Aerobic Process Research Articles

Treatment of Agricultural Waste Using a Combination of Anaerobic, Aerobic, and Adsorption Processes

The generation of waste in agricultural and livestock industries, followed by inadequate treatment and uncontrolled disposal to natural recipients, results in significant environmental pollution. Thus, the efficient and integrated management of high-organic-load waste produced in such activities is a key factor for sustainability and the protection of aqueous matrices. In this work, we investigate an integrated management approach for the treatment of agricultural, high-organic-load waste via a combination of processes, with an ultimate goal to improve the characteristics of the final waste and enhance the valorization of the nutrients contained in it. Towards this direction, a waste mixture comprising pig waste, cheese dairy, and food residues was sequentially treated in a laboratory scale by anaerobic digestion, followed by activated sludge (aerobic–anoxic treatment), and last by adsorption using natural zeolite. The efficiency of two different adsorption routes was examined (magnetically agitated zeolite or packed zeolite column), while the effect of the granule sizes of zeolite (0–1 mm or 1.5–3 mm) was also evaluated with regards to the remediation of the final effluent. Excellent adsorption capacities were observed in all cases, with the larger-sized zeolite exhibiting a superior performance, while the granule size of zeolite significantly affected the lifetime of the packed columns, as the smaller-sized zeolite columns reached their saturation point faster than the larger-sized zeolite analogue. The average ammonium nitrogen removal in the column experiment was ~92%, while total phosphorus was ~68%, respectively. Overall, an almost complete remediation of the final effluent was observed when compared with the physicochemical parameters of the initial waste, with a ~96% chemical oxygen demand, ~79% total nitrogen, ~96% total phosphorus, and ~82% phenols concentration decrease, signifying the high performance of the sequential treatment strategy proposed herein.

Palm oil mill effluent processing via hybrid plasma and acoustic treatment

The large quantities of palm oil mill effluent (POME) that need to be processed daily to meet global palm oil demand creates a significant pollution problem. The two-stage anaerobic–aerobic process conventionally used to treat POME before its discharge to minimize its environmental impact, however, involves long retention times. We demonstrate in this work that it is possible to significantly reduce such treatment times through the introduction of plasma and MHz-order sound waves in the form of surface acoustic waves (SAWs) to the second stage aerobic treatment process, which, considerably improve the reduction of the POMEs' total suspended solids (TSS) concentration, chemical oxygen demand (COD) and biological oxygen demand (BOD); the plasma exposure enhances oxygen dissolution and the dissolution of the organic compounds, whereas the SAW promotes convective mass transfer and decomposition of the bacteria. With plasma pretreatment alone before aerobic treatment, it is possible to achieve a twofold reduction in the total treatment time to achieve target TSS, COD and BOD values, whereas irradiating the POME with the SAWs during aerobic treatment was found to reduce treatment times by up to fourfold. Combining both methods into a serial treatment process was then observed to lead to overall reduction in the total treatment duration by up to fivefold, therefore highlighting the promise of the hybrid technology for adoption in industry-scale treatment systems, particularly given the simplicity and cost effectiveness of plasma generation and the low cost and chip-scale dimensions of the SAW devices that facilitate ease of scale-up through massive parallelization.

Օդակյաց վերքային վարակի պարագայում հեմոմիկրոցիրկուլյացիայի վիճակի վերաբերյալ / On the state of hemomicrocirculation in the aerobic wound infection

The article discusses various aspects of the morphofunctional changes occurring in organs and tissues undergoing aerobic wound processes. In recent years, morphofunctional changes undergoing aerobic wound process have been thoroughly examined, numerous studies have been carried out in order to clarify its morphological, histochemical, immunological, metabolic, and bacteriological aspects, the nature and features of the very wound inflammation process have been refined. Nevertheless, extremely insufficient studies have been carried out into the visceral presentations in aerobic wounds. Quite possibly, it is the structural changes in the internal organs that serve as the basis for the known complications, which in clinical conditions appear as signs of bacteremia, septicemia, and increasing intoxication. In this regard, the study of the state of microcirculation pathways not only in the lesion, but also in different organs and systems is of rather big interest, since the nature of microcirculatory disorders largely determines the characteristics of the course of pathological process at the tissue, organ, and system levels. To sum up the abovementioned, from a morphofunctional point of view, the author of the study has examined the microvasculature of the mesentery under conditions of inducing an aerobic purulent wound process in rats. It has been established that the most severe changes in the system of mesenteric microcirculation pathways occur on the 7th day of the regional pathological process. Changes appear in the form of signs of endothelial cell degeneration, increased vascular permeability, perivascular edema, and lymphocytic infiltration. In the mechanism of increased vascular permeability, tissue basophils play an important role, which is determined by the processes and their intensive degranulation and the histamine delivery into the perivascular space.

ЭФФЕКТИВНОСТЬ РАЗЛИЧНЫХ РЕЖИМОВ ИНТЕНСИВНОЙ АЭРОБНОЙ ПЕРЕРАБОТКИ КОМПОСТНЫХ СМЕСЕЙ НА ОСНОВЕ ОСАДКА СТОЧНЫХ ВОД

The article defines the efficiency of using various modes of intensive aerobic processing of compost mixtures based on sewage sludge (WWS) into biocomposts. The use of intensive aerobic processing in comparison with traditional composting technologies made it possible to reduce the loss of organic matter and nitrogen in compost based on WWS by half. Complete disinfection of the compost mixture based on WWS from pathogenic vegetative microflora is achieved by its aerobic processing in thermophilic mode (at a temperature of 55°C and above) for 48 hours.

Engineering cytochrome P450s for selective alkene to carbonyl oxidation.

The Wacker-Tsuji oxidation is an important aerobic oxidation process to synthesize ethanal from ethene and methyl ketones from 1-alkenes. Current challenges in aerobic alkene oxidation include selective carbonyl product formation beyond methyl ketones. This includes the regioselective oxidation of the terminal carbon atom of 1-alkenes, the regioselective ketone formation with internal alkenes as well as the enantioselective alkene to carbonyl oxidation. Recently, the potential of high-valent metal-oxo species for direct alkene to carbonyl oxidation was explored as carbonyl product formation is frequently reported as a side reaction of alkene epoxidation by cytochrome P450s. It was shown that such promiscuous P450s can be engineered via directed evolution to perform alkene to carbonyl oxidation reactions with high activity and selectivity. Here, we report a protocol to convert promiscuous P450s into efficient and selective enzymes for Wacker-type alkene oxidation. One round of directed evolution is described in detail, which includes the generation and handling of site-saturation libraries, recombinant protein expression, library screening in a 96-well plate format and the rescreening of variants with beneficial mutations. These protocols might be useful to engineer various P450s for selective alkene to carbonyl oxidation, and to engineer enzymes in general.

Effect of vacuum negative pressure aerobic hydrolysis pretreatment on corn stover anaerobic fermentation

Lignin degradation restricts corn stover anaerobic fermentation efficiency. The vacuum negative pressure aerobic hydrolysis pretreatment of corn stover was tested, and the optimal combined pretreatment conditions were presented in this paper. Because of the physical characteristics of light weight and large specific porosity of stover, it led to the formation of a scum layer during the fermentation process and thus reduced the gas production rate. In the pretreatment design, the vacuum conditions (0.02-0.08 MPa) and dwell time (5-20 min) were selected to see the changes of volumetric weight, swelling and specific porosity of corn stover, resulting in an increase of the volumetric weight by 7.18%-28.72%, increase of the swelling by 3.18%-58.59%, and decrease of the specific porosity by 9.34%-38.59%, as compared with the CK group. Continuous vacuum negative pressure treatment could discharge the air inside the stover destroy the microstructure, and cause the stover to settle more easily during the aerobic hydrolysis process. The optimal aerobic hydrolysis temperature and time were determined to be 39℃ and 12.65 h, respectively. With the optimal pretreatment, the corn stover anaerobic fermentation test realized the cumulative methane yield as 260.44 Ml/g·VS, 22.71% higher than that of CK group; meanwhile, the hydraulic retention time was shortened by 32.39%. Keywords: corn stover, vacuum, negative pressure, pretreatment, aerobic hydrolysis, anaerobic fermentation DOI: 10.25165/j.ijabe.20231602.7975 Citation: Xu Y H, Song Y N, Jiang H, Zhang H Q, Sun Y. Effect of vacuum negative pressure aerobic hydrolysis pretreatment on corn stover anaerobic fermentation. Int J Agric & Biol Eng, 2023; 16(2): 241–248.

Anaerobic Digestion and Composting as Methods of Bio-Waste Management

Abstract The management of biodegradable waste from various sectors of economy is an essential element in terms of environmental protection. The paper discusses issues related to the possibility of bio-waste treatment using anaerobic digestion technologies and composting processes, highlighting the conditions for the processes and their advantages and disadvantages. The challenges of overproduction of bio-waste faced by highly developed countries around the world are also presented. Research showed that the anaerobic digestion of this waste combines both biofuel production and a circular economy. The popularity of this method is linked, among others to a low cost of raw materials and wide range of possible uses for biogas (i.e. electricity, heat, or biomethane). In addition, an alternative bio-waste management option, compost production, was discussed. The study aimed to compare anaerobic and aerobic bio-waste management processes.

Evaluation of the Recovery of Stored Granules to Promote Practical Wastewater Treatment by Aerobic Granular Sludge Process

Evaluation of the Recovery of Stored Granules to Promote Practical Wastewater Treatment by Aerobic Granular Sludge Process

Treatment of municipal wastewater of Fez city (Morocco) using a sequence of aerobic and Fenton processes

Treatment of municipal wastewater of Fez city (Morocco) using a sequence of aerobic and Fenton processes

The copper-catalyzed oxidative radical process of site selective C–N bond cleavage in twisted amides: batch and continuous-flow chemistry

Copper-superoxo radical activation in twisted amides which mediates the aerobic oxidative process to produce primary amides by selective C–N bond cleavage in batch and continuous-flow method.

PECULIARITIES OF PARAMETERS OF AEROBIC AND ANAEROBIC PRODUCTIVITY DEPENDING ON THE COMPONENTS OF BODY WEIGHT IN YOUNG MALES FROM THE MOUNTAINOUS DISTRICTS OF ZAKARPATTIA.

The aim: To establish differences in the aerobic and anaerobic capacity in young males with different components of body weight who live in the mountainous districts of Zakarpattia region. Materials and methods: 124 young men aged 17-21 were examined to determine the aerobic and anaerobic capabilities of the body, taking into account the components of body weight. Results: The level of aerobic productivity, which reflects physical health, depends on the component composition of the body. The highest level of aerobic capacity in terms of the VО2 max rel. is found in young males who have normal body weight with a high and a very high relative content of skeletal muscle, a low relative content of fat, and a normal level of visceral fat. As a consequence, their physical health exceeds "safe health level", namely 42 ml∙min-1∙kg-1, and corresponds to "average" according to Ya.P. Piarnat's criteria. Conclusions: A high relative fat content negatively affects the functional capabilities of the body of young males in both aerobic and anaerobic modes of energy supply. With the growth in the relative content of skeletal muscles, the increase of the aerobic capacity of the body, as well as the growth of the capacity of alactic and lactic energy supply processes is observed. None of the examined males had "good" or "excellent" parameters of aerobic processes.

G-Reactor at Micro-Plan

The stirrer reactor govern the industrial pharmaceutical productions up to the present, however the complex transmission systems may increase the costs exponentially with the power rates and the hermetic rector sealing. G-reactor improves the analogous reactors with simple pneumatic power device to heavy duty performances at high technological risks by pathogens and per substitution of complex transmissions by own-design; a single compression unit produces the sterile air to the power input of micro-plants and the oxygen of aerobic processes; important economic technical profits is foreseen; microplants distinguishes by small installations for compressed air and the services with overall automatic control available; the reliable performance for the human health, variable speed and standard impeller system, simple sterilization, safe sampling and supplies, foam-breaks to avoiding chemicals and simple automatic flow control distinguish the installations. The mathematical simulation of G-reactor performances to the mixing operations at gas-liquid systems to mass-transfer is shown; a solved example to a specific process illustrates the calculus fundamentals; the software enables the calculus of consumption parameters to the reactor scale-up and micro-plants of maximum capacity; the descriptive data analysis is discussed for the primary technical evaluations and general conclusions. The innovation is proposed for the small production scale of drugs and the unit operations of the chemical industry; a brief technical description of micro-plants and the production of sterile air may lead to the process engineering and the preliminary analysis of costs. The prophylactic treatment of the residual gas flow is shown.

FACTORS THAT ENSURE AN ADEQUATE LEVEL OF PHYSICAL FITNESS IN FEMALE STUDENTS OF HIGHER EDUCATION INSTITUTIONS

The article discusses the factors that ensure the appropriate level. It was determined that physical capacity is the maximum mechanical work that a person is able to perform. Assessment of a person's physical capacity is necessary for solving a wide range of practical problems: determining the state of health, the results of sports training, and others.
 It has been proven that physical performance depends on many factors: body composition and anthropometric indicators, muscle strength and endurance, the state of the musculoskeletal system, functional and endocrine systems. Factors such as energy potential, completeness of its use and cost-effectiveness of movements are also important. It has been established that work capacity is ensured by both aerobic and anaerobic processes of energy generation, and according to the preference of one of them, aerobic physical work capacity, anaerobic and mixed are distinguished.
 Despite the fact that the indicators of physical development of student youth show positive dynamics, the general state of health of modern youth is deteriorating, which negatively affects their physical and mental capacity. The most acute social problem in Ukraine is the deterioration of the health of children and youth. Negative factors that reduce the level of health are improper nutrition, hypokinesia, psycho-emotional overstrain, and bad habits.
 Effective means of improving not only physical, but also emotional health of a person include aqua fitness. Nowadays, there is no doubt about the possibility of a positive effect of physical exercises in water on the state of physical and mental health, improving the activity of the cardiovascular, respiratory, and hormonal systems and developing the physical qualities of a person.

Characterization of Biofilm Microbiome Formation Developed on Novel 3D-Printed Zeolite Biocarriers during Aerobic and Anaerobic Digestion Processes

Background: Aerobic or anaerobic digestion is involved in treating agricultural and municipal waste, and the addition of biocarriers has been proven to improve them further. We synthesized novel biocarriers utilizing zeolites and different inorganic binders and compared their efficiency with commercially available biocarriers in aerobic and anaerobic digestion systems. Methods: We examined BMP and several physicochemical parameters to characterize the efficiency of novel biocarriers on both systems. We also determined the SMP and EPS content of synthesized biofilm and measured the adherence and size of the forming biofilm. Finally, we characterized the samples by 16S rRNA sequencing to determine the crucial microbial communities involved. Results: Evaluating BMP results, ZSM-5 zeolite with bentonite binder emerged, whereas ZSM-5 zeolite with halloysite nanotubes binder stood out in the wastewater treatment experiment. Twice the relative frequencies of archaea were found on novel biocarriers after being placed in AD batch reactors, and >50% frequencies of Proteobacteria after being placed in WWT reactors, compared to commercial ones. Conclusions: The newly synthesized biocarriers were not only equally efficient with the commercially available ones, but some were even superior as they greatly enhanced aerobic or anaerobic digestion and showed strong biofilm formation and unique microbiome signatures.

Carbon footprint of dairy manure management chains in response to nutrient recovery by aerobic pre-treatment

Aerobic pre-treatment of liquid dairy manure has previously been reported as an effective nutrient export and emissions mitigation approach. The first objective of this study was to experimentally determine the optimal intermittent aeration ratio for nutrient recovery from liquid dairy manure through an on-site pilot-scale reactor to partially reduce the required energy for the aerobic process. The second objective was to theoretically investigate the total carbon footprints of direct manure spreading on croplands and permanent manure storage in open anaerobic lagoons in response to nutrient removal by the optimal determined intermittent aerobic treatment ratio. Four scenarios (S) were included; S1 was the traditional scenario of manure spread on croplands without the aerobic pre-treatment, S2 was the modified scenario of manure spread on croplands that included the aerobic pre-treatment, S3 was the traditional scenario of manure storage in lagoons, and S4 was the modified scenario of manure storage in lagoons that included the aerobic pre-treatment. The results showed that comparable nutrient removal efficiencies could be obtained with a 5:1 intermittent aeration ratio. Total nitrogen (TN) and total phosphorus (TP) were recovered were 41.5 ± 1.3% and 37.0 ± 4.0%, respectively, in ammonium sulfate and phosphorus-rich sludge, while 55.3 ± 1.4% of the chemical oxygen demand (COD) was removed. The estimated total carbon footprint for S1, S2, S3, and S4 were 24.4, 37.9, 45.3, and 45.9 kg CO2-eqton−1, respectively. However, the total carbon footprint of S2′ and S4′, which used renewable-based energy to run the reactor instead of fossil-based energy used in S2 and S4, were estimated to 29.5 and 37.5 kg CO2-eqton−1, respectively. Clearly, applying the aerobic pre-treatment increased the total carbon footprint of all cases except S4′, in which the total carbon footprint was mitigated by −17.2%. Accordingly, the aerobic pre-treatment is only recommended in the case of S4’ from a carbon footprint point of view although it is an effective nutrient recovery technology.

Ethylated analogue of Zingerone: A new and eco-respectful preservative in cosmetics.

This article describes the eco-design of a new preservative in cosmetics based on bio-inspiration of natural extracts from traditional medicines. In order to reach the multiple specification targets, various structures have been synthesized and evaluated to select the one demonstrating broad antimicrobial spectrum with favorable environmental profile and application potential to a wide variety of formulas. In order to evaluate the antimicrobial activity of the synthesized structures, the method of the challenge test consisting in an artificial contamination of the sample with collection microbial strains and evaluation of the number of revivable microorganisms was used to select the most promising candidate. Validation of its antimicrobial potential was later confirmed on Gram positive and Gram negative bacteria, yeast and mold with measurement of its Minimum Inhibitory Concentration (MIC) in comparison with known preservatives. Environmental impact assessment of the selected candidate was achieved with the help of ready biodegradability and aquatic ecotoxicity tests performed according to appropriate Organization tes a strfor Economic Co-operation and Development (OECD) and European Union (EU) guidelinesy. Bio-inspired from turmeric and ginger extracts, an ethylated analog of Zingerone (EZ) with the chemical name 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one demonstrates the strongest activity on Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa and Candida albicans. Moreover, EZ shows a solubility in water two times higher than that of Zingerone thus increasing its interest as a potential preservative. Finally, its assessment of ready biodegradability and aquatic ecotoxicity in OECD-EU tests with a favorable environmental profile confirms its unique interest and fully justifies its use in cosmetic formulas as an eco-respectful preservative. Bio-inspiration based on technologies without noteworthy side effects but also on eco-design, particularly through the use of measures of potential environmental impact very upstream of a development, are two fundamental elements for the launching of new eco-friendly cosmetic ingredients. This approach has thus validated the strong potential of EZ as a preservative of eco-respectful formulas. The selection of EZ is also a very good example of the achievement of two key objectives targeted by cosmetic companies for the development of a novel active ingredient: environmental performance and technical performance.

Integrated bioprocess of microbial lipids production in Yarrowia lipolytica using food-waste derived volatile fatty acids

The ability of Yarrowia lipolytica to assimilate volatile fatty acids (VFAs) generated during the acidogenic fermentation of food waste (FW) and to accumulate intracellular lipids was investigated in single and two-stage batch (TSC) cultures. The TSC strategy, where the growth phase in FW-derived VFAs was followed by the lipogenic phase in crude glycerol resulted in a 10-fold improvement of intracellular lipids accumulation comparatively to the single batch culture. The biotechnological process proposed herein is a reliable and sustainable option for the combined valorization of food waste - via production of VFAs by acidogenesis - and crude glycerol. The integration of an anaerobic and aerobic process generates a value chain from wastes and by-products to microbial lipids production. Furthermore, microbial lipids produced by Y. lipolytica NCYC 2904 from FW-derived VFAs and crude glycerol have a composition similar to vegetable oils (C16–C18 fatty acids), making them suitable feedstocks for the biodiesel industry.

Comparative analysis of floc characteristics and microbial communities in anoxic and aerobic suspended growth processes.

A fully anoxic suspended growth process is an appealing alternative to conventional activated sludge (AS) due to considerable aeration reduction and improved carbon processing efficiency for biological nutrient removal (BNR). With development of the hybrid membrane aerated biofilm reactor (MABR) technology, implementation of a fully anoxic suspended growth community in BNR facilities became practical. To better understand potential limitations with the elimination of aeration, we carried out microscopic examination and 16S rRNA gene-based microbial community profiling to determine how an anoxic suspended growth would differ from the conventional aerobic process in floc characteristics, microbial diversity, microbial temporal dynamics, and community assembly pattern. Fewer filamentous populations were found in the anoxic mixed liquor, suggesting easily sheared flocs. The anoxic microbial community had distinct composition and structure, but its diversity and temporal dynamics were similar to the conventional aerobic community. A variety of well-studied functional guilds were also identified in the anoxic community. The anoxic microbial community assembly was more stochastic than the conventional aerobic community, but deterministic assembly was still significant with a large core microbiome adapted to the anoxic condition. PRACTITIONER POINTS: Flocs developed under the anoxic conditions had less filamentous backbones, implying reduced flocculation capacity and easily sheared flocs. Knowledge about the ecophysiology of Thauera, Thiothrix, and Trichococcus can help achieve good properties of the anoxic flocs. A diverse microbial community sustainably adapted to the fully anoxic condition, containing a variety of filaments, denitrifiers, and PAOs. The anoxic microbial community displayed a similar degree of diversity and temporal dynamics compared to the aerobic counterpart. The anoxic community's assembly was more stochastic, so it may be less subject to changes in environmental variables.

The Dynamic Shift of Bacterial Communities in Hybrid Anaerobic Baffled Reactor (ABR)—Aerobic Granules Process for Berberine Pharmaceutical Wastewater Treatment

Because of its anticancer, anti-inflammatory, and antibiotic properties, berberine has been used extensively in medication. The extensive production of berberine results in the generation of wastewater containing concentrated residual berberine. However, to date, limited related studies on the biological treatment of berberine wastewaters have been carried out. A lab-scale anaerobic baffled reactor (ABR)–aerobic granular sludge (AGS) process was developed for berberine removal from synthetic wastewater. The system showed effective removal of the berberine. In order to better understand the roles of the bacterial community, the ABR–aerobic granular sludge system was operated in the state with the highest BBR removal rate in this study. The bacterial community dynamics were studied using the 16S rDNA clone library. The results showed that the hybrid ABR-AGS process achieved 92.2% and 94.8% overall removals of berberine and COD, respectively. Bacterium was dominant species in ABR, while the CFB group bacteria and Betaproteobacteria were dominant species in AGS process. The uncultured bacterium clone B135, Bacillus endophyticus strain a125, uncultured bacterium mle1-42, uncultured bacterium clone OP10D15, and uncultured bacterium clone B21.29F54 in ABR, and uncultured bacterium clone F54, uncultured bacterium clone ZBAF1-105, uncultured bacterium clone SS-9, and uncultured bacterium clone B13 in AGS process were identified as functional species in the biodegradation of berberine and/or its metabolites. Both anaerobic and aerobic bacterial communities could adapt appropriately to different berberine selection pressures because the functional species’ identical functions ensured comparable pollutant removal performances. The information provided in this study may help with future research in gaining a better understanding of berberine biodegradation.

Predicting the impact of temperature on metabolic fluxes using resource allocation modelling: Application to polyphosphate accumulating organisms

The understanding of microbial communities and the biological regulation of its members is crucial for implementation of novel technologies using microbial ecology. One poorly understood metabolic principle of microbial communities is resource allocation and biosynthesis. Resource allocation theory in polyphosphate accumulating organisms (PAOs) is limited as a result of their slow imposed growth rate (typical sludge retention times of at least 4 days) and limitations to quantify changes in biomass components over a 6 hours cycle (less than 10% of their growth). As a result, there is no direct evidence supporting that biosynthesis is an exclusive aerobic process in PAOs that alternate continuously between anaerobic and aerobic phases. Here, we apply resource allocation metabolic flux analysis to study the optimal phenotype of PAOs over a temperature range of 4 °C to 20 °C. The model applied in this research allowed to identify optimal metabolic strategies in a core metabolic model with limited constraints based on biological principles. The addition of a constraint limiting biomass synthesis to be an exclusive aerobic process changed the metabolic behaviour and improved the predictability of the model over the studied temperature range by closing the gap between prediction and experimental findings. The results validate the assumption of limited anaerobic biosynthesis in PAOs, specifically “Candidatus Accumulibacter” related species. Interestingly, the predicted growth yield was lower, suggesting that there are mechanistic barriers for anaerobic growth not yet understood nor reflected in the current models of PAOs. Moreover, we identified strategies of resource allocation applied by PAOs at different temperatures as a result of the decreased catalytic efficiencies of their biochemical reactions. Understanding resource allocation is paramount in the study of PAOs and their currently unknown complex metabolic regulation, and metabolic modelling based on biological first principles provides a useful tool to develop a mechanistic understanding.