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关键词： Scaling-up   Milliliter-scale   Airlift bioreactors   CFD   Optical sensors  

摘要： Many researchers have limited access to fully equipped laboratory-scale batch bioreactors and chemostats due to their relatively high cost. This becomes particularly prohibitive when multiple replicas of the same experiment are required, but not enough bioreactors are available to operate simultaneously. Additionally, experiments using shaken flasks are common but show significant limitations in terms of maintaining homogeneous conditions in liquid cultures or installing instrumentation for monitoring. Here, we proposed to tackle this significant hurdle by providing a route to make available the manufacture of low-cost, milliliter-scale bioreactors. This approach seems plausible for enabling proof-of-concept experiments before moving to a larger scale without significant investments. The conceptually designed systems were based on external-loop bioreactors due to their flexibility, simplicity, and ease of assembling and testing. Designs were initially evaluated in silico with the aid of COMSOL Multiphysics. The successfully evaluated systems were then constructed via additive manufacturing and assembled for hydrodynamics testing via tracer methods. This was enabled by a newly home-made optical absorbance sensor (OAS) for in-line and real-time measurements. Both the in silico and experimental results indicated close to ideal mixing conditions and low shear stress. Cell growth curves were prepared by culturing Escherichia coli and following its cell density in real-time. Our cell growth rate and maximum cell density were similar to those previously obtained in closely related systems. Therefore, the proposed bioreactors are an affordable alternative for batch and continuous cell growth studies rapidly and inexpensively.

关键词： Membrane bioreactor (MBR)   Powdered activated carbon (PAC)   Micro-polluted water   Membrane foulants   Fouling characterization  

摘要： To identify the characteristics of fouling in the powdered activated carbon e membrane bioreactor (PAC-MBR) for micro-polluted water treatment, a pilot-scale PAC-MBR was continuously operated for 4 months without chemical cleaning. The membrane autopsy suggested that physically recoverable and irrecoverable fouling accounted for 56.6 and 43.4% of the total fouling, respectively, and intermediate blocking model showed the best fitting for fouling evolution. Colloidal matter, which had a large proportion of protein and polysaccharide, was the major contributor to the physically recoverable fouling resistance, while polysaccharide and humic substances were the major contributors to the physically irrecoverable fouling resistance. By comparing the MBRs with and without PAC, it was found that PAC increased fouling rate because it exerted a marginal effect on foulants reduction and membrane scouring, but a synergistic effect on cake layer formation. These fouling characteristics in PAC-MBR were different from those in the MBRs for municipal wastewater treatment, which could be ascribed to the poornutrient of the micro-polluted water. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： Membrane bioreactor (MBR)   Powdered activated carbon (PAC)   Mixed liquor properties   Membrane fouling   Fouling models  

摘要： Owing to the lack of comprehensive studies on the impacts of a high concentration of powdered activated carbon (PAC) in a ceramic membrane bioreactor (MBR), its performance (at 20 g/L) in terms of mixed liquor properties, hydraulic performance and fouling mechanism was elucidated in this study. In addition to the increase in floc size by 29%, zeta potential of the mixed liquor in PAC-MBR increased (from -19 +/- 2 mV to -11 +/- 2 mV), which was due to the sorption of soluble microbial products on PAC. Importantly, even at a high dose of 20 g/L, membrane fouling was reduced by 33% in PAC-MBR and was attributed to the membrane scouring by PAC and reduced SMP and EPS concentration in the mixed liquor. The viability of the four single and five combined fouling models was assessed to explain the membrane fouling mechanisms in ceramic MBRs for the first time. The intermediate-standard and cake-intermediate models well explained the fouling mechanism in the 'control' and PAC-MBR, respectively, and the intermediate fouling was the major component of the combined models. This study clarifies that MBR could be operated at a high PAC concentration without compromising the effluent quality, mixed liquor properties and membrane hydraulic performance.

关键词： Miniature bioreactor   Parallel operation   Fermentation   Online monitoring  

摘要： Miniaturized stirred-tank bioreactor systems provide a scalable platform for high-throughput bioprocess development. Online measurement of process variables is a major demand to enable efficient process monitoring and control in parallel operated bioreactors. One miniaturized laser light source and two photodiodes were placed around a cylindrical disposable bioreactor made of polystyrene for individual and contact-free measurement of optical density (OD). One photodiode was positioned at an angle of 28 degrees to the laser for measuring the scattered light, a second photodiode was positioned face to face with the laser for measuring the transmitted light. Miniaturized lasers with wavelengths of 650 nm (orange), 780 nm (NIR) and 850 nm (IR) were evaluated. The best results were achieved with a laser emitting at 850 nm. Both signals (scattered and transmitted light) were influenced by the stirrer speed (usually constant) and the microorganisms under study. After individual calibration, online OD monitoring of pH-controlled fed-batch processes was successfully shown with Escherichia coli, Corynebacterium glutamicum, and Trichosporon oleaginosus. Online OD measurements based on the transmitted light signals showed low standard deviation at low cell densities, whereas scattered light signals were more accurate at higher cell densities. Correlations were reliable up to cell dry weight concentrations of 46 g L-1 in stirred-tank bioreactors on a milliliter scale.

关键词： Osmotic membrane bioreactor   Outer-selective hollow fiber   Forward osmosis membrane   Membrane fouling   Submerged membrane module  

摘要： This paper investigated the membrane fouling mitigation efficacy and performance of a home-made submerged module containing outer selective hollow fiber thin film composite forward osmosis (OSHF TFC FO) membrane in osmosis membrane bioreactor (OMBR) system treating municipal wastewater for desalination. Initial tests, optimization of draw solution flowrate and pumping mode for the submerged module were carried out before it was applied into the OMBR system. Overall, the OMBR system exhibited an initial water flux of approximately 6.3 LMH using 35 g/L NaCl as draw solution, and high removal efficiencies of bulk organic matter and nutrients. Moreover, membrane fouling was effectively mitigated with slow rate of flux decline during 33-day operation of the OMBR system. These results indicated that the submerged membrane module of OSHF TFC FO membrane has stable and reliable performances making it suitable for OMBR supplication without the need of air scouring to prevent membrane fouling.

关键词： Olive-tree pruning   Hydrolyzate   Fermentation   Biotransformations  

摘要： Processes efficiency for second-generation ethanol production depends mainly on the type of lignocellulosic raw material. Therefore, the optimization (considering a central composite design) for each step involved in olive-tree pruning biomass valorization was studied: (1) alkaline pretreatment of the original feedstock, (2) diluted acid hydrolysis of pretreated solids and (3) fermentation of the hemicellulosic hydrolyzates for ethanol production by Scheffersomyces stipitis. The recommended alkaline pretreatment conditions were 30 min, 90 degrees C and 0.5% w/v NaOH, with losses of 88.3% of acetyl groups from starting biomass, but only 6.9% of D-xylose. Comparing both, in natura and previously treated acid hydrolyzates at the most effective conditions (2.0% w/v H2SO4 and 60 min) revealed more inhibitory effect for non-treated liquor, with 4.8, 2.1 and 1.6 times higher concentrations of acetic acid, furans and phenolic compounds, respectively. A significant improvement in ethanol production was observed in treated hemicellulose liquor (20.4 g dm(-3), Y-P/S = 0.20 g g(-1) and Q(p) = 0.21 g dm(-3)h(-1)). In contrast, the yeast could not satisfactorily ferment the reference hydrolyzate. Biomass pretreatment with alkali previously to dilute acid hydrolysis was a suitable strategy for olive-tree pruning biomass biotransformation, substantially decreasing the hydrolyzate toxicity, without requiring an additional detoxification step.

关键词： Ethanol fed-batch bioreactor   Pichia pastoris (Komagataella phaffii)   hybrid-architectured ADH2 promoter   therapeutic protein   specific rates  

摘要： We presented ethanol fed-batch bioreactor operations (FBBOs) designed for enhanced recombinant human growth hormone (rhGH) production in Pichia pastoris constructed with novel hybrid-architectured ADH2 promoter, PADH2-Cat8-L2. The parameters in the fed-batch fermentation of ethanol were investigated, and the boundaries of the production domain in terms of the design parameters were determined. Two FBBO design methods were used, and a platform aiming to adjust cellular metabolism for the generation of constant specific growth rate (mu) and substrate concentration (C-EtOH) was established. The highest overall productivity (r(P),(ov)) was generated with model-based continuous feed-stream (CFS) design with mu(preD) = 0.035 h(-1) up to t(max) <= 9 h as r(P),(ov) = 3.0 mg L-1 h(-1) and C-rhGH = 34 mg L-1. The ethanol-stat FBBO at C-EtOH,(set) = 0.5 g L-1 allowed increased product titer with high productivity and the highest C-rhGH =90.1 mg L-1 at t(max) = 24 h. The effect of C-EtOH on specific rates for cell reactions was represented by the Haldane model in which the cell generation and rhGH production were simulated with low mean relative errors of 6.5 and 16%, respectively. The results indicate the need for an upgraded CFS design model with kinetic expressions involving substrate inhibition. We conclude that a two-step hybrid fed-batch design strategy to be started (i) with the initial-period of the model-based FBBO, in turn, proceeded (ii) with the controlled feeding with ethanol-stat FBBO enables a gradual approach to the hypothetical performance of FBBOs.

关键词： Sewage sludge   Food waste   Anaerobic co-digestion   High-solid AnMBR   Fouling mechanism  

摘要： Disposal of the increasingly huge amounts of sewage sludge (SeS) has become an impending problem worldwide. To solve this problem, a high-solid anaerobic membrane bioreactor (AnMBR) was used for the anaerobic co-digestion (AcoD) of SeS and food waste (FW). This study investigated the effects of SeS ratio on the methanogenic performance of the AcoD with a gradual increase value from 0 to 25%, 50%, 75% and 100% (total solids based). The results showed that the highest methanogenic performance was achieved at mono FW digestion. As for the co-digestion, the optimal FW/SeS ratio for methanogenic performance was 75%:25% among all the mixing ratios. The COD based biogas yield and methane yield were 0.498 L-biogas/g-CODfed and 0.295 L-CH4/g-CODfed at this optimal mixing ratio, which were 67.7% and 67.6% higher than those of the mono SeS digestion, respectively. The upgraded values were attributed to the improved hydrolysis ratio (by 8.14%) and the balanced carbon-to-nitrogen (C/N) ratio by co-digestion with FW, which synergistically stimulated methanogenesis ratio by 81.0%. The continuous membrane filtration property was investigated and four typical trans-membrane pressure (TMP) variation curves at different fouling degrees were determined. The membrane could sustainably operate at a flux of 6 L/m(2)/h (LMH) at the mixed liquor total solids (MLTS) concentration of 25 30 g/L. The combination of continuous membrane filtration property, particle size distribution of the mixed liquor and the external forces analysis was firstly applied to unravel the membrane fouling mechanism of a high-solid AnMBR. The result of this study will contribute to the establishment of an efficient FW and SeS treatment strategy. (c) 2020 Elsevier Ltd. All rights reserved.

关键词： Multiple stratified environments   Nitrogen transformation   Microbial community distribution   Gene complementary  

摘要： A pilot-scale upgraded gravity-driven submerged membrane (GDSM) reactor was constructed to enhance nitrogen removal. It was artificially formed multiple stratified environments (dissolved oxygen (DO) and substrate supply (TOC, TN, COD, NH4+-N, NO2--N, and NO3--N)) by embedding moving water baffles to control water-flow process in bulk liquid with slow-flowing liquid state. Significant diversity and relative abundance of microorganisms associated with nitrogen transformation paths (i.e., ammonia-oxidizing archaea, ammonia-oxidizing bacteria, nitrite oxidizing bacteria, and denitrifying bacteria) were tailored to distribute on different spatial and temporal regions, and performed their dominant functions. The process simultaneously integrated diverse and effective nitrogen transformation paths (i.e., nitrification, partial nitrification, denitrification, anammox, and dissimilatory nitrate reduction) to achieve high nitrogen removal, with NH4+-N, TN, and COD eliminated by 94.68 +/- 2.55%, 55.16 +/- 5.53%, and 80.17 +/- 6.75%, respectively. Gene expressions involved in the nitrogen transformations were estimated by qPCR to explore the shifts of dominant nitrogen transforming bioreactions in multiple stratified environments. Pearson correlation coefficients supported that the functional genes had more stable and active ability by complementing each other. As a result, an endogenous integration of diverse nitrogen transformation paths was achieved in a single system by artificially tailoring the distributions of microbial communities and gene expressions with enhanced nitrogen removal. (c) 2020 Published by Elsevier Ltd.

关键词： Aerobic granular sludge   Membrane bioreactor   Quorum sensing   Signaling molecule   Extracellular polymeric substance   Microbial community  

摘要： The investigation aimed at revealing the N-acyl-homoserine lactone (AHL)-mediated quorum sensing (QS) of aerobic granular sludge (AGS) system in a membrane bioreactor (MBR) with internal circulation. During the experimental period, the MBR was operated under a continuous-flow mode, in which, AGS was cultivated directly. The specific AHL molecules were determined and the correlation between the AHL-mediated QS, extracellular polymeric substance (EPS) production and microbial community was explored. Two kinds of specific signaling molecule, N-octanoyl-DL- homoserine lactone (C8-HSL) and N-tetradecanoyl-DL-homoserine lactone (C14-HSL), were detected in the cultivated AGS, but C14-HSL was the major one, which was detected to be ranging from 86.58 ng/gMLSS to 594.00 ng/gMLSS among all samples. Most importantly, the concentration of C14-HSL was positively correlated to the production of LB-EPS and TB-EPS (r > 0.906, P < 0.034, minimum 'r' and maximum 'p'), which demonstrated it's a crucial component in the formation of AGS and determined its stability. The results indicated that the structure of microbial community showed weak correlation with the content of AHLs and EPS if without the pressure of microbial selection. But, the conditions within the bioreactor determined the microbial community, and the contained functional bacteria released signaling molecules to promote the granulation.