Microbial Degradation Research Articles

Strategic Use of Vegetable Oil for Mass Production of 5-Hydroxyvalerate-Containing Polyhydroxyalkanoate from δ-Valerolactone by Engineered Cupriavidus necator.

Although efforts have been undertaken to produce polyhydroxyalkanoates (PHA) with various monomers, the low yield of PHAs because of complex metabolic pathways and inhibitory substrates remains a major hurdle in their analyses and applications. Therefore, we investigated the feasibility of mass production of PHAs containing 5-hydroxyvalerate (5HV) using δ-valerolactone (DVL) without any pretreatment along with the addition of plant oil to achieve enough biomass. We identified that PhaCBP-M-CPF4, a PHA synthase, was capable of incorporating 5HV monomers and that C. necator PHB-4 harboring phaCBP-M-CPF4 synthesized poly(3HB-co-3HHx-co-5HV) in the presence of bean oil and DVL. In fed-batch fermentation, the supply of bean oil resulted in the synthesis of 49 g/L of poly(3HB-co-3.7 mol% 3HHx-co-5.3 mol%5HV) from 66 g/L of biomass. Thermophysical studies showed that 3HHx was effective in increasing the elongation, whereas 5HV was effective in decreasing the melting point. The contact angles of poly(3HB-co-3HHx-co-5HV) and poly(3HB-co-3HHx) were 109 and 98°, respectively. In addition, the analysis of microbial degradation confirmed that poly(3HB-co-3HHx-co-5HV) degraded more slowly (82% over 7 days) compared to poly(3HB-co-3HHx) (100% over 5 days). Overall, the oil-based fermentation strategy helped produce more PHA, and the mass production of novel PHAs could provide more opportunities to study polymer properties.

Janus nanoparticles synthesized from hydrophobic carbon dots and carboxymethyl cellulose: Novel antimicrobial additives for fresh food applications

The aim of this study was to synthesis Janus nanoparticles (JPs) using beeswax-based hydrophobic carbon dots to form the non-polar face and hydrophilic carboxymethyl cellulose to form the hydrophilic face. Size, morphology, composition, and optical properties of the JPs were characterized. Scanning electron microscopy and light scattering analysis showed these nanoparticles were spheroids with average diameters around 4 nm. A cytotoxicity assay (L929 cells) showed that the hydrophobic carbon dots and JPs exhibited significant toxicity (decrease in cell viability) at 1.5 and 5 mg/mL, respectively. For the hydrophobic carbon dots, the minimum inhibitory concentration was 0.02 mg/mL for Escherichia coli and 0.04 mg/mL for Listeria monocytogenes, whereas for the JPs it was 0.04 mg/mL for both bacteria. Both the hydrophobic carbon dots and JPs also exhibited appreciable antioxidant activity. These particles were then incorporated into minced beef as novel preservatives. At 0.05% concentration, both kinds of nanoparticles caused a significant reduction in chemical and microbial degradation of the meat during storage. The JPs had a greater effect on mesophile (3.3 log10 CFU/g reduction) than on psychrophile (2.8 log10 CFU/g reduction) microbial populations within the meat. The preparation of JPs based on carbon dots, reduced cytotoxicity and improved their antimicrobial properties. JPs developed in this study may be used as novel preservatives with antimicrobial and antioxidant properties in foods.

EDDS application destabilizes soil organic matter in phytoremediation: Insights from quantity and molecular composition of dissolved organic matter

The stability of soil organic matter (SOM) is crucial for metal transport and carbon cycling. S,S-ethylenediaminedisuccinic acid (EDDS) is widely used to enhance phytoremediation efficiency for heavy metals in contaminated soils, yet its specific impacts on SOM have been underexplored. This study investigates the effects of EDDS on SOM stability using a rhizobox experiment with ryegrass. Changes in soil dissolved organic matter (DOM) quantity and molecular composition were analyzed via Fourier transform ion cyclotron resonance mass spectrometry. Results showed that the use of EDDS increased the uptake of Cu, Cd and Pb by ryegrass, but simultaneously induced the destabilization and transformation of SOM. After 7 days of EDDS application, dissolved organic carbon (DOC) and nitrogen (DON) concentrations in rhizosphere soils increased significantly by 3.44 and 10.2 times, respectively. In addition, EDDS reduced lipids (56.3%) and proteins/amino sugars-like compounds (52.1%), while increasing tannins (9.11%) and condensed aromatics-like compounds (24.4%) in the rhizosphere DOM. These effects likely stem from EDDS's dual action: extracting Fe/Al from SOM-mineral aggregates, releasing SOM into the DOM pool, and promoting microbial degradation of bioavailable carbon through chain scission and dehydration. Our study firstly revealed that the application of EDDS in phytoremediation increased the mineralization of SOM and release of CO2 from soil to the atmosphere, which is important to assess the carbon budget of phytoremediation and develop climate-smart strategy in future.

Microbial Degradation of Herbicides in Sugarcane Cultivation: A Study on Eradicane- and Tebuthiuron-Tolerant Bacteria

Microbial Degradation of Herbicides in Sugarcane Cultivation: A Study on Eradicane- and Tebuthiuron-Tolerant Bacteria

Chemo-Enzymatic Depolymerization of Functionalized Low-Molecular-Weight Polyethylene.

Polyethylene (PE) is the most commonly used plastic type in the world, contributing significantly to the plastic waste crisis. Microbial degradation of PE in natural environments is unlikely due to its inert saturated carbon-carbon backbones, which are difficult to break down by enzymes, challenging the development of a biocatalytic recycling method for PE waste. Here, we demonstrated the depolymerization of low-molecular-weight (LMW) PE using an enzyme cascade that included a catalase-peroxidase, an alcohol dehydrogenase, a Baeyer Villiger monooxygenase, and a lipase after the polymer was chemically pretreated with m-chloroperoxybenzoic acid (mCPBA) and ultrasonication. In a preparative experiment with gram-scale pretreated polymers, GC-MS and weight loss determinations confirmed ~27% polymer conversion including the formation of medium-size functionalized molecules such as ω-hydroxy acids and α,ω-carboxylic acids. Additional polymer property analyses using AFM showed that enzymatic depolymerization reduced the particle sizes of this mCPBA- and enzyme-treated LMWPE. This multi-enzyme catalytic concept with distinct chemical steps represents a unique starting point for future development of bio-based recycling methods for polyolefin waste.

Chemo‐Enzymatic Depolymerization of Functionalized Low‐Molecular‐Weight Polyethylene

Polyethylene (PE) is the most commonly used plastic type in the world, contributing significantly to the plastic waste crisis. Microbial degradation of PE in natural environments is unlikely due to its inert saturated carbon‐carbon backbones, which are difficult to break down by enzymes, challenging the development of a biocatalytic recycling method for PE waste. Here, we demonstrated the depolymerization of low‐molecular‐weight (LMW) PE using an enzyme cascade that included a catalase‐peroxidase, an alcohol dehydrogenase, a Baeyer Villiger monooxygenase, and a lipase after the polymer was chemically pretreated with m‐chloroperoxybenzoic acid (mCPBA) and ultrasonication. In a preparative experiment with gram‐scale pretreated polymers, GC‐MS and weight loss determinations confirmed ~27% polymer conversion including the formation of medium‐size functionalized molecules such as ω‐hydroxy acids and α,ω‐carboxylic acids. Additional polymer property analyses using AFM showed that enzymatic depolymerization reduced the particle sizes of this mCPBA‐ and enzyme‐treated LMWPE. This multi‐enzyme catalytic concept with distinct chemical steps represents a unique starting point for future development of bio‐based recycling methods for polyolefin waste.

Applying fluorescence and 2D-correlation spectroscopy to elucidate changes in the chemical composition of DOM from soils with different vegetation types

ABSTRACT To understand the decomposition of the dissolved organic matter (DOM), four different soils (from grassland, spruce forest, oak forest, and agricultural land) were incubated at 15 °C, and the DOM changes were monitored using UV-Vis, synchronized fluorescence and 2D-correlation spectroscopy. The DOM fraction of the agricultural and grassland soils showed a significant increase in both SUVA values in the middle of the incubation ranging from an initial 3–5 L mg−1 m−1 to 40–50 L mg−1 m−1. Synchronous fluorescence spectroscopy revealed that at the beginning of incubation, on day 3, there was an increase in the proportion of low molecular-weight, readily biodegradable compounds (PLF, protein-like fluorescence), while from day 8 onwards, microbial degradation generated a large number of medium-molecular-weight molecules (MHLF, microbial humus-like fluorescence). At further sampling dates, the proportion of compounds of microbial origin decreased systematically, due to a decrease in microbial activity caused by the lack of substrate. 2D-correlation measurements revealed further details of the changes in the quality of DOM, revealing two distinct patterns in the DOM dynamics of the soils, the sequence MHLF→PLF being observed for grassland and arable land and PLF→HLF for forest soils, probably due to the different N supplies of the soils.

Abrupt increase in Arctic-Subarctic wildfires caused by future permafrost thaw

Unabated 21st-century climate change will accelerate Arctic-Subarctic permafrost thaw which can intensify microbial degradation of carbon-rich soils, methane emissions, and global warming. The impact of permafrost thaw on future Arctic-Subarctic wildfires and the associated release of greenhouse gases and aerosols is less well understood. Here we present a comprehensive analysis of the effect of future permafrost thaw on land surface processes in the Arctic-Subarctic region using the CESM2 large ensemble forced by the SSP3-7.0 greenhouse gas emission scenario. Analyzing 50 greenhouse warming simulations, which capture the coupling between permafrost, hydrology, and atmosphere, we find that projected rapid permafrost thaw leads to massive soil drying, surface warming, and reduction of relative humidity over the Arctic-Subarctic region. These combined processes lead to nonlinear late-21st-century regime shifts in the coupled soil-hydrology system and rapid intensification of wildfires in western Siberia and Canada.

Microbial degradation of contaminants of emerging concern: metabolic, genetic and omics insights for enhanced bioremediation.

The perpetual release of natural/synthetic pollutants into the environment poses major risks to ecological balance and human health. Amongst these, contaminants of emerging concern (CECs) are characterized by their recent introduction/detection in various niches, thereby causing significant hazards and necessitating their removal. Pharmaceuticals, plasticizers, cyanotoxins and emerging pesticides are major groups of CECs that are highly toxic and found to occur in various compartments of the biosphere. The sources of these compounds can be multipartite including industrial discharge, improper disposal, excretion of unmetabolized residues, eutrophication etc., while their fate and persistence are determined by factors such as physico-chemical properties, environmental conditions, biodegradability and hydrological factors. The resultant exposure of these compounds to microbiota has imposed a selection pressure and resulted in evolution of metabolic pathways for their biotransformation and/or utilization as sole source of carbon and energy. Such microbial degradation phenotype can be exploited to clean-up CECs from the environment, offering a cost-effective and eco-friendly alternative to abiotic methods of removal, thereby mitigating their toxicity. However, efficient bioprocess development for bioremediation strategies requires extensive understanding of individual components such as pathway gene clusters, proteins/enzymes, metabolites and associated regulatory mechanisms. "Omics" and "Meta-omics" techniques aid in providing crucial insights into the complex interactions and functions of these components as well as microbial community, enabling more effective and targeted bioremediation. Aside from natural isolates, metabolic engineering approaches employ the application of genetic engineering to enhance metabolic diversity and degradation rates. The integration of omics data will further aid in developing systemic-level bioremediation and metabolic engineering strategies, thereby optimising the clean-up process. This review describes bacterial catabolic pathways, genetics, and application of omics and metabolic engineering for bioremediation of four major groups of CECs: pharmaceuticals, plasticizers, cyanotoxins, and emerging pesticides.

Biocompatible sensors for ammonia gas detection

In this work, three different dyes have been tested for the determination of gaseous ammonia. This gas is one of the products of microbial degradation and therefore its presence is an indicator of deterioration and could be used as a food freshness indicator.Three different sensors have been prepared and tested, two of them using the natural pigments curcumin and anthocyanin and the other one using bromothymol blue. All of them are biocompatible and therefore allowed to use in contact with food.Different compositions, materials for deposition, stability and reversibility for ammonia gas detection have been studied under high humidity conditions simulating real packaged food conditions. Colorimetry is the technique used to obtain the analytical parameter, the H coordinate of the HSV colour space, simply using a camera, avoiding the use of complex instrumentation.Sensibility, toxicity grade and stability found show that the sensor could be implemented in packaged food and form the basis of a freshness indicator for the food industry.

Persistence and degradation of tembotrione in loamy soil: Effect of various organic amendments, moisture regimes and temperatures

In the present study, persistence and degradation of tembotrione, a triketone herbicide, was studied in loamy soil collected from maize field. Effects of organic amendments, moistures and temperatures on tembotrione dissipation were evaluated. Soil samples were processed according to the modified QuEChERS involving dichloromethane solvent and MgSO4 without PSA. Analysis using LC-MS/MS showed >95% recoveries of tembotrione its two metabolites TCMBA and M5 from fortified soils. Tembotrione residues dissipated with time and 85.55 to 98.53% dissipation was found on 90th day under different treatments. Tembotrione dissipation increased with temperature and moisture content of the soil. Among organic amendments, highest dissipation was observed in vermicompost amended soil. Minimum and maximum half-lives of tembotrione were recorded under 35 °C (15.7 days) and air-dry (33 days) conditions, respectively. Residues of tembotrione declined with time while that of TCMBA increased steadily up to 10-45th day in different treatments and declined thereafter. Residues of M5 were not detected in our experiments. Tembotrione persistence was negatively correlated with the organic carbon (%), moisture regimes, and temperature. A good correlation between soil microbial biomass carbon and degradation was found. A two-way ANOVA indicated significant differences between the treatments at 95% confidence level (p < 0.05).

Isolation and characterization of a novel bacterium that promotes the degradation of poly(glycolic acid) by its extracellular esterase under thermophilic conditions

Poly(glycolic acid) (PGA) is widely utilized in the shale oil and gas industry owing to its biodegradable nature, as well as superior mechanical and barrier properties. However, PGA degradability is limited by environmental conditions such as temperature and pH, and using acids to optimize the degradation can have adverse environmental impact. Thus, it is essential to identify methods that can effectively promote the degradation of PGA under mild conditions, such as microbial degradation. In the present study, strain DB14, a bacterium that promotes PGA degradation, was isolated from drain water of a steam pipeline. Sequence analysis of the 16S rRNA gene of the bacterium revealed that it is mostly closely related to Geobacillus icigianus; however, it also differed from Geobacillus icigianus in several physiological properties. To investigate PGA degradation by strain DB14, a PGA film and disc were incubated with the strain. The residual weight of the PGA film (thickness: 170 μm) significantly reduced after incubation, whereas the decrease in the thickness of the PGA disc (thickness: 3 mm) was relatively small. The penetration of water, the bacterium, and the extracellular enzymes into the interior from the reaction-erosion front of the PGA disc may be inhibited by the high barrier performance of PGA. Strain DB14 was also found to change the pH of the surrounding environment to approximately 8–9. To investigate the effect of pH on PGA degradability, degradation tests with crude extracellular enzymes derived from strain DB14 were conducted in various buffers. The results showed that the degradation activity was highest at pH 8, which implied that DB14 efficiently maximized the hydrolytic capacity of its enzyme for degrading PGA. Thus, this study provides a basis for developing environmentally friendly technologies that can promote the degradation of PGA molding articles, especially those used in wellbores for oil and gas recovery.

Tetracycline removal by immobilized indigenous bacterial consortium using biochar and biomass: Removal performance and mechanisms

The significant influx of antibiotics into the environment represents ecological risks and threatens human health. Microbial degradation stands as a highly effective method for reducing antibiotic pollution. This study explored the potential of immobilized microbial consortia to efficiently degrade tetracycline. Concurrently, the suitability of different immobilization materials were assessed, with reed charcoal-immobilized consortia exhibiting the highest efficiency in removing tetracycline (92%). Similarly, wheat-bran-loaded bacterial consortia displayed a remarkable 11.43-fold increase in tetracycline removal compared with free consortia. Moreover, adding the carriers increased the nutrients, while the activities of both intracellular and extracellular catalases increased significantly post-immobilization, thus highlighting this enzyme’s crucial role in tetracycline degradation. Finally, analysis of the microbial communities revealed the prevalence of Achromobacter and Parapedobacter, signifying their potential as key degraders. Overall, the immobilized consortia not only hold promise for application in the bioremediation of tetracycline-contaminated environment but also provide theoretical underpinnings for environmental remediation by microorganisms.

Degradation of Azo-dye (Disperse Red) Using Rhizosphere Bacterial Consortium

This study investigates the degradation of the azo dye (Disperse Red) using a rhizosphere bacterial consortium. Standard microbiological and molecular techniques were employed to isolate and identify organisms from rhizosphere soil. Degradation of azodye was carried out in a fabricated anoxic and oxic chambers with hydraulic retention time of 40hrs. Initial identification of the bacterial isolates through Gram’s reaction and biochemical tests revealed the presence of organisms belonging to the genera Pseudomonas, Lysinibacillus, and Citrobacter. Molecular and phylogenetic analyses confirmed the isolates as Pseudomonas aeruginosa, Lysinibacillus sphaericus, Pseudomonas chengduensis, and Citrobacter freundii. During the preliminary testing, the degradation efficiency was assessed under varying glucose concentrations. Higher decolorization rate of 56.17% was observed in the medium with 10% glucose after 72 hours, while the medium with 5% glucose achieved a 44.17% colour reduction. Notably, lower degradation rates recorded were 11.96% and 12.85% for the 5% and 10% dye enhance glucose mineral salt media, respectively. However, During the actual degradation testing in a double-chamber system enhanced with biochar, the first anaerobic cycle achieved a maximum decolorization of 71.95% after 94 hours, with the first aerobic cycle further enhancing degradation to 90.51%. The second anaerobic cycle increased degradation to 94.78%, and the final aerobic cycle achieved a decolorization of 98.47%. These results show that the rate of Disperse Red degradation is highly dependent on glucose levels and alternating anaerobic-aerobic conditions. This study demonstrates the potential of using rhizosphere bacterial consortia to bioremediate wastewater contaminated with azo dyes, offering an efficient and sustainable method of environmental management. The results underline the need of optimizing ambient conditions to increase microbial degradation processes.

Development of multilayer composite film based on protein‐polysaccharides with the addition of onion waste extracts and their impact on the shallot quality

AbstractAt present, multilayer composite film is attractive in the production of biodegradable films due to its essential film properties. The current study mainly focused on overcoming the problems of poor water barrier and mechanical strength observed in monolayer films (SA‐CMC and G/SA‐CMC) made from gluten (G), sodium alginate (SA), and carboxymethylcellulose (CMC). The film was developed with the addition of onion waste extracts (OWEs), primarily from peel and stalk, to enhance functional properties. The multilayer composite film consists of three layers: an outer layer made of G, an inner layer made of SA, CMC, and a middle layer made of G/SA‐CMC. The developed composite film exhibited improved physical properties (thickness: 0.348–0.629 mm and moisture: 20.889%–21.403%), mechanical properties (tensile strength: 21.943–20.640 MPa), and barrier properties (WVP: 0.212–0.516 g/m.s.Pa × 10−14) compared to monolayer films (SA‐CMC and G/SA‐CMC). The addition of OWEs enhanced the multilayer film's phenolic (20.076 and 36.175 mgGAE/g) and antioxidant activity (73.850% and 42.667%). The study found that the multilayer control film had minimal changes in weight loss (9.75% ± 0.18%) and firmness (6.68 ± 0.64 N) compared to OWEs‐added films (9.93% ± 0.49–10.02% ± 0.14% and 6.61 ± 0.37 to 6.64 ± 0.18 N). However, fresh‐peeled shallot onion packed with control film exhibited higher bacterial counts (6.70 ± 0.42 CFU/g) and yeast and mold counts (5.08 ± 0.20 CFU/g) than those packed with the OWEs‐added film (6.49 ± 0.28–6.56 ± 0.27 CFU/g and 4.75 ± 0.18–4.89 ± 0.21 CFU/g), indicating that OWEs protect the onions from microbial degradation. Overall, the multilayer control film (without OWEs) showed better results for storing the fresh‐peeled shallot onion at 4°C for 21 days.Highlights Onion waste extracts have potent high antioxidant and antimicrobial properties Multilayer film's physical, mechanical, barrier, and functional properties improved Addition of onion waste extracts increased the film's antimicrobial activity Control film showed a better effect for storing fresh‐peeled shallot onion Developed film can store fresh‐peeled shallot onion for 21 days at 4°C.

Effects of plastic aging on biodegradation of polystyrene by Tenebrio molitor larvae: Insights into gut microbiome and bacterial metabolism

Plastics aging reduces resistance to microbial degradation. Plastivore Tenebrio molitor rapidly biodegrades polystyrene (PS, size: < 80 μm), but the effects of aging on PS biodegradation by T. molitor remain uncharacterized. This study examined PS biodegradation over 24 days following three pre-treatments: freezing with UV exposure (PS1), UV exposure (PS2), and freezing (PS3), compared to pristine PS (PSv) microplastic. The pretreatments deteriorated PS polymers, resulting in slightly higher specific PS consumption (602.8, 586.1, 566.7, and 563.9 mg PS·100 larvae−1·d−1, respectively) and mass reduction rates (49.6 %, 49.5 %, 49.2 %, and 48.7 %, respectively) in PS1, PS2, and PS3 compared to PSv. Improved biodegradation correlated with reduced molecular weights and the formation of oxidized functional groups. Larvae fed more aged PS exhibited greater gut microbial diversity, with microbial community and metabolic pathways shaped by PS aging, as supported by co-occurrence network analysis. These findings indicated that the aging treatments enhanced PS biodegradation by only limited extent but impacted greater on gut microbiome and bacterial metabolic genes, indicating that the T. molitor host have highly predominant capability to digest PS plastics and alters gut microbiome to adapt the PS polymers fed to them.

Characteristics and functional bacteria of an efficient benzocaine-mineralizing bacterial consortium

The extensive use of pharmaceutical and personal care products (PPCPs) has led to widespread residual pollution, which increases the risk of the development of drug resistance in pathogenic microorganisms. Benzocaine is a PPCP that is widely used medical anesthesia and in sunscreen. Microorganisms are essential for the degradation of residual PPCPs. However, no studies have reported the microbial degradation of benzocaine. In this study, through continuous enrichment of the initial consortium HJ1, the highly efficient benzocaine-degrading consortium HJ7 was obtained, HJ7 exhibited a degradation rate that was 1.92 times greater than that of HJ1. Methyl 4-aminobenzoate and 4-aminobenzoic acid were identified as major intermediate products during benzocaine biodegradation by consortium HJ1 or HJ7. Methylobacillus (57.8 % ± 0.9 %) and Pseudomonas (22.1 % ± 0.7 %), which are thought to harbor essential species for benzocaine degradation, were significantly enriched in consortium HJ7. Two benzocaine-degrading strains, Pseudomonas sp. A8 and Microbacterium sp. A741, and one methyl 4-aminobenzoate-degrading strain, Achromobacter sp. A5, were isolated from consortium HJ7, and they synergistically mineralized benzocaine. These findings not only provide new insights into the biotransformation of benzocaine but also provide strain resources for the bioremediation of residual benzocaine in the environment.

Critical review on unveiling the toxic and recalcitrant effects of microplastics in aquatic ecosystems and their degradation by microbes.

Production of synthetic plastic obtained from fossil fuels are considered as a constantly growing problem and lack in the management of plastic waste has led to severe microplastic pollution in the aquatic ecosystem. Plastic particles less than 5mm are termed as microplastics (MPs), these are pervasive in water and soil, it can also withstand longer period of time with high durability. It can be broken down into smaller particles and can be adsorbed by various life-forms. Most marine organisms tend to consume plastic debris that can be accumulated easily into the vertebrates, invertebrates and planktonic entities. Often these plastic particles surpass the food chain, resulting in the damage of various organs and inhibiting the uptake of food due to the accumulation of microplastics. In this review, the physical and chemical properties of microplastics, as well as their effects on the environment and toxicity of their chemical constituents are discussed. In addition, the paperalso sheds light on the potential of microorganisms such as bacteria, fungi, and algae whichplaya pivotal role in the process of microplasticsdegradation. The mechanism of microbial degradation, the factors that affect degradation, and the current advancements in genetic and metabolic engineering of microbes to promote degradation are also summarized. The paper also provides information on the bacterial, algal and fungal degradation mechanism including the possible enzymes involved in microplastic degradation. It also investigates the difficulties, limitations, and potential developments that may occur in the field of microbial microplastic degradation.

Combined transcriptomics and cellular analyses reveal the molecular mechanism by which Candida tropicalis ZD-3 adapts to and degrades gossypol

Microbial degradation techniques are often considered an environmentally friendly and cost-effective strategy for reducing gossypol toxicity. However, the mechanism by which Candida tropicalis degrades gossypol remains unclear. In the current study, we aimed to establish the mechanisms of biodegradation and adaptation mechanisms by C. tropicalis ZD-3. The toxicological evaluation results revealed that ZD-3 adapts to gossypol primarily by activating the antioxidant defense system to alleviate the oxidative stress response induced by gossypol. Transcriptomic analyses further suggested that ZD-3 protects against gossypol toxicity via cell wall remodeling. The intracellular enzyme CTRG_04744 gene was significantly up-regulated under gossypol stress, and then expressed in Pichia pastoris. The purified AKR_Z1 degraded 92 % of gossypol within 48 h. In addition, the aldehyde group of gossypol was effectively eliminated to achieve the desired detoxification. Collectively, these results provide theoretical guidance for the continued development of bio-efficient strategies capable of degrading gossypol.

Adaptation of a microbial consortium to pelagic Sargassum modifies its taxonomic and functional profile that improves biomethane potential.

In recent years, pelagic Sargassum has invaded the Caribbean coasts, and anaerobic digestion has been proposed as a sustainable management option. However, the complex composition of these macroalgae acts as a barrier to microbial degradation, thereby limiting methane production. Microbial adaptation is a promising strategy to improve substrate utilization and stress tolerance. This study aimed to investigate the adaptation of a microbial consortium to enhance methane production from the pelagic Sargassum. Microbial adaptation was performed in a fed-batch mode for 100days by progressive feeding of Sargassum. The evolution of the microbial community was analyzed by high-throughput sequencing of 16S rRNA amplicons. Additionally, 16S rRNA data were used to predict functional profiles using the iVikodak platform. The results showed that, after adaptation, the consortium was dominated by the bacterial phyla Bacteroidota, Firmicutes, and Atribacterota, as well as methanogens of the families Methanotrichaceae and Methanoregulaceae. The abundance of predicted genes related to different metabolic functions was affected during the adaptation stage when Sargassum concentration was increased. At the end of the adaptation stage, the abundance of the predicted genes increased again. The adapted microbial consortium demonstrated a 60% increase in both biomethane potential and biodegradability index. This work offers valuable insights into the development of treatment technologies and the effective management of pelagic Sargassum in coastal regions, emphasizing the importance of microbial adaptation in this context.