Aiba Model Research Articles

Biohydrogen production kinetics from cacao pod husk hydrolysate in dark fermentations: Effect of pretreatment, substrate concentration, and inoculum

This study aims to explore the impact of pretreatment on cacao pod husk (CPH) and investigate the kinetics of biohydrogen production in a dark fermentation (DF) batch reactor with consideration for substrate and inoculum concentration. As the first study focused on biohydrogen production from CPH, the Taguchi orthogonal array was utilized to determine the optimal pretreatment condition for powdered CPH. This study examined different substrate concentrations (3–100 g VS/L) and inoculum concentrations (5 and 10 % v/v). The study showed that biohydrogen production was significantly increased by 74.4 ± 0.1 % by pretreatment with 5.5 % HCl compared to the untreated CPH as control. Furthermore, the optimal performance was achieved by 35 g VS/L of CPH in the mixture with inoculated by 10 % v/v inoculum, resulting in a biohydrogen production and concentration of 257.05 ± 7.97 mL/L and 23.87 ± 0.15 %, respectively. The inoculum's microbial community analysis using Illumina 16S sequencing showed a dominance of the Ethanoligenes (30.4 %), which was positively correlated with the profiles of hydrogen production and the proportion of VFAs. The Aiba model with an exponential substrate concentration and inhibitory constant (R2 of 0.93) was statistically the most precise mathematical model to predict the specific growth rate during the fermentative biohydrogen production by CPH substrate.

Phenol degradation at high salinity by a resuscitated strain Pseudomonas sp. SAS26: kinetics and pathway

Exploration of novel salt-tolerant phenol-degrading bacterial strains are often limited by unculturability of functional bacteria, as they are prone to entering a viable but non-culturable (VBNC) state in response to complex stressful environmental conditions. Thus, resuscitating the VBNC bacteria provides a huge microbial source to screen effective degraders for bioaugmentation. In this study, a resuscitated strain Pseudomonas sp. SAS26, which exhibited the highest phenol-degrading ability, was selected to investigate its phenol degradation performance at high salinity. The results indicated that SAS26 was capable of efficiently degrading phenol at NaCl concentrations of 0–30 g/L, with decreased efficiency observed at 40–60 g/L. At 10 g/L NaCl, complete degradation of 1800 mg/L phenol was achieved within 48 h. At a higher NaCl concentration of 30 g/L, SAS26 could fully degrade 1500 mg/L phenol within 60 h, with the highest degradation rate of 0.360 g/(g CDW·h) observed at approximately 24 h. The modeling of phenol degradation at high salinity demonstrated that the Webb model was the most appropriate for describing the degradation kinetics, followed by the Yano and Aiba models. Furthermore, the analysis of the enzyme activities and catA gene expression suggested that SAS26 initially converted phenol to catechol via phenol hydroxylase, and then oxidized catechol by the catalysis of catechol 1,2-dioxygenase via the ortho-cleavage pathway. These results revealed the high-efficient phenol-degrading capability of the resuscitated strain SAS26 at high salinity, which shed light on cultivating effective bio-inoculants for treating high-saline phenolic wastewater.

Bioremediation of propylbenzenes by a novel marine microalga Rhinomonas reticulata S6A isolated from Daya Bay: acute toxicity, growth kinetics and biodegradation performance

This study investigated the degradation characteristics of propylbenzenes (PBZs, including isopropylbenzene and n-propylbenzene), with high leakage risks and ecological hazards, by a newly isolated marine microalga named Rhinomonas reticulata S6A which is a promising candidate for eco-friendly bioremediation from marine. About 72% and 56% of n-PBZ and i-PBZ can be degraded after 7 days in culture. The acute toxicity of n-PBZ (96h - EC50 = 2.38 mg/L) was higher than that of i-PBZ (96h - EC50 = 3.65 mg/L). The growth inhibition kinetics of this strain were consistent with the Edwards model (R2 = 0.998) and Aiba model (R2 = 0.999). The optimal concentrations for the degradation of n-PBZ and i-PBZ were calculated to be 2.42 mg/L and 2.78 mg/L, respectively. The degradation trends of PBZs conformed to the zero-order kinetic model, and k increased with initial concentrations. The moderate increase in inoculation density could accelerate the degradation of PBZs, with the maximum specific growth rates (r) of 1.116/d (n-PBZ) and 1.230/d (i-PBZ) at the initial inoculation density of 104 cells/mL, while over-inoculation (initial microalgae density more than 105 cells/mL) was not conducive to the degradation of the pollutants. There is not much data on the biodegradation of PBZs in the aquatic environment, so it would be worthwhile to try to apply the new microalgae to explore the fate of PBZs.

Response of mixed community anammox biomass against sulfide, nitrite and recalcitrant carbon in terms of inhibition coefficients and functional gene expressions

Anaerobic ammonium oxidation (anammox) has evolved as a carbon and energy-efficient nitrogen management bioprocess. However, factors such as inhibitory chemicals still challenge the easy operation of this powerful bioprocess. This research systematically evaluated the inhibition kinetics of sulfide, nitrite, and recalcitrant carbon under a genomic framework. The inhibition at the substrate and genetic levels of sulfide, nitrite and recalcitrant carbon on anammox activity was studied using batch tests. Nitrite inhibition of anammox followed substrate inhibition and was best described by the Aiba model with an inhibition coefficient KI,NO2− of 324.04 mg N/L. Hydrazine synthase (hzsB) gene (anammox biomarker) expression was increased over time when incubated with nitrite up to 400 mg N/L. However, despite having the highest specific nitrite removal (SNR), the expression of hzsB at 100 and 200 mg N/L of nitrite was more muted than in most other samples with lower SNRs. Sulfide severely inhibited anammox activities. The inhibition was fitted with a Monod-based model with a KI,S2− of 4.39 mg S/L. At a sulfide concentration of 5 mg/L, the hzsB expression decreased throughout the experiment from its original value at he beginning. Recalcitrant carbon of filtrate from thermal hydrolysis process pretreated anaerobic digester had a minimal effect on maximum specific anammox activity (MSAA), and thus the value of the inhibition coefficient could not be calculated. At the same time, its hzsB expression profile was similar to that in the control. Resiliency and recovery tests indicated that the inhibition of nitrite (up to 400 mg N/L) and recalcitrant carbon (in 100% filtrate) were reversible. About 32% of MSAA was recovered after repeated exposures to sulfide at 2.5 mg/L, while at 5 mg/L, the inhibition was irreversible. Findings from this study will be helpful for the successful design and implementation of anammox in full-scale applications.

Optimization of the algal species Chlorella miniata growth: Mathematical modelling and evaluation of temperature and light intensity effects

Growth of Chlorella miniata , a green microalga was investigated during this study under various temperature and light intensity values with the purpose of determining growth rate changes of the microalgae with cultivation parameters, experiments were carried out using airlift photobioreactors with a study volume of 6 L. Culturing conditions were between 66 and 385 μmol photon m −2 s −1 and between 14 and 30 °C for light intensity and ambient temperature, respectively. Acquired data were then used to test various mathematical models for coherency with experimental results. Aiba Model for light intensity and Skewed Normal Distribution Model for temperature parameters performed superior compared to the rest of the mathematical models used during the study. Utilizing both mathematical models a novel model was deduced to express effects of both light intensity and temperature parameters in combination on algal growth. Then the developed model was used to calculate the optimum growth condition of the species. The proposed mathematical model showed good coherency with experimental data and an average relative error of 1.97% for both temperature and light intensity effects on algal growth. The theoretical optimum temperature and light intensity for the maximum specific growth rate were calculated to be 22.43 °C and 291.5 μmol photon m −2 s −1 respectively. • The theoretical optimum temperature for growth was calculated to be 22.43 °C. • The theoretical optimum light intensity for growth was calculated to be 291.5 μmol photon m −2 s −1 . • Aiba model was selected for describing light intensity growth relationship. • Skewed Normal Distribution Model was selected for temperature growth relationship.

Kinetics Modelling of Pseudomonas stutzeri strain DN2 Growth Behaviour in Tributyltin Chloride

A predictive model was performed to describe Pseudomonas stutzeri strain DN2 growth behaviour in tributyltin chloride, using primary Modelling and a polynomial model as a secondary predictive model. In this investigation, data predicted using the modified Logistic (ML) was the most accurate. The Bias Factor (Bf) and Accuracy Factor (Af) values for the (ML) model were 1.39 and 1.51, indicating that the predictions were within a reliable range. The low RMSE value of 0.14, R2 and adj R2 (0.99) value closer to 1, showing that modified logistics is better than the other models at describing the growth behaviour of Pseudomonas stutzeri strain DN2 in toxic tributyltin chloride. Both the Aiba and Haldane models on the other hand, among the secondary model best fit the behaviours having low RMSE and MSE values and adjR2 value closer to 1. In this study, the primary and secondary kinetics of Pseudomonas stutzeri strain DN2 growth behaviour in tributyltin chloride was explored and it was shown in this study that the modified logistic and the Haldane models better suit the growth behavior of Pseudomonas stutzeri strain DN2 in tributyltin chloride. The parameters obtained from the modelling exercise will be very valuable in transferring the laboratory results to the field.

Determination of photoautotrophic growth and inhibition kinetics by the Monod and the Aiba models and bioenergetics of local microalgae strain

The usage of fossil fuels results in a high amount of greenhouse gas (GHG) emissions and renewable green energy requirements entail saving ecological balance. Therefore, microalgae cultivation is widespread as a suitable raw material to produce renewable and sustainable fuel. Mathematical models are useful tools for the estimation of different conditions of a system. In this study, mathematical models were developed for monitoring the cultivation of local species of microalgae based on the chlorophyll-a and biomass concentration. Coefficients that were calculated from the Monod kinetic model were μmax; 0.03 day−1, KS, Ci; 0.53 mM with an R2 value of 0.93 and from the Aiba inhibition kinetic model was μmax and KS, Ci 1.48 day−1 and 0.08 mM with an R2 value of 0,73. According to the literature, there was no model was developed for the determination of kinetic coefficients based on chlorophyll-a production due to the inorganic carbon consumption. While both growth and inhibition models were developed for the inorganic carbon consumption, chlorophyll-a concentration was used for the growth model and biomass concentration was used for the inhibition model which caused and directly affected by the decrease of light penetration. The maximum biomass and chlorophyll-a concentrations were found as 1.2 g/L and 27.8 mg/L respectively with 10.24 mg/L. day−1 nitrogen and 1.19 mg/L.day−1 phosphorus uptake rate.

A novel process of salt tolerance partial denitrification and anammox (ST-PDA) for treating saline wastewater

In the study, the salt-tolerant partial denitrification and Anammox (ST-PDA) process was established, meanwhile, the feasibility of salinity inhibition model as the boundary control method and the subsequent operation performance were studied. Study indicated that the performance of salt-tolerant PD sludge was the optimum under the 10 g·L-1 salinity, and AnAOB also maintained high activity at the salinity. Haldane and Aiba models verified that NO3–-N (substrate) and FNA (product) would have negative consequences for performance of ST-PDA system. However, the effect of FNA would be eliminated by self-alkalization in the denitrification process. A 90% nitrogen removal rate was achieved and the average effluent total nitrogen of 17.8 mg·L-1 was maintained in the system. The high throughput sequencing revealed that the species richness decreased with the salinity increased, while Thauera played a major role in nitrogen removal in saline environment. The study provides a novel insights for salt-containing industrial wastewater.

Mathematical Modelling of Canola Oil Biodegradation and Optimisation of Biosurfactant Production by an Antarctic Bacterial Consortium Using Response Surface Methodology

An Antarctic soil bacterial consortium (reference BS14) was confirmed to biodegrade canola oil, and kinetic studies on this biodegradation were carried out. The purpose of this study was to examine the ability of BS14 to produce biosurfactants during the biodegradation of canola oil. Secondary mathematical equations were chosen for kinetic analyses (Monod, Haldane, Teissier–Edwards, Aiba and Yano models). At the same time, biosurfactant production was confirmed through a preliminary screening test and further optimised using response surface methodology (RSM). Mathematical modelling demonstrated that the best-fitting model was the Haldane model for both waste (WCO) and pure canola oil (PCO) degradation. Kinetic parameters including the maximum degradation rate (μmax) and maximum concentration of substrate tolerated (Sm) were obtained. For WCO degradation these were 0.365 min−1 and 0.308%, respectively, while for PCO they were 0.307 min−1 and 0.591%, respectively. The results of all preliminary screenings for biosurfactants were positive. BS14 was able to produce biosurfactant concentrations of up to 13.44 and 14.06 mg/mL in the presence of WCO and PCO, respectively, after optimisation. The optimum values for each factor were determined using a three-dimensional contour plot generated in a central composite design, where a combination of 0.06% salinity, pH 7.30 and 1.55% initial substrate concentration led to the highest biosurfactant production when using WCO. Using PCO, the highest biosurfactant yield was obtained at 0.13% salinity, pH 7.30 and 1.25% initial substrate concentration. This study could help inform the development of large-scale bioremediation applications, not only for the degradation of canola oil but also of other hydrocarbons in the Antarctic by utilising the biosurfactants produced by BS14.

Study on Spirulina platensis growth employing non-linear analysis of biomass kinetic models

Spirulina platensis has been considered a promising source of food supplement to combat malnutrition worldwide. Numerous investigations have stated its immune activity, ability to absorb CO2 during the growth period, and antioxidant potential. Well-known theoretical biomass kinetic model sheds are capable of qualitative analysis of the fast microalgae growth. In this regard, we considered eight popular biomass models: Monod, Haldane, Andrews & Noack, Teissier, Hinshelwood, Yano & Koga, Webb and, Aiba model comprising analytical investigation within the numerical simulation. Besides, in this study, we establish a new mathematical biomass growth model by merging the well-known Hinshelwood and Yano & Koga models. We explored the most suitable Spirulina growth model to minimize the overstated and understated growth trends in the assorted eight biomass kinetic models. Our findings show microalgae biomass growth and substrate diminishes along with time, and these results were compared with available experimental data. Results present a high value of R2(0.9862), a low value of RSS (0.0813), AIC (-9.7277), and BIC (-8.2148) implied significantly fitted with the investigated data for the growth of Spirulina platensis compared with popular eight studied models.

Removal of 4-Chlorophenol by Bacillus flexus as free and immobilized system: Effect of process variables and kinetic study

In this work, Bacillus flexus GS1 IIT (BHU) as free and immobilized cells on low-density polyethylene (LDPE) were used to remove 4-Chlorophenol (4-CP) from the synthetic wastewater. The effect of the process variables, namely process time, pH, temperature, and 4-CP concentration, were optimized and obtained as 7.0 days, 7.0, 30 °C, and 50 mg/L, respectively. At optimum conditions, the maximum removal efficiencies (REs) were obtained to be 90.34 and 78.12% for the immobilized and free cells, respectively, at 50 mg/L concentration of 4-CP. Furthermore, a packed bed bioreactor (PBBR) was continuously operated for 60 days with the immobilized LDPE. The maximum RE of 82.4% and elimination capacity (EC) of 29.6 mg/L/d were obtained at 50 mg/L of the initial concentration of 4-CP. The growth kinetic parameters for Bacillus sp. were obtained to be: μmax: 0.205 h−1, Ks: 3.3 mg/L, Ki: 220 mg/L for Aiba model; μmax: 0.197 h−1, Ks: 1.4 mg/L, Ki: 220 mg/L for Edward model; and mumax: 0.185 h−1, Ks: 1.6 mg/L, Ki: 200 mg/L for Andrew-Haldane model, respectively.

A Novel Process of Salt Tolerance Partial Denitrification and Anammox (ST-PDA) for Treating Saline Wastewater

In the study, the salt-tolerant partial denitrification and Anammox (ST-PDA) process was established, meanwhile, the feasibility of salinity inhibition model as the boundary control method and the subsequent operation performance were studied. Study indicated that the performance of salt-tolerant PD sludge was the optimum under the 10 g·L-1 salinity, and AnAOB also maintained high activity at the salinity. Haldane and Aiba models verified that NO3--N (substrate) and FNA (product) would have negative consequences for performance of ST-PDA system. However, the effect of FNA would be eliminated by self-alkalization in the denitrification process. A 90% nitrogen removal rate was achieved and the average effluent total nitrogen of 17.8 mg·L-1 was maintained in the system. The high throughput sequencing revealed that the species richness decreased with the salinity increased, while Thauera played a major role in nitrogen removal in saline environment. The study provides a novel insights for salt-containing industrial wastewater.

Manganese-contaminated groundwater treatment by novel bacterial isolates: kinetic study and mechanism analysis using synchrotron-based techniques

The occurrence of manganese in groundwater causes coloured water and pipe rusting in water treatment systems. Consumption of manganese-contaminated water promotes neurotoxicity in humans and animals. Manganese-oxidizing bacteria were isolated from contaminated areas in Thailand for removing manganese from water. The selected bacterium was investigated for its removal kinetics and mechanism using synchrotron-based techniques. Among 21 isolates, Streptomyces violarus strain SBP1 (SBP1) was the best manganese-oxidizing bacterium. At a manganese concentration of 1 mg L−1, SBP1 achieved up to 46% removal. The isolate also successfully removed other metal and metalloid, such as iron (81%) and arsenic (38%). The manganese concentration played a role in manganese removal and bacterial growth. The observed self-substrate inhibition best fit with the Aiba model. Kinetic parameters estimated from the model, including a specific growth rate, half-velocity constant, and inhibitory constant, were 0.095 h−1, 0.453 mg L−1, and 37.975 mg L−1, respectively. The synchrotron-based techniques indicated that SBP1 removed manganese via combination of bio-oxidation (80%) and adsorption (20%). The study is the first report on biological manganese removal mechanism using synchrotron-based techniques. SBP1 effectively removed manganese under board range of manganese concentrations. This result showed the potential use of the isolate for treating manganese-contaminated water.

A novel strategy for accelerating the recovery of a Fe(II)-inhibited anammox reactor by intermittent addition of betaine: Performance, kinetics and statistical analysis

In this manuscript, Fe(II) inhibition of anammox and its recovery were investigated, and the performance, kinetics and statistical features were comprehensively studied simultaneously. Anammox was suppressed and completely inhibited by the addition of 109.29 and 378.57 mg/L Fe(II), respectively, via uncompetitive inhibition. Nitrite inhibition of anammox was best fitted by the Edwards model and Aiba model. EDTA-2Na wash (0.5, 1.0, 1.5, and 2.0 mM) had a limited effect on anammox recovery, while the addition of 2.0 mM betaine accelerated anammox recovery. Prolonged betaine addition caused an unintended reduction of anammox activity, though it self-recovered after the withdrawal of betaine. The modified Boltzmann model most accurately simulated the processes of anammox recovery using the EDTA-2Na wash, betaine regulation and self-recovery, and the modified Stover-Kincannon model was able to assess the results of anammox recovery. The one-sample t-test was successfully applied to determine the effects of these three recovery strategies on inhibited anammox, which were short-term disinhibition or long-term recovery effects. The above-mentioned results demonstrate that an intermittent addition of betaine, which is a better alternative to frequently-used but poorly-degradable EDTA, may be a useful and environmentally friendly recovery strategy for Fe(II)-inhibited anammox reactor.

Isolation, characterization and growth kinetics of phenol hyper-tolerant bacteria from sewage-fed aquaculture system

Pollution of aquatic resources is increasing day-by-day, and phenolic compounds are common pollutants negatively impacting aquatic biodiversity and production. This study aimed at isolation of phenol hyper-tolerant bacteria from polluted aquaculture resource so that they might be useful in aquaculture systems. Four phenol hyper-tolerant bacterial strains were isolated from sewage fed East Kolkata Wetlands, a Ramsar site. By 16S rDNA sequence, cell morphology and biochemical characteristics the strains PDB2, PDB13, PDB16, and PDB26 were identified as Acinetobacter sp., Acinetobacter junii, Pseudomonas citronellolis, and Bacillus cereus, respectively. Pseudomonas citronellolis strain PDB16, described in this study, is possibly the first report of phenol hyper-tolerant strain in this species. All the four strains degraded 600 mg L−1 phenol within 5 days and expressed catechol 1,2-dioxygenase but lacked catechol 2,3-dioxygenase enzyme suggesting that the bacteria used the ortho-cleavage pathway for phenol degradation. In growth kinetic study Edwards and Aiba model, rather than the most popular Haldane model, gave the best fit indicating behavioral divergence of these strains with those from petroleum contaminated environments. The phenol degrading bacteria isolated from a polluted sewage fed aquaculture system might be useful in degradation and remediation of polluted aquaculture resources as well as inland open waters.

Effects of heavy rare earth element (yttrium) on partial-nitritation process, bacterial activity and structure of responsible microbial communities

Yttrium (Y(III)) is mined commercially for industrial purposes due to its excellent physical properties. However, the effects of Y(III) in mining-wastewater on the performance of partial-nitritation process and ammonia-oxidizing bacteria (AOB) have not been explored. To elucidate Y(III) effects on biological mechanisms, kinetics was conducted to establish a correlation between Y(III) dosage and specific-oxygen-uptake-rate (SOUR). The mechanism(s) demonstrated by bacterial population to resist against toxic effects from Y(III) dose was also investigated using scanning electron microscopy-(SEM), energy-dispersive X-ray spectroscopy-(EDS), confocal laser scanning microscopy-(CLSM)，Fourier transform infrared-(FTIR) spectroscopy, and 2-dimensional correlation infrared-(2DCOS-IR) approach. The study revealed a strong correlation between ammonium oxidation rate (AOR) and Y(III) dosage. AOR promotion was more pronounced when Y(III) concentration was ≤20 mg/L (maximum AOR of 12.39 mgN/L/h, at 5 mg/L), whereas inhibition when Y(III) in influent was >20 mg/L (minimum AOR of 7.34 mgN/L/h, at 500 mg/L). Aiba model demonstrated high-performance (R2 = 0.962) when Y(III) concentration ranged 0–20 mg/L, whereas linear model fitted well (R2 of 0.984) to experimental data when Y(III) dose ranged 20–500 mg/L. The maximum change in SOUR (Vmax), half-rate constant (Km), and inhibition constant (Ki) reached 1.04 d−1, 20.12 mg/L, and 4.87 mg/L, respectively, an indication that dosage of Y(III) could affect the partial-nitritation process. SEM-EDS showed that the content of extracellular polymeric substances (EPS) increased along with increasing Y(III) dosage. When 20 mg/L of Y(III) was dosed, the fraction of Y(III) within the surface elemental composition of the sludge increased gradually whereas that of calcium decreased. To further comprehend the EPS production, CLSM results further revealed β-polysaccharide as the dominant component in the EPS. FTIR/2DCOD-IR showed that the chelation of polyguluronic sections within β-polysaccharide, together with hydrazine might be the main pathways of cell resistance, but β- glucan, may have caused the hormesis.

Kinetics of Cyanide Degradation by Azotobacter vinelandii

Cyanide is extremely toxic to living organisms. It is utilized in industries for gold and silver extraction, pharmaceuticals, plastic processing, electroplating, and agricultural chemistry. Cyanide can persevere for a long time in the soil and its bio-degradation is the best economical practice. A formerly isolated cyanide-degrading bacterium Azotobacter vinelandii exhibited substrate inhibition to degradation rate. Significant degradation inhibition constants were achieved reliably by means of non-linear regression modeling of the degradation rate profile utilizing models for substrate inhibition like Haldane, Teissier-Edward, Monod, Yano and Koga, Luong, Edward (Webb) Luong and Aiba models. Aiba model was selected as the top model established on statistical assessments like root mean square error, adjusted coefficient of determination, bias factor and accuracy factor. The calculated values for the Aiba constants qmax (the maximum specific substrate degradation rate (h−1), Ks (concentration of substrate at the half maximal degradation rate (mM) and Ki (inhibition constant (mM)) were 0.060 (95% CI, 0.024 to 0.096), 0.302 (95% CI, 0.381 to 0.222) and 0.953 (95% CI, 0.568 to 1.338), respectively. The novel constants gotten from the modeling application can be valuable for advanced secondary modeling implicating the influence of media conditions and some other dynamics on cyanide biodegradation by this bacterium.

Sustainable biohydrogen production by dark fermentation using carbon monoxide as the sole carbon and energy source

Abstract This study evaluated the kinetics of biomass growth, biohydrogen production and substrate utilization using carbon monoxide as the sole carbon and energy source. Experiments were conducted at different initial CO concentration in the range 1.8–5.12 mmol/L over a period of 144 h in order to assess the effect of CO concentration on biomass growth, substrate utilization and H2 production. Complete utilization (100%) of CO was achieved up to an initial concentration of 3.8 mmol/L and it gradually decreased to 84.5% for 4.4 mmol/L and 83.7% for 5.12 mmol/L. The experimental results of CO utilization were fitted to substrate utilization kinetic models reported in the literature, and it followed a modified Gompertz model. A maximum yield of H2 on CO was found to be 70.8% and a maximum H2 production of 29.9 mmol/L was obtained for an initial CO concentration of 5.12 mmol/L. The experimental results on biohydrogen production matched well with the values predicted using the modified Gompertz model. Furthermore, the experimental data on specific growth rate of the ananerobic biomass at different H2 concentration was fitted to different product inhibition models and the best fit was obtained with Aiba model. This study showed product inhibition on both specific growth rate of biomass and H2 production due to H2 accumulation in the gas phase. A very good correlation between the experimental specific growth rate and the Han-Levenspiel model predicted values were obtained with a high determination coefficient (R2) value of more than 0.96.

Optimizing biomethane production of mesophilic chicken manure and sheep manure digestion: Mono-digestion and co-digestion kinetic investigation, autofluorescence analysis and microbial community assessment

Optimization of mesophilic methane production from Chicken manure (CM) and Sheep manure (SM) at total solid (TS) of 8% and 1.6% were obtained by sequence tests in mono-digestion. However, the positive synergy of co-digestion with an optimum CM/SM of 2.5 (310 mLCH4/gVSadded) resulted in a high hydrolytic capacity and methane production. The modified Gompertz model (R2 > 0.98) and modified Aiba model (R2 > 0.88) illustrated co-digestion significantly improved the methane generation rate with strong ammonia tolerance. Dissolved Organic Matter (DOM) variation in response to the metabolic rate of microbial community illustrated that the SMP-like and protein-like components half-split by EEM–PARAFAC were significantly negative corresponded to bio-methane production. Moreover, the canonical correlation analysis (CCA) resulted a significant difference between the substrate and DOM composition. Potential functional metabolic illustrated statistically significance difference between mono and co-digestion, however, Methanosaeta and Syntrophobacter predominated the syntrophic methanogenesis. The constructed complex metabolic cooperation caused the co-digestion stable and high efficiency.

Enhanced Nitrogen and Carbon Removal Performance of Simultaneous ANAMMOX and Denitrification (SAD) with Trehalose Addition Treating Saline Wastewater

Enhanced nitrogen and carbon removal performance of simultaneous ANAMMOX and denitrification (SAD) process with trehalose addition treating saline wastewater was investigated in a sequencing batch reactor (SBR). The optimal nitrogen removal was achieved at 0.25 mmol·L-1 trehalose, during which NH4+-N, NO2--N, NO3--N, and COD could be completely removed. Compared to no addition of trehalose, ammonium removal efficiency (ARE), nitrite removal efficiency (NRE) and total nitrogen removal efficiency (TNRE) increased by 50%, 43% and 46%. Ammonium removal rate (ARR) and nitrite removal rate (NRR) increased by 81.25% and 75%, respectively. With increasing concentration of trehalose to 0.5 mmol·L-1, ARE was only 58.82% and the effluent concentration of NH4+-N was 33.25 mg·L-1. Compared to the Haldane model and the Aiba model, the Luong model was the most suitable to simulate the nitrogen removal performance of SAD with trehalose addition treating saline wastewater. The NRRmax, KS, Sm, and n fitted from Luong model were 0.954 kg·(m3·d)-1, 0 mg·L-1, 184.785 mg·L-1, and 0.718, respectively. Compared to the modified Logistic model and the modified Boltzman model, the modified Gompertz model was the most suitable to describe the degradation of a substrate in a single cycle.