Sole Carbon Research Articles

Carbon substrates promotes stress resistance and drug tolerance in clinical isolates of Candida tropicalis.

Candida tropicalis is a human pathogen and one of the most prevalent non-Candida albicans Candida (NCAC) species causing invasive infections. Azole antifungal resistance in C. tropicalis is also gradually increasing with the increasing incidence of infections. The pathogenic success of C. tropicalis depends on its effective response in the host microenvironment. To become a successful pathogen, cellular metabolism, and physiological status determine the ability of the pathogen to counter diverse stresses inside the host. However, to date, limited knowledge is available on the impact of carbon substrate metabolism on stress adaptation and azole resistance in C. tropicalis. In this study, we determined the impact of glucose, fructose, and sucrose as the sole carbon source on the fluconazole resistance and osmotic (NaCl), oxidative (H2O2) stress adaptation in C. tropicalis clinical isolates. We confirmed that the abundance of carbon substrates influences or increases drug resistance and osmotic and oxidative stress tolerance in C. tropicalis. Additionally, both azole-resistant and susceptible isolates showed similar stress adaptation phenotypes, confirming the equal efficiency of becoming successful pathogens irrespective of drug susceptibility profile. To the best of our knowledge, our study is the first on C. tropicalis to demonstrate the direct relation between carbon substrate metabolism and stress tolerance or drug resistance.

Physiological basis for atmospheric methane oxidation and methanotrophic growth on air.

Atmospheric methane oxidizing bacteria (atmMOB) constitute the sole biological sink for atmospheric methane. Still, the physiological basis allowing atmMOB to grow on air is not well understood. Here we assess the ability and strategies of seven methanotrophic species to grow with air as sole energy, carbon, and nitrogen source. Four species, including three outside the canonical atmMOB group USCα, enduringly oxidized atmospheric methane, carbon monoxide, and hydrogen during 12 months of growth on air. These four species exhibited distinct substrate preferences implying the existence of multiple metabolic strategies to grow on air. The estimated energy yields of the atmMOB were substantially lower than previously assumed necessary for cellular maintenance in atmMOB and other aerobic microorganisms. Moreover, the atmMOB also covered their nitrogen requirements from air. During growth on air, the atmMOB decreased investments in biosynthesis while increasing investments in trace gas oxidation. Furthermore, we confirm that a high apparent specific affinity for methane is a key characteristic of atmMOB. Our work shows that atmMOB grow on the trace concentrations of methane, carbon monoxide, and hydrogen present in air and outlines the metabolic strategies that enable atmMOB to mitigate greenhouse gases.

Molecular Detection and Phylogenetic Analysis of the alkB Gene in Klebsiella oxytoca Strains Isolated from the Gut of Tenebrio molitor.

The challenge in polystyrene disposal has caused researchers to look for urgent innovative and ecofriendly solutions for plastic degradation. Some insects have been reported to use polystyrene as their sole carbon source, and this has been linked to the presence of microbes in their guts that aid in plastic digestion. Thus, this study focuses on the molecular detection and phylogenetic analysis of the alkane-1-monooxygenase (alkB) gene in Klebsiella oxytoca strains isolated from the gut of Tenebrio molitor. The alkB gene encodes for alkane-1-monooxygenase, an enzyme involved in the oxidation of inactivated alkanes. This gene can be used as a marker to assess bacteria's ability to biodegrade polystyrene. Three bacterial strains were isolated from the guts of T. molitor mealworms and were confirmed using polymerase chain reaction (PCR) of the 16S ribosomal RNA gene. The primers used in the amplification of the 16S ribosomal RNA region were designed using NCBI, a bioinformatics tool. To detect the presence of the alkB gene in the isolated bacterial strains, a set of primers used in the amplification of this gene was manually designed from the conserved regions of the alkB nucleotide sequences of eleven bacterial species from GenBank. TCOFFE online tool was used to align the alkB sequences of the bacteria, while Jalview and ConSurf were used to view the alignment. The amplified alkB gene was then sequenced using the Sanger sequencing technique, blasted on NCBI to look for similar sequences, and a phylogenetic tree was constructed. Based on the 16S ribosomal RNA gene sequences, the isolated bacterial strains were confirmed to be Klebsiella oxytoca NBRC 102593, Klebsiella oxytoca JCM 1665, and Klebsiella oxytoca ATCC 13182. The alkB gene sequence identical to fourteen alkB gene sequences derived from Actinobacteria whole genome was detected in Klebsiella oxytoca for the first time to the best of our knowledge. The novel nucleotide sequence was published in the NCBI database under accession number OP959069. This gene sequence was found to be for the enzyme alkane-1-monooxygenase and may be one of the enzymes responsible for polystyrene degradation by the putative Klebsiella oxytoca ATCC 13182 in T. molitor.

Degradation and inhibition kinetics of phenanthrene by Alcaligenes ammonioxydans, [VITRPS2] strain isolated from petroleum-contaminated soil

Phenanthrene, a common three-ring polyaromatic hydrocarbon [PAH], originates from sources like grilled meals, tobacco, crude oil, coal tar, and automobile exhaust. Recognized as a hazardous PAH, it is often targeted for bioremediation due to its sustainability and potential for full mineralization. In this study, we focus on biodegrading phenanthrene using the strain Alcaligenes ammonioxydans [VITRPS2], isolated from petroleum-contaminated soil. At 5 mg/ml, degradation occurred at a rate constant of 0.0181/day, with half-life values of 2.7 and 4.49 according to first and second-order kinetics, respectively. Employing a one-factor-at-a-time [OFAT] approach, we optimized biodegradation conditions within Luria–Bertani [LB] media. Under optimal conditions—pH 8.0, 8% inoculum concentration, and 37 °C incubation over seven days—the strain achieved maximal growth with phenanthrene as the sole carbon source. It exhibited a degradation efficiency of up to 72% for phenanthrene under these conditions. Gas chromatography-mass spectrometry [GC–MS] analysis revealed principal metabolites of the breakdown pathway, including salicylic acid, catechol, and various phthalic acid derivatives. This underscores the strain's potential for remediating environments polluted by PAH metabolites, showcasing its remarkable capability for complete phenanthrene degradation.Graphical abstract

The growth and nutrient removal properties of heterotrophic microalgae Chlorella sorokiniana in simulated wastewater containing volatile fatty acids

To reduce the high cost of organic carbon sources in waste resource utilization in the cultivation of microalgae, volatile fatty acids (VFAs) derived from activated sludge were used as the sole carbon source to culture Chlorella sorokiniana under the heterotrophic cultivation. The addition of VFAs in the heterotrophic condition enhanced the total nitrogen (TN) and phosphorus (TP) removal of C. sorokiniana, which proved the advantageous microalgae in using VFAs in the heterotrophic culture after screening in the previous study. To discover the possible mechanism of nitrogen and phosphorus adsorption in heterotrophic conditions by microalgae, the effect of different ratios of VFAs (acetic acid (AA): propionic acid (PA): butyric acid (BA)) on the nutrient removal and growth properties of C. sorokiniana was studied. In the 8:1:1 group, the highest efficiency (77.19%) of VFAs assimilation, the highest biomass (0.80 g L−1) and lipid content (31.35%) were achieved, with the highest TN and TP removal efficiencies of 97.44 % and 91.02 %, respectively. Moreover, an aerobic denitrifying bacterium, Pseudomonas, was determined to be the dominant genus under this heterotrophic condition. This suggested that besides nitrate uptake and utilization by C. sorokiniana under the heterotrophy, the conduct of the denitrification process was also the main reason for obtaining high nitrogen removal efficiency.

Biodegradation of polyurethanes by Staphylococcus warneri and by microbial co-culture

With the increasing production and use of polyurethanes (PUs), it is necessary to develop sustainable techniques for the remediation of plastic pollution. The use of microorganisms capable of biodegrading PUs may be an environmentally desirable solution for controlling these plastic contaminants. To contribute to the discovery of alternatives for the mitigation of plastics in the environment, this study aimed to explore the potential of StaphylococcuswarneriUFV_01.21, isolated from the gut of Galleria mellonellalarvae, for biodegradation of PU in pure culture and microbial co-culture with Serratia liquefaciensL135. S. warneri grew using Impranil® PU as the sole carbon source in pure culture and co-culture. With six days of incubation, the biodegradation of Impranil® in Luria Bertani broth was 96, 88 and 76%, while in minimal medium, it was 58, 54 and 42% for S. warneri, S. liquefaciens, and co-culture, respectively. In addition, S. warneri in pure culture or co-culture was able to biodegrade, adhere and form biofilms on the surfaces of Impranil® disks and poly[4,4′-methylenebis (phenyl isocyanate)-alt-1,4-butanediol/di(propylene glycol)/polycaprolactone] (PCLMDI) films. Scanning electron microscopy also revealed biodegradation by detecting the formation of cracks, furrows, pores, and roughness on the surfaces of inoculated PU, both with pure culture and microbial co-culture. This study is the first to demonstrate the potential of S. warneriin PU biodegradation.

Long chain unsaturated fatty acids alter growth and reduce biofilm formation of Cronobacter sakazakii

AbstractCronobacter sakazakii is a foodborne pathogen predominately transmitted through contaminated dried foods and affects populations including neonates, infants, and the elderly. Following several recent outbreaks, it is now a notifiable infection in those under 12 months of age. Current control methods include strict manufacturing guidelines, with monitoring of this genus a legal requirement in powdered infant formula production. Fatty acids have long been known as antimicrobials, with long‐chain fatty acids increasingly identified as agents that target virulence factors. This study gives insight into the changes promoted by three long‐chain unsaturated fatty acids (oleic, linoleic, and α‐linolenic) on C. sakazakii growth, morphology, and biofilm formation. Each fatty acid was individually introduced to C. sakazakii 29544 both as a sole carbon source and as an addition to complex media. Following comparison to the untreated control, bacterial cells treated with these fatty acids showed a significant and media‐dependent impact on growth and biofilm inhibition. With further characterization, long‐chain fatty acids, including α‐linolenic acid, could be utilized as a control method with minimal safety constraints regarding their use in the food production environment.

Polyhydroxyalkanoate Copolymer Production by Recombinant Ralstonia eutropha Strain 1F2 from Fructose or Carbon Dioxide as Sole Carbon Source

Ralstonia eutropha strain H16 is a chemoautotrophic bacterium that oxidizes hydrogen and accumulates poly[(R)-3-hydroxybutyrate] [P(3HB)], a prominent polyhydroxyalkanoate (PHA), within its cell. R. eutropha utilizes fructose or CO2 as its sole carbon source for this process. A PHA-negative mutant of strain H16, known as R. eutropha strain PHB−4, cannot produce PHA. Strain 1F2, derived from strain PHB−4, is a leucine analog-resistant mutant. Remarkably, the recombinant 1F2 strain exhibits the capacity to synthesize 3HB-based PHA copolymers containing 3-hydroxyvalerate (3HV) and 3-hydroxy-4-methyvalerate (3H4MV) comonomer units from fructose or CO2. This ability is conferred by the expression of a broad substrate-specific PHA synthase and tolerance to feedback inhibition of branched amino acids. However, the total amount of comonomer units incorporated into PHA was up to around 5 mol%. In this study, strain 1F2 underwent genetic engineering to augment the comonomer supply incorporated into PHA. This enhancement involved several modifications, including the additional expression of the broad substrate-specific 3-ketothiolase gene (bktB), the heterologous expression of the 2-ketoacid decarboxylase gene (kivd), and the phenylacetaldehyde dehydrogenase gene (padA). Furthermore, the genome of strain 1F2 was altered through the deletion of the 3-hydroxyacyl-CoA dehydrogenase gene (hbdH). The introduction of bktB-kivd-padA resulted in increased 3HV incorporation, reaching 13.9 mol% from fructose and 6.4 mol% from CO2. Additionally, the hbdH deletion resulted in the production of PHA copolymers containing (S)-3-hydroxy-2-methylpropionate (3H2MP). Interestingly, hbdH deletion increased the weight-average molecular weight of the PHA to over 3.0 × 106 on fructose. Thus, it demonstrates the positive effects of hbdH deletion on the copolymer composition and molecular weight of PHA.

Polyethylene terephthalate (PET)-degrading bacteria in the pelagic deep-sea sediments of the Pacific Ocean

Polyethylene terephthalate (PET) plastic pollution is widely found in deep-sea sediments. Despite being an international environmental issue, it remains unclear whether PET can be degraded through bioremediation in the deep sea. Pelagic sediments obtained from 19 sites across a wide geographic range in the Pacific Ocean were used to screen for bacteria with PET degrading potential. Bacterial consortia that could grow on PET as the sole carbon and energy source were found in 10 of the 19 sites. These bacterial consortia showed PET removal rate of 1.8%–16.2% within two months, which was further confirmed by the decrease of carbonyl and aliphatic hydrocarbon groups using attenuated total reflectance–Fourier-transform infrared analysis (ATR-FTIR). Analysis of microbial diversity revealed that Alcanivorax and Pseudomonas were predominant in all 10 PET degrading consortia. Meanwhile, Thalassospira, Nitratireductor, Nocardioides, Muricauda, and Owenweeksia were also found to possess PET degradation potential. Metabolomic analysis showed that Alcanivorax sp. A02-7 and Pseudomonas sp. A09-2 could turn PET into mono-(2-hydroxyethyl) terephthalate (MHET) even in situ stimulation (40 MPa, 10 °C) conditions. These findings widen the currently knowledge of deep-sea PET biodegrading process with bacteria isolates and degrading mechanisms, and indicating that the marine environment is a source of biotechnologically promising bacterial isolates and enzymes.

Tapping into fungal potential: Biodegradation of plastic and rubber by potent Fungi

Plastic polymers are present in most aspects of routine daily life. Their increasing leakage into the environment poses a threat to environmental, animal, and human health. These polymers are often resistant to microbial degradation and are predicted to remain in the environment for tens to hundreds of years. Fungi have been shown to degrade complex polymers and are considered good candidates for bioremediation (biological pollutant reduction) of plastics. Therefore, we screened 18 selected fungal strains for their ability to degrade polyurethane (PU), polyethylene (PE), and tire rubber. As a proxy for plastic polymer mineralization, we quantified O2 consumption and CO2 production in an enclosed biodegradation system providing plastic as the sole carbon source. In contrast to most studies we demonstrated that the tested fungi attach to, and colonize the different plastic polymers without any pretreatment of the plastics and in the absence of sugars, which were suggested essential for priming the degradation process. Functional polymer groups identified by Fourier-transform infrared spectroscopy (FTIR), and changes in fungal morphology as seen in light and scanning electron microscopy (SEM) were used as indicators of fungal adaptation to growth on PU as a substrate. Thereby, SEM analysis revealed new morphological structures and deformation of the cell wall of several fungal strains when colonizing PU and utilizing this plastic polymer for cell growth. Strains of Fusarium, Penicillium, Botryotinia cinerea EN41, and Trichoderma demonstrated a high potential to degrade PU, rubber, and PE. Growing on PU, over 90 % of the O2 was consumed in <14 days with 300–500 ppm of CO2 generated in parallel. Our study highlights a high bioremediation potential of some fungal strains to efficiently degrade plastic polymers, largely dependent on plastic type.

L-Lactate production from carbon dioxide in the red alga Cyanidioschyzon merolae

Lactate/lactic acid is a commodity chemical used in various products such as bioplastics. The optical isomers of lactate are l- and d-lactate. Both the lactate enantiomers are required to manufacture lactate derived bioplastics. Eukaryotic microalgae and cyanobacteria can produce l-lactate or d-lactate using carbon dioxide as their sole carbon source. However, eukaryotic microalgae and cyanobacteria with high l-lactate productivity have not yet been identified. Cyanidioschyzon merolae is a hot-spring red alga preferring an acidic pH and high temperature. The entire genomic sequence was determined. C. merolae contains five l-lactate dehydrogenases that catalyze l-lactate-generating reactions during lactate fermentation. This study revealed that C. merolae produces l-lactate with high productivity during dark anaerobic cultivation. Nitrogen starvation before dark anaerobic cultivation increased the l-lactate productivity in C. merolae. l-Lactate accounted for over 90% of the total organic acids excreted by C. merolae cells. C. merolae exhibited a high l-lactate productivity under cultivation at a neutral pH. The l-lactate productivity in C. merolae at 16.0–19.4 mg/L/h was higher than that in a unicellular cyanobacterium at 2.7 mg/L/h. These findings indicate that C. merolae is one of the candidates for a host of l-lactate production from carbon dioxide.

Erythromycin mediates co-flocculation between cyanobacterium Synechocystis sp. PCC 6803 and filamentous fungi in liquid cultivation without organic compounds

Photoautotrophic cyanobacteria assimilate the greenhouse gas carbon dioxide as their sole carbon source for producing useful bioproducts. However, harvesting the cells from their liquid media is a major bottleneck in the process. Thus, an easy-to-harvest method, such as auto-flocculation, is desirable. Here, we found that cyanobacterium Synechocystis sp. PCC 6803 co-flocculated with a natural fungal contamination in the presence of the antibiotic erythromycin (EM) but not without EM. The fungi in the co-flocculated biomass were isolated and found to consist of five species with the filamentous Purpureocillium lilacinum and Aspergillus protuberus making up 71% of the overall fungal population. The optimal co-cultivation for flocculation was an initial 5 mg (fresh weight) of fungi, an initial cell density of Synechocystis of 0.2 OD730, 10 µM EM, and 14 days of cultivation in 100 mL of BG11 medium with no organic compound. This yielded 248 ± 28 mg/L of the Synechocystis-fungi flocculated biomass from 560 ± 35 mg/L of total biomass, a 44 ± 2% biomass flocculation efficiency. Furthermore, the EM treated Synechocystis cells in the Synechocystis-fungi flocculate had a normal cell color and morphology, while those in the axenic suspension exhibited strong chlorosis. Thus, the occurrence of the Synechocystis-fungi flocculation was mediated by EM, and the co-flocculation with the fungi protected Synechocystis against the development of chlorosis. Transcriptomic analysis suggested that the EM-mediated co-flocculation was a result of down-regulation of the minor pilin genes and up-regulation of several genes including the chaperone gene for pilin regulation, the S-layer protein genes, the exopolysaccharide-polymerization gene, and the genes for signaling proteins involved in cell attachment and abiotic-stress responses. The CuSO4 stress can also mediate Synechocystis-fungi flocculation but at a lower flocculation efficiency than that caused by EM. The EM treatment may be applied in the co-culture between other cyanobacteria and fungi to mediate cell bio-flocculation.

Degradation of pretilachlor and fenclorim and effects of these compounds on bacterial communities under anaerobic condition.

Pretilachlor and safener fenclorim are the main components of herbicides widely applied to control weeds. Although some pure cultures of bacteria and fungi which degraded these compounds under aerobic conditions were isolated, no isolated pretilachlor- and fenclorim-degrading bacterial strains under anaerobic condition had been available. In this study, the degradation of these compounds and the effects of them on bacterial community structures were investigated under anaerobic conditions. The dissipation rates of pretilachlor and fenclorim in slurries were in the order: soil from paddy field ≈ sediment from river > sediment from mangrove. Moreover, three pretilachlor-degrading bacterial strains (Pseudomonas sp. Pr1, Proteiniclasticum sp. Pr2 and Paracoccus denitrificans Pr3) and two fenclorim-degrading strains (Dechloromonas sp. Fe1 and Ralstonia pickettii Fe2) isolated from a slurry of paddy soil utilized the substrates as sole carbon and energy sources under anaerobic conditions. The degradation of pure pretilachlor and fenclorim at various concentrations by corresponding mixed pure cultures followed the Michaelis-Menten model, with the maximum degradation was 3.10 ± 0.31µM/day for pretilachlor, and 2.08 ± 0.18µM/day for fenclorim. During the degradation, 2-chloro-N-(2,6-diethylphenyl) acetamide and 2,6-dimethylaniline were produced in pretilachlor degradation, and benzene was a product of fenclorim degradation. The synergistic degradation of both substrates by all isolated bacteria reduced the metabolites concentrations accumulated in media. This study provides valuable information on effects of pretilachlor and fenclorim on bacterial communities in soil and sediments, and degradation of these substrates by isolated bacteria under anaerobic condition.

Utilization of Agricultural Waste for the Cultivation of Pleurotus Mushrooms in Thailand

Thailand is one of the major agricultural production countries in the world. Therefore, large amounts of agricultural waste are generated as by-products of the agroindustry. The wastes are usually discarded or burnt, resulting in environmental pollution. The main goal of this research was to evaluate the use of agricultural waste for mushroom cultivation. A total of 15 mushroom isolates were recovered from mother spawns and basidiocarps. They were screened for their cellulolytic enzyme activity on Czapek agar using carboxymethyl cellulose (CMC) as the sole carbon source. Two isolates of the oyster mushrooms, Pleurotus pulmonarius PP6 and Pleurotus ostreatus PO3, produced the best enzyme activities. To observe the mycelial growth on agricultural waste, the two oyster mushroom candidates were cultured in jars containing five different types of agricultural waste: corn husk, rice straw, coconut meal, coconut husk and sugarcane bagasse, and the jars were incubated at 25°C for six weeks. The results show that both isolates grew best on coconut meal, producing very densely packed mycelia. Meanwhile, corn husk and rice straw were also good sources for oyster mushroom cultivation. This study shows that these three substrates have the potential to be utilized in mushroom cultivation on a commercial scale.

Biodegradation of ochratoxin A by Brevundimonas diminuta HAU429: Characterized performance, toxicity evaluation and functional enzymes

Ochratoxin A (OTA) is a notorious mycotoxin commonly contaminating food products worldwide. In this study, an OTA-degrading strain Brevundimonas diminuta HAU429 was isolated by using hippuryl-L-phenylalanine as the sole carbon source. The biodegradation of OTA by strain HAU429 was a synergistic effect of intracellular and extracellular enzymes, which transformed OTA into ochratoxin α (OTα) through peptide bond cleavage. Cytotoxicity tests and cell metabolomics confirmed that the transformation of OTA into OTα resulted in the detoxification of its hepatotoxicity since OTA but not OTα disturbed redox homeostasis and induced oxidative damage to hepatocytes. Genome mining identified nine OTA hydrolase candidates in strain HAU429. They were heterologously expressed in Escherichia coli, and three novel amidohydrolase BT6, BT7 and BT9 were found to display OTA-hydrolyzing activity. BT6, BT7 and BT9 showed less than 45 % sequence identity with previously identified OTA-degrading amidohydrolases. BT6 and BT7 shared 60.9 % amino acid sequence identity, and exhibited much higher activity towards OTA than BT9. BT6 and BT7 could completely degrade 1 μg mL−1 of OTA within 1 h and 50 min, while BT9 hydrolyzed 100 % of OTA in the reaction mixture by 12 h. BT6 was the most thermostable retaining 38 % of activity after incubation at 70 °C for 10 min, while BT7 displayed the highest tolerance to ethanal remaining 76 % of activity in the presence of 6 % ethanol. This study could provide new insights towards microbial OTA degradation and promote the development of enzyme-catalyzed OTA detoxification during food processing.

Analysis of the effect of oat β-glucan on gut microbiota and clarification of their interaction relationship

Oat β-glucan is catabolized by gut microbiota, however, the interaction relationship between β-glucan and gut microbiota is unclear. We aim to investigate the primary intestinal microbial species responsible for oat β-glucan degradation and explore their interaction. The result of in vitro fermentation showed that β-glucan significantly altered gut microbiota composition and primary microbial species responding to β-glucan was Lactobacillus. A total of 4 strains of Lactobacillus murinus were in vitro obtained and inoculated in the medium containing β-glucan as the sole carbon source to verify their association with β-glucan, and result showed that 4 strains of L. murinus could indeed degrade β-glucan. Genome analysis suggested that 4 strains of L. murinus contained abundant carbohydrate enzymes-encoding genes, among which genes encoding glycoside hydrolases family 1 (GH1) were most likely associated with β-glucan degradation. Further analysis revealed that GH1 could bind to β-glucan units through hydrogen bonding. Our study provides a novel insight into the research on interplay between dietary components and gut microbiota, and strategy for the exploration of potential carbohydrate hydrolase from gut microbiota for cereal β-glucan processing.

Behaviours of methane metabolism and community dynamics of methane anaerobic oxidation microbes on carbonate rocks with long-term cultivation in cold seep environment

The anaerobic oxidation of methane (AOM) and sulfate reduction processes in cold seep environments can control methane emission sources and thus mitigate the pressure of increasing global greenhouse gas concentrations. The surfaces of carbonate rocks in cold seep host an abundance of microorganisms that participate in AOM reactions. Investigating the metabolism and conversion of methane by these microbes is instrumental in advancing the exploration and utilization of deep-sea methane energy. Previous studies primarily focused on in-situ investigations of microbial communities on carbonate rocks in cold seep environments, while the dynamic balance of carbonate mineralization caused by microbial community changes and the characteristics of methane consumption in carbonate samples remains unclear. In this study, we used methane as the sole carbon source, enriched and cultured carbonate samples under high pressure, and monitored the community dynamics regularly. The results demonstrated that methane consumption and metabolic pathways played a crucial role in influencing community succession and carbonate mineralization. AOM processes, coupled with sulfate reduction and nitrate reduction, which are dominated by ANME-2c, facilitate the precipitation of calcium carbonate. Conversely, the acetate production process, dominated by ANME-1, may hinder the efficiency of calcium carbonate mineralization. Additionally, the impact of bacterial groups in the enrichment process, through the production of extracellular enzymes, organic acid pathways, and the expression of carbonic anhydrase pathways on carbonate mineralization, should not be disregarded. These findings highlight the significance of diverse pathway methane metabolism in the dynamics of methane consumption, deep-sea microbial communities, carbonate kinetics, and marine biological carbon sequestration processes.

Biodegradation of polyethylene (PE), polypropylene (PP), and polystyrene (PS) microplastics by floc-forming bacteria, Bacillus cereus strain SHBF2, isolated from a commercial aquafarm.

The ubiquitous proximity of the commonly used microplastic (MP) particles particularly polyethylene (PE), polypropylene (PP), and polystyrene (PS) poses a serious threat to the environment and human health globally. Biological treatment as an environment-friendly approach to counter MP pollution has recent interest when the bio-agent has beneficial functions in their ecosystem. This study aimed to utilize beneficial floc-forming bacteria Bacillus cereus SHBF2 isolated from an aquaculture farm in reducing the MP particles (PE, PP, and PS) from their environment. The bacteria were inoculated for 60 days in a medium containing MP particle as a sole carbon source. On different days of incubation (DOI), the bacterial growth analysis was monitored and the MP particles were harvested to examine their weight loss, surface changes, and alterations in chemical properties. After 60 DOI, the highest weight loss was recorded for PE, 6.87 ± 0.92%, which was further evaluated to daily reduction rate (k), 0.00118 day-1, and half-life (t1/2), 605.08 ± 138.52 days. The OD value (1.74 ± 0.008 Abs.) indicated the higher efficiency of bacteria for PP utilization, and so for the colony formation per define volume (1.04 × 1011 CFU/mL). Biofilm formation, erosions, cracks, and fragments were evident during the observation of the tested MPs using the scanning electron microscope (SEM). The formation of carbonyl and alcohol group due to the oxidation and hydrolysis by SHBF2 strain were confirmed using the Fourier transform infrared spectroscopic (FTIR) analysis. Additionally, the alterations of pH and CO2 evolution from each of the MP type ensures the bacterial activity and mineralization of the MP particles. The findings of this study have confirmed and indicated a higher degree of biodegradation for all of the selected MP particles. B. cereus SHBF2, the floc-forming bacteria used in aquaculture, has demonstrated a great potential for use as an efficient MP-degrading bacterium in the biofloc farming system in the near future to guarantee a sustainable green aquaculture production.

Biodegradation of Nitrile Gloves as Sole Carbon Source of Pseudomonas aeruginosa in Liquid Culture.

Nitrile gloves have become a significant environmental pollutant after the COVID-19 pandemic due to their single-use design. This study examines the capability of P. aeruginosa to use nitrile gloves as its sole carbon energy source. Biodegradation was determined by P. aeruginosa adapting to increasing nitrile glove concentrations at 1%, 3%, and 5% (w/v). The growth kinetics of P. aeruginosa were evaluated, as well as the polymer weight loss. Topographic changes on the glove surfaces were examined using SEM, and FT-IR was used to evaluate the biodegradation products of the nitrile gloves. Following the establishment of a biofilm on the glove surface, the nitrile toxicity was minimized via biodegradation. The result of the average weight loss of nitrile gloves was 2.25%. FT-IR analysis revealed the presence of aldehydes and aliphatic amines associated with biodegradation. SEM showed P. aeruginosa immersed in the EPS matrix, causing the formation of cracks, scales, protrusions, and the presence of semi-spherical particles. We conclude that P. aeruginosa has the capability to use nitrile gloves as its sole carbon source, even up to 5%, through biofilm formation, demonstrating the potential of P. aeruginosa for the degradation of nitrile gloves.

Potencial Citric Acid Production by Fungi Using Hemicellulosic Hydrolysate of Coffee Husk as Substrate

Objective: The aim of this experimental assay was to produce citric acid via submerged fermentation, using hemicellulose hydrolysate from coffee husks as main substrate. Theoretical framework: Obtaining citric acid through fermentation processes, especially submerged fermentation, has become viable due to the use of low-cost materials, such as industrial subproducts derived from green biomass. Methodology: The hemicellulose hydrolysate was obtained from the acid hydrolysis process of the coffee husk. The strains of the fungi Aspergillus niger, Aspergillus westerdijkiae and Rhizopus sp. were employed to carry out the fermentation assays. A bioreactor consisting of a 500 ml flat-bottomed flask was used, with an inlet for supplying air and an outlet for removing samples Results and Conclusion: The obtained results showed an increase in number of spores of the studied fungi as well as citric acid accumulation during the first 72 h of fermentation. On the other hand, after 96 h of fermentation citric acid concentration began to decrease indicating its consumption by the studied fungi, probably due to the lack of nitrogen sources and the cellular stress caused by the mixed composition of the hemicellulose hydrolysate. Implications of the research: There is a need to study the interaction between the nitrogenous nutrients to be added to the fermentation medium and the concentration of reducing sugars as the sole carbon source in the lignocellulosic hydrolysate. Originality/value: This work highlights the potential production of citric acid by fungi using a coffee husk as a renewable biomass.