Search Results (56)

Excessive alcohol consumption is associated with systemic health risks due to the production of acetaldehyde, a primary carcinogen that not only pollutes the environment but also endangers human health. In this study, a promising bacterial strain for biodegrading both ethanol and acetaldehyde was successfully isolated from the traditional fermented food Jiaosu and identified as Acetobacter ghanensis JN01 based on average nucleotide identity (ANI) analysis. Initial ethanol of 1 g/L was completely biodegraded within 4 h, while initial acetaldehyde of 1 g/L was also rapidly removed at 2 or 1 h by whole cells or cell-free extracts (CEs) of JN01, respectively, which indicated that JN01 indeed has a strong ability in the biodegradation of both ethanol and acetaldehyde. Whole-genome sequencing revealed a 2.85 Mb draft genome of JN01 with 57.0% guanine–cytosine (GC) content and the key metabolic genes (adh1, adh2, and aldh) encoding involving alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), co-located with NADH dehydrogenase genes and ethanol-responsive regulatory motifs, supporting the metabolic pathway of transforming ethanol to acetaldehyde, and, subsequently, converting acetaldehyde to acetic acid. Furthermore, selected in vitro safety-related traits of JN01 were also assessed, which is very important in the development of microbial catalysts against both ethanol and acetaldehyde. Full article

Plastic waste accumulation is one of the most pressing environmental challenges of the 21st century, owing to the widespread use of synthetic polymers and the limitations of conventional recycling methods. Among available strategies, chemical upcycling via depolymerization has emerged as a promising circular approach that converts plastic waste back into valuable monomers and chemical feedstocks. This article provides an in-depth narrative review of recent progress in the upcycling of major plastic types such as PET, PU, PS, and engineering plastics through thermal, chemical, catalytic, biological, and mechanochemical depolymerization methods. Each method is critically assessed in terms of efficiency, scalability, energy input, and environmental impact. Special attention is given to innovative catalyst systems, such as microsized MgO/SiO₂ and Co/CaO composites, and emerging enzymatic systems like engineered PETases and whole-cell biocatalysts that enable low-temperature, selective depolymerization. Furthermore, the conversion pathways of depolymerized products into high-purity monomers such as BHET, TPA, vanillin, and bisphenols are discussed with supporting case studies. The review also examines life cycle assessment (LCA) data, techno-economic analyses, and policy frameworks supporting the adoption of depolymerization-based recycling systems. Collectively, this work outlines the technical viability and sustainability benefits of depolymerization as a core pillar of plastic circularity and monomer recovery, offering a path forward for high-value material recirculation and waste minimization. Full article

Geniposide, the predominant bioactive constituent identified in the traditional Chinese medicine herb Gardenia jasminoides, demonstrates clinically significant pharmacological properties. However, the clinical application of geniposide is significantly limited by its insufficient lipophilicity and consequent compromised oral bioavailability. To enhance the lipophilicity and bioavailability of geniposide, a novel whole-cell-mediated catalytic approach was developed for the first time. Aspergillus oryzae whole cells exhibited the highest catalytic activity among microbial strains screened for geniposide decanoylation in the organic solvents. The optimal reaction conditions were identified as follows: acetonitrile served as the reaction solvent, with a substrate molar ratio of 15:1, a whole-cell dosage of 20 mg/mL, and the reaction temperature maintained at 50 °C. Under these optimized conditions, the initial reaction rate was 6.1 mmol/L·h, the conversion reached 99%, and the regioselectivity exceeded 99%. In addition, nine geniposide esters were successfully synthesized, exhibiting outstanding conversion efficiency and high regioselectivities. The pronounced regioselectivity exhibited by Aspergillus oryzae cells toward the 6′-hydroxy group of the glycoside ring in geniposide can be attributed to the lower steric hindrance at this position relative to other hydroxyl moieties, which may enter into the enzyme’s active site more easily to attack the acyl-enzyme intermediate. Full article

In this work, an anode current collector with a scaled step-hole structure (called SF-type) and a cathode current collector with a perforated cross-tilt structure (called X-type) were designed and fabricated for application in passive direct methanol fuel cells (DMFCs). A whole-cell test showed that the combination of an anode SF-type current collector and cathode conventional current collector increased the optimal methanol concentration from 6 M to 8 M and the maximum power density to 5.40 mW cm⁻², which improved the cell performance by 51.6% compared to that of the conventional design under ambient testing conditions. The combination of the anode conventional current collector and cathode X-type current collector achieved a maximum power density of 5.65 mW cm⁻² with a 58.7% performance improvement, while the optimal methanol concentration was increased to 10 M. Furthermore, the combination of anode SF-type and cathode X-type obtained the highest power density at 6.22 mW cm⁻². Notably, the anode and cathode catalyst loadings used in this study were 2.0 mg cm⁻², which is lower than the commonly used loading, thus reducing the fuel cell cost. Full article

A one-pot, one-step protocol combining hydrogen transfer initiated dehydration (HTID) of 1,3-propanediol (1,3-PDO), catalysed by [Cp*IrCl₂(NHC)] (Cp* = pentamethylcyclopentadienyl; NHC = carbene ligand) complexes (1-5H and 1-3F), and self-aldol condensation (SAC) of propanal (2), allowed selective production of C6 aldehyde 2-methyl-pent-2-enal (3), in ionic liquids with high substrate conversion. This shows, for the first time, the conversion of 1,3-propanediol to C6 aldehydes in one pot via a catalytic hydrogen borrowing methodology. The Ir(III) pre-catalysts and the ionic liquids were recyclable. C6 aldehyde 2-methyl-pent-2-enal could also be selectively produced in the presence of water and in neat 1,3-PDO. The efficient, selective delivery of a value-added chemical from 1,3-PDO, a major product of many whole-cell bacterial fermentation processes, shows that the combination of chemo-catalytic processing of the chemical platform via Cp*IrCl₂(NHC)-catalysed HTID/SAC with bio-catalysis has the potential to allow direct valorisation of the bio-renewable feedstocks, such as waste glycerol and sugars, into valuable chemicals. Full article

Developing reusable and easy-to-operate biocatalysts is of significant interest in biodiesel production. Here, magnetic whole-cell catalysts constructed through immobilizing recombinant Escherichia coli cells (containing MAS1 lipase) into Fe₃O₄–chitosan magnetic microspheres (termed MWCC@MAS1) were used for fatty acid methyl ester (FAME) production from waste cooking oil (WCO). During the preparation process of immobilized cells, the effects of chitosan concentration and cell concentration on their activity and activity recovery were investigated. Optimal immobilization was achieved with 3% (w/v) chitosan solution and 10 mg wet cell/mL cell suspension. Magnetic immobilization endowed the whole-cell catalysts with superparamagnetism and improved their methanol tolerance, enhancing the recyclability of the biocatalysts. Additionally, we studied the effects of catalyst loading, water content, methanol content, and reaction temperature on FAME yield, optimizing these parameters using response surface methodology and Box–Behnken design. An experimental FAME yield of 89.19% was gained under the optimized conditions (3.9 wt% catalyst loading, 22.3% (v/w) water content, 23.0% (v/w) methanol content, and 32 °C) for 48 h. MWCC@MAS1 demonstrated superior recyclability compared to its whole-cell form, maintaining about 86% of its initial productivity after 10 cycles, whereas the whole-cell form lost nearly half after just five cycles. These results suggest that MWCC@MAS1 has great potential for the industrial production of biodiesel. Full article

Terpenoids and steroids are secondary plant and animal metabolites and are widely used to produce highly effective pharmacologically significant compounds. One of the promising approaches to the transformation of these compounds to form bioactive metabolites is their transformation using microorganisms. Rhodococcus spp. are one of the most developed objects in biotechnology due to their exceptional metabolic capabilities and resistance to extreme environmental conditions. In this review, information on the processes of biotransformation of terpenoid and steroid compounds by actinomycetes of the genus Rhodococcus and their molecular genetic bases are most fully collected and analyzed for the first time. Examples of the use of both native whole-cell catalysts and mutant strains and purified enzyme systems for the production of derivatives of terpenoids and steroids are given. Full article

Yarrowia lipolytica is a robust yeast species that has gained significant attention as a biofactory for various biotechnological applications and undoubtedly can be referred to as a hidden treasure trove due to boasting a diverse array of enzymes with wide-ranging applications in multiple industries, including biofuel production, food processing, biotechnology, and pharmaceuticals. As the biotechnology field continues to expand, Y. lipolytica is poised to play a pivotal role in developing eco-friendly and economically viable bioprocesses. Its versatility and potential for large-scale production make it a promising candidate for sustainably addressing various societal and industrial needs. The current review article aimed to highlight the diverse enzymatic capabilities of Y. lipolytica and provide a detailed analysis of its relevance in biocatalysis, including the use of whole-cell catalysts and isolated enzymes. The review focused on wild-type yeast strains and their species-dependant properties and selected relevant examples of Y. lipolytica used as a host organism for overexpressing some enzymes. Furthermore, the application of Y. lipolytica’s potential in enantiomers resolution, lipids processing, and biodiesel synthesis, as well as the synthesis of polymers or esterification of different substrates for upgrading biologically active compounds, was discussed. Full article

Bacillus subtilis spores offer several advantages that make them attractive for protein display. For example, protein folding issues associated with unfolded polypeptide chains crossing membranes are circumvented. In addition, they can withstand physical and chemical extremes such as heat, desiccation, radiation, ultraviolet light, and oxidizing agents. As a result, the sequence of the displayed protein can be easily obtained even under harsh screening conditions. Next, immobilized proteins have many economic and technological advantages. They can be easily separated from the reaction and the protein stability is increased in harsh environments. In traditional immobilization methods, proteins are expressed and purified and then they are attached to a matrix. In contrast, immobilization occurs naturally during the sporulation process. They can be easily separated from the reaction and the protein stability is increased in harsh environments. Spores are also amenable to high-throughput screening for protein engineering and optimization. Furthermore, they can be used in a wide array of biotechnological and industrial applications such as vaccines, bioabsorbants to remove toxic chemicals, whole-cell catalysts, bioremediation, and biosensors. Lastly, spores are easily produced in large quantities, have a good safety record, and can be used as additives in foods and drugs. Full article

d-tagatose is a low-calorie alternative to sucrose natural monosaccharide that is nearly as sweet. As a ketohexose, d-tagatose has disease-relieving and health-promoting properties. Due to its scarcity in nature, d-tagatose is mainly produced through chemical and biological methods. Compared to traditional chemical methods, biological methods use whole cells and isolated enzymes as catalysts under mild reaction conditions with few by-products and no pollution. Nowadays, biological methods have become a very important topic in related fields due to their high efficiency and environmental friendliness. This paper introduces the functions and applications of d-tagatose and systematically reviews its production, especially by l-arabinose isomerase (L-AI), using biological methods. The molecular structures and catalytic mechanisms of L-AIs are also analyzed. In addition, the properties of L-AIs from different microbial sources are summarized. Finally, we overview strategies to improve the efficiency of d-tagatose production by engineering L-AIs and provide prospects for the future bioproduction of d-tagatose. Full article

Ginsenoside compound K (CK) has garnered considerable attention due to its versatile pharmacological properties, including anti-inflammatory, anti-allergic, anti-aging, anti-diabetic, and hepatoprotective effects, along with neuroprotection. The conventional approach to synthesizing ginsenoside CK involves enzymatic conversion. However, the purification of enzymes necessitates effort and expense, and enzymes are prone to inactivation. Additionally, whole-cell catalysis suffers from inefficiency due to limited cell permeability. To address these challenges, we harnessed the YiaT protein as an anchoring motif, establishing a surface display system for β-glycosidase Bgp3. This innovative system served as a whole-cell catalyst for the efficient synthesis of ginsenoside CK. We further optimized the YiaT-Bgp3 system, enhancing display levels and significantly increasing ginsenoside CK production. Optimal conditions were achieved at an IPTG concentration of 0.5 mM, an induction temperature of 16 °C, a ginsenoside substrate concentration of 15 mg/mL, and a catalytic temperature of 30 °C. Ultimately, the YiaT-Bgp3 system synthesized 5.18 ± 0.08 mg/mL ginsenoside CK within 24 h, with a conversion of 81.83 ± 1.34%. Furthermore, the YiaT-Bgp3 system exhibited good reusability, adding to its practicality and value. This study has successfully developed an efficient whole-cell Bgp3 biocatalyst, offering a convenient, highly productive, and economically viable solution for the industrial production of ginsenoside CK. Full article

The very slow anodic oxygen evolution reaction (OER) greatly limits the development of large-scale hydrogen production via water electrolysis. By replacing OER with an easier urea oxidation reaction (UOR), developing an HER/UOR coupling electrolysis system for hydrogen production could save a significant amount of energy and money. An Al-doped cobalt ferrocyanide (Al-Co₂Fe(CN)₆) nanocube array was in situ grown on nickel foam (Al-Co₂Fe(CN)₆/NF). Due to the unique nanocube array structure and regulated electronic structure of Al-Co₂Fe(CN)₆, the as-prepared Al-Co₂Fe(CN)₆/NF electrode exhibited outstanding catalytic activities and long-term stability to both UOR and HER. The Al-Co₂Fe(CN)₆/NF electrode needed potentials of 0.169 V and 1.118 V (vs. a reversible hydrogen electrode) to drive 10 mA cm⁻² for HER and UOR, respectively, in alkaline conditions. Applying the Al-Co₂Fe(CN)₆/NF to a whole-urea electrolysis system, 10 mA cm⁻² was achieved at a cell voltage of 1.357 V, which saved 11.2% electricity energy compared to that of traditional water splitting. Density functional theory calculations demonstrated that the boosted UOR activity comes from Co sites with Al-doped electronic environments. This promoted and balanced the adsorption/desorption of the main intermediates in the UOR process. This work indicates that Co-based materials as efficient catalysts have great prospects for application in urea electrolysis systems and are expected to achieve low-cost and energy-saving H₂ production. Full article

Many enzymes have latent activities that can be used in the conversion of non-natural reactants for novel organic conversions. A classic example is the conversion of benzaldehyde to a phenylacetyl carbinol, a precursor for ephedrine manufacture. It is often tacitly assumed that purified enzymes are more promising catalysts than whole cells, despite the lower cost and easier maintenance of the latter. Competing substrates inside the cell have been known to elicit currently hard-to-predict selectivities that are not easily measured inside the living cell. We employ NMR spectroscopic assays to rationally combine isomers for selective reactions in commercial S. cerevisiae. This approach uses internal competition between alternative pathways of aldehyde clearance in yeast, leading to altered selectivities compared to catalysis with the purified enzyme. In this manner, 4-fluorobenzyl alcohol and 2-fluorophenylacetyl carbinol can be formed with selectivities in the order of 90%. Modification of the cellular redox state can be used to tune product composition further. Hyperpolarized NMR shows that the cellular reaction and pathway usage are affected by the xenochemical. Overall, we find that the rational construction of ternary or more complex substrate mixtures can be used for in-cell NMR spectroscopy to optimize the upgrading of similar xenochemicals to dissimilar products with cheap whole-cell catalysts. Full article

Douchi is a traditional Chinese fermented soybean product, in which acetoin is a key flavor substance. Here, the α-acetolactate decarboxylase gene aldC was cloned from Lactiplantibacillus (L.) plantarum and overexpressed in Lactococcus (L.) lactis NZ9000 by nisin induction. The ALDC crude enzyme solution produced an enzyme activity of 35.16 mU. Next, whole cells of the recombinant strain NZ9000/pNZ8048-aldC were employed as the catalyst to produce acetoin in GM17 medium. An optimization experiment showed that an initial OD₆₀₀ of 0.6, initial pH of 7.5, nisin concentration of 20 ng/mL, induction temperature of 37 °C and static induction for 8 h were the optimal induction conditions, generating the maximum acetoin production (106.93 mg/L). Finally, after incubation under the optimal induction conditions, NZ9000/pNZ8048-aldC was used for whole-cell biocatalytic acetoin production, using soybean as the substrate. The maximum acetoin yield was 79.43 mg/L. To our knowledge, this is the first study in which the aldC gene is overexpressed in L. lactis and whole cells of the recombinant L. lactis are used as a biocatalyst to produce acetoin in soybean. Thus, our study provides a theoretical basis for the preparation of fermented foods containing high levels of acetoin and the biosynthesis of acetoin in food materials. Full article

Nitrilases have a high potential for application in organic chemistry, environmental technology, and analytics. However, their industrial uses require that they are produced in highly active and robust forms at a reasonable cost. Some organic syntheses catalyzed by nitrilases have already reached a high level of technological readiness. This has been enabled by the large-scale production of recombinant catalysts. Despite some promising small-scale methods being proposed, the production of cyanide-converting nitrilases (cyanide hydratase and cyanide dihydratase) is lagging in this regard. This review focuses on the prospects of cyanide(di)hydratase-based catalysts. The current knowledge of these enzymes is summarized and discussed in terms of the origin and distribution of their sequences, gene expression, structure, assays, purification, immobilization, and uses. Progresses in the production of other nitrilase catalysts are also tackled, as it may inspire the development of the preparation processes of cyanide(di)hydratases. Full article