•Comprehensively review 3 common BC production methods, i.e., static culture; agitated culture; bioreactor.•Detailed discuss BC production methods with their properties and final applications ...relations.•Indicate existing problems associated with different BC production methods and their applications.•Provide suitable culture approaches for BC applications in different fields.
Bacterial cellulose (BC) is an organic compound produced by certain types of bacteria. In natural habitats, the majority of bacteria synthesize extracellular polysaccharides, such as cellulose, which form protective envelopes around the cells. Many methods are currently being investigated to enhance cellulose growth. The various celluloses produced by different bacteria possess different morphologies, structures, properties, and applications. However, the literature lacks a comprehensive review of the different methods of BC production, which are critical to BC properties and their final applications. The aims of this review are to provide an overview of the production of BC from different culture methods, to analyze the characteristics of particular BC productions, to indicate existing problems associated with different methods, and to choose suitable culture approaches for BC applications in different fields. The main goals for future studies have also been discussed here.
In the biotechnological desulfurization process under haloalkaline conditions, dihydrogen sulfide (H2S) is removed from sour gas and oxidized to elemental sulfur (S8) by sulfide-oxidizing bacteria. ...Besides S8, the byproducts sulfate (SO4 2–) and thiosulfate (S2O3 2–) are formed, which consume caustic and form a waste stream. The aim of this study was to increase selectivity toward S8 by a new process line-up for biological gas desulfurization, applying two bioreactors with different substrate conditions (i.e., sulfidic and microaerophilic), instead of one (i.e., microaerophilic). A 111-day continuous test, mimicking full scale operation, demonstrated that S8 formation was 96.6% on a molar H2S supply basis; selectivity for SO4 2– and S2O3 2– were 1.4 and 2.0% respectively. The selectivity for S8 formation in a control experiment with the conventional 1-bioreactor line-up was 75.6 mol %. At start-up, the new process line-up immediately achieved lower SO4 2– and S2O3 2– formations compared to the 1-bioreactor line-up. When the microbial community adapted over time, it was observed that SO4 2– formation further decreased. In addition, chemical formation of S2O3 2– was reduced due to biologically mediated removal of sulfide from the process solution in the anaerobic bioreactor. The increased selectivity for S8 formation will result in 90% reduction in caustic consumption and waste stream formation compared to the 1-bioreactor line-up.
Hydrogen applicability in the power, chemical and petrochemical industries is constantly growing. Efficient methods of hydrogen generation from renewable sources, including waste products, are ...currently being developed, even though hydrogen is mainly produced through steam reforming or thermal cracking of natural gas or petroleum fractions. In paper alternative methods of hydrogen production with a particular emphasis on dark fermentation are discussed. The review compiles essential information on strains of bacteria used in the production of hydrogen from waste products in the agroindustry and from lignocellulosic biomass. The effect of such parameters as kind of raw material, method of processing, temperature, pH, substrate concentration, partial pressure of hydrogen, hydraulic retention time, method of inoculum preparation and the type and operating parameters of a reactor on the yield of dark fermentation is discussed. The review aims at presentation of current state of knowledge on the dark fermentation process utilizing waste materials as substrates. The results of investigations with emphasis on the most important issues regarding operating parameters of dark fermentation are also included.
•Hydrogen can be produced from biomass by biotechnological methods.•Utilization of lignocellulose within dark fermentation requires pretreatment.•Optimization of lignocellulosic biomass pretreatment improves fermentation results.•Improvement of the efficiency of hydrogen generation requires constant research.•Scale-up should result in high-potential strategies for hydrogen technologies.
•Low viscous DES-water blends can be used in continuous processes for biocatalysis.•The pH control increases the conversion, using DES in a fed-batch reactor.•Fed-batch reactor reached the highest ...concentration of product 33 g/L.•The semicontinuous and continuous bioreactors reached similar productivities.•Biocatalyst stability was high in a packed-bed reactor, without loss for 10 days.
This work explores for the first time the use of Deep Eutectic Solvents (DES) with phosphate buffer 100 mM pH 7 as cosolvent (10% v/v) in biocatalytic reactions in fed-batch and packed-bed bioreactors. The lipase-catalyzed esterification of glycerol and benzoic acid is studied, as it involves two substrates with different polarities (for which DES are needed). In the fed-batch bioreactor, the highest conversion (90%) was obtained at a substrate flow rate of 0.01 mL/min. The fed-batch operation increased the conversion by 59% compared to the batch mode. Regarding productivity, semi-continuous and continuous bioreactors showed analogous results. Upon recirculation of the reaction media in the continuous bioreactor, a conversion of 67% was achieved in 7 cycles of operation. The stability of the biocatalyst in the packed-bed bioreactor decreased only 2% in 10 days, demonstrating the attractiveness that low viscous DES-water mixtures with continuous processes may have.
•A new nonlinear control strategy that synergistically combines supervised and reinforcement learning based control paradigms is proposed.•A machine learning based control strategy is proposed for ...the challenging and economically important bioreactor control problem.•Simulation results indicate that the proposed partially supervised RL control strategy is superior to both pure RL and inverse model ANN nonlinear control strategies for bioreactor control on a wide variety of performance metrics.•Experiment results demonstrating the control of a quadruple interacting tank system using the proposed PSRL algorithm are presented.•Experimental as well as simulation results clearly demonstrate the superior convergence of the proposed PSRL algorithm.
In recent years, researchers have explored the application of Reinforcement Learning (RL) and Artificial Neural Networks (ANNs) to the control of complex nonlinear and time varying industrial processes. However RL algorithms use exploratory actions to learn an optimal control policy and converge slowly while popular inverse model ANN based control strategies require extensive training data to learn the inverse model of complex nonlinear systems. In this paper a novel approach that avoids the need for extensive training data to construct an exact inverse model in the inverse ANN approach, the need for an exact and stable inverse to exist and the need for exhaustive and costly exploration in pure RL based strategies is proposed. In this approach an initial approximate control policy learnt by an artificial neural network is refined using a reinforcement learning strategy. This Partially Supervised Reinforcement Learning (PSRL) strategy is applied to the economically important problem of control of a semi-continuous batch-fed bioreactor used for yeast fermentation. The bioreactor control problem is formulated as a Markov Decision Process (MDP) and solved using pure RL and PSRL algorithms. Model based and model-free RL control experiments and simulations are used to demonstrate the superior performance of the PSRL strategy compared to the pure RL and inverse model ANN based control strategies on a variety of performance metrics.
•P. stutzeri XL-2 was successfully bioaugmented in a SBBR.•A better performance on biofilm formation and TN removal was achieved.•Less accumulation of NO2−-N and NO3−-N was found in the bioaugmented ...SBBR.•P. stutzeri XL-2 played a significant role in this bioaugmentation.•A single aerobic bioreactor for ammonium-rich wastewater treatment is provided.
Pseudomonas stutzeri XL-2, with the capability of heterotrophic nitrification-aerobic denitrification and biofilm-forming, was applied in a sequencing batch biofilm reactor (SBBR) for bioaugmented treatment of ammonium-rich wastewater. The bioaugmented system SBBR 1 showed a rapid development of biofilm and relatively shorter time for biofilm hanging compared with the control system SBBR 2 without strain XL-2 inoculation. At different NH4+-N loads of 100, 200 and 300 mg/L, the effluent TN removal ratios ranged in 88.7–97.0%, 85.1–93.5% and 87.8–92.5% respectively in SBBR 1, while only ranged in 77.4–85.4%, 77.1–84.3% and 79.8–85.0% in SBBR 2. Less accumulation of NO2−-N and NO3−-N resulted in the better performance on TN removal in SBBR 1. Microbial community structure analysis revealed that strain XL-2 successfully proliferated in SBBR 1 and contributed to the less accumulation of NO2−-N and NO3−-N as well as biofilm formation.
•Five types of biomass from MBBR, IFAS, and MBR were compared for the degradation of OSPW.•MBBR and IFAS-biofilm showed high AEF and classical NAs removal, MBR-flocs showed high COD removal.•NAs ...degradation was highly dependent on the carbon number and NA cyclization number according to UPLC/HRMS analysis.•Denitrifiers were more abundant in suspended phase of activated sludge flocs.
This study compared microbial characteristics and oil sands process-affected water (OSPW) treatment performance of five types of microbial biomass (MBBR-biofilm, IFAS-biofilm, IFAS-floc, MBR-aerobic-floc, and MBR-anoxic-floc) cultivated from three types of bioreactors (MBBR, IFAS, and MBR) in batch experiments. Chemical oxygen demand (COD), ammonium, acid extractable fraction (AEF), and naphthenic acids (NAs) removals efficiencies were distinctly different between suspended and attached bacterial aggregates and between aerobic and anoxic suspended flocs. MBR-aerobic-floc and MBR-anoxic-floc demonstrated COD removal efficiencies higher than microbial aggregates obtained from MBBR and IFAS, MBBR and IFAS biofilm had higher AEF removal efficiencies than those obtained using flocs. MBBR-biofilm demonstrated the most efficient NAs removal from OSPW. NAs degradation efficiency was highly dependent on the carbon number and NA cyclization number according to UPLC/HRMS analysis. Mono- and di-oxidized NAs were the dominant oxy-NA species in OSPW samples. Microbial analysis with quantitative polymerase chain reaction (q-PCR) indicated that the bacterial 16S rRNA gene abundance was significantly higher in the batch bioreactors with suspended flocs than in those with biofilm, the NSR gene abundance in the MBR-anoxic bioreactor was significantly lower than that in aerobic batch bioreactors, and denitrifiers were more abundant in the suspended phase of the activated sludge flocs.
Antibiotics, the most frequently prescribed drugs of modern medicine, are extensively used for both human and veterinary applications. Antibiotics from different wastewater sources (e.g., municipal, ...hospitals, animal production, and pharmaceutical industries) ultimately are discharged into wastewater treatment plants. Sorption and biodegradation are the two major removal pathways of antibiotics during biological wastewater treatment processes. This review provides the fundamental insights into sorption mechanisms and biodegradation pathways of different classes of antibiotics with diverse physical–chemical attributes. Important factors affecting sorption and biodegradation behavior of antibiotics are also highlighted. Furthermore, this review also sheds light on the critical role of extracellular polymeric substances on antibiotics adsorption and their removal in engineered biological wastewater treatment systems. Despite major advancements, engineered biological wastewater treatment systems are only moderately effective (48–77%) in the removal of antibiotics. In this review, we systematically summarize the behavior and removal of different antibiotics in various biological treatment systems with discussion on their removal efficiency, removal mechanisms, critical bioreactor operating conditions affecting antibiotics removal, and recent innovative advancements. Besides, relevant background information including antibiotics classification, physical–chemical properties, and their occurrence in the environment from different sources is also briefly covered. This review aims to advance our understanding of the fate of various classes of antibiotics in engineered biological wastewater treatment systems and outlines future research directions.
•Spirulina biorefinery contribute to greenhouse gases fixation and effluent treatment.•More than 30% of the world biomass production is from genus Spirulina.•Biorefineries are the best alternative ...for the economic performance of Spirulina.
Microalgae biorefinery systems have been extensively studied from the perspective of resources, energy expenditure, biofuel production potential, and high-added value products. The genus Spirulina (Arthrospira) stands out among the microalgae of commercial importance. It accounts for over 30% of biomass produced globally because of high protein concentration and, carotenoid and phycocyanin content. Spirulina cultivation can be used to reduce greenhouse gases and for effluent treatment. Furthermore, its cellular morphology facilitates biomass recovery, which contributes to the process cost reduction. Spirulina biomass is widely applicable in food, feed, cosmetics, biofertilizers, biofuels, and biomaterials. A feasibility analysis of Spirulina biorefinery would provide specific information for the decision-making for the improvement of the Spirulina production process. In that context, this review aimed to present a parameter assessment to contribute to the economic viability of Spirulina production in a biorefinery system.
Since the discovery of microbiological metal dissolution, numerous biohydrometallurgical approaches have been developed to use microbially assisted aqueous extractive metallurgy for the recovery of ...metals from ores, concentrates, and recycled or residual materials. Biohydrometallurgy has helped to alleviate the challenges related to continually declining ore grades by transforming uneconomic ore resources to reserves. Engineering techniques used for biohydrometallurgy span from above ground reactor, vat, pond, heap and dump leaching to underground in situ leaching. Traditionally biohydrometallurgy has been applied to the bioleaching of base metals and uranium from sulfides and the biooxidation of sulfidic refractory gold ores and concentrates before cyanidation. More recently the interest in using bioleaching for oxide ore and waste processing, as well as extracting other commodities such as rare earth elements has been growing. Bioprospecting, adaptation, engineering and storing of microorganisms has increased the availability of suitable biocatalysts for biohydrometallurgical applications. Moreover, the advancement of microbial characterisation methods has increased the understanding of microbial communities and their capabilities in the processes. This paper reviews recent progress in biohydrometallurgy and microbial characterisation.
•Biohydrometallurgy has been mostly used for sulfidic gold, base metal and uranium ores.•Interest in waste bioleaching and extracting other commodities is increasing.•In situ and vat bioleaching are gaining interest along with heaps and bioreactors.•Bioprospecting, adaptation, engineering increase the availability of novel strains.•Microbial characterisation increases the understanding on biocatalysts.
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