Ontology highlight
ABSTRACT:
PROVIDER: PRJNA553333 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR9657750_1.fastq.gz | Fastqsanger.gz | |||
| SRR9657750_2.fastq.gz | Fastqsanger.gz | |||
| SRR9657751_1.fastq.gz | Fastqsanger.gz | |||
| SRR9657751_2.fastq.gz | Fastqsanger.gz | |||
| SRR9657752_1.fastq.gz | Fastqsanger.gz |
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Project description:The effect of respiration (aerobic cultivation in the presence of heme and vitamin K2) was compared with unsupplemented aerobic cultivation with Lactobacillus plantarum. Two-condition experiment, aerobic vs respiring cells. Biological replicates: 3 aerobic cultures, 3 respiring cultures, independently grown and harvested. One replicate per array. Respiring cultures are called reactor 1-3; Aerobic cultures are called reactor 4-6 In the subsequent analysis data from reactor 4 were not used. There was likely a mistake made during quenching. This was concluded as new labeling/hybridisation gave same (bad) results (128a); slide 128b was dye-swap.
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Project description:This study explores the use of short settling times as a strategy to enhance microbial selection and prevent bulking induced by nutrient shortage in an aerobic dynamic feeding (ADF) process using mixed microbial cultures (MMCs) for polyhydroxyalkanoate (PHA) production from fermentation digestate. A 5.0-L aerobic reactor was operated under three conditions: Long Settling (LS, 30 minutes), Short Settling (SS, 10 minutes), and Short Settling under Nutrient Shortage (SS-NS, 10 minutes with reduced nutrient load). Short settling significantly improved biomass settleability, reducing the Sludge Volume Index (SVI) from 126 to 25 mL g⁻¹, and promoted the formation of dense flocs enriched in PHA-accumulating bacteria, as confirmed by transmission electron microscopy. Process kinetics revealed enhanced substrate uptake rates and improved storage yields under SS conditions, despite an elevated C/P ratio. Notably, nutrient shortage conditions were inadvertently reached by the proliferation of Polytoma mirum in the feeding tank. Although Polytoma mirum did not affect VFA composition, its presence significantly reduced nitrogen and phosphorus concentrations. These nutrient shortage conditions were maintained for at least 30 days until the system began to exhibit stress, as demonstrated by an increased SVI (178.6 mL g⁻¹). Microbial community analyses indicated marked shifts: the eukaryotic assemblage transitioned from sessile to motile ciliates under SS, while bacterial diversity within the PHA‐accumulating fraction remained high, with key taxa such as Sphaerotilus and Neomegalonema becoming more prevalent under phosphorus-limited conditions. Overall, short settling not only improved microbial selection but also prevented bulking by retaining well-aggregated biomass, thereby mitigating nutrient shortage conditions.
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Project description:This study investigates the role of carbon-to-phosphorus (C/P) ratios in shaping microbial community dynamics and polyhydroxyalkanoates (PHA) production in sequencing batch reactors (SBR) fed with volatile fatty acids. Three conditions, characterized by fixed organic loading rates but varying C/P ratios (Run 1 = 170 Cmol Pmol-1; Run 2 = 235 Cmol Pmol-1; Run 3 = 400 Cmol Pmol-1), were tested to explore their impact on PHA accumulation, biomass growth, and reactor stability. Results indicate that the moderate phosphorus limitation of Run 2 achieves the best overall performance, with a PHA volumetric productivity of 2.02 g PHA L-1 d-1 and process stability. Conversely, higher C/P ratio increased the storage yield but lowered the productivity (1.55 gPHA L-1 d-1), compromising sludge settleability and reactor stability, indicating impaired microbial functionality. Full-length 16S/18S rRNA gene sequencing using PacBio technology enabled high-resolution profiling of microbial communities, revealing ecological shifts across conditions. Run 2 exhibited the highest bacterial and eukaryotic diversity, featuring multiple PHA-accumulating bacteria (mainly Sphaerotilus, Leadbetterella, and uncultured Rhodobacteraceae) and a well-structured eukaryotic community dominated by K-strategist bacterivorous protists, e.g. Rhogostoma (Rhizaria) and Vorticella (Ciliophora, Oligohymenophorea) and predatory protozoa, e.g. Tokophrya (Ciliophora, Suctoria). In contrast, Sphaerotilus dominated under suboptimal conditions and may be linked to bulking. These results suggest that eukaryotic diversity may support system stability through selective predation. Transmission electron microscopy (TEM) further confirmed the presence of intracellular PHA granules and polyphosphate reserves, reinforcing the connection between nutrient limitation and adaptive microbial strategies. Overall, these findings highlight the critical role of the C/P ratio in shaping the performance of mixed microbial cultures, demonstrating that a well-balanced nutrient supply can enhance PHA production while maintaining microbial community stability. The results contribute to optimizing the selection process for mixed microbial cultures, offering valuable insights into the impact of carbon-to-nutrient ratios in the feeding strategy.
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