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Carbon capture and storage is essential to achieve the goals of the Paris Agreement. Photosynthesis is nature’s technology for capturing carbon. Drawing inspiration from lichens, we developed a 3D cyanobacteria photosynthetic biocomposite (i.e. mimicking lichen) using an acrylic latex polymer applied to a loofah sponge. The rate of CO2 uptake by the biocomposite was 1.57 ± 0.08 g CO2 g-1 of biomass d-1. The uptake rate is based on dry biomass at the beginning of the experiment and includes CO2 used to grow new biomass as well as CO2 contained in storage compounds such as carbohydrates. These uptake rates were 14-20 times higher than slurry control measures and could potentially be scaled up to capture 570 t CO2 t-1 biomass per year-1, equivalent to 5.5-8.17 × 106 hectares of land use , removing 8-12 GtCO2 CO2 per year. In contrast, forest bioenergy with carbon capture and storage is 0.4–1.2 × 109 ha. The biocomposite remained functional for 12 weeks without additional nutrients or water, after which the experiment was terminated. Within humanity’s multi-faceted technological stance to combat climate change, engineered and optimized cyanobacterial biocomposites have the potential for sustainable and scalable deployment to increase CO2 removal while reducing water, nutrient and land use losses.
Climate change is a real threat to global biodiversity, ecosystem stability and people. To mitigate its worst effects, coordinated and large-scale decarburization programs are needed, and, of course, some form of direct removal of greenhouse gases from the atmosphere is required. Despite positive decarbonization of electricity generation2,3, there are currently no economically sustainable technological solutions to reduce atmospheric carbon dioxide (CO2)4, although flue gas capture is progressing5. Instead of scalable and practical engineering solutions, people should turn to natural engineers for carbon capture – photosynthetic organisms (phototrophic organisms). Photosynthesis is nature’s carbon sequestration technology, but its ability to reverse anthropogenic carbon enrichment on meaningful time scales is questionable, enzymes are inefficient, and its ability to deploy at appropriate scales is questionable. A potential avenue for phototrophy is afforestation, which cuts trees for bioenergy with carbon capture and storage (BECCS) as a negative-emissions technology that can help reduce net CO21 emissions. However, to achieve the Paris Agreement temperature target of 1.5°C using BECCS as the main method would require 0.4 to 1.2 × 109 ha, equivalent to 25–75% of the current global arable land6. In addition, the uncertainty associated with the global effects of CO2 fertilization calls into question the potential overall efficiency of forest plantations7. If we are to reach the temperature targets set by the Paris Agreement, 100 seconds of GtCO2 of greenhouse gases (GGR) must be removed from the atmosphere each year. The UK Department of Research and Innovation recently announced funding for five GGR8 projects including peatland management, enhanced rock weathering, tree planting, biochar and perennial crops to feed the BECCS process. The costs of removing more than 130 MtCO2 from the atmosphere per year are 10-100 US$/tCO2, 0.2-8.1 MtCO2 per year for peatland restoration, 52-480 US$/tCO2 and 12-27 MtCO2 per year for weathering of rocks, 0.4-30 USD/year. tCO2, 3.6 MtCO2/yr, 1% increase in forest area, 0.4-30 US$/tCO2, 6-41 MtCO2/yr, biochar, 140-270 US$/tCO2, 20 –70 Mt CO2 per year for permanent crops using BECCS9.
A combination of these approaches could potentially reach the 130 Mt CO2 per year target, but the costs of rock weathering and BECCS are high, and biochar, although relatively cheap and non-land-use related, requires feedstock for the biochar production process. offers this development and number to deploy other GGR technologies.
Instead of looking for solutions on land, look for water, especially single-celled phototrophs such as microalgae and cyanobacteria10. Algae (including cyanobacteria) capture approximately 50% of the world’s carbon dioxide, although they account for only 1% of the world’s biomass11. Cyanobacteria are nature’s original biogeoengineers, laying the foundation for respiratory metabolism and the evolution of multicellular life through oxygenic photosynthesis12. The idea of using cyanobacteria to capture carbon is not new, but innovative methods of physical placement open up new horizons for these ancient organisms.
Open ponds and photobioreactors are default assets when using microalgae and cyanobacteria for industrial purposes. These culture systems use a suspension culture in which cells float freely in a growth medium14; however, ponds and photobioreactors have many disadvantages such as poor CO2 mass transfer, intensive use of land and water, susceptibility to biofouling, and high construction and operation costs15,16. Biofilm bioreactors that do not use suspension cultures are more economical in terms of water and space, but are at risk of desiccation damage, prone to biofilm detachment (and hence loss of active biomass), and are equally prone to biofouling17.
New approaches are needed to increase the rate of CO2 uptake and address the problems that limit slurry and biofilm reactors. One such approach is photosynthetic biocomposites inspired by lichens. Lichens are a complex of fungi and photobionts (microalgae and/or cyanobacteria) that cover approximately 12% of the Earth’s land area18. The fungi provide physical support, protection, and anchoring of the photobiotic substrate, which in turn provide the fungi with carbon (as excess photosynthetic products). The proposed biocomposite is a “lichen mimetic”, in which a concentrated population of cyanobacteria is immobilized in the form of a thin biocoating on a carrier substrate. In addition to cells, the biocoating contains a polymer matrix that can replace the fungus. Water-based polymer emulsions or “latexes” are preferred because they are biocompatible, durable, inexpensive, easy to handle and commercially available19, 20, 21, 22, 23, 24, 25, 26.
The fixation of cells with latex polymers is greatly influenced by the composition of the latex and the process of film formation. Emulsion polymerization is a heterogeneous process used to produce synthetic rubber, adhesive coatings, sealants, concrete additives, paper and textile coatings, and latex paints27. It has a number of advantages over other polymerization methods, such as high reaction rate and monomer conversion efficiency, as well as ease of product control27,28. The choice of monomers depends on the desired properties of the resulting polymer film, and for mixed monomer systems (i.e., copolymerizations), the properties of the polymer can be changed by selecting different ratios of monomers that form the resulting polymer material. Butyl acrylate and styrene are among the most common acrylic latex monomers and are used here. In addition, coalescing agents (eg Texanol) are often used to promote uniform film formation where they can alter the properties of the polymer latex to produce a strong and “continuous” (coalescing) coating. In our initial proof-of-concept study, a high surface area, high porosity 3D biocomposite was fabricated using a commercial latex paint applied to a loofah sponge. After long and continuous manipulations (eight weeks), the biocomposite showed limited ability to retain cyanobacteria on the loofah scaffold because cell growth weakened the structural integrity of the latex. In the current study, we aimed to develop a series of acrylic latex polymers of known chemistry for continuous use in carbon capture applications without sacrificing polymer degradation. In doing so, we have demonstrated the ability to create lichen-like polymer matrix elements that provide improved biological performance and significantly increased mechanical elasticity compared to proven biocomposites. Further optimization will accelerate the uptake of biocomposites for carbon capture, especially when combined with cyanobacteria metabolically modified to enhance CO2 sequestration.
Nine latexes with three polymer formulations (H = “hard”, N = “normal”, S = “soft”) and three types of Texanol (0, 4, 12% v/v) were tested for toxicity and strain correlation. Adhesive. from two cyanobacteria. Latex type significantly influenced S. elongatus PCC 7942 (Shirer-Ray-Hare test, latex: DF=2, H=23.157, P=<0.001) and CCAP 1479/1A (two-way ANOVA, latex: DF=2, F= 103.93, P = < 0.001) (Fig. 1a). The concentration of texanol did not significantly affect the growth of S. elongatus PCC 7942, only N-latex was non-toxic (Fig. 1a), and 0 N and 4 N maintained growth of 26% and 35%, respectively (Mann-Whitney U, 0 N vs. 4 N: W = 13.50, P = 0.245; 0 N versus control: W = 25.0, P = 0.061; 4 N versus control: W = 25.0, P = 0.061) and 12 N maintained growth comparable to biological control (Mann-Whitney University, 12 N vs. control: W = 17.0, P = 0.885). For S. elongatus CCAP 1479/1A, both latex mixture and texanol concentration were important factors, and a significant interaction was observed between the two (two-way ANOVA, latex: DF=2, F=103.93, P=<0.001, Texanol: DF=2, F=5.96, P=0.01, Latex*Texanol: DF=4, F=3.41, P=0.03). 0 N and all “soft” latexes promoted growth (Fig. 1a). There is a tendency to improve growth with decreasing styrene composition.
Toxicity and adhesion testing of cyanobacteria (Synechococcus elongatus PCC 7942 and CCAP 1479/1A) to latex formulations, relationship with glass transition temperature (Tg) and decision matrix based on toxicity and adhesion data. (a) Toxicity testing was performed using separate plots of percentage growth of cyanobacteria normalized to control suspension cultures. Treatments marked with * are significantly different from controls. (b) Cyanobacteria growth data versus Tg latex (mean ± SD; n = 3). (c) The cumulative number of cyanobacteria released from the biocomposite adhesion test. (d) Adhesion data versus Tg of the latex (mean ± StDev; n = 3). e Decision matrix based on toxicity and adhesion data. The ratio of styrene to butyl acrylate is 1:3 for “hard” (H) latex, 1:1 for “normal” (N) and 3:1 for “soft” (S). The previous numbers in the latex code correspond to the content of Texanol.
In most cases, cell viability decreased with increasing texanol concentration, but there was no significant correlation for any of the strains (CCAP 1479/1A: DF = 25, r = -0.208, P = 0.299; PCC 7942: DF = 25, r = – 0.127, P = 0.527). On fig. 1b shows the relationship between cell growth and glass transition temperature (Tg). There is a strong negative correlation between texanol concentration and Tg values (H-latex: DF=7, r=-0.989, P=<0.001; N-latex: DF=7, r=-0.964, P=<0.001; S- latex: DF=7, r=-0.946, P=<0.001). The data showed that the optimal Tg for growth of S. elongatus PCC 7942 was around 17 °C (Figure 1b), while S. elongatus CCAP 1479/1A favored Tg below 0 °C (Figure 1b). Only S. elongatus CCAP 1479/1A had a strong negative correlation between Tg and toxicity data (DF=25, r=-0.857, P=<0.001).
All latexes had good adhesion affinity, and none of them released more than 1% of cells after 72 h (Fig. 1c). There was no significant difference between the latexes of the two strains of S. elongatus (PCC 7942: Scheirer-Ray-Hara test, Latex*Texanol, DF=4, H=0.903; P=0.924; CCAP 1479/1A: Scheirer-Ray test). – Hare test, latex*texanol, DF=4, H=3.277, P=0.513). As the concentration of Texanol increases, more cells are released (Figure 1c). compared to S. elongatus PCC 7942 (DF=25, r=-0.660, P=<0.001) (Figure 1d). Furthermore, there was no statistical relationship between Tg and cell adhesion of the two strains (PCC 7942: DF=25, r=0.301, P=0.127; CCAP 1479/1A: DF=25, r=0.287, P=0.147).
For both strains, “hard” latex polymers were ineffective. In contrast, 4N and 12N performed best against S. elongatus PCC 7942, while 4S and 12S performed best against CCAP 1479/1A (Fig. 1e), although there is clearly room for further optimization of the polymer matrix. These polymers have been used in semi-batch net CO2 uptake tests.
Photophysiology was monitored for 7 days using cells suspended in an aqueous latex composition. In general, both the apparent photosynthesis rate (PS) and the maximum PSII quantum yield (Fv/Fm) decrease with time, but this decrease is uneven and some PS datasets show a biphasic response, suggesting a partial response, although real-time recovery shorter PS activity (Fig. 2a and 3b). The biphasic Fv/Fm response was less pronounced (Figures 2b and 3b).
(a) Apparent photosynthesis rate (PS) and (b) maximum PSII quantum yield (Fv/Fm) of Synechococcus elongatus PCC 7942 in response to latex formulations compared to control suspension cultures. The ratio of styrene to butyl acrylate is 1:3 for “hard” (H) latex, 1:1 for “normal” (N) and 3:1 for “soft” (S). The previous numbers in the latex code correspond to the content of Texanol. (mean ± standard deviation; n = 3).
(a) Apparent photosynthesis rate (PS) and (b) maximum PSII quantum yield (Fv/Fm) of Synechococcus elongatus CCAP 1479/1A in response to latex formulations compared to control suspension cultures. The ratio of styrene to butyl acrylate is 1:3 for “hard” (H) latex, 1:1 for “normal” (N) and 3:1 for “soft” (S). The previous numbers in the latex code correspond to the content of Texanol. (mean ± standard deviation; n = 3).
For S. elongatus PCC 7942, latex composition and Texanol concentration did not affect PS over time (GLM, Latex*Texanol*Time, DF = 28, F = 1.49, P = 0.07), although composition was an important factor ( GLM). , latex*time, DF = 14, F = 3.14, P = <0.001) (Fig. 2a). There was no significant effect of Texanol concentration over time (GLM, Texanol*time, DF=14, F=1.63, P=0.078). There was a significant interaction affecting Fv/Fm (GLM, Latex*Texanol*Time, DF=28, F=4.54, P=<0.001). The interaction between latex formulation and Texanol concentration had a significant effect on Fv/Fm (GLM, Latex*Texanol, DF=4, F=180.42, P=<0.001). Each parameter also affects Fv/Fm over time (GLM, Latex*Time, DF=14, F=9.91, P=<0.001 and Texanol*Time, DF=14, F=10.71, P=< 0.001). Latex 12H maintained the lowest average PS and Fv/Fm values (Fig. 2b), indicating that this polymer is more toxic.
PS of S. elongatus CCAP 1479/1A was significantly different (GLM, latex * Texanol * time, DF = 28, F = 2.75, P = <0.001), with latex composition rather than Texanol concentration (GLM, Latex*time, DF=14, F=6.38, P=<0.001, GLM, Texanol*time, DF=14, F=1.26, P=0.239). “Soft” polymers 0S and 4S maintained slightly higher levels of PS performance than control suspensions (Mann-Whitney U, 0S versus controls, W = 686.0, P = 0.044, 4S versus controls, W = 713, P = 0.01) and maintained an improved Fv. /Fm (Fig. 3a) shows more efficient transport to Photosystem II. For Fv/Fm values of CCAP 1479/1A cells, there was a significant latex difference over time (GLM, Latex*Texanol*Time, DF=28, F=6.00, P=<0.001) (Figure 3b). ).
On fig. 4 shows the average PS and Fv/Fm over a 7 day period as a function of cell growth for each strain. S. elongatus PCC 7942 did not have a clear pattern (Fig. 4a and b), however, CCAP 1479/1A showed a parabolic relationship between PS (Fig. 4c) and Fv/Fm (Fig. 4d) values as the ratios of styrene and butyl acrylate grow with change.
Relationship between growth and photophysiology of Synechococcus longum on latex preparations. (a) Toxicity data plotted against apparent photosynthetic rate (PS), (b) maximum PSII quantum yield (Fv/Fm) of PCC 7942. c Toxicity data plotted against PS and d Fv/Fm CCAP 1479/1A. The ratio of styrene to butyl acrylate is 1:3 for “hard” (H) latex, 1:1 for “normal” (N) and 3:1 for “soft” (S). The previous numbers in the latex code correspond to the content of Texanol. (mean ± standard deviation; n = 3).
The biocomposite PCC 7942 had a limited effect on cell retention with significant cell leaching during the first four weeks (Figure 5). After the initial phase of CO2 uptake, cells fixed with 12 N latex began to release CO2, and this pattern persisted between days 4 and 14 (Fig. 5b). These data are consistent with observations of pigment discoloration. Net CO2 uptake started again from day 18. Despite cell release (Fig. 5a), the PCC 7942 12 N biocomposite still accumulated more CO2 than the control suspension over 28 days, albeit slightly (Mann-Whitney U-test, W = 2275.5; P = 0.066). The rate of absorption of CO2 by latex 12 N and 4 N is 0.51 ± 0.34 and 1.18 ± 0.29 g CO2 g-1 of biomass d-1. There was a statistically significant difference between treatment and time levels (Chairer-Ray-Hare test, treatment: DF=2, H=70.62, P=<0.001 time: DF=13, H=23.63, P=0.034), but it wasn’t. there was a significant relationship between treatment and time (Chairer-Ray-Har test, time*treatment: DF=26, H=8.70, P=0.999).
Half-batch CO2 uptake tests on Synechococcus elongatus PCC 7942 biocomposites using 4N and 12N latex. (a) Images show cell release and pigment discoloration, as well as SEM images of the biocomposite before and after testing. White dotted lines indicate the sites of cell deposition on the biocomposite. (b) Cumulative net CO2 uptake over a four-week period. “Normal” (N) latex has a ratio of styrene to butyl acrylate of 1:1. The previous numbers in the latex code correspond to the content of Texanol. (mean ± standard deviation; n = 3).
Cell retention was significantly improved for strain CCAP 1479/1A with 4S and 12S, although the pigment slowly changed color over time (Fig. 6a). Biocomposite CCAP 1479/1A absorbs CO2 for a full 84 days (12 weeks) without additional nutritional supplements. SEM analysis (Fig. 6a) confirmed the visual observation of small cell detachment. Initially, the cells were encased in a latex coating that maintained its integrity despite cell growth. The CO2 uptake rate was significantly higher than the control group (Scheirer-Ray-Har test, treatment: DF=2; H=240.59; P=<0.001, time: DF=42; H=112; P=<0.001 ) (Fig. 6b). The 12S biocomposite achieved the highest CO2 uptake (1.57 ± 0.08 g CO2 g-1 biomass per day), while the 4S latex was 1.13 ± 0.41 g CO2 g-1 biomass per day, but they did not differ significantly (Mann-Whitney U. test, W = 1507.50; P = 0.07) and no significant interaction between treatment and time (Shirer-Rey-Hara test, time * treatment: DF = 82; H = 10 .37; P = 1.000).
Half lot CO2 uptake testing using Synechococcus elongatus CCAP 1479/1A biocomposites with 4N and 12N latex. (a) Images show cell release and pigment discoloration, as well as SEM images of the biocomposite before and after testing. White dotted lines indicate the sites of cell deposition on the biocomposite. (b) Cumulative net CO2 uptake over the twelve-week period. “Soft” (S) latex has a ratio of styrene to butyl acrylate of 1:1. The previous numbers in the latex code correspond to the content of Texanol. (mean ± standard deviation; n = 3).
S. elongatus PCC 7942 (Shirer-Ray-Har test, time*treatment: DF=4, H=3.243, P=0.518) or biocomposite S. elongatus CCAP 1479/1A (two-ANOVA, time*treatment: DF=8 , F = 1.79, P = 0.119) (Fig. S4). Biocomposite PCC 7942 had the highest carbohydrate content at week 2 (4 N = 59.4 ± 22.5 wt%, 12 N = 67.9 ± 3.3 wt%), while the control suspension had highest carbohydrate content at week 4 when (control = 59.6 ± 2.84% w/w). The total carbohydrate content of the CCAP 1479/1A biocomposite was comparable to the control suspension except at the start of the trial, with some changes in the 12S latex at week 4. The highest values for the biocomposite were 51.9 ± 9.6 wt% for 4S and 77.1 ± 17.0 wt% for 12S.
We set out to demonstrate design possibilities for enhancing the structural integrity of thin film latex polymer coatings as an important component of the lichen mimic biocomposite concept without sacrificing biocompatibility or performance. Indeed, if the structural challenges associated with cell growth are overcome, we expect significant performance improvements over our experimental biocomposites, which are already comparable to other cyanobacteria and microalgae carbon capture systems.
Coatings must be non-toxic, durable, support long-term cell adhesion, and must be porous to promote efficient CO2 mass transfer and O2 degassing. Latex-type acrylic polymers are easy to prepare and are widely used in the paint, textile, and adhesive industries30. We combined cyanobacteria with a water-based acrylic latex polymer emulsion polymerized with a specific ratio of styrene/butyl acrylate particles and various concentrations of Texanol. Styrene and butyl acrylate were chosen to be able to control the physical properties, especially the elasticity and coalescence efficiency of the coating (critical for a strong and highly adhesive coating), allowing the synthesis of “hard” and “soft” particle aggregates. Toxicity data suggest that “hard” latex with a high styrene content is not conducive to the survival of cyanobacteria. Unlike butyl acrylate, styrene is considered toxic to algae32,33. Cyanobacteria strains reacted quite differently to latex, and the optimum glass transition temperature (Tg) was determined for S. elongatus PCC 7942, while S. elongatus CCAP 1479/1A showed a negative linear relationship with Tg.
The drying temperature affects the ability to form a continuous uniform latex film. If the drying temperature is below the Minimum Film Forming Temperature (MFFT), the polymer latex particles will not fully coalesce, resulting in adhesion only at the particle interface. The resulting films have poor adhesion and mechanical strength and may even be in powder form29. MFFT is closely related to Tg, which can be controlled by monomer composition and the addition of coalescents such as Texanol. Tg determines many of the physical properties of the resulting coating, which may be in a rubbery or glassy state34. According to the Flory-Fox equation35, Tg depends on the type of monomer and the relative percentage composition. The addition of coalescent can lower the MFFT by intermittent suppression of the Tg of the latex particles, which allows film formation at lower temperatures, but still forms a hard and strong coating because the coalescent slowly evaporates over time or has been extracted 36 .
Increasing the concentration of Texanol promotes film formation by softening the polymer particles (reducing Tg) due to absorption by the particles during drying, thereby increasing the strength of the cohesive film and cell adhesion. Because the biocomposite is dried at ambient temperature (~18–20°C), the Tg (30 to 55°C) of the “hard” latex is higher than the drying temperature, meaning that particle coalescence may not be optimal, resulting in B films that remain vitreous, poor mechanical and adhesive properties, limited elasticity and diffusivity30 ultimately lead to greater cell loss. Film formation from “normal” and “soft” polymers occurs at or below the Tg of the polymer film, and film formation is improved by improved coalescence, resulting in continuous polymer films with improved mechanical, cohesive, and adhesive properties. The resulting film will remain rubbery during CO2 capture experiments due to its Tg being close to (“normal” blend: 12 to 20 ºC) or much lower (“soft” blend: -21 to -13 °C ) to ambient temperature 30 . “Hard” latex (3.4 to 2.9 kgf mm–1) is three times harder than “normal” latex (1.0 to 0.9 kgf mm–1). The hardness of “soft” latexes cannot be measured by microhardness due to their excessive rubberiness and stickiness at room temperature. Surface charge can also affect adhesion affinity, but more data are needed to provide meaningful information. However, all latexes effectively retained the cells, releasing less than 1%.
The productivity of photosynthesis decreases over time. Exposure to polystyrene leads to membrane disruption and oxidative stress38,39,40,41. The Fv/Fm values of S. elongatus CCAP 1479/1A exposed to 0S and 4S were almost twice as high compared to the suspension control, which is in good agreement with the CO2 uptake rate of the 4S biocomposite, as well as with lower mean PS values. values. Higher Fv/Fm values indicate that electron transport to PSII may deliver more photons42, which may result in higher CO2 fixation rates. However, it should be noted that photophysiological data were obtained from cells suspended in aqueous latex solutions and may not necessarily be directly comparable to mature biocomposites.
If latex creates a barrier to light and/or gas exchange resulting in light and CO2 restriction, it can cause cellular stress and reduce performance, and if it affects O2 release, photorespiration39. The light transmission of the cured coatings was evaluated: “hard” latex showed a slight decrease in light transmission between 440 and 480 nm (improved in part by increasing the concentration of Texanol due to improved film coalescence), while “soft” and “regular” latex showed a slight decrease in light transmission. shows no noticeable loss of loss. The assays, as well as all incubations, were performed at low light intensity (30.5 µmol m-2 s-1), so any photosynthetically active radiation due to the polymer matrix will be compensated and may even be useful in preventing photoinhibition. at damaging light intensities.
Biocomposite CCAP 1479/1A functioned during the 84 days of testing, without nutrient turnover or significant loss of biomass, which is a key objective of the study. Cell depigmentation may be associated with a process of chlorosis in response to nitrogen starvation to achieve long-term survival (resting state), which may help cells resume growth after sufficient nitrogen accumulation has been achieved. The SEM images confirmed that the cells remained inside the coating despite cell division, demonstrating the elasticity of the “soft” latex and thus showing a clear advantage over the experimental version. “Soft” latex contains about 70% butyl acrylate (by weight), which is much higher than the stated concentration for a flexible coating after drying44.
The net uptake of CO2 was significantly higher than that of the control suspension (14–20 and 3–8 times higher for S. elongatus CCAP 1479/1A and PCC 7942, respectively). Previously, we used a CO2 mass transfer model to show that the main driver of high CO2 uptake is a sharp CO2 concentration gradient at the surface of the biocomposite31 and that biocomposite performance can be limited by resistance to mass transfer. This problem can be overcome by incorporating non-toxic, non-film-forming ingredients into the latex to increase the porosity and permeability of the coating26, but cell retention may be compromised as this strategy will inevitably result in a weaker film20. The chemical composition can be changed during polymerization to increase porosity, which is the best option, especially in terms of industrial production and scalability45.
The performance of the new biocomposite compared to recent studies using biocomposites from microalgae and cyanobacteria showed advantages in adjusting the cell loading rate (Table 1)21,46 and with longer analysis times (84 days versus 15 hours46 and 3 weeks21).
The volumetric content of carbohydrates in cells compares favorably with other studies47,48,49,50 using cyanobacteria and is used as a potential criterion for carbon capture and utilization/recovery applications, such as for BECCS fermentation processes49,51 or for the production of biodegradable bioplastics52 . As part of the rationale for this study, we assume that afforestation, even considered in the BECCS negative emissions concept, is not a panacea for climate change and consumes an alarming share of the world’s arable land6. As a thought experiment, it was estimated that between 640 and 950 GtCO2 would need to be removed from the atmosphere by 2100 to limit global temperature rise to 1.5°C53 (about 8 to 12 GtCO2 per year). Achieving this with a better performing biocomposite (574.08 ± 30.19 t CO2 t-1 biomass per year-1) would require volume expansion from 5.5 × 1010 to 8.2 × 1010 m3 (with comparable photosynthetic efficiency), containing from 196 to 2.92 billion liters of polymer. Assuming that 1 m3 of biocomposites occupies 1 m2 of land area, the area required to absorb the target annual total CO2 will be between 5.5 and 8.17 million hectares, which is equivalent to 0.18-0.27% of suitable for the life of the lands in the tropics, and reduce the land area. need for BECCS by 98-99%. It should be noted that the theoretical capture ratio is based on the CO2 absorption recorded in low light. As soon as the biocomposite is exposed to more intense natural light, the rate of CO2 uptake increases, further reducing land requirements and tipping the scales further towards the biocomposite concept. However, the implementation must be at the equator for constant backlight intensity and duration.
The global effect of CO2 fertilization, i.e. the increase in vegetation productivity caused by increased CO2 availability, has decreased on most land areas, probably due to changes in key soil nutrients (N and P) and water resources7. This means that terrestrial photosynthesis may not lead to an increase in CO2 uptake, despite elevated CO2 concentrations in the air. In this context, ground-based climate change mitigation strategies such as BECCS are even less likely to succeed. If this global phenomenon is confirmed, our lichen-inspired biocomposite could be a key asset, transforming single-celled aquatic photosynthetic microbes into “ground agents.” Most terrestrial plants fix CO2 through C3 photosynthesis, while C4 plants are more favorable to warmer, drier habitats and are more efficient at higher CO254 partial pressures. Cyanobacteria offer an alternative that could offset the alarming predictions of reduced carbon dioxide exposure in C3 plants. Cyanobacteria have overcome photorespiratory limitations by developing an efficient carbon enrichment mechanism in which higher partial pressures of CO2 are presented and maintained by ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCo) within carboxysomes around. If the production of cyanobacterial biocomposites can be increased, this could become an important weapon for mankind in the fight against climate change.
Biocomposites (lichen mimics) offer clear advantages over conventional microalgae and cyanobacteria suspension cultures, providing higher CO2 uptake rates, minimizing pollution risks, and promising competitive CO2 avoidance. Costs significantly reduce the use of land, water and nutrients56. This study demonstrates the feasibility of developing and manufacturing a high-performance biocompatible latex that, when combined with a loofah sponge as a candidate substrate, can provide efficient and effective CO2 uptake over months of surgery while keeping cell loss to a minimum. Biocomposites could theoretically capture approximately 570 t CO2 t-1 of biomass per year and may prove to be more important than BECCS afforestation strategies in our response to climate change. With further optimization of the polymer composition, testing at higher light intensities, and combined with elaborate metabolic engineering, nature’s original biogeoengineers can once again come to the rescue.
Acrylic latex polymers were prepared using a mixture of styrene monomers, butyl acrylate and acrylic acid, and the pH was adjusted to 7 with 0.1 M sodium hydroxide (table 2). Styrene and butyl acrylate make up the bulk of the polymer chains, while acrylic acid helps keep the latex particles in suspension57. The structural properties of latex are determined by the glass transition temperature (Tg), which is controlled by changing the ratio of styrene and butyl acrylate, which provides “hard” and “soft” properties, respectively58. A typical acrylic latex polymer is 50:50 styrene:butyl acrylate 30, so in this study latex with this ratio was referred to as “normal” latex, and latex with a higher styrene content was referred to as a latex with a lower styrene content. called “soft” as “hard”.
A primary emulsion was prepared using distilled water (174 g), sodium bicarbonate (0.5 g) and Rhodapex Ab/20 surfactant (30.92 g) (Solvay) to stabilize the 30 monomer droplets. Using a glass syringe (Science Glass Engineering) with a syringe pump, a secondary aliquot containing styrene, butyl acrylate and acrylic acid listed in Table 2 was added dropwise at a rate of 100 ml h-1 to the primary emulsion over 4 hours (Cole-Palmer, Mount Vernon, Illinois). Prepare a solution of polymerization initiator 59 using dHO and ammonium persulfate (100 ml, 3% w/w).
Stir the solution containing dHO (206 g), sodium bicarbonate (1 g) and Rhodapex Ab/20 (4.42 g) using an overhead stirrer (Heidolph Hei-TORQUE value 100) with a stainless steel propeller and heat to 82°C in a water jacketed vessel in a VWR Scientific 1137P heated water bath. A reduced weight solution of monomer (28.21 g) and initiator (20.60 g) was added dropwise to the jacketed vessel and stirred for 20 minutes. Vigorously mix the remaining monomer (150 ml h-1) and initiator (27 ml h-1) solutions to keep the particles in suspension until they are added to the water jacket over 5 h using 10 ml syringes and 100 ml respectively in a container. completed with a syringe pump. The stirrer speed was increased due to the increase in slurry volume to ensure slurry retention. After adding the initiator and the emulsion, the reaction temperature was raised to 85°C, stirred well at 450 rpm for 30 minutes, then cooled to 65°C. After cooling, two displacement solutions were added to the latex: tert-butyl hydroperoxide (t-BHP) (70% in water) (5 g, 14% by weight) and isoascorbic acid (5 g, 10% by weight). . Add t-BHP drop by drop and leave for 20 minutes. Erythorbic acid was then added at a rate of 4 ml/h from a 10 ml syringe using a syringe pump. The latex solution was then cooled to room temperature and adjusted to pH 7 with 0.1M sodium hydroxide.
2,2,4-Trimethyl-1,3-pentanediol monoisobutyrate (Texanol) – low toxicity biodegradable coalescent for latex paints 37,60 – was added with a syringe and pump in three volumes (0, 4, 12% v/v) as coalescing agent for latex mixture to facilitate film formation during drying37. The latex solids percentage was determined by placing 100 µl of each polymer in pre-weighed aluminum foil caps and drying in an oven at 100°C for 24 hours.
For light transmission, each latex mixture was applied to a microscope slide using a stainless steel drop cube calibrated to produce 100 µm films and dried at 20°C for 48 hours. Light transmission (focused on photosynthetically active radiation, λ 400–700 nm) was measured on an ILT950 SpectriLight spectroradiometer with a sensor at a distance of 35 cm from a 30 W fluorescent lamp (Sylvania Luxline Plus, n = 6) – where the light source was cyanobacteria and organisms Composite materials are preserved. SpectrILight III software version 3.5 was used to record illuminance and transmission in the λ 400–700 nm61 range. All samples were placed on top of the sensor, and uncoated glass slides were used as controls.
Latex samples were added to a silicone baking dish and allowed to dry for 24 hours before being tested for hardness. Place the dried latex sample on a steel cap under a x10 microscope. After focusing, the samples were evaluated on a Buehler Micromet II microhardness tester. The sample was subjected to a force of 100 to 200 grams and the load time was set to 7 seconds to create a diamond dent in the sample. The print was analyzed using a Bruker Alicona × 10 microscope objective with additional shape measurement software. The Vickers hardness formula (Equation 1) was used to calculate the hardness of each latex, where HV is the Vickers number, F is the applied force, and d is the average of the indent diagonals calculated from the height and width of the latex. indent value. “Soft” latex cannot be measured due to adhesion and stretch during the indentation test.
To determine the glass transition temperature (Tg) of the latex composition, polymer samples were placed in silica gel dishes, dried for 24 hours, weighed to 0.005 g, and placed in sample dishes. The dish was capped and placed in a differential scanning colorimeter (PerkinElmer DSC 8500, Intercooler II, Pyris data analysis software)62. The heat flow method is used to place reference cups and sample cups in the same oven with a built-in temperature probe to measure the temperature. A total of two ramps were used to create a consistent curve. The sample method was repeatedly raised from -20°C to 180°C at a rate of 20°C per minute. Each start and end point is stored for 1 minute to account for temperature lag.
To evaluate the ability of the biocomposite to absorb CO2, samples were prepared and tested in the same way as in our previous study31. The dried and autoclaved washcloth was cut into strips of approximately 1×1×5 cm and weighed. Apply 600 µl of the two most effective biocoatings of each cyanobacteria strain to one end of each loofah strip, covering approximately 1 × 1 × 3 cm, and dry in the dark at 20°C for 24 hours. Due to the macroporous structure of the loofah, some of the formula was wasted, so cell loading efficiency was not 100%. To overcome this problem, the weight of the dry preparation on the loofah was determined and normalized to the reference dry preparation. Abiotic controls consisting of loofah, latex, and sterile nutrient medium were prepared in a similar way.
To perform a half-batch CO2 uptake test, place the biocomposite (n = 3) in a 50 ml glass tube so that one end of the biocomposite (without the biocoating) is in contact with 5 ml of growth medium, allowing the nutrient to be transported by capillary action. . The bottle is sealed with a butyl rubber cork with a diameter of 20 mm and crimped with a silvery aluminum cap. Once sealed, inject 45 ml of 5% CO2/air with a sterile needle attached to a gas-tight syringe. The cell density of the control suspension (n = 3) was equivalent to the cell load of the biocomposite in the nutrient medium. The tests were carried out at 18 ± 2 °C with a photoperiod of 16:8 and a photoperiod of 30.5 µmol m-2 s-1. Head space was removed every two days with a gas-tight syringe and analyzed with a CO2 meter with infrared absorption GEOTech G100 to determine the percentage of CO2 absorbed. Add an equal volume of CO2 gas mixture.
% CO2 Fix is calculated as follows: % CO2 Fix = 5% (v/v) – write %CO2 (equation 2) where P = pressure, V = volume, T = temperature, and R = ideal gas constant.
Reported CO2 uptake rates for control suspensions of cyanobacteria and biocomposites were normalized to non-biological controls. The functional unit of g biomass is the amount of dry biomass immobilized on the washcloth. It is determined by weighing loofah samples before and after cell fixation. Accounting for cell load mass (biomass equivalent) by individually weighing the preparations before and after drying and by calculating the density of the cell preparation (equation 3). Cell preparations are assumed to be homogeneous during fixation.
Minitab 18 and Microsoft Excel with the RealStatistics add-in were used for statistical analysis. Normality was tested using the Anderson-Darling test, and equality of variances was tested using the Levene test. Data satisfying these assumptions were analyzed using two-way analysis of variance (ANOVA) with Tukey’s test as post hoc analysis. Two-way data that did not meet the assumptions of normality and equal variance were analyzed using the Shirer-Ray-Hara test and then the Mann-Whitney U-test to determine significance between treatments. Generalized linear mixed (GLM) models were used for non-normal data with three factors, where the data were transformed using the Johnson transform63. Moment correlations of Pearson products were performed to evaluate the relationship between Texanol concentration, glass transition temperature, and latex toxicity and adhesion data.
Post time: Jan-05-2023