Addressing the energy crisis: using microbes to make biofuels

Efficient synthesis of vanillylamine through bioamination of lignin-derived vanillin by recombinant E. coli containing ω-transaminase from Caulobacter sp. D5 in dimethyl sulfoxide-water

Lignin is a plentiful and readily accessible renewable resource. Vanillylamine is a crucial raw material used to synthesize pharmaceuticals and high-value furan compounds that can be acquired by aminating lignin-derived vanillin (Van). However, effectually achieving the biocatalytic synthesis of vanillylamine has remained challenging. In this study, a dimethyl sulfoxide (DMSO)-H2O (1:9, vol/vol) bioreaction medium was constructed, and a recombinant E. coli ATA1012 carrying ω-transaminase from Caulobacter sp. D5 was used as the ω-transaminase biocatalyst to acquire the effectual biocatalytic synthesis of vanillylamine. Under optimized bioreaction conditions (37 ℃ and pH 7.5) by supplementary of isopropylamine (IPA) (Van/IPA = 1:5, mol/mol), 80-100 mM Van could be effectually converted by ATA1012 whole cells in DMSO-H2O (1:9, vol/vol) within 12 h, yielding 91.2 %-95.4 % vanillylamine, with >99 % selectivity. An efficient amination process was developed using ATA1012 with superior transaminase catalytic activity and substrate tolerance to effectively convert Van to vanillylamine in a DMSO-H2O medium.

Saccharomyces cerevisiae cellular engineering for the production of FAME biodiesel

The unsustainable and widespread utilization of fossil fuels continues to drive the rapid depletion of global supplies. Biodiesel has emerged as one of the most promising alternatives to conventional diesel, leading to growing research interest in its production. Microbes can facilitate the de novo synthesis of a type of biodiesel in the form of fatty acid methyl esters (FAMEs). In this study, Saccharomyces cerevisiae metabolic activity was engineered to facilitate enhanced FAME production. Initially, free fatty acid concentrations were increased by deleting two acetyl-CoA synthetase genes (FAA1, FAA4) and an acyl-CoA oxidase gene (POX1). Intracellular S-adenosylmethionine (SAM) levels were then enhanced via the deletion of an adenosine kinase gene (ADO1) and the overexpression of a SAM synthetase gene (SAM2). Lastly, the S. cerevisiae strain overproducing free fatty acids and SAM were manipulated to express a plasmid encoding the Drosophila melanogaster Juvenile Hormone Acid O-Methyltransferase (DmJHAMT). Using this combination of engineering approaches, a FAME concentration of 5.79 ± 0.56 mg/L was achieved using these cells in the context of shaking flask fermentation. To the best of our knowledge, this is the first detailed study of FAME production in S. cerevisiae. These results will provide a valuable basis for future efforts to engineer S. cerevisiae strains for highly efficient production of biodiesel.

Biosynthesis of fragrance 2-phenylethanol from sugars by Pseudomonas putida

BACKGROUND

Petrochemicals contribute to environmental issues, with concerns ranging from energy consumption and carbon emission to pollution. In contrast, microbial biorefineries offer eco-friendly alternatives. The solvent-tolerant Pseudomonas putida DOT-T1E serves as a suitable host for producing aromatic compounds, specifically L-phenylalanine and its derivative, 2-phenylethanol (2-PE), which find widespread applications in various industries.

RESULTS

This study focuses on enhancing 2-PE production in two L-phenylalanine overproducing strains of DOT-T1E, namely CM12-5 and CM12-5Δgcd (xylABE), which grow with glucose and glucose-xylose, respectively. To synthesize 2-PE from L-phenylalanine, these strains were transformed with plasmid pPE-1, bearing the Ehrlich pathway genes, and it was found higher 2-PE production with glucose (about 50-60 ppm) than with xylose (< 3 ppm). To understand the limiting factors, we tested the addition of phenylalanine and intermediates from the Ehrlich and shikimate pathways. The results identified intracellular L-phenylalanine as a key limiting factor for 2-PE production. To overcame this limitation, a chorismate mutase/prephenate dehydratase variant-insentive to feedback inhibition by aromatic amino acids-was introduced in the producing strains. This led to increased L-phenylalanine production and subsequently produced more 2-PE (100 ppm). Random mutagenesis of the strains also produced strains with higher L-phenylalanine titers and increased 2-PE production (up to 120 ppm). The improvements resulted from preventing dead-end product accumulation from shikimate and limiting the catabolism of potential pathway intermediates in the Ehrlich pathway. The study explored agricultural waste substrates, such as corn stover, sugarcane straw and corn-syrup as potential C sources. The best results were obtained using 2G substrates at 3% (between 82 and 100 ppm 2-PE), with glucose being the preferred sugar for 2-PE production among the monomeric sugars in these substrates.

CONCLUSIONS

The findings of this study offer strategies to enhance phenylalanine production, a key substrate for the synthesis of aromatic compounds. The ability of P. putida DOT-T1E to thrive with various C-sources and its tolerance to substrates, products, and potential toxicants in industrial wastes, are highlighted. The study identified and overcome possible bottlenecks for 2-PE production. Ultimately, the strains have potential to become efficient microbial platforms for synthesizing 2-PE from agro-industrial waste materials.

Sustainable energy storage: Mangifera indica leaf waste-derived activated carbon for long-life, high-performance supercapacitors

Biomass waste-derived activated carbon has a wide range of applications, including air and water purification, gas separation, energy storage, and catalysis. This material has become increasingly popular in recent years as a result of the growing demand for sustainable and eco-friendly materials. In this study, Mangifera indica leaf waste-derived activated carbon has been investigated as an electrode material for high-performance supercapacitors. The dried Mangifera indica leaves were first carbonized using FeCl3 and then activated using KOH to increase their surface area and pore structure at different temperatures. The activated carbon prepared at 725 °C has shown a high specific capacitance of 521.65 F g-1 at a current density of 0.5 A g-1 and also achieved an energy density of 17.04 W h kg-1 at a power density of 242.50 W kg-1 in the 6 M KOH electrolyte. Significantly, it has demonstrated remarkable electrochemical cycling stability, retaining 96.60% of its initial capacity even after undergoing 10 001 cycles at a scan rate of 500 mV s-1. The superior electrochemical performance of the activated carbon can be attributed to its high surface area of 1232.63 m2 g-1, well-distributed pore size, and excellent degree of graphitization, which all facilitate the rapid diffusion of ions and enhance the accessibility of the electrolyte to the electrode surface. Hence, this study provides a promising route for utilizing waste biomass as a low-cost, sustainable electrode material for energy storage devices.

Recent Advances of Benzodithiophene-Based Donor Materials for Organic Solar Cells

Recently, the power conversion efficiency (PCE) of organic solar cells (OSCs) has increased dramatically, making a big step toward the industrial application of OSCs. Among numerous OSCs, benzodithiophene (BDT)-based OSCs stand out in achieving efficient PCE. Notably, single-junction OSCs using BDT-based polymers as donor materials have completed a PCE of over 19%, indicating a dramatic potential for preparing high-performance large-scale OSCs. This paper reviews the recent progress of OSCs based on BDT polymer donor materials (PDMs). The development of BDT-based OSCs is concisely summarized. Meanwhile, the relationship between the structure of PDMs and the performance of OSCs is further described in this review. Besides, the development and prospect of single junction OSCs are also discussed.

Solar bioreactors used for the industrial production of microalgae

Microalgae are excellent sources of biomass containing several important compounds for human and animal nutrition-proteins, lipids, polysaccharides, pigments and antioxidants as well as bioactive secondary metabolites. In addition, they have a great biotechnological potential for nutraceuticals, and pharmaceuticals as well as for CO2 sequestration, wastewater treatment, and potentially also biofuel and biopolymer production. In this review, the industrial production of the most frequently used microalgae genera-Arthrospira, Chlorella, Dunaliella, Haematococcus, Nannochloropsis, Phaeodactylum, Porphyridium and several other species is discussed as concerns the applicability of the most widely used large-scale systems, solar bioreactors (SBRs)-open ponds, raceways, cascades, sleeves, columns, flat panels, tubular systems and others. Microalgae culturing is a complex process in which bioreactor operating parameters and physiological variables closely interact. The requirements of the biological system-microalgae culture are crucial to select the suitable type of SBR. When designing a cultivation process, the phototrophic production of microalgae biomass, it is necessary to employ SBRs that are adequately designed, built and operated to satisfy the physiological requirements of the selected microalgae species, considering also local climate. Moreover, scaling up microalgae cultures for commercial production requires qualified staff working out a suitable cultivation regime. KEY POINTS: • Large-scale solar bioreactors designed for microalgae culturing. • Most frequently used microalgae genera for commercial production. • Scale-up requires suitable cultivation conditions and well-elaborated protocols.

Weaponising microbes for peace

There is much human disadvantage and unmet need in the world, including deficits in basic resources and services considered to be human rights, such as drinking water, sanitation and hygiene, healthy nutrition, access to basic healthcare, and a clean environment. Furthermore, there are substantive asymmetries in the distribution of key resources among peoples. These deficits and asymmetries can lead to local and regional crises among peoples competing for limited resources, which, in turn, can become sources of discontent and conflict. Such conflicts have the potential to escalate into regional wars and even lead to global instability. Ergo: in addition to moral and ethical imperatives to level up, to ensure that all peoples have basic resources and services essential for healthy living and to reduce inequalities, all nations have a self-interest to pursue with determination all available avenues to promote peace through reducing sources of conflicts in the world. Microorganisms and pertinent microbial technologies have unique and exceptional abilities to provide, or contribute to the provision of, basic resources and services that are lacking in many parts of the world, and thereby address key deficits that might constitute sources of conflict. However, the deployment of such technologies to this end is seriously underexploited. Here, we highlight some of the key available and emerging technologies that demand greater consideration and exploitation in endeavours to eliminate unnecessary deprivations, enable healthy lives of all and remove preventable grounds for competition over limited resources that can escalate into conflicts in the world. We exhort central actors: microbiologists, funding agencies and philanthropic organisations, politicians worldwide and international governmental and non-governmental organisations, to engage - in full partnership - with all relevant stakeholders, to 'weaponise' microbes and microbial technologies to fight resource deficits and asymmetries, in particular among the most vulnerable populations, and thereby create humanitarian conditions more conducive to harmony and peace.

Insights into the susceptibility of Pseudomonas putida to industrially relevant aromatic hydrocarbons that it can synthesize from sugars

Pseudomonas putida DOT-T1E is a highly solvent tolerant strain for which many genetic tools have been developed. The strain represents a promising candidate host for the synthesis of aromatic compounds-opening a path towards a green alternative to petrol-derived chemicals. We have engineered this strain to produce phenylalanine, which can then be used as a raw material for the synthesis of styrene via trans-cinnamic acid. To understand the response of this strain to the bioproducts of interest, we have analyzed the in-depth physiological and genetic response of the strain to these compounds. We found that in response to the exposure to the toxic compounds that the strain can produce, the cell launches a multifactorial response to enhance membrane impermeabilization. This process occurs via the activation of a cis to trans isomerase that converts cis unsaturated fatty acids to their corresponding trans isomers. In addition, the bacterial cells initiate a stress response program that involves the synthesis of a number of chaperones and ROS removing enzymes, such as peroxidases and superoxide dismutases. The strain also responds by enhancing the metabolism of glucose through the specific induction of the glucose phosphorylative pathway, Entner-Doudoroff enzymes, Krebs cycle enzymes and Nuo. In step with these changes, the cells induce two efflux pumps to extrude the toxic chemicals. Through analyzing a wide collection of efflux pump mutants, we found that the most relevant pump is TtgGHI, which is controlled by the TtgV regulator.

Unravelling Metagenomics Approach for Microbial Biofuel Production

Renewable biofuels, such as biodiesel, bioethanol, and biobutanol, serve as long-term solutions to fossil fuel depletion. A sustainable approach feedstock for their production is plant biomass, which is degraded to sugars with the aid of microbes-derived enzymes, followed by microbial conversion of those sugars to biofuels. Considering their global demand, additional efforts have been made for their large-scale production, which is ultimately leading breakthrough research in biomass energy. Metagenomics is a powerful tool allowing for functional gene analysis and new enzyme discovery. Thus, the present article summarizes the revolutionary advances of metagenomics in the biofuel industry and enlightens the importance of unexplored habitats for novel gene or enzyme mining. Moreover, it also accentuates metagenomics potentials to explore uncultivable microbiomes as well as enzymes associated with them.

Microbial biotechnology to assure national security of supplies of essential resources: energy, food and water, medical reagents, waste disposal and a circular economy

The core responsibility of governments is the security of their citizens, and this means inter alia protecting their safety, nutrition and health. Microbiology and microbial biotechnology have key roles to play in improving supply security of essential resources. In this paper, we discuss the urgent need to fully and immediately exploit existing microbial biotechnologies to maximize supply security of energy, food and medical supplies, and of waste management, and to invest in new research specifically targetting supply security of essential resources.