Search Results (130)

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

Background/Objectives: Rhodococcus rhodochrous IEGM 107 cells exhibit pronounced catalytic activity toward mono- and diterpenoids. However, the genetics and enzymatic foundations underlying this activity remain poorly understood. Methods: Using new-generation sequencing, the R. rhodochrous IEGM 107 whole genome was sequenced. Bioinformatic analysis and PCR were employed to identify and characterize genes, with a focus on cytochromes P450 (CYP450s). Results: The catalytic potential of R rhodochrous IEGM 107 was revealed. Its CYP450 genes were detected and analyzed, providing information on the enzymatic base of the strain related to the biotransformation of terpenoids. Conclusions: These findings enhance the understanding of the molecular and genetic basis for terpenoid transformations in R. rhodochrous actinomycetes. The results provide a foundation for future studies on gene expression and enzyme characterization aimed at developing efficient and selective biocatalysts for mono- and diterpenoid transformations. Full article

The development of yeast cell factories for efficient xylose utilization and xylitol production is crucial for advancing sustainable biotechnological processes. Xylose, a major component of lignocellulosic biomass, presents challenges for microbial conversion due to its complex metabolic pathways. This study presents the genomic perspective and xylitol production capability of a novel xylose utilizing yeast Cyberlindnera fabianii TBRC 4498. Genome sequencing and functional annotation revealed key metabolic networks and genes involved in the xylose metabolism pathway, providing insights into the strain’s performance. The Cy. fabianii TBRC 4498 had excellent growth and xylose assimilation at a broad range of xylose concentrations from 40 to 140 g/L, with the highest growth rate at 80 g/L of xylose. The highest xylitol production yield (83.19 g/L) was detected from 120 g/L of xylose at 30 °C for 72 h, equivalent to 0.65 g xylitol/g xylose and 1.16 g/L/h productivity. Remarkably, Cy. fabianii TBRC 4498 produced high-purity xylitol, achieving over 95% homogeneity without forming undesirable byproducts, such as acid or ethanol. These results demonstrated the potential of Cy. fabianii TBRC 4498 as a whole-cell biocatalyst for xylitol production using high xylose concentrations, offering a promising microbial cell factory for large-scale xylitol production from lignocellulosic sugar. Full article

Surface display technology has revolutionized whole-cell biocatalysis by enabling efficient enzyme immobilization on microbial cell surfaces. Compared with traditional enzyme immobilization, this technology has the advantages of high enzyme activity, mild process, simple operation and low cost, which thus has been widely studied and applied in various fields. This review explores the principles, optimization strategies, applications in the food industry, and future prospects. We summarize the membrane and anchor protein structures of common host cells (Escherichia coli, Bacillus subtilis, and yeast) and discuss cutting-edge optimization approaches, including host strain genetic engineering, rational design of anchor proteins, innovative linker peptide engineering, and precise regulation of signal peptides and promoters, to maximize surface display efficiency. Additionally, we also explore its diverse applications in food processing and manufacturing, additive synthesis, food safety, and other food-related industries (such as animal feed and PET packaging degradation), demonstrating their potential to address key challenges in the food industry. This work bridges fundamental research and industrial applications, offering valuable insights for advancing agricultural and food chemistry. 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

Three fungal strains were employed for the stereoselective oxidation of the cheap and commercially available substrate 2-phenylethanol, which resulted in chiral building blocks being received. The whole-cell biocatalysts were as follows: Beauveria bassiana DSM 1344, Beauveria brongniartii DSM 6651, and Rhizopus arrhizus DSM 1185. The main product of Beauveria bassiana bioconversion was 1-phenylethane-1,2-diol, obtained, depending on the form of the biocatalyst, as an R-enantiomer (e.g., 99.9%) with fresh biomass application or as a racemic mixture in cases of immobilization in agar-agar. The best and most innovative results for the synthesis of the R-enantiomer of diol were received under precisely defined conditions as a result of a scaling study conducted on an automatic batch reactor. This is a pioneering result, since, in previous studies, fresh mycelium of Aspergillus niger resulted in this product being received as the (S) enantiomer. Also, the use of Rhizopus arrhizus DSM 1185 (immobilized in polyurethane foams) presented important results, as the bioconversion of phenyl ethanol led, indeed, to the racemic mixture of 1-phenylethane-1,2-diol but was accompanied by a noticeable tyrosol synthesis, which had not been reported previously. Full article

Lipases are enzymes of great application importance in the food industry, in the cosmetic and detergent industries, in pharmacy and medicine, and in organic chemistry. Among lipases of various origins, those from microorganisms are currently the most commonly used. An excellent producer of lipases seems to be the nonconventional Yarrowia lipolytica yeast, but the biosynthesis of valuable metabolites depends on many factors. This study aimed to investigate the biodiversity of extracellular enzymes produced by four strains of Y. lipolytica, and to determine the optimal conditions of catalysis for the enzymes, according to temperature and pH, in a model hydrolysis reaction. Based on the obtained results, the biodiversity and strain dependence in lipase biosynthesis were observed. Using a Central Composite Design, it was found that temperature is the main factor in determining lipase activity. The enzymes produced by four different strains exhibited other substrate specificity, which was investigated using Latin square design methodology. Only two examined yeast strains, KKP 379 and W29, produced extracellular lipases at a high activity level towards medium- and long-chain fatty acid esters. Moreover, extracellular lipase from wild-type strain KKP 379 was further characterized, followed by exploring the activity of whole-cell biocatalyst and lyophilized enzyme solutions, and it was acknowledged that it was a “true” lipase with the highest affinity to p-nitrophenyl oleate. Full article

Enzyme immobilization is a crucial method in biotechnology and organic chemistry that significantly improves the stability, reusability, and overall effectiveness of enzymes across various applications. Lipases are one of the most frequently applied enzymes in food. The current study investigated the potential of utilizing selected agri-food and waste materials—buckwheat husks, pea hulls, loofah sponges, and yerba mate waste—as carriers for the immobilization of Sustine^® 121 lipase and Yarrowia lipolytica yeast biomass as whole-cell biocatalyst and lipase sources. Various lignocellulosic materials were pretreated through extraction processes, including Soxhlet extraction with hexane and ethanol, as well as alkaline and acid treatments for loofah sponges. The immobilization process involved adsorbing lipases or yeast cells onto the carriers and then evaluating their hydrolytic and synthetic activities. Preparations’ activities evaluation revealed that alkaline-pretreated loofah sponge yielded the highest hydrolytic activity (0.022 U/mg), while yerba mate leaves under brewing conditions demonstrated superior synthetic activity (0.51 U/mg). The findings underscore the potential of lignocellulosic materials from the agri-food industry as effective supports for enzyme immobilization, emphasizing the importance of material selection and pretreatment methods in optimizing enzymatic performance through giving an example of circular economy application in food processing and waste management. Full article

Plant-associated yeasts play significant ecological roles within the microbiomes of soils and pollinating insects. In previous studies, we have shown that yeasts can assist pollinators in locating nectar, which is crucial for their nutrition and the reproduction of many angiosperms. Additionally, in soil, yeasts can also act as plant growth promoters. Given the importance of yeasts for plant development, this review first explores the biochemical processes underlying the ecological role of these microorganisms in soil, insects, and in direct association with plants. Based on this premise, we discuss the influence of these relationships on agricultural production, the biological mechanisms through which pesticides negatively affect yeast cells, and how these microorganisms can tolerate widely used agrochemicals. Finally, we address key studies in the literature that support the potential of these microorganisms as bioremediation agents. In this context, we emphasize different experiences with both indigenous and genetically engineered yeasts, which may display enzymes in their surfaces that convert pesticides into less harmful or nontoxic molecules. Our review indicates that yeasts can be effectively harnessed in organic agriculture to promote plant growth and bioremediate contaminated soil or food. Full article

This study explored the enantiocomplementary bioreduction of substituted 1-(arylsulfanyl)propan-2-ones in batch mode using four wild-type yeast strains and two different recombinant alcohol dehydrogenases from Lactobacillus kefir and Rhodococcus aetherivorans. The selected yeast strains and recombinant alcohol dehydrogenases as whole-cell biocatalysts resulted in the corresponding 1-(arylsulfanyl)propan-2-ols with moderate to excellent conversions (60–99%) and high selectivities (ee > 95%). The best bioreductions—in terms of conversion (>90%) and enantiomeric excess (>99% ee)—at preparative scale resulted in the expected chiral alcohols with similar conversion and selectivity to the screening reactions. 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

Cellobionic acid (CBA) can be obtained through the oxidation of cellobiose, the monomer of cellulose. CBA serves as a plant-based alternative to its stereoisomer lactobionic acid, which is used in the pharmaceutical, cosmetic, and food industries. Gluconobacter oxydans is a well-established whole-cell biocatalyst with membrane-bound dehydrogenases (mDH) for regio-specific oxidations. As G. oxydans wildtype cells show low cellobiose oxidation activities, the glucose mDH from Pseudomonas taetrolens was overexpressed in G. oxydans BP9, a multi mDH deletion strain. Whole-cell biotransformation studies were performed with resting cells of the engineered G. oxydans in stirred tank bioreactors. Initial biomass specific cellobionate formation rates increased with increasing cellobiose concentrations up to 190 g L⁻¹, and were constant until the solubility limit. The maximal volumetric CBA formation rates and the oxygen uptake rates increased linearly with the concentration of engineered G. oxydans. This enables the estimation of the maximum biocatalyst concentration limited by the maximum oxygen transfer rate of any bioreactor. Thus, 5.2 g L⁻¹ G. oxydans was sufficient to produce 502 g L⁻¹ CBA with >99% yield in a simple aerobic batch process. The highly concentrated CBA will reduce downstream processing costs considerably after cell separation. Full article

L-Arabinose isomerase (L-AI) has been commonly used as an efficient biocatalyst to produce D-tagatose via the isomerization of D-galactose. However, it remains a significant challenge to efficiently synthesize D-tagatose using the native (wild type) L-AI at an industrial scale. Hence, it is extremely urgent to redesign L-AI to improve its catalytic efficiency towards D-galactose, and herein a structure-based molecular modification of Lactobacillus plantarum CY6 L-AI (LpAI) was performed. Among the engineered LpAI, both F118M and F279I mutants showed an increased D-galactose isomerization activity. Particularly, the specific activity of double mutant F118M/F279I towards D-galactose was increased by 210.1% compared to that of the wild type LpAI (WT). Besides the catalytic activity, the substrate preference of F118M/F279I was also largely changed from L-arabinose to D-galactose. In the enzymatic production of D-tagatose, the yield and conversion ratio of F118M/F279I were increased by 81.2% and 79.6%, respectively, compared to that of WT. Furthermore, the D-tagatose production of whole cells expressing F118M/F279I displayed about 2-fold higher than that of WT cell. These results revealed that the designed site-directed mutagenesis is useful for improving the catalytic efficiency of LpAI towards D-galactose. 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

Polyamide is a thermoplastic polymer widely used for several applications, including cables in offshore oil and gas operations. Due to its growing annual production worldwide, this poorly biodegradable material has been a source of pollution. Given this scenario, the need has arisen to develop environmentally friendly techniques to degrade this waste, and biotechnology has emerged as a possible solution to mitigate this problem. This study aimed to investigate the potential of Yarrowia lipolytica to biodepolymerize polyamide fibers (PAF). Microbial cultures were grown in shaken flasks containing different concentrations of PAF (0.5 and 2 g·L⁻¹) and in a bioreactor with and without pH adjustment. PAF mass loss was up to 16.8%, achieved after 96 h of cultivation in a bioreactor without pH adjustment. Additionally, NMR analyses revealed that the amorphous regions of PAF, which are more susceptible to depolymerization, were reduced by 6% during cultivation. These preliminary results indicate the biotechnological potential of Y. lipolytica to depolymerize PAF. Full article