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关键词： Stochastic nonlinear bioreactor dynamics   Structural stability   Fokker-Planck equation   State probability density function   Stochastic metastability   Monod kinetics   Haldane kinetics   Extinction and revival  

摘要： The nonlinear stochastic dynamics of a class of two-state bioreactors with isotonic or nonisotonic kinetics is analytically characterized with Fokker-Planck (FP) theory, with emphasis on: (i) the spatiotemporal geometry of the two-state probability density function (PDF) motion, (ii) conditions for metastability-based bio-extinction/revival (inexistent in deterministic systems), and (iii) state PDF behavior of the optimal (maximum yield) operation. It is found that, depending on the kind of kinetics: (i) the stationary state PDF is mono or bimodal, (ii) the state PDF motions can be either non-metastable along deterministic-diffusion time scale, or metastable towards probabilistic extinction/revival along deterministic-diffusion-escape time scale, and (iii) the optimal operation can have robust (or fragile) stationary PDF, depending on the particular kinetics and operation condition. The developments and results are illustrated with representative examples with Monod and Haldane kinetics, and put in perspective with the ones drawn before with Monte Carlo (MC) and FP methods. (C) 2021 Published by Elsevier Ltd.

关键词： Azotobacter vinelandii   Alginate   G   M ratio   Molecular weight   Oxygen transfer rate   Scale-up  

摘要： Alginates can be used to elaborate hydrogels, and their properties depend on the molecular weight (MW) and the guluronic (G) and mannuronic (M) composition. In this study, the MW and G/M ratio were evaluated in cultures of Azotobacter vinelandii to 3 and 30 L scales at different oxygen transfer rates (OTRs) under diazotrophic conditions. An increase in the maximum OTR (OTRmax) improved the alginate production, reaching 3.3 +/- 0.2 g L-1. In the cultures conducted to an OTR of 10.4 mmol L-1 h(-1) (500 rpm), the G/M increased during the cell growth phase and decreased during the stationary phase;whereas, in the cultures at 19.2 mmol L-1 h(-1) was constant throughout the cultivation. A higher alginate MW (520 +/- 43 kDa) and G/M ratio (0.86 +/- 0.01) were obtained in the cultures conducted at 10.4 mmol L-1 h(-1). The OTR as a criterion to scale up alginate production allowed to replicate the concentration and the alginate production rate;however, it was not possible reproduce the MW and G/M ratio. Under a similar specific oxygen uptake rate (qO(2)) (approximately 65 mmol g(-1) h(-1)) the alginate MW was similar (approximately 365 kDa) in both scales. The evidences revealed that the qO(2) can be a parameter adequate to produce alginate MW similar in two bioreactor scales. Overall, the results have shown that the alginate composition could be affected by cellular respiration, and from a technological perspective the evidences contribute to the design process based on oxygen consumption to produce alginates defined.

关键词： Arsenic   Arsenite-oxidizing bacteria (AOB)   Biofilm bioreactor   Arsenic-contaminated groundwater   Arsenite oxidation   Reductants in groundwater  

摘要： Microbial oxidation of As(III) by biofilm bioreactors followed by adsorption is a promising and environment friendly approach to remediate As(III) contaminated groundwater;however, poor activity, stability and expandability of the bioreactors hampered their industrious applications. To resolve this issue, we constructed a new biofilm bioreactor using a powerful chemoautotrophic As(III)-oxidizing bacterium Rhizobium sp. A219. This strain has strong ability to form biofilms and possesses very high As(III)-oxidizing activities in both planktonic and biofilm forms. Perlites were used as the biofilm carriers. Long-term operations suggest that the bioreactor has very high efficiency, stability and scalability under different geochemical conditions, and it is cheap and easy to construct and operate. During the operations, it is only required to supply air, nothing else. All the common contaminants in groundwater slightly affected the bioreactor As(III)-oxidizing activity. The common contaminants in groundwater can be largely removed through assimilation by the bacterial cells as nutrition. The bioreactor completely oxidize 1.0, 5.0, 10.0, 20.0 and 30.0 mg/L As(III) in 12, 18, 20, 25 and 30 min, respectively. Approximately 18, 18, 12, 12 and 21 min were needed to oxidize 1.1 mg/L As(III) at 20, 25, 30, 35 and 40 degrees C, respectively. The bioreactor works well under the pH values of 5-8, and the most optimal was 7.0. The data suggest that this bioreactor possesses the highest efficiency and stability, and thus has the great potential for industrial applications among all the described As(III)-oxidizing bioreactors derived from a single bacterium. (C) 2021 Elsevier Ltd. All rights reserved.

关键词： Anaerobic ammonium oxidation (anammox)   Partial nitritation   Membrane bioreactor (MBR)   Candidatus Brocadia   Candidatus Scalindua   Microbial community  

摘要： Partial nitritation combined with anaerobic ammonium oxidation (anammox), hereafter referred to as PNA, is a promising biological nitrogen-removal process for ammonia-rich wastewater;however, the PNA application process to low-strength ammonia wastewater (i.e., mainstream anammox) remains challenging. In this study, two single-stage PNA processes using a membrane bioreactor (MBR) inoculated with the anammox enrichment culture of Candidatus Brocadia sinica (Brocadia-MBR) or Candidatus Scalindua sp. (Scalindua-MBR) were operated for low-strength ammonia wastewater treatment. Single-stage PNA process was established in both MBRs, showing rates of total nitrogen (TN) removal from 0.58 g-N L-1 day(-1) to 0.66 g-N L-1 day(-1), and 81%-89% TN-removal efficiency under optimal dissolved oxygen. Microbial community analysis showed that three ammonia-oxidizing bacteria (AOB), one nitrite-oxidizing bacteria (NOB), one Candidatus Brocadia were detected in the Brocadia-MBR, whereas one AOB, no NOB, and one Candidatus Scalindua were detected in Scalindua-MBR. The operational conditions in this study resulted in the out competition of anammox bacteria in both MBRs.

关键词： Conidia   Solid-state culture   Trichoderma asperellum   Water stress  

摘要： A new prototype of a disposable solid-state culture bioreactor (DSSCB) belonging to the packed-bed category is developed for the production of fungal conidia. The bioreactor has the advantages of being autoclavable, lightweight and disposable. With a working volume of 39.52 L, it can be used for large-scale production of fungal conidia. The DSSCB was successfully tested under forced aeration for the production of conidia (2.1 x 10(10)/g dry substrate in 140 h) fromTrichoderma asperellum, a biocontrol fungus. A mixture of sugarcane bagasse, wheat bran, olive pomace, potato flakes and vine shoots was used as substrate. The DSSCB allowed an overall production of 1.26 x 10(14)conidia. Based on its configuration, the fermented substrate can be easily transported and used in either solid or liquid form, for biocontrol application. This is a significant advance in the field of biomass production in solid-state culture as problems associated with the decontamination of the bioreactor prior to its reuse can be avoided. The study demonstrated that the DSSCB is suitable for the production of conidia usingT. asperellum. [GRAPHICS] .

关键词： Anaerobic digestion   Anaerobic co-digestion   Anaerobic membrane bioreactor (AnMBR)   Food waste   Techno-economic analysis  

摘要： The implementation of anaerobic membrane bioreactor as mainstream technology would reduce the load of sidestream anaerobic digesters. This research evaluated the techno-economic implications of co-digesting sewage sludge and food waste in such wastewater treatment plants to optimise the usage of the sludge line infrastructure. Three organic loading rates (1.0, 1.5 and 2.0 kg VS m- 3 d-1) and different strategies to manage the additional nutrients backload were considered. Results showed that the higher electricity revenue from co-digesting food waste offsets the additional costs of food waste acceptance infrastructure and biosolids disposal. However, the higher electricity revenue did not offset the additional costs when the nutrients backload was treated in the sidestream (partial-nitritation/anammox and struvite precipitation). Biosolids disposal was identified as the most important gross cost contributor in all the scenarios. Finally, a sensitivity analysis showed that food waste gate fee had a noticeable influence on co-digestion economic feasibility.

关键词： Tissue-engineering   Testis   Animal model  

摘要： We determined histological aspects of implanted human decellularized testicular matrix (DTM) in C57BL6 as a primitive step for further testis tissue engineering. A total of 4 immature human testicles were obtained after bilateral orchiectomy from patients with testicular feminization syndrome. The optimal decellularization protocol was determined and the efficacy of decellularization was evaluated in two of the testicles. The remaining scaffolds were cut in 3 x 3 mm(3) pieces and implanted between the tight muscles in 32 C57BL6. Biopsies were taken at 2, 4, 8, and 24 weeks postoperatively and stained with PLZF, protamine, and tekt1 markers. Histological examination of DTMs confirmed complete absence of nuclear remnants and preservation of the extracellular matrix. Successful cell seeding was observed in all follow-ups confirmed by H&E and IHC staining that increased continuously during the whole study. Interestingly, spermatogonial stem-like cells were observed on decellularized implants that were well differentiated during the follow-ups. Natural bioreactors may provide a good cell source for testes tissue regeneration. This technique may provide testis bioscaffold as a three-dimensional platform and further successful cell seeding to produce a functional testis. This novel technique may be beneficial for patients who require testicular supplementation.

关键词： Perfusion bioreactors   Modeling   Flux modes   Parameter estimation  

摘要： This paper discusses the challenges associated with the reliable and optimal operation of perfusion biore-actors and presents methods for modeling and identification of perfusion bioreactors as well as the vision for their integration. After presenting a generic model of perfusion bioreactors, the paper shows how to use the concept of basis flux modes to uniquely compute reaction rates. The advantage of this concept with respect to elementary flux nodes and similar concepts in metabolic flux analysis is the reduced number of flux modes that need to be modeled. In addition, a procedure to identify the model and estimate the parameters for each reaction using Monod-type kinetics is presented. It is shown that the rational structure of these kinetic models results in optimization problems that are amenable to tractable computation of globally optimal parameter estimates. The methods are illustrated via examples with simulated or experimental data. (C) 2021 Elsevier Ltd. All rights reserved.

关键词： Anaerobic dynamic membrane bioreactor   Sludge anaerobic digestion   Microbial community   Methanogenic pathway   Solids retention time (SRT)  

摘要： An anaerobic dynamic membrane bioreactor (AnDMBR), which enabled the decoupling of hydraulic retention time (HRT) and solids retention time (SRT), was used for enhancing sludge digestion, with the associated mechanisms elucidated. With the increase of SRT, the biogas production and sludge reduction rate were both enhanced. The specific biogas production and volatile solids (VS) reduction rate were improved to 0.79 L/g VS and 55.9% under SRT 50 d, respectively. Microbial community analysis revealed that Chloroflexi, which is capable of degrading metabolites and dead cells, was enriched at longer SRT. Further analysis showed that both acetoclastic and hydrogenotrophic methanogenesis contributed to the enhanced biogas production under higher SRT compared to the dominance of acetoclastic methanogenesis under lower SRT. The enhanced utilization of organic matter and acetate at longer SRT further confirmed the mechanisms. The results highlighted the potential of AnDMBR for high-efficient sludge digestion.

关键词： High environmental sustainability   Biological processes   Performance indicators   Modelling framework  

摘要： Integrated Membrane Bioreactor (MBR) models, combination of biological and physical models, have been representing powerful tools for the accomplishment of high environmental sustainability. This paper, produced by the International Water Association (IWA) Task Group on Membrane Modelling and Control, reviews the state-of-the-art, identifying gaps for future researches, and proposes a new integrated MBR modelling framework. Integrated Membrane Bioreactor (MBR) models, combination of biological and physical models, have been representing powerful tools for the accomplishment of high environmental sustainability. This paper, produced by the International Water Association (IWA) Task Group on Membrane Modelling and Control, reviews the state-of-the-art, identifying gaps for future researches, and proposes a new integrated MBR modelling framework. In particular, the framework aims to guide researchers and managers in pursuing good performances of MBRs in terms of effluent quality, operating costs (such as membrane fouling, energy consumption due to aeration) and mitigation of greenhouse gas emissions.