinery Context

Opportunistic Features of Non-Clostridium botulinum Strains Containing bont Gene Cluster

The cluster of genes determining the production of botulinum toxins is an attribute of not only the Clostridium botulinum species. This cluster is also found in other members of the Clostridium genus, such as C. baratii, C. butyricum, and C. sporogenes. The occurrence of a botulinum-like cluster has also been recorded in strains of other genera, i.e., Enterococcus faecium, as well as in a Gram-negative species isolated from freshwater sediments; however, the biological activity of bont-related genes has not been noted. It can be said that the mentioned species have a dual nature. Another species with a dual nature is C. butyricum. This bacterium is a common human and animal gut commensal bacterium and is also frequently found in the environment. Although non-toxigenic strains are currently used as probiotics in Asia, other strains have been implicated in pathological conditions, such as botulism in infants or necrotizing enterocolitis in preterm neonates. Additionally, C. baratii strains are rare opportunistic pathogens associated with botulism intoxication. They have been isolated from food and soil and can be carried asymptomatically or cause botulism outbreaks in animals and humans. In addition to the mentioned clostridia, the other microorganisms considered as non-toxigenic have also been suspected of carrying botulinum cluster Gram-negative bacteria, such as Chryseobacterium piperi isolated from freshwater sediments; however, the biological activity of bont-related genes has not been noted. Additionally, Enterococcus faecium strains have been discovered carrying BoNT-related clusters (BoNT/En). Literature data regarding the heterogeneity of BoNT-producing strains indicate the requirement to reclassify C. botulinum species and other microorganisms able to produce BoNTs or possess botulinum-like gene clusters. This article aims to show the dual nature of Clostridium strains not belonging to the C. botulinum species that are sporadically able to carry bont clusters, which are usually considered saprophytic and even probiotic, and bont-like clusters in microorganisms from other genera. The aim was also to consider the genetic mechanisms of botulinum cluster expression in strains that are considered opportunistic and the microbiological safety aspects associated with their occurrence in the environment.

Gold Nanoparticles in Nanobiotechnology: From Synthesis to Biosensing Applications

Nanobiotechnology has ushered in a new era of scientific discovery where the unique properties of nanomaterials, such as gold nanoparticles, have been harnessed for a wide array of applications. This review explores gold nanoparticles' synthesis, properties, and multidisciplinary applications, focusing on their role as biosensors. Gold nanoparticles possess exceptional physicochemical attributes, including size-dependent optical properties, biocompatibility, and ease of functionalization, making them promising candidates for the development of biosensing platforms. The review begins by providing a comprehensive overview of gold nanoparticle synthesis techniques, highlighting the advantages and disadvantages of various approaches. It then delves into the remarkable properties that underpin their success in biosensing, such as localized surface plasmon resonance and enhanced surface area. The discussion also includes the functionalization strategies that enable specific binding to biomolecules, enhancing the sensitivity and selectivity of gold-nanoparticle-based biosensors. Furthermore, this review surveys the diverse applications of gold nanoparticles in biosensing, encompassing diagnostics, environmental monitoring, and drug delivery. The multidisciplinary nature of these applications underscores the versatility and potential of gold nanoparticles in addressing complex challenges in healthcare and environmental science. The review emphasizes the pressing need for further exploration and research in the field of nanobiotechnology, particularly regarding the synthesis, properties, and biosensing applications of gold nanoparticles. With their exceptional physicochemical attributes and versatile functionalities, gold nanoparticles present a promising avenue for addressing complex challenges in healthcare and environmental science, making it imperative to advance our understanding of their synthesis, properties, and applications for enhanced biosensing capabilities and broader scientific innovation.

Biobutanol production from underutilized substrates using Clostridium: Unlocking untapped potential for sustainable energy development

The increasing demand for sustainable energy has brought biobutanol as a potential substitute for fossil fuels. The Clostridium genus is deemed essential for biobutanol synthesis due to its capability to utilize various substrates. However, challenges in maintaining fermentation continuity and achieving commercialization persist due to existing barriers, including butanol toxicity to Clostridium, low substrate utilization rates, and high production costs. Proper substrate selection significantly impacts fermentation efficiency, final product quality, and economic feasibility in Clostridium biobutanol production. This review examines underutilized substrates for biobutanol production by Clostridium, which offer opportunities for environmental sustainability and a green economy. Extensive research on Clostridium, focusing on strain development and genetic engineering, is essential to enhance biobutanol production. Additionally, critical suggestions for optimizing substrate selection to enhance Clostridium biobutanol production efficiency are also provided in this review. In the future, cost reduction and advancements in biotechnology may make biobutanol a viable alternative to fossil fuels.

From waste management to circular economy: Leveraging thermophiles for sustainable growth and global resource optimization

Waste of any origin is one of the most serious global and man-made concerns of our day. It causes climate change, environmental degradation, and human health problems. Proper waste management practices, including waste reduction, safe handling, and appropriate treatment, are essential to mitigate these consequences. It is thus essential to implement effective waste management strategies that reduce waste at the source, promote recycling and reuse, and safely dispose of waste. Transitioning to a circular economy with policies involving governments, industries, and individuals is essential for sustainable growth and waste management. The review focuses on diverse kinds of environmental waste sources around the world, such as residential, industrial, commercial, municipal services, electronic wastes, wastewater sewerage, and agricultural wastes, and their challenges in efficiently valorizing them into useful products. It highlights the need for rational waste management, circularity, and sustainable growth, and the potential of a circular economy to address these challenges. The article has explored the role of thermophilic microbes in the bioremediation of waste. Thermophiles known for their thermostability and thermostable enzymes, have emerged to have diverse applications in biotechnology and various industrial processes. Several approaches have been explored to unlock the potential of thermophiles in achieving the objective of establishing a zero-carbon sustainable bio-economy and minimizing waste generation. Various thermophiles have demonstrated substantial potential in addressing different waste challenges. The review findings affirm that thermophilic microbes have emerged as pivotal and indispensable candidates for harnessing and valorizing a range of environmental wastes into valuable products, thereby fostering the bio-circular economy.

Two-Stage and One-Stage Anaerobic Co-digestion of Vinasse and Spent Brewer Yeast Cells for Biohydrogen and Methane Production

This study aimed to evaluate the two-stage and one-stage anaerobic co-digestion of vinasse and spent brewer yeast cells (SBY) for biohydrogen and methane production. Optimization of the vinasse-to-SBY ratio and fly ash concentration of the two-stage and one-stage production processes was investigated. In the two-stage process, the vinasse-to-SBY ratio and fly ash concentration were optimized, and the leftover effluent was used for methane production. The optimum conditions for biohydrogen production were a vinasse-to-SBY ratio of 7:3% v/w and fly ash concentration of 0.4% w/v, in which the maximum hydrogen yield was 43.7 ml-H2/g-VSadded. In contrast, a vinasse-to-SBY ratio of 10:0% v/w and fly ash concentration of 0.2% w/v were considered optimal for methane production, and resulted in a maximum methane yield of 214.6 ml-CH4/g-VSadded. For the one-stage process, a vinasse-to-SBY ratio of 10:0% v/w and fly ash concentration of 0.1% w/v were considered optimal, and resulted in a maximum methane yield of 243.6 ml-CH4/g-VSadded. In the two-stage process, the energy yield from hydrogen (0.05-0.47 kJ/g-VSadded) was 0.62%-11.78%, and the major fraction was approximately 88.22%-99.38% gain from methane (3.19-7.73 kJ/g-VSadded). For the one-stage process, the total energy yield distribution ranged from 4.20 to 8.77 kJ/g-VSadded.

Influence of medium modifications (optimization) on high nematicidal activity of the fermentation broth of Clostridium beijerinckii

Introduction: The nematode species Meloidogyne incognita has been responsible for significant financial losses within the agricultural sector. Nematophagous bacteria, characterised by their extensive distribution and broad spectrum of hosts, exhibit remarkable efficacy as natural antagonists against nematodes. Sneb518 (Clostridium beijerinckii) fermentation broth displayed substantial biocontrol activity against M. incognita in previous research. Optimizing fermentation conditions is a fundamental technique for dramatically enhancing end product performance. There has been no such study conducted yet on enhancing the nematicidal activities of Sneb518 (Clostridium beijerinckii) fermentation using response surface methodology (RSM). Methods: The influence of strain Sneb518 fermentation media and conditions on nematicidal activity was examined using the three-factor technique and a Plackett-Burman design, and the interaction between various fermentation factors was examined using a Box-Behnken design. The present study employed response surface methodology (RSM) to examine and enhance the nematicidal activity of Sneb518 culture filtrates by identifying and optimising the influential components. Results: Glucose, peanut cake flour, and potassium chloride as carbon, nitrogen, and inorganic salts displayed considerably increased nematicidal potential in the present study. Furthermore, the corrected mortality of J2 ranged from 52.24% to 91.15% when utilizing the Box-Behnken design. These findings clearly support the application of RSM for medium optimization. Moreover, the outcomes of the validation experiment corresponded to the model predictions. Discussion: This research has enhanced the biocontrol ability of C. beijerinckii to control M. incognita and this research has led to the advancement of new biocontrol agents.

Harnessing lignocellulosic biomass for butanol production through clostridia for sustainable waste management: recent advances and perspectives

The escalating waste generation rates, driven by population growth, urbanization, and consumption patterns, have made waste management a critical global concern with significant environmental, social, and economic repercussions. Among the various waste sources, lignocellulosic biomass represents a significant proportion of agricultural, agro-industrial, and municipal wastes. Biofuels are gaining attention as a promising substitute to fossil fuels, and butanol is one such biofuel that has been identified as a potential candidate due to its compatibility with existing fuel infrastructure, lower volatility, and higher energy density. Sustainable management of lignocellulosic biomass waste and its utilization in fermentation are viable alternatives to produce butanol via the promising microbial catalyst clostridia. This review provides an overview of lignocellulosic biomass waste management, focusing on recent advances in strain development for butanol production from renewable biomass with an emphasis on future perspectives.

Is a floodplain forest a valuable source for lignin-degrading anaerobic microbial communities: A metagenomic approach

Lignin is one of the most substantial obstacles in the evaluation of lignocellulosic compounds. Although there are numerous approaches for the enhancement of lignin digestion in the literature, there has yet to be an optimized system to date. In this study, samples taken from Igneada floodplain forests were enriched anaerobically at 25 °C and 37 °C, with alkali lignin as the sole carbon source. The activity of the anaerobic lignin-degrading microbial consortium was detected more efficiently at 37 °C, where biogas production exceeded 3.5 mLgas/mLmedium. It was observed that the microbial community initially dominated by Proteobacteria (around 60%) changed completely after enrichment and was led by members of the Firmicutes phylum (up to 90%). The dominant species (Sporomusa termitida, Desulfitobacterium hafniense, Citrobacter freundii, Citrobacter portucalensis, Alkalibacter rhizosphaerae, and Gudongella oleilytica) occupying more than 50% in the final enrichment culture were only around 2% in the raw samples. Therefore, this study, one of the few in which enriched environmental samples were sequenced using MinION, demonstrated that longoses are exceptional reservoirs for lignin-digesting anaerobic microorganisms.

Main genome characteristics of butanol-producing Clostridium sp. UCM В-7570 strain

The rapid development of new molecular methods and approaches, sequencing technologies, has provided new insights into genetic and structural features of bacterial genomes. Information about the genetic organization of metabolic pathways and their regulatory elements has greatly contributed to the increase in the number of studies related to the construction of new bacterial strains with improved characteristics. In this study, the entire genome of the producing strain Clostridium sp. UCM В-7570 from the "Collection of producing strains of microorganisms and plant lines for food and agricultural biotechnology" of Institute of Food Biotechnology and Genomics of the National Academy of Sciences of Ukraine was sequenced and characterized. The genome was assembled into the scaffold with a total size of 4,470,321 bp and a GC content of 29.7%. The total number of genes identified was 4262, of which 4057 encoded proteins, 10 were rRNA operons, and 80 were tRNA genes. The genes of the sequenced genome encoding enzymes involved in butanol fermentation were found and analyzed. They were organized into cluster structures, and their protein sequences were found to be similar to the corresponding strains of C. acetobutylicum, C. beijerinckii, and C. pasteurianum type strains with the highest similarity to the latter. Thus, Clostridium sp. UCM В-7570 producing strain was identified as C. pasteurianum and suggested for metabolic engineering purposes.

Monitoring tert-Butylhydroquinone Content and Its Effect on a Biolubricant during Oxidation

The use of biolubricants as a replacement for petroleum-based products is becoming more and more important, due to the current global energy and crude oil scenario. Thus, the production of biolubricants (which could take place in biorefineries) should be as efficient as possible, obtaining high-quality products with suitable viscosity or oxidation stability values to compete with oil refineries. One of the ways to produce biolubricants is through double transesterification from vegetable oils, where the role of catalysts (usually homogeneous) is vital, as they can improve the yield of the process. However, they should be removed after the chemical reaction, which is difficult once the biolubricant is obtained. Otherwise, they could act as catalysts during oxidation, contributing to a further decrease in oxidation stability and provoking significant changes. To avoid this, antioxidant addition could be an interesting choice. The aim of this work was to assess TBHQ addition in frying oil biolubricants, monitoring properties such as viscosity, acid number, absorbance or TBHQ content (through voltammetry) during oxidation. TBHQ addition (2114 mg·L^-1) kept the main quality parameters during oxidation compared to control samples. In contrast, TBHQ content decreased during oxidation (to 160 mg·L^-1), which proved its antioxidant effect.

Efficient Cross-Coupling of Acetone with Linear Aliphatic Alcohols over Supported Copper on a Fluorite-Type Pr2Zr2O7

In cross-coupling of biomass-derived acetone and alcohols contributing to the production of carbon-elongated chemicals and fuels, the essential catalyst components are metal dispersion for alcohol dehydrogenation and, more importantly, basicity for carbon–carbon coupling. Herein, we report the potential of co-precipitated praseodymia–zirconia solid solution (Pr2Zr2O7) as a support of Cu catalyst for the conversion of acetone and butanol into C7 and C11 products. Cu/Pr2Zr2O7 exhibits a high yield of C7 and C11 (ca. 84%) compared to Cu/ZrO2 and Cu/PrO1.83. Moreover, it is robust under the employed solvent-free conditions owing to a solid solution of Pr2Zr2O7 compared to PrO1.83 showing phase transition to PrOHCO3. It is also tolerant to up to 5 wt % water of the reactant mixture, recyclable once adequate post-treatment is employed after the reaction, and can convert the acetone–butanol–ethanol mixture into C5–C11 products at the nearly equivalent yield (82%) to the acetone–butanol mixture. Therefore, the Cu/Pr2Zr2O7 reported herein is an efficient catalyst for the coupling of acetone with linear aliphatic alcohols into biofuel precursors.

Novel Candidate Microorganisms for Fermentation Technology: From Potential Benefits to Safety Issues

Fermentation is one of the oldest known production processes and the most technologically valuable in terms of the food industry. In recent years, increasing nutrition and health awareness has also changed what is expected from fermentation technology, and the production of healthier foods has started to come a little more forward rather than increasing the shelf life and organoleptic properties of foods. Therefore, in addition to traditional microorganisms, a new generation of (novel) microorganisms has been discovered and research has shifted to this point. Novel microorganisms are known as either newly isolated genera and species from natural sources or bacterial strains derived from existing bacteria. Although novel microorganisms are mostly studied for their use in novel food production in terms of gut-microbiota modulation, recent innovative food research highlights their fermentative effects and usability, especially in food modifications. Herein, Clostridium butyricum, Bacteroides xylanisolvens, Akkermansia muciniphila, Mycobacterium setense manresensis, and Fructophilic lactic acid bacteria (FLAB) can play key roles in future candidate microorganisms for fermentation technology in foods. However, there is also some confusion about the safety issues related to the use of these novel microorganisms. This review paper focuses on certain novel candidate microorganisms for fermentation technology with a deep view of their functions, benefits, and safety issues.

The effects of pH on the production of volatile fatty acids and microbial dynamics in long-term reactor operation

Volatile fatty acids, intermediate products of anaerobic digestion, are one of the most promising biobased products. In this study, the effects of acidic (pH 5), neutral (without pH adjustment) and alkali (pH 10) pH on production efficiency and composition of volatile fatty acids (VFAs) and bacterial community profile were analyzed. The anaerobic sequencing batch reactors were fed cheese production wastewater as substrate and inoculated by anaerobic granular seed sludge. The results showed that acidic pH improved VFA production yield (0.92 at pH 5; 0.42 at pH 10 and 0.21 gCOD/gVS at neutral pH). Furthermore, propionic acid was dominant under both pH 10 (64 ± 20%) and neutral pH (72 ± 8%), whereas, acetic acid (23 ± 20%4), propionic acid (22 ± 3%), butyric acid (21 ± 4%) and valeric acid (15 ± 8%) were almost equally distributed under pH 5. Adaptation of bacterial community to different pH conditions might steer the acid profile: Bacteroidetes (50.07 ± 2%) under pH 10, Proteobacteria (40.74 ± 7%) under neutral pH and Firmicutes (47.64 ± 9%) under pH 5 were the most dominant phylum, respectively. Results indicated pH plays a significant role in VFA production, acid composition, and bacterial community structure. However, in order to gain a concrete understanding effects of pH, characterization of intracellular and extracellular metabolites with dynamics of the microbial community is required.

Unlocking the bacterial domain for industrial biotechnology applications using universal parts and tools

Synthetic biology can play a major role in the development of sustainable industrial biotechnology processes. However, the development of economically viable production processes is currently hampered by the limited availability of host organisms that can be engineered for a specific production process. To date, standard hosts such as Escherichia coli and Saccharomyces cerevisiae are often used as starting points for process development since parts and tools allowing their engineering are readily available. However, their suboptimal metabolic background or impaired performance at industrial scale for a desired production process, can result in increased costs associated with process development and/or disappointing production titres. Building a universal and portable gene expression system allowing genetic engineering of hosts across the bacterial domain would unlock the bacterial domain for industrial biotechnology applications in a highly standardized manner and doing so, render industrial biotechnology processes more competitive compared to the current polluting chemical processes. This review gives an overview of a selection of bacterial hosts highly interesting for industrial biotechnology based on both their metabolic and process optimization properties. Moreover, the requirements and progress made so far to enable universal, standardized, and portable gene expression across the bacterial domain is discussed.

Core-, pan- and accessory genome analyses of Clostridium neonatale: insights into genetic diversity

Clostridium neonatale is a potential opportunistic pathogen recovered from faecal samples in cases of necrotizing enterocolitis (NEC), a gastrointestinal disease affecting preterm neonates. Although the C. neonatale species description and name validation were published in 2018, comparative genomics are lacking. In the present study, we provide the closed genome assembly of the C. neonatale ATCC BAA-265^T (=250.09) reference strain with a manually curated functional annotation of the coding sequences. Pan-, core- and accessory genome analyses were performed using the complete 250.09 genome (4.7 Mb), three new assemblies (4.6–5.6 Mb), and five publicly available draft genome assemblies (4.6–4.7 Mb). The C. neonatale pan-genome contains 6840 genes, while the core-genome has 3387 genes. Pan-genome analysis revealed an ‘open’ state and genomic diversity. The strain-specific gene families ranged from five to 742 genes. Multiple mobile genetic elements were predicted, including a total of 201 genomic islands, 13 insertion sequence families, one CRISPR-Cas type I-B system and 15 predicted intact prophage signatures. Primary virulence classes including offensive, defensive, regulation of virulence-associated genes and non-specific virulence factors were identified. The presence of a tet(W/N/W) gene encoding a tetracycline resistance ribosomal protection protein and a 23S rRNA methyltransferase ermQ gene were identified in two different strains. Together, our results revealed a genetic diversity and plasticity of C. neonatale genomes and provide a comprehensive view of this species genomic features, paving the way for the characterization of its biological capabilities.

ACETONE-BUTYL FERMENTATION PECULIARITIES OF THE BUTANOL STRAINS -PRODUCER

The aim of this review was to generalize and analyze the features of acetone-butyl fermentation as a type of butyric acid fermentation in the process of obtaining butanol as an alternative biofuel. Methods. The methods of analysis and generalization of analytical information and literature sources were used in the review. The results were obtained using the following methods such as microbiological (morphological properties of strains), chromatographic (determination of solvent concentration), spectrophotometric (determination of bacterial concentration), and molecular genetic (phylogenetic analysis of strains). Results. The process of acetone-butyl fermentation was analyzed, the main producer strains were considered, the features of the relationship between alcohol formation and sporulation were described, the possibility of butanol obtaining from synthesis gas was shown, and the features of the industrial production of butanol were considered. Conclusions. The features of the mechanism of acetone-butyl fermentation (the relationships between alcohol formation and sporulation, the duration of the acid-forming and alcohol-forming stages during batch fermentation depending on the change in the concentration of H2, CO, partial pressure, organic acids and mineral additives) and obtaining an enrichment culture during the production of butanol as an alternative fuel were shown. The possibility of using synthesis gas as a substrate for reducing atmospheric emissions during the fermentation process was shown. The direction of increasing the productivity of butanol-producing strains to create a competitive industrial biofuel technology was proposed.

Impacts of Syngas Composition on Anaerobic Fermentation

Energy consumption places growing demands on modern lifestyles, which have direct impacts on the world’s natural environment. To attain the levels of sustainability required to avoid further consequences of changes in the climate, alternatives for sustainable production not only of energy but also materials and chemicals must be pursued. In this respect, syngas fermentation has recently attracted much attention, particularly from industries responsible for high levels of greenhouse gas emissions. Syngas can be obtained by thermochemical conversion of biomass, animal waste, coal, municipal solid wastes and other carbonaceous materials, and its composition depends on biomass properties and gasification conditions. It is defined as a gaseous mixture of CO and H2 but, depending on those parameters, it can also contain CO2, CH4 and secondary components, such as tar, oxygen and nitrogenous compounds. Even so, raw syngas can be used by anaerobic bacteria to produce biofuels (ethanol, butanol, etc.) and biochemicals (acetic acid, butyric acid, etc.). This review updates recent work on the influence of biomass properties and gasification parameters on syngas composition and details the influence of these secondary components and CO/H2 molar ratio on microbial metabolism and product formation. Moreover, the main challenges, opportunities and current developments in syngas fermentation are highlighted in this review.

Residual Gas for Ethanol Production by Clostridium carboxidivorans in a Dual Impeller Stirred Tank Bioreactor (STBR)

Recycling residual industrial gases and residual biomass as substrates to biofuel production by fermentation is an important alternative to reduce organic wastes and greenhouse gases emission. Clostridium carboxidivorans can metabolize gaseous substrates as CO and CO2 to produce ethanol and higher alcohols through the Wood-Ljungdahl pathway. However, the syngas fermentation is limited by low mass transfer rates. In this work, a syngas fermentation was carried out in serum glass bottles adding different concentrations of Tween® 80 in ATCC® 2713 culture medium to improve gas-liquid mass transfer. We observed a 200% increase in ethanol production by adding 0.15% (v/v) of the surfactant in the culture medium and a 15% increase in biomass production by adding 0.3% (v/v) of the surfactant in the culture medium. The process was reproduced in stirred tank bioreactor with continuous syngas low flow, and a maximum ethanol productivity of 0.050 g/L.h was achieved.

Biorefinery Gets Hot: Thermophilic Enzymes and Microorganisms for Second-Generation Bioethanol Production

To mitigate the current global energy and the environmental crisis, biofuels such as bioethanol have progressively gained attention from both scientific and industrial perspectives. However, at present, commercialized bioethanol is mainly derived from edible crops, thus raising serious concerns given its competition with feed production. For this reason, lignocellulosic biomasses (LCBs) have been recognized as important alternatives for bioethanol production. Because LCBs supply is sustainable, abundant, widespread, and cheap, LCBs-derived bioethanol currently represents one of the most viable solutions to meet the global demand for liquid fuel. However, the cost-effective conversion of LCBs into ethanol remains a challenge and its implementation has been hampered by several bottlenecks that must still be tackled. Among other factors related to the challenging and variable nature of LCBs, we highlight: (i) energy-demanding pretreatments, (ii) expensive hydrolytic enzyme blends, and (iii) the need for microorganisms that can ferment mixed sugars. In this regard, thermophiles represent valuable tools to overcome some of these limitations. Thus, the aim of this review is to provide an overview of the state-of-the-art technologies involved, such as the use of thermophilic enzymes and microorganisms in industrial-relevant conditions, and to propose possible means to implement thermophiles into second-generation ethanol biorefineries that are already in operation.

Exploiting Microbes in the Petroleum Field: Analyzing the Credibility of Microbial Enhanced Oil Recovery (MEOR)

Crude oil is a major energy source that is exploited globally to achieve economic growth. To meet the growing demands for oil, in an environment of stringent environmental regulations and economic and technical pressure, industries have been required to develop novel oil salvaging techniques. The remaining ~70% of the world’s conventional oil (one-third of the available total petroleum) is trapped in depleted and marginal reservoirs, and could thus be potentially recovered and used. The only means of extracting this oil is via microbial enhanced oil recovery (MEOR). This tertiary oil recovery method employs indigenous microorganisms and their metabolic products to enhance oil mobilization. Although a significant amount of research has been undertaken on MEOR, the absence of convincing evidence has contributed to the petroleum industry’s low interest, as evidenced by the issuance of 400+ patents on MEOR that have not been accepted by this sector. The majority of the world’s MEOR field trials are briefly described in this review. However, the presented research fails to provide valid verification that the microbial system has the potential to address the identified constraints. Rather than promising certainty, MEOR will persist as an unverified concept unless further research and investigations are carried out.

Physicochemical Properties of Biobutanol as an Advanced Biofuel

Biobutanol is a renewable, less polluting, and potentially viable alternative fuel to conventional gasoline. Biobutanol can be produced from same sources as bioethanol, and it has many advantages over the widespread bioethanol. This paper systematically analyzes biobutanol fuel as an alternative to bioethanol in alcohol–gasoline mixtures and the physicochemical properties. Based on the conducted analyses, it was found that biobutanol mixtures have a more suitable behavior of vapor pressure without the occurrence of azeotrope, do not form a separate phase in lower temperature, it has higher energy density, but slightly reduce the octane number and a have higher viscosity. However, in general, biobutanol has many advantageous properties that could allow its use in gasoline engines instead of the commonly used bioethanol.

From circular synthesis to material manufacturing: advances, challenges, and future steps for using flow chemistry in novel application area

We review the emerging use of flow technologies for circular chemistry and material manufacturing, highlighting advances, challenges, and future directions.

Catalytic Biomass to Renewable Biofuels and Biomaterials

As the only renewable carbon source, biomass can be converted into biofuels, chemicals, and biomaterials, such as ethanol, butanol, glucose, furfural, biochar, and bio-oils, and is considered as a substitute for fossil oil [...]