Green Alga Desmodesmus Research Articles

Mitigating Effect of Trans-Zeatin on Cadmium Toxicity in Desmodesmus armatus.

Phytohormones, particularly cytokinin trans-zeatin (tZ), were studied for their impact on the green alga Desmodesmus armatus under cadmium (Cd) stress, focusing on growth, metal accumulation, and stress response mechanisms. Using atomic absorption spectroscopy for the Cd level and high-performance liquid chromatography for photosynthetic pigments and phytochelatins, along with spectrophotometry for antioxidants and liquid chromatography-mass spectrometry for phytohormones, we found that tZ enhances Cd uptake in D. armatus, potentially improving phycoremediation of aquatic environments. Cytokinin mitigates Cd toxicity by regulating internal phytohormone levels and activating metal tolerance pathways, increasing phytochelatin synthase activity and phytochelatin accumulation essential for Cd sequestration. Treatment with tZ and Cd also resulted in increased cell proliferation, photosynthetic pigment and antioxidant levels, and antioxidant enzyme activities, reducing oxidative stress. This suggests that cytokinin-mediated mechanisms in D. armatus enhance its capacity for Cd uptake and tolerance, offering promising avenues for more effective aquatic phycoremediation techniques.

Study of spectral lines behaviour with a double pulse 1064–1064 nm laser-induced breakdown spectroscopy system at the direct analysis of algae on the filter

The nickel and zinc contamination of algae on a cellulose filter was studied with double pulse 1064–1064 nm laser-induced breakdown spectroscopy (LIBS). Samples of the green alga Desmodesmus subspicatus were contaminated with zinc and nickel. The surface concentrations on the filter calculated from the reference Inductively Coupled Plasma Mass Spectrometry analysis were 25 and 64 ng cm−2 for nickel and zinc respectively. The algae are resting on the filter after drying and a double adhesive tape was used to fix the sample on the microscopic glass. During optimization method a compromise of 23–30 mJ pulse energies were set for maintaining a detectable or highest signal intensity of the analyte and not destroying the filter. Best conditions for maximum analyte signal and minimum deviation between the spectral behaviour of the analyte and the compared line of Na I, K I, Mg I, Mg II, Mn I, Mn II, Ca I, Ca II, and C I was 700 ns gate delay and 0 s interpulse delay. The deviation was rather more influenced with the signal-to-noise ratio of the analyte line than the closeness of the upper-level energies of the compared lines. The filter without algae showed systematically lower electron number density and total emissivity by units of percents than the filter with algae.

Study of bioaccumulation of Cr, Ni and Zn by the green alga Desmodesmus subspicatus and assessment of the toxic effect of selected elements and their mixtures on algae cells

Toxicity assessment of K2Cr2O7, ZnCl2 and NiCl2.6H2O focusing on the green unicellular alga Desmodesmus subspicatus showed that Ni was the most toxic (EC50 = 0.121 mg L−1), followed by Cr (EC50 = 0.357 mg L−1) and Zn (EC50 = 0.968 mg L−1). The alga was exposed to solutions of the individual metals and their mixtures (Zn + Ni, Zn + Ni + Cr). After 48, 72 and 96 h of exposure, the accumulation of Zn, Ni and Cr in algal cells was assessed. Moreover, the change in toxicity of the metals, the concentration of selected biogenic elements (Ca, Na, Mg, S, K, P, Mn) in algal cells and the rate of metal removal from the solutions were also analysed. In the case of single-metal solutions, for Zn and Cr, the toxicity and accumulation in algal cells decreased over the 96 h of the experiment, whereas for Ni as well as for the binary and ternary mixtures the toxicity and accumulation increased. Significant correlations between the amount of metals accumulated in the cells and the inhibition of growth rates were observed. The content of selected biogenic elements in algal cells decreased over time in all treatments with added metals as well as in the control group, and after 96 h was higher in all treatments with addition of Ni compared to the control group and single-metal solutions of Zn and Cr. The highest removal of the metal from the solution occurred in the case of the single metal solution of Zn, where 83.4% of Zn was removed from the solution in 96 h.

The algal microbiome protects Desmodesmus intermedius from high light and temperature stress

The mutualistic impacts of bacterial communities on algal growth and biomass accumulation are well documented, but it is unknown how temperature and light stress influence these mutualistic interactions. Here, we generated a bacteria-free (axenic) culture of the green alga Desmodesmus intermedius C046 and compared its growth and yield in the laboratory to its native xenic counterpart - featuring a microbiome that has been maintained with its algal host for at least 5 years – under unstressed and high light, high temperature stress conditions. We then added exogenous microbiomes from high light marine environments to the axenic culture to quantify the contribution of these newly generated microbial consortia in improving D. intermedius growth, yield, and resilience to high light and heat. The native microbiome increased growth and biomass accumulation, under both unstressed and stressed conditions. Three of the five newly derived microbiomes had increased growth compared to the axenic and negligible, decreased, or increased growth impacts compared to the xenic culture. Stress conditions led to decreased algal exudation, larger algal cells when grown alone, but smaller algal cells with an associated microbiome. Our results suggest that the algal microbiome plays a role in microalgal response to heat and light stress, and efforts for screening new algal strains for high biomass productivity under those stress conditions should include a strategy for microbiome optimization.

Growth characteristics and fatty acids of the thermotolerant green alga <i>Desmodesmus</i> sp. isolated from a freshwater puddle in Ibaraki, Japan

We investigated the growth, thermotolerance, and fatty acid composition of the green alga Desmodesmus sp., which was isolated from a freshwater puddle in Ibaraki, Japan. Incubation experiments on the isolated strain were performed at a range of temperatures (20–40°C) with continuous illumination (110 µmol photons m−2 s−1) and nutrient-replete medium. High specific growth rates of 1.14–1.62 day−1 were observed at 20–35°C, but growth rates declined to 0.59 day−1 at 40°C. Lipid contents were 13.2%–14.4% (% dry weight) at 20–35°C and increased to 21.3% at 40°C. Some microalgae are known to regulate membrane fluidity by changing their fatty acid compositions in response to changes in ambient temperature. We found that the major polyunsaturated fatty acid (PUFA; C18:3 ω3) of Desmodesmus sp. was negatively correlated with water temperature. By contrast, no significant relationship was identified between temperature and the ratio of saturated to unsaturated fatty acids. The negative relationship between ω3 PUFA composition and temperature was stronger among thermotolerant as opposed to non-thermotolerant microalgae. This suggests that thermotolerant Desmodesmus sp. can grow at high temperatures by altering its fatty acid composition to affect membrane fluidity.

Feasibility of direct analysis of algae contamination with chromium and copper on the filter with laser-induced breakdown spectroscopy and laser ablation inductively coupled plasma mass spectrometry

The chromium and copper contamination of algae on a filter was directly monitored with laser-induced breakdown spectroscopy (LIBS) as a demonstration of LIBS capabilities. Liquid samples of the green alga Desmodesmus subspicatus were intentionally contaminated with chromium, incubated, filtered, and the filters with the algae were analysed. Inductively coupled plasma mass spectrometry (ICP-MS) was used as a reference method. One half of the filter with the algae was dissolved and analysed as a solution with ICP-MS and the second half was subjected to the LIBS and laser ablation-ICP-MS analysis. Chromium and copper were attributable to the algae contamination and detectable with LIBS. The results from the LIBS provided almost equivalent information about the relative changes of the Cr and Cu concentration in the algae. The sensitivity of LIBS with a Czerny-Turner spectrometer was fully comparable with the ICP-MS procedure. The trends from LIBS were more similar to the LA-ICP-MS ones. It means that the algae growth inhibition in dependence on the chromium or copper content can be alternatively monitored with LIBS instead of the complicated decomposition procedure in ICP-MS analysis.

The specificity of changes in key performance indicators of green algae of the family Scenedesmaceae under the influence of cerium

The effect of various concentrations (1 μM – 100 mM) of citrate-stabilized cerium dioxide nanoparticles or cerium ions (3+) on the biomass production of two species of unicellular green algae Desmodesmus armatus (Chod.) Hegew and Acutodesmus dimorphus (Turpin) Tsarenko was studied, the amount of chlorophyll, proteins and lipids in the algae biomass was determined. It was shown that at the concentrations of 0.01 M to 0.1 M nanoparticles and cerium salt have pronounced toxic effects on the algal cultures, manifested by a sharp increase in the level of lipids in the biomass combined with the decrease in chlorophyll and protein. At lower concentrations, cerium dioxide nanoparticles stimulate algae biomass accumulation, probably due to a change in key metabolic pathways, accompanied by an increase in the accumulation of carbohydrates in the biomass. For cerium salt, these effects are less pronounced. Thus, depending on the concentration of the objects used, it is possible to obtain an increase in the food biomass production enriched with lipids or carbohydrates as appropriate to the biotechnological objectives.

Evaluation of toxicity and bioaccumulation of metals from transport and their effect on the mineral composition of green alga Desmodesmus subspicatus using ICP MS/MS

Evaluation of toxicity and bioaccumulation of metals from transport and their effect on the mineral composition of green alga Desmodesmus subspicatus using ICP MS/MS

Observations of a Desmodesmus (Chodat) S.S. Ann, Friedl & E. Hegewald (Sphaeropleales, Chlorophyta) and two Didymocystis Korshikov (Chlorellales, Chlorophyta) in Lake Tanganyika

The occurrence of three species belonging to the small coenobia forming green algae Desmodesmus and Didymocystis is reported from the northernmost part of Lake Tanganyika, East Africa. During a monitoring between September 2011 and October 2013 the highest number of cells of Desmodesmus bicellularis and Didymocystis comasii were observed in August and September, at the end of the dry season. On the other hand, the third taxon, Didymocystis cf. inermis, was only sporadically observed between September 2011 and March 2012. According to existing databases, it should be the first records from Africa of these three species. However, D. bicellularis (as Didymocystis bicellularis) was already reported in 2003 in phytoplankton samples of the pelagic zone from more southern located places in Lake Tanganyika.

A Chlorophyte Alga Utilizes Alternative Electron Transport for Primary Photoprotection.

The green alga Desmodesmus armatus is an emerging biofuel platform that produces high amounts of lipids and biomass in mass culture. We observed D. armatus in light-limiting, excess-light, and sinusoidal-light environments to investigate its photoacclimation behaviors and the mechanisms by which it dissipates excess energy. Chlorophyll a/b ratios and the functional absorption cross section of PSII suggested a constitutively small light-harvesting antenna size relative to other green algae. In situ and ex situ measurements of photo-physiology revealed that nonphotochemical quenching is not a significant contributor to photoprotection; however, cells do not suffer substantial photoinhibition despite its near absence. We performed membrane inlet mass spectrometry analysis to show that D. armatus has a very high capacity for alternative electron transport (AET) measured as light-dependent oxygen consumption. Up to 90% of electrons generated at PSII can be dissipated by AET in a water-water cycle during growth in rapidly fluctuating light environments, like those found in industrial-scale photobioreactors. This work highlights the diversity of photoprotective mechanisms present in algal systems, indicating that nonphotochemical quenching is not necessarily required for effective photoprotection in some algae, and suggests that engineering AET may be an attractive target for increasing the biomass productivity of some strains.

Selective grazing behaviour of chironomids on microalgae under pesticide pressure

The herbicide diuron and the insecticide imidacloprid are amongst the most frequently detected pesticides in French rivers, and each is known to affect many aquatic organisms. However, the question of whether and how both pesticides together might induce multi-stress conditions, which could induce indirect effects such as the modification of biological interactions within freshwater microbial communities has not received much attention. This study was undertaken to determine the effect of diuron and imidacloprid alone and in combination on the feeding behaviour of chironomid larvae.An initial experiment measured the impact of the different contamination conditions at environmental concentrations (5 μg L−1 for each pesticide) on the grazing rate of chironomids on three microalgae species, independently. Two diatom species, Gomphonema gracile (two different morphotypes: normal and teratogen) and Planothidium lanceolatum, and one green alga Desmodesmus sp. were offered as food, during 24 h. Chironomids grazing rates varied according to the pesticide and algae species. Indeed, diuron impacted algae more strongly and probably affected their palatability, leading chironomids to increase grazing pressure on less nutritionally interesting algae. Imidacloprid, by targeting insect larvae, increased or inhibited their grazing capacity depending on the food source.In a second experiment (cafeteria design), the food selectivity of chironomids on previous algae was determined under similar contamination conditions during 4 h: under diuron, larvae switched equally between the microalgae and were as mobile as in the control without pesticide. However, imidacloprid and the pesticide mixture condition altered chironomid movements and grazing behaviour.By investigating the impact of an herbicide and an insecticide, alone and in combination, on the responses of food (algae growth rate) and biological (mortality) and behavioural (mobility, food selection) responses of chironomid larvae, this study provided new insights on the direct and indirect effects of pesticide contamination on a simplified trophic web.

Effects of metal quantity and quality to the removal of zinc and copper by two common green microalgae (Chlorophyceae) species

SUMMARYAppearance of metals as pollutants in the environment is an increasing global problem. Microalgae as subjects of biological remediation methods may provide a cost‐effective and environmentally friendly alternative to the removal of metals during wastewater treatment. Despite the high number of data in the topic, there is still little information on how the type and the concentration of the metal affect the process of removal. In this study, correlations among the algal species, quality and quantity of metals and characteristics of metal removal mechanism were investigated at lower metal concentrations (0.2–5.0 mg L−1) during zinc and copper removal of the green algae Desmodesmus communis and Monoraphidium pusillum. Analyses of the results proved that there is a statistically significant interaction (P < 0.05) between algal species and quality and concentration of the metals, that is, they have a significant effect on the mode and extent of removal. Both metals were mainly extracellularly bound, but at concentrations of 0.2–1.4 mg L−1, intracellular proportion could exceed the extracellular adsorption. Although there were differences between the two algae, generally copper appeared in a higher intracellular proportion than zinc in the whole studied concentration range. Overall, the quality and initial concentration of the metal is decisive for the way of removal, the knowledge of which is useful for planning post treatment retention times or post treatment processes of the used biomass during wastewater treatment.

Effects of Copper and pH on the Growth and Physiology of Desmodesmus sp. AARLG074.

Copper (Cu) is a heavy metal that is widely used in industry and as such wastewater from mining or industrial operations can contain high levels of Cu. Some aquatic algal species can tolerate and bioaccumulate Cu and so could play a key role in bioremediating and recovering Cu from polluted waterways. One such species is the green alga Desmodesmus sp. AARLG074. The aim of this study was to determine how Desmodesmus is able to tolerate large alterations in its external Cu and pH environment. Specifically, we set out to measure the variations in the Cu removal efficiency, growth, ultrastructure, and cellular metabolite content in the algal cells that are associated with Cu exposure and acidity. The results showed that Desmodesmus could remove up to 80% of the copper presented in Jaworski’s medium after 30 min exposure. There was a decrease in the ability of Cu removal at pH 4 compared to pH 6 indicating both pH and Cu concentration affected the efficiency of Cu removal. Furthermore, Cu had an adverse effect on algal growth and caused ultrastructural changes. Metabolite fingerprinting (FT-IR and GC-MS) revealed that the polysaccharide and amino acid content were the main metabolites affected under acid and Cu exposure. Fructose, lactose and sorbose contents significantly decreased under both acidic and Cu conditions, whilst glycerol and melezitose contents significantly increased at pH 4. The pathway analysis showed that pH had the highest impact score on alanine, aspartate and glutamate metabolism whereas Cu had the highest impact on arginine and proline metabolism. Notably both Cu and pH had impact on glutathione and galactose metabolism.

Assimilation of inorganic nitrogen for scaling up Desmodesmus communis (Scenedesmaceae) biomass production

The feasibility of the green alga Desmodesmus communis for biomass production was investigated, firstly testing different nitrogen forms in the growth medium and the effect of CO2-enriched air supply, secondarily scaling up the cultivation system in 70 L photobioreactors (PBRs). Maximum nitrogen uptake rate obtained in the performed kinetic experiment was higher for ammonium than for nitrate (188.0 vs 11.7 μmol g−1 h−1); however, D. communis cultured in PBRs with only aeration grew faster with nitrate reaching a biomass yield (1.23 g L−1) and a productivity (0.036 g L−1 day−1) about twofold higher than with ammonium, which caused a pH decrease in the medium affecting the algal growth. CO2 supply allowed algal growth optimization, maintaining a high productivity with both nitrogen sources, slightly higher with nitrate (0.050 vs 0.038 g L−1 day−1). Additionally, nitrate-supplied cells showed higher lipids (19.0 vs 9.4%) and proteins (33.0 vs 27.2%) values than those grown with ammonium. The semi-continuous scaled-up cultivation performed for 5 months attests the potential utilization of this species for valuable algal biomass production exploitable in various industrial applications.

Effects of herbicide mixtures on freshwater microalgae with the potential effect of a safener

Freshwater microalgae are primary producers and cosmopolitan species subjected to the effects of herbicides. In this work, thein vitroalgal growth inhibitory effects of 11 agrochemicals (9 herbicides, 1 metabolite, and 1 safener) were quantified. Chemical compounds were applied singly and in specific mixtures. Three species were used in axenic condition: the green algaDesmodesmus subspicatus(Chodat), the diatomsNitzschia palea(Kützing) W. Smith andNavicula pelliculosa(Kützing) Hilse. When exposed to single compounds,N. paleaandN. pelliculosawere only sensitive to atrazine/desethylatrazine and the safener benoxacor (BE), respectively.D. subspicatuswas equally sensitive to four herbicides including atrazine and its metabolite and significantly more sensitive to iodosulfuron-methyl-sodium (IODO). The mixture of these five compounds induced a significantly higher growth inhibition of about 1.5-fold than IODO alone, which could be attributed to the four other herbicides. The mixture of all compounds was twofold less toxic than IODO onD. subspicatus. A halogen atom is present in IODO as in the herbicides to which the safener BE − known to induce glutathione-S-transferases − is associated in agrochemical preparations. We then showed that IODO was less toxic when combined with non-toxic concentrations of BE. These results indicated that the toxicity of the most active herbicide studied was decreased by a non-herbicide compound present in agrochemical formulations of other herbicides. These results suggest the importance to take into account the chemistry and the mechanisms of action for each compound in a risk assessment approach of a complex mixture.

Indole-3-acetic-acid-induced phenotypic plasticity in Desmodesmus algae

Phenotypic plasticity is the ability of a single genotype of an organism to exhibit variable phenotypes in response to fluctuating environments. It plays a crucial role in their evolutionary success. In natural environments, the importance of interactions between microalgae and other microorganisms is generally well appreciated, but the effects of these interactions on algal phenotypic plasticity has not been investigated. In this study, it revealed that indole-3-acetic acid (IAA), the most common naturally occurring plant hormone, can exert stimulatory at low concentrations and inhibitory effects at high concentrations on the growth of the green alga Desmodesmus. The morphological characteristics of Desmodesmus changed drastically under exposure to IAA compared with the algae in the control environment. The proportion of Desmodesmus unicells in monocultures increased with the IAA concentration, and these unicells exhibited less possibility of sedimentation than large cells. Furthermore, we discovered that lipid droplets accumulated in algal cells grown at a high IAA concentration. Results also demonstrated that the presence of algal competitor further stimulated inducible morphological changes in Desmodesmus populations. The relative abundance of competitors influenced the proportion of induced morphological changes. The results indicate that phenotypic plasticity in microalgae can be a response to fluctuating environments, in which algae optimize the cost–benefit ratio.

The artificial humic substance HS1500 does not inhibit photosynthesis of the green alga Desmodesmus armatus in vivo but interacts with the photosynthetic apparatus of isolated spinach thylakoids in vitro.

Humic substances (HSs) can influence the growth and composition of freshwater phytoplankton assemblage. Since HSs contain many phenolic and quinonic moieties and cause growth reductions in eco-physiological field experiments, HSs are considered photosystem II herbicides. To test this specific mode of action in vivo and in vitro, respectively, we used intact cells of the green alga Desmodesmus armatus, as well as thylakoids isolated from spinach (Spinacia oleracea) as a model system for the green algal chloroplast. Photosynthetic electron transport was measured as oxygen evolution and variable chlorophyll fluorescence. The in vivo effect of the artificial humic substance HS1500 on algae consisted of no impact on photosynthesis-irradiance curves of intact green algae compared to untreated controls. In contrast, addition of HS1500 to isolated thylakoids resulted in light-induced oxygen consumption (Mehler reaction) as an in vitro effect. Fluorescence induction kinetics of HS-treated thylakoids revealed a large static quenching effect of HS1500, but no inhibitory effect on electron transport. For the case of intact algal cells, we conclude that the highly hydrophilic and rather large molecules of HS1500 are not taken up in effective quantities and, therefore, cannot interfere with photosynthesis. The in vitro tests show that HS1500 has no inhibitory effect on photosystem II but operates as a weak, oxygen-consuming Hill acceptor at photosystem I. Hence, the results indicate that eco-physiological field experiments should focus more strongly on effects of HSs on extracellular features, such as reducing and red-shifting the underwater light field or influencing nutrient availability by cation exchange within the plankton network.

Perfluoroalkyl phosphonic acids adsorption behaviour and removal by wastewater organisms

In this study we have experimentally assessed different physicochemical parameters such as the distribution constant between octanol – water and between water and sludge for three perfluoroakyl substances (PFASs) widely used in waxes and coating materials: perfluorohexane (PFHxPA), perfluorooctane (PFOPA) and perfluorodecane (PFDPA) phosphonic acids. Distribution coefficients were assessed based on the procedures described in the OECD guideline 123 for partition coefficients while the studies of adsorption-desorption in sludge based on the indirect method of the OECD guideline 106. Besides, the removal behaviour of selected compounds has been evaluated using the green algae Desmodesmus subspicatus and microorganisms present in an effluent wastewater. These last experiments were carried out using laboratory scale bioreactors under aerobic conditions according to the OECD guideline 309. The main results of this study showed the resistance to biodegradation of selected compounds by both treatments, <5% was eliminated using D. subspicatus and similar results were obtained by aerobic degradation with wastewater microorganisms. However, it was observed that PFDPA induced changes in algae colour while it was detected to be accumulated in a floccula generated by the microorganisms present in wastewater. According to distribution coefficients the three compounds have values of logDow below 3, indicating their capability to be present in both phases. Finally, the results of the adsorption/desorption experiments showed that PFOPA and PFDPA reach the equilibrium after 10 days of contact with a sorption percentage higher than 40% and 70%, respectively.

Iterative screening of an evolutionary engineered Desmodesmus generates robust field strains with pesticide tolerance

Microalgae hold remarkable promise to produce food, fuel, and nutraceuticals. To satisfy industrial economics, microalgae are commonly cultivated outdoors in open ponds that are subject to invasions by a suite of pests including predators, competitors, and parasites. Although pests can be mitigated and/or controlled by biocides or pesticides, therapeutic doses of these chemicals often adversely affect the productivity and yield of the target crop. To combat this tradeoff imposed by pesticide treatment, if pesticides are to be used, robust strains with increased pesticide tolerance must be developed and validated for growth at commercial scales. In this study, we evolutionarily engineered strains of the green algae Desmodesmus armatus to tolerate treatment with Omega 500F®, a broad-spectrum agricultural fungicide that is used to treat pest invasions in open, outdoor microalgal ponds. An algal clone library generated through UV mutagenesis was screened for strains that exhibited the greatest growth rates under batch and semi-continuous culture in the lab with and without exposure to Omega. We then screened strains at increasing spatial (i.e., from 96-well plates to 33,000 L raceways) and temporal (i.e., from 5 days to months) scales to select for those strains that were most robust. Our process resulted in the cultivation of two robust field strains that demonstrated tolerance to repetitive dosing with Omega without apparent trade-offs in productivity. This work highlights the utility of non-GM methods, specifically UV mutagenesis, to improve cultivation strains for the production of biomass and bioproducts from microalgae. Moreover, it demonstrates the importance of iterative validation steps in facilitating a successful lab to field transition of engineered strains.

Immobilized microalgae for nutrient recovery from source-separated human urine

Shortages in nutrients and freshwater for a growing population are critical global issues. Source separation of waste streams combined with decentralized resource recovery is a promising approach to address this problem. Urine contains within 1% of household wastewater up to 80% of nitrogen (N) and 50% of phosphorus (P). Since microalgae are efficient at nutrient uptake, growing them in urine is a promising technology to clean urine and produce biomass as fertilizer. The aim of this study was to develop a process for nutrient recovery from minimally diluted human urine using immobilized cultivation of microalgae on porous substrate photobioreactors (PSBRs). Treatment of urine, unamended except for a 1:1 dilution with tap water, was performed with the green alga Desmodesmus abundans, chosen among 96 algal strains derived from urine-specific enrichments and culture collections. A growth rate of 7.2 g dry weight m−2 day−1 and removal efficiencies for N and P of 13.1 and 94.1% were determined. Pre-treatment of urine with activated carbon was found to eliminate potentially detrimental effects of pharmaceuticals. In combination with other technologies, PSBRs could be applied in decentralized resource recovery systems, helping to close the link between sanitation and food production.