Supplementary Carbon Source Research Articles

Food Waste Fermentation Liquid as a Supplementary Carbon Source for Enhanced Biological Nitrogen Removal from Rural Wastewater

Food Waste Fermentation Liquid as a Supplementary Carbon Source for Enhanced Biological Nitrogen Removal from Rural Wastewater

Maximizing diclofenac bioremoval efficiency using Chlorella vulgaris strain H1 and Chlorella sorokiniana strain H2: Unveiling the impact of acetic acid on microalgae

BackgroundDiclofenac (DFC) is a commonly detected pharmaceutical pollutant in wastewater, posing environmental risks. Microalgae have emerged as potential candidates for bioremediation due to their ability to degrade pollutants. This study focuses on investigating the biodegradation potential of two newly isolated microalgae strains, Chlorella vulgaris strain H1 and Chlorella sorokiniana strain H2, towards DFC removal. The optimization of pH is crucial for enhancing the efficiency of bioremediation processes. Therefore, in addition to assessing the biodegradation potential of microalgae, this study also investigates the impact of adjusting the pH of the culture medium using acetic acid as an additional carbon source on the biodegradation process. MethodsThrough genetic analysis using 18S rDNA sequencing, the microalgae strains were identified. Various parameters including growth dynamics, chlorophyll content, cell proliferation, photosynthetic activity, and DFC biodegradation efficiency were comprehensively assessed. Additionally, the impact of incorporating acetic acid as an additional carbon source in the culture medium on the biodegradation process was examined. Significant FindingsC. sorokiniana strain H2 demonstrated superior biodegradation rates compared to C. vulgaris strain H1 across varying DFC concentrations. Specifically, C. sorokiniana strain H2 exhibited remarkable biodegradation rates of 84 %, 83.72 %, and 29.57 % for DFC concentrations of 12.5 mg L−1, 25 mg L−1, and 100 mg L−1, respectively. In contrast, C. vulgaris strain H1 showed lower biodegradation rates of 66.64 %, 29.24 %, and 1.83 % for the corresponding DFC concentrations. The study highlights the potential of C. sorokiniana strain H2 as a promising candidate for the removal of pharmaceutical pollutants like DFC from wastewater. Furthermore, the use of acetic acid as a supplementary carbon source enhanced the biodegradation efficiency, suggesting a potential strategy for optimizing bioremediation processes.

Enhancing nitrogen removal by simultaneous nitritation and denitritation in a multi-cycle SBR with supplementation of solid carbon sources

Simultaneous nitritation and denitritation have the potential to significantly improve nitrogen removal in sewage treatment processes. However, their application in low-strength sewage treatment systems presents challenges. This study explored the impact of four solid carbon sources (SCSs) on N-removal via nitrite in a multi-cycle SBR with biocarriers. Results showed that both N-removal efficiencies and nitrite accumulation rates increased with higher COD/N ratios, indicating that high COD/N ratios can improve the competition between denitrifiers and nitrite-oxidizing bacteria for nitrite, leading to stable simultaneous nitritation and denitritation. The supplementation of SCSs further enhanced this high-efficiency N-removal process, with polybutylene succinate (PBS) and polycaprolactone (PCL) showing greater increases in N-removal via nitrite than poly-hydroxybutyrate (PHB) and poly-hydroxyalkanoate (PHA). Moreover, PBS showed the most significant increase in denitrification efficiency in anoxic conditions, while PHA was the most effective external SCS at a moderate level of dissolved oxygen. These findings suggest that the incorporation of external SCSs can facilitate the simultaneous nitritation and denitrification process in multi-cycle SBRs, underscoring the importance of selecting an appropriate SCS for optimizing nitrogen removal in sewage treatment projects.

Large-scale cultivation of Synechocystis sp. PCC6803 for the production of Poly(3-hydroxybutyrate) and its potential applications in the manufacturing of bulk and medical prototypes

Polyhydroxyalkanoates (PHAs) are biopolymers produced by microorganisms under nutrient limiting conditions and in the presence of excess carbon source. PHAs have gained popularity as a sustainable alternative to traditional plastics. However, large scale production of PHAs is economically challenging due to the relatively high costs of organic carbon. Alternative options include using organisms capable of phototrophic or mixotrophic growth. This study aimed at the production of poly(3-hydroxybutyrate) P(3HB), a type of PHA, at pilot scale using the freshwater cyanobacterium Synechocystis sp. PCC6803. First, to identify optimal conditions for P(3HB) production from Synechocystis sp. PCC6803, different supplemental carbon source concentrations and salinity levels were tested at laboratory scale. The addition of 4 g/L acetate with no added NaCl led to P(3HB) accumulation of 10.7 % dry cell weight on the 28th day of cultivation. Although acetate additions were replicated in an outdoor 400 L serpentine photobioreactor, P(3HB) content was lower, implying uncontrolled conditions impact on biopolymer production efficiency. An optimized P(3HB) extraction methodology was developed to remove pigments, and the biopolymer was characterized and subjected to 3D printing (fused deposition modelling) to confirm its processability. This study thus successfully led to the large-scale production of P(3HB) using sustainable and environmentally friendly cyanobacterial fermentation.

Effects of engineering injection and supplement mode of in-situ biogeochemical transformation enhancement EVO-FeSO4 on the remediation of tetrachloroethylene contaminated aquifer

Traditional in situ biogeochemical transformation suffers from competition among crucial microorganisms and inadequate formation of reactive minerals, thus leading to the accumulation of toxic intermediates. In this study, three regulation schemes were proposed to solve these problems from the perspective of engineering mode. Results showed intermittent injection mode effectively reduced the accumulation of toxic intermediates but the reduction rate of tetrachloroethylene was decreased. And periodical supplementation of carbon and sulfur sources accelerated the removal of tetrachloroethylene but failed to reduce the accumulation of toxic products. While, regular supplementation of sulfate effectively weakened the competition of methanogens and increased the iron sulfide proportion on the surface of the minerals, thus reducing the accumulation of toxicity. Based on the results, this study obtained an effective engineering approach for practical site application. In addition, the main forms of active minerals capable of β-eliminating contaminants during biogeochemical transformation were identified in this study, including FeS, FeS2, and Fe3S4. Furthermore, the engineered regulatory mechanism of this study was summarized through the analysis of microbial community structure and mineral morphology. The amendment promotes the production of minerals and thus controls the transformation pathway of contaminants by altering the abundance of sulfate-reducing bacteria and dissimilatory iron reducing bacteria. This mechanism can provide a basis for subsequent theoretical studies.

Electrochemical detection of poly(3-hydroxybutyrate) production from Burkholderia glumae MA13 using a molecularly imprinted polymer-reduced graphene oxide modified electrode.

Thedevelopment and application of an electrochemical sensor is reported fordetection of poly(3-hydroxybutyrate) (P3HB) - a bioplastic derived from agro-industrial residues. To overcome the challenges of molecular imprinting of macromolecules such as P3HB, this study employed methanolysis reaction to break down the P3HB biopolymer chains into methyl 3-hydroxybutyrate (M3HB) monomers. Thereafter, M3HB were employed as the target molecules in the construction of molecularly imprinted sensors. The electrochemical device was then prepared by electropolymerizing a molecularly imprinted poly (indole-3-acetic acid) thin film on a glassy carbon electrode surface modified with reduced graphene oxide (GCE/rGO-MIP) in the presence of M3HB. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), scanning electron microscopy with field emission gun (SEM-FEG), Raman spectroscopy, attenuated total reflection Fourier-transform infrared (ATR-FTIR) and X-ray Photoelectron Spectroscopy (XPS) were employed to characterize the electrode surface. Under ideal conditions, the MIP sensor exhibited a wide linear working range of 0.1 - 10nM and a detection limit of 0.3pM (n = 3). The sensor showed good repeatability, selectivity, and stability over time. For the sensor application, the bioproduction of P3HB was carried out in a bioreactor containing the Burkholderia glumae MA13 strain and sugarcane byproducts as a supplementary carbon source. The analyses were validated through recovery assays, yielding recovery values between 102 and 104%. These results indicate that this MIP sensor can present advantages in the monitoring of P3HB during the bioconversion process.

Optimizing nitrogen removal in constructed wetlands for low C/N ratio wastewater treatment: Insights from fermentation liquid utilization

The inefficient nitrogen removal in constructed wetlands (CWs) can be attributed to insufficient carbon sources for low carbon-to-nitrogen (C/N) ratio wastewater. In this study, sugarcane bagasse fermentation liquid (SBFL) was used as a supplemental carbon source in intermittently aerated CWs to enhance nitrogen removal. The impact of different regulated influent C/N ratios on nitrogen removal and greenhouse gas (GHG) emissions was investigated. Results demonstrated that SBFL addition significantly enhanced the denitrification capacity, resulting in faster NO3--N removal compared to sucrose. Moreover, intermittently aerated CWs significantly improved NH4+-N removal efficiency compared to non-aerated CWs. The highest total nitrogen removal efficiency (98.3 %) was achieved at an influent C/N ratio of 5 in intermittently aerated CWs with SBFL addition. The addition of SBFL resulted in a reduction of N2O emissions by 17.8 %–43.7 % compared to sucrose. All CWs exhibited low CH4 emissions, with SBFL addition (0.035–0.066 mg·m-2h-1) resulting in lower emissions compared to sucrose. Additionally, higher abundance of denitrification (nirK, nirS and nosZ) genes as well as more abundant denitrifying bacteria were shown in CWs of SBFL inputs. The results of this study provide a feasible strategy for applying SBFL as a carbon source to improve nitrogen removal efficiency and mitigate GHG emissions in CWs.

Bioenergy feedstock production in Chlamydomonas reinhardtii (microalgae) cultivated under mixotrophic growth with cellulose hydrolysate from agricultural waste.

In the present study, cellulose purified from finger millet agricultural waste is subjected to enzymatic hydrolysis, and the hydrolysate (predominantly glucose) is used as a carbon source supplement in the media for the mixotrophic growth of Chlamydomonas reinhardtii. Interestingly, a switch between excess starch production and excess lipid (triacylglycerols, TAG) production occurs by a small change in hydrolysate concentration in the media. Starch production increased 4.5-fold with respect to the photoautotrophic control, with a glucose concentration of 3mg/mL in the media after hydrolysate addition. This culture had TAG production enhancement by 1.5-fold. However, mixotrophic cultivation with 4mg/mL glucose concentration in the media with hydrolysate addition resulted in TAG productivity enhancement by 4.2-fold compared to control and starch amount increase of 1.3-fold. The organic carbon source (glucose) and the inorganic carbon source (citrate ions) in the hydrolysate together played a role in this delicate switching between starch and lipid pathways. Proteins, starch, and TAG molecules are analyzed in the microalgal cells grown under different conditions with FTIR spectroscopy, a rapid, high-throughput method of biomolecular estimation. High-resolution single-cell AFM studies of the cell wall structure reveal enhanced corrugations in surface morphology during mixotrophic growth with cellulose hydrolysate, illustrating an adaptive mechanism with improved mechanical stress management. Lipid droplet morphology at the single-cell level points to two distinct mechanisms of lipid accumulation: one in which the lipids are segregated as droplets, and the other in which lipid molecules are uniformly dispersed in the cytosol as unresolved, ultra-small droplets. The present study therefore analyzes both the bulk and the single-cell level changes when cellulose hydrolysate is used as a carbon source for Chlamydomonas reinhardtii mixotrophic cultivation, which serves a four-fold purpose: value from waste, fixation of atmospheric CO2, production of lipids for biodiesel, and starch for bioethanol.

Mitigating nitrous oxide emissions from low carbon to nitrogen ratio wastewater treatment: Utilizing sugarcane bagasse fermentation liquid for constructed wetlands

Sugarcane bagasse was recycled to produce fermentation liquid (FL) as a supplementary carbon source that was added to constructed wetlands (CWs) for regulating influent carbon to nitrogen ratio (C/N), and then being applied to investigate nitrogen transformations and greenhouse gas emissions. Results showed that this FL achieved faster NO3−-N removal and lower N2O fluxes than sucrose did, and the lowest N2O flux (67.6 μg m−2h−1) was achieved when FL was added to CWs in a C/N of 3. In contrast, CH4 emissions were higher by the FL addition than by the sucrose addition, although the fluxes under both additions were in a lower range of 0.06–0.17 mg m−2h−1. The utilization of FL also induced significant variations in microbial communities and increased the abundance of denitrification genes. Results showed the application of FL from sugarcane bagasse can be an effective strategy for improving nitrogen removal and mitigating N2O emissions in CWs.

Engineering EPS in Halomonas bluephagenesis leads to self-flocculation and filamentation for convenient downstream processing

The halophile Halomonas bluephagenesis has established itself as a cost-effective chassis in industrial bioproduction. However, downstream processing (DSP) expense is a persistent challenge. This study uses genetic knockout of exopolysaccharides (EPS-KO) in six industrially relevant H. bluephagenesis strains, each producing distinct polyhydroxyalkanoate (PHA), to evaluate their impact on reducing DSP costs. Remarkably, EPS-KO cells exhibited an unprecedented filamentous morphology, reaching lengths over 50 times (10–75 μm) that of standard cells. This unexpected behavior initially posed a challenge to industrial applicability due to rapid cell lysis under fermentation agitation. Systematic media supplementation of salt, carbon source, nitrogen, and essential minerals significantly influenced morphology, and tailored nutrient schemes that mitigated filamentation while maintaining production levels were designed. Scaled production in a 5000 L bioreactor demonstrated 85 % PHA and 96 g/L cell dry weight after 40 h fermentation, consistent with non-KO cells. During fermentation, EPS-KO enhanced cell-wall penetrability, reducing the need for high-cost γ-butyrolactone by 40 %. Additionally, a new innovative 5000 L FlipFlow bioreactor design cut rotation speed by 50 % and air input by 25 %. During DSP, centrifugation time decreased tenfold due to rapid cell self-flocculation (15–30 min), and the water and enzyme required for PHA purification was reduced by 30 % and 35 %, respectively. This study highlights the use of EPS-KO cells, a controlled media strategy, and low shear force FlipFlow bioreactor to successfully reduce DSP costs without sacrificing productivity. These novel findings represent a notable advancement in cost-saving strategies while presenting the intriguing discovery of media-controlled filamentous cell behavior.

Robust, fully quantifiable and scalable bioprocess utilizing spent sulfite liquor with Corynebacterium glutamicum

In this study, a bioprocessing strategy was designed to valorize ultra-filtered spent sulfite liquor (UF-SSL) without prior detoxification steps as well as using it purely as a carbon source supplement to defined or complex media. Hence, a minimal medium for the bioconversion of UF-SSL with Corynebacterium glutamicum was developed and process robustness and reproducibility were validated. Process quantifiability was ensured by development of a biomass measurement technique for matrices with high water-insoluble solids and verified using elemental balancing. Mechanistic modeling based on Monod equations was used to identify batch kinetics. In a final step, scale-up of the developed process was performed to showcase process maturity towards commercialisation.

Ibuprofen degradation by mixed bacterial consortia: Metabolic pathway and microbial community analysis

Degradation of ibuprofen, one of the most consumed drugs globally, by a mixed bacterial consortium was investigated. A contaminated hospital soil was used to enrich a bacterial consortium possessing the ability to degrade 4 mg/L ibuprofen in 6 days, fed on 6 mM acetate as a supplementary carbon source. Maximum ibuprofen degradation achieved was 99.51%, and for optimum ibuprofen degradation modelled statistically, the initial ibuprofen concentration, and temperature were determined to be 0.515 mg/L and 35 °C, respectively. The bacterial community analyses demonstrated an enrichment of Pseudomonas, Achromobacter, Bacillus, and Enterococcus in the presence of ibuprofen, suggesting their probable association with the biodegradation process. The biodegradation pathway developed using open-source metabolite predictors, GLORYx and BioTransformer suggested multiple degradation routes. Hydroxylation and oxidation were found to be the major mechanisms in ibuprofen degradation. Mono-hydroxylated metabolites were identified as well as predicted by the bioinformatics-based packages. Oxidation, dehydrogenation, super-hydroxylation, and hydrolysis were some other identified mechanisms.

Using rice straw-augmented ecological floating beds to enhance nitrogen removal in carbon-limited wastewater

Agricultural biomass used as solid carbon substrates in ecological floating beds (EFBs) has been proven to be applicable in nitrogen removal for carbon-limited wastewater treatment. However, the subtle interactions among plants, rhizosphere microorganisms, and supplementary carbon sources have not been thoroughly studied. This study combined rice straw mats with different aquatic macrophytes in EFBs to investigate denitrification efficiency in carbon-limited eutrophic waters. Results showed that rice straw significantly enhanced the nitrogen removal efficiency of EFBs, while enriching nitrogen-fixing and denitrifying bacteria (such as Rhizobium, Rubrivivax, and Rhodobacter, etc.). Additionally, during the denitrification process in EFBs, rice straw can release humic acid-like fraction as electron donors to support the metabolic activities of microorganisms, while aquatic macrophytes provide a more diverse range of dissolved organic matters, facilitating a sustainable denitrification process. These findings help to understand the synergistic effect of denitrification processes within wetland ecosystems using agricultural biomass.

Refractory dissolved organic matters in sludge leachate trigger the combination of anammox and denitratation for advanced nitrogen removal

The cost-effective treatment of sludge leachate (SL) with high nitrogen content and refractory dissolved organic matter (rDOM) has drawn increasing attention. This study employed, for the first time, a rDOM triggered denitratation-anammox continuous-flow process to treat landfill SL. Moreover, the mechanisms of exploiting rDOM from SL as an inner carbon source for denitratation were systematically analyzed. The results demonstrated outstanding nitrogen and rDOM removal performance without any external carbon source supplement. In this study, effluent concentrations of 4.27 ± 0.45 mgTIN/L and 5.58 ± 1.64 mgTN/L were achieved, coupled with an impressive COD removal rate of 65.17 % ± 1.71 %. The abundance of bacteria belonging to the Anaerolineaceae genus, which were identified as rDOM degradation bacteria, increased from 18.23 % to 35.62 %. As a result, various types of rDOM were utilized to different extents, with proteins being the most notable, except for lignins. Metagenomic analysis revealed a preference for directing electrons towards NO3−-N reductase rather than NO2−-N reductase, indicating the coupling of denitratation bacteria and anammox bacteria (Candidatus Brocadia). Overall, this study introduced a novel synergy platform for advanced nitrogen removal in treating SL using its inner carbon source. This approach is characterized by low energy consumption and operational costs, coupled with commendable efficiency.

Iron-electrolysis assisted anammox/denitrification system for intensified nitrate removal and phosphorus recovery in low-strength wastewater treatment

Two iron-electrolysis assisted anammox/denitrification (EAD) systems, including the suspended sludge reactor (ESR) and biofilm reactor (EMR) were constructed for mainstream wastewater treatment, achieving 84.51±4.38 % and 87.23±3.31 % of TN removal efficiencies, respectively. Sludge extracellular polymeric substances (EPS) analysis, cell apoptosis detection and microbial analysis demonstrated that the strengthened cell lysate/apoptosis and EPS production acted as supplemental carbon sources to provide new ecological niches for heterotrophic bacteria. Therefore, NO3−-N accumulated intrinsically during anammox reaction was reduced. The rising cell lysis and apoptosis in the ESR induced the decline of anammox and enzyme activities. In contrast, this inhibition was scavenged in EMR because of the more favorable environment and the significant increase in EPS. Moreover, ESR and EMR achieved efficient phosphorus removal (96.98±5.24 % and 96.98±4.35 %) due to the continued release of Fe2+ by the in-situ corrosion of iron anodes. The X-ray diffraction (XRD) indicated that vivianite was the dominant P recovery product in EAD systems. The anaerobic microenvironment and the abundant EPS in the biofilm system showed essential benefits in the mineralization of vivianite.

Optimization of Some Culture Conditions and Medium Composition for the Production of Bacitracin from Lactobacillus helveticus DF

The objective of this study was to evaluate the effects of some culture conditions and components of the culture medium on the production of bacteriocin from Lactobacillus helveticus DF to get maximum bacteriocin yield. The results showed that the best culture conditions for maximum bacteriocin production were; pH 6, incubation temperature 37°C, incubation period 48 hours and the best culture medium MRS at anaerobic condition. Optimization of the medium ingredients was also investigated.The production of active antimicrobial peptide bacteriocin, active against Gram positive and Gram negative microorganisms including P.aeruginosa (B) and E. Feacalis (A), by L. helveticus DF isolated from feces of infants is influenced by complex nitrogen sources and carbon sources in the production medium. Medium components, especially pepton, beef extract and yeast extract, and their concentration contributed to increase in the production during the stationary phase. The Optimal nitrogen sources for their production were 1.5% , 2%, 2% (w/v) of pepton, beef extract and yeast extract respectively, accordingly, the present result evidenced that the increment in bacteriocin production was attributed with nitrogen source. Bacteriocin production by L. helveticus DF emphasized that, the higher bacteriocin yield was attained in the medium supplied with Tween 80 compared to medium without addition of tween 80, optimal concentration for their production 0.75%. Carbon source supplementation in culture media favored the maximum bacteriocin yield by L. helveticus DF, maximum bacteriocin yield when cultured in MRS supplemented with glucose and mannose (2%w/v). Bacteriocin production was affected differently by the presence of different concentrations of K2HPO4 or KH2PO4. Optimal bacteriocin production was recorded in the presence of 0.25% K2HPO4. The results of this study showed that the best production medium was named modified MRS medium which composed of 2% glucose, 2% mannose, 1.5% peptone, 2% yeast extract, 2% beef extract, 0.25% K2HPO4 and 0.75% tween 80, adjusted at pH 6 and incubated at 37°C for 48 hours (under anaerobic conditions) and with inoculum size of 4 % of cells number 1×109 cell/ml. After optimization, Bacteriocin activity was increase to 80 and 160 AU\ML against E. Feacalis (A) and P.aeruginosa (B) respectively.

Establishment of an Efficient Expression and Regulation System in Streptomyces for Economical and High-Level Production of the Natural Blue Pigment Indigoidine.

Indigoidine, as a kind of natural blue pigment, is widely used in textiles, food, and pharmaceuticals and is mainly synthesized from l-glutamine via a condensation reaction by indigoidine synthetases, most of which originates from Streptomyces species. However, due to the complex metabolic switches of Streptomyces, most of the researchers choose to overexpress indigoidine synthetases in the heterologous host to achieve high-level production of indigoidine. Considering the advantages of low-cost culture medium and simple culture conditions during the large-scale culture of Streptomyces, here, an updated regulation system derived from the Streptomyces self-sustaining system, constructed in our previous study, was established for the highly efficient production of indigoidine in Streptomyces lividans TK24. The updated system was constructed via promoter mining and σhrdB expression optimization, and this system was applied to precisely and continuously regulate the expression of indigoidine synthetase IndC derived from Streptomyces albus J1704. Finally, the engineered strain was cultured with cheap industrial glycerol as a supplementary carbon source, and 14.3 and 46.27 g/L indigoidine could be achieved in a flask and a 4 L fermentor, respectively, reaching the highest level of microbial synthesis of indigoidine. This study will lay a foundation for the industrial application of Streptomyces cell factories to produce indigoidine.

Application of alkali-heated corncobs enhanced nitrogen removal and microbial diversity in constructed wetlands for treating low C/N ratio wastewater.

Lack of carbon source is the main limiting factor in the denitrification of low C/N ratio wastewater in the constructed wetlands (CWs). Agricultural waste has been considered as a supplementary carbon source but research is still limited. To solve this problem, ferric carbon (Fe-C) + zeolite, Fe-C + gravel, and gravel were used as substrates to build CWs in this experiment, aiming to investigate the effects of different carbon sources (rice straw, corncobs, alkali-heated corncobs) on nitrogen removal performance and microbial community structure in CWs for low C/N wastewater. The results demonstrated that the microbial community and effluent nitrogen concentration of CWs were mainly influenced by the carbon source rather than the substrate. Alkali-heated corncobs significantly enhanced the removal of NO2--N, NH4+-N, NO3-N, and TN. Carbon sources addition increased microbial diversity. Alkali-heated corncobs addition significantly increased the abundance of heterotrophic denitrifying bacteria (Proteobacteria and Bacteroidota). Furthermore, alkali-heated corncobs addition increased the copy number of nirS, nosZ, and nirK genes while greenhouse gas fluxes were lower than common corncobs. In summary, alkali-heated corncobs can be considered as an effective carbon source.

The Feasibility of Integrating Spray-Dried and Freeze-Dried Oat β-Glucans into a Synbiotic Formulation with Akkermansia muciniphila

The objective of this research was to investigate the feasibility of integrating oat (1 → 3, 1 → 4)-β-D-glucan (β-glucan) dried by two different techniques (freeze drying and spray drying) into a synbiotic formulation with Akkermansia muciniphila. The study evaluated the impact of this synbiotic formulation on the growth of A. muciniphila and its effect on the fermentation process. The extracted oat β-glucans underwent freeze-drying (FD) and spray-drying (SD) processes before being introduced as supplementary carbon sources (1%) to brain heart infusion (BHI) medium containing A. muciniphila MSCL 1582. The BHI medium containing inulin, D-glucose, and BHI without added substrates served as the control. Bacterial growth and short-chain fatty acid (SCFA) production were measured before and after 72 h of fermentation. A light microscope and KOVA slides were used for the A. muciniphila count, and SCFA levels were measured via gas chromatography. Our findings revealed that oat β-glucans could effectively function as prebiotic substrates in complementary synbiotic composition with A. muciniphila, without inhibiting growth and causing metabolic impairment. Both FD and SD techniques demonstrated equivalent and favorable impacts on the fermentative capacity of A. muciniphila, rendering them suitable choices for the drying of β-glucans. Incorporating oat β-glucan into synbiotic formulations offers potential benefits, contributing to A. muciniphila growth and the fermentation process.

Improving denitrification performance of biofilm technology with salt-tolerant denitrifying bacteria agent for treating high-strength nitrate and sulfate wastewater from lab-scale to pilot-scale

This study focused on the application of salt-tolerant denitrifying bacteria (DBA) in an optimized biofilm process to treat high sulfate-nitrate wastewater from lab-scale to pilot-scale. Lab-scale results demonstrated the salinity, DBA inoculum, supplementary carbon and phosphorus source significantly varied the startup periods at the range of 36–74 d, and the optimum initial start-up conditions were as follows: >0.6 g/L of DBA, 2–4 of C/N ratio, 0.3–0.6 mg/L of phosphorus and a salinity-gradient domestication method. A pilot scale of biofilm technology with DBA was further developed for treating real wastewater from the desulfuration and denitration with both high nitrate (≈200 mg/L) and sulfate (2.7%). The denitrification efficiency reached above 90% after one-month gradient-salinity of 0.5%-2.7%. Mature biofilm had dominant genera Hyphomicrobium (31.80%-61.35%), Methylotenera (0.85%-20.21%) and Thauera (1.42%-8.40%), etc. Notably, the largest genera Hyphomicrobium covered the complete denitrification genes.