{"id":119046,"date":"2022-11-25T07:29:00","date_gmt":"2022-11-25T06:29:00","guid":{"rendered":"https:\/\/renewable-carbon.eu\/news\/?p=119046"},"modified":"2022-11-22T12:04:50","modified_gmt":"2022-11-22T11:04:50","slug":"engineered-living-photosynthetic-biocomposites-for-intensified-biological-carbon-capture","status":"publish","type":"post","link":"https:\/\/renewable-carbon.eu\/news\/engineered-living-photosynthetic-biocomposites-for-intensified-biological-carbon-capture\/","title":{"rendered":"Engineered living photosynthetic biocomposites for intensified biological carbon capture"},"content":{"rendered":"\n

<\/h2>\n\n\n\n\n\n

Abstract<\/h3>\n\n\n\n

Carbon capture and storage is required to meet Paris Agreement targets. Photosynthesis is nature\u2019s carbon capture technology. Drawing inspiration from lichen, we engineered 3D photosynthetic cyanobacterial biocomposites (i.e., lichen mimics) using acrylic latex polymers applied to loofah sponge. Biocomposites had CO2<\/sub> uptake rates of 1.57\u2009\u00b1\u20090.08 g CO2<\/sub> g\u22121<\/sup>biomass<\/sub> d\u22121<\/sup>. Uptake rates were based on the dry biomass at the start of the trial and incorporate the CO2<\/sub>used to grow new biomass as well as that contained in storage compounds such as carbohydrates. These uptake rates represent 14\u201320-fold improvements over suspension controls, potentially scaling to capture 570 tCO2<\/sub> t\u22121<\/sup>biomass<\/sub> yr\u22121<\/sup>, with an equivalent land consumption of 5.5\u20138.17\u2009\u00d7\u2009106<\/sup> ha, delivering annualized CO2<\/sub> removal of 8\u201312 GtCO2<\/sub>, compared with 0.4\u20131.2\u2009\u00d7\u2009109<\/sup> ha for forestry-based bioenergy with carbon capture and storage. The biocomposites remained functional for 12 weeks without additional nutrient or water supplementation, whereupon experiments were terminated. Engineered and optimized cyanobacteria biocomposites have potential for sustainable scalable deployment as part of humanity\u2019s multifaceted technological stand against climate change, offering enhanced CO2<\/sub> removal with low water, nutrient, and land use penalties.<\/p>\n\n\n\n

Introduction<\/h3>\n\n\n\n

Climate change poses an existential threat to global biodiversity, ecosystem stability and to humanity. To curtail its worst effects will require coordinated and extensive decarbonization programs and will certainly need some form of direct removal of greenhouse gases from the atmosphere1<\/a><\/sup>. Despite positive indicators towards decarbonizing electricity generation2<\/a>,3<\/a><\/sup>, there are yet no economically sustainable technological solutions for the drawdown of atmospheric carbon dioxide (CO2<\/sub>)4<\/a><\/sup>; although capture from flue gas is progressing5<\/a><\/sup>. In lieu of scalable and practical engineered solutions, humanity must look to nature\u2019s own carbon capture engineers; photosynthetic organisms (phototrophs). Photosynthesis is nature\u2019s carbon capture technology; however, its capacity to reverse anthropogenic carbon enrichment within a meaningful timescale is equivocal, with enzymatic inefficiencies and the capacity for deployment at an appropriate scale being questioned. One potential vehicle for phototrophy is through afforestation, with the trees harvested for use in bioenergy with carbon capture and storage (BECCS) which, as a negative emissions technology, can contribute to reducing net CO2<\/sub>\u00a0emissions1<\/a><\/sup>. <\/p>\n\n\n\n

However, to reach the 1.5\u00a0\u00b0C Paris Agreement target, BECCS as the main approach would consume between 0.4 and 1.2\u2009\u00d7\u2009109<\/a><\/sup>\u00a0ha of land, equivalent to 25\u201375% of current global cropland6<\/a><\/sup>. Further, uncertainties surrounding the global CO2<\/sub>\u00a0fertilization effect cast doubt on afforestation\u2019s potential overall effectiveness7<\/a><\/sup>. If we are to meet the temperature targets set by the Paris agreement, greenhouse gas removal (GGR) from the atmosphere is required on the scale of 100\u00a0s of GtCO2<\/sub>\u00a0per year. Recently, UK Research and Innovation announced funding for five GGR projects8<\/a><\/sup>\u00a0including management of peatlands, enhanced rock weathering, tree planting, biochar, and the growth of perennial crops for feeding to a BECCS process. To remove in excess of 130 MtCO2<\/sub>\u00a0per annum from the atmosphere would cost 10\u2013100\u00a0US$\/tCO2<\/sub>\u00a0at 0.2 to 8.1 MtCO2<\/sub>\u00a0per annum for peatland restoration, 52\u2013480\u00a0US$\/tCO2<\/sub>\u00a0at 12\u201327 MtCO2<\/sub>\u00a0per annum for rock weathering, 0.4\u201330\u00a0US$\/tCO2<\/sub>\u00a0at 3.6 MtCO2<\/sub>\u00a0per annum with a 1% increase in woodland area, 0.4\u201330\u00a0US$\/tCO2<\/sub>\u00a0at 6\u201341\u00a0MtCO2<\/sub>\u00a0per annum for biochar, and 140\u2013270\u00a0US$ per tCO2<\/sub>\u00a0at 20\u201370\u00a0Mt CO2<\/sub>\u00a0per annum for perennial crops with BECCS9<\/a><\/sup>.<\/p>\n\n\n\n

Taken together these methods have the potential to meet the target of 130 MtCO2<\/sub> per annum but the cost of rock weathering and BECCS are high and, biochar whilst being relatively inexpensive and having no land use issues, requires a feedstock for the process that generates the biochar. This suggests that there is scope to develop and deploy other GGR technologies.<\/p>\n\n\n\n

Rather than looking to the land for solutions there is just cause to look to the water; specifically, to unicellular phototrophs such as microalgae and cyanobacteria10<\/a><\/sup>. Algae (including cyanobacteria) fix approximately 50% of global CO2<\/sub>, despite contributing only 1% of global biomass11<\/a><\/sup>. Cyanobacteria are nature\u2019s original bio-geoengineers that, through oxygenic photosynthesis, laid the very foundations for respiratory metabolism and the evolution of multicellular life12<\/a><\/sup>. The idea of applying cyanobacteria for carbon capture is not new13<\/a><\/sup>; however, innovative approaches towards their physical deployment are opening new horizons for these most ancient organisms.<\/p>\n\n\n\n

Open ponds and photobioreactors are the default assets when using microalgae and cyanobacteria for industrial applications. These culture systems exploit suspension cultivation, whereby the cells are free floating within a growth medium14<\/a><\/sup>; however, ponds and photobioreactors suffer many drawbacks such as poor CO2<\/sub> mass transfer, high land and water usage, are vulnerable to biological contamination, and can be expensive to build and operate15<\/a>,16<\/a><\/sup>. Biofilm bioreactors that circumvent suspension cultivation are more water and space efficient; however, they risk damage from desiccation, are prone to biofilm detachment (and thereby loss of the active biomass), and are no less vulnerable to biological contamination17<\/a><\/sup>.<\/p>\n\n\n\n

New approaches are needed that intensify CO2<\/sub> uptake rate and overcome the challenges that limit suspension and biofilm reactors. Photosynthetic biocomposites inspired by lichens are one such approach. Lichens are composite organisms comprising a fungus and a photobiont (microalgae and\/or cyanobacteria), covering circa 12% of the Earth\u2019s landmass18<\/a><\/sup>. The fungus provides physical support, protection and anchorage to the substratum for the photobiont, which in turn contributes carbon (as excess photosynthate) to the fungus. The proposed biocomposites are \u2018lichen mimics\u2019 wherein a concentrated population of cyanobacteria are immobilized as a thin biocoating to a supporting substratum. In addition to the cells, the biocoating comprises a polymer matrix that substitutes for the fungus. Water-based polymer emulsions or \u2018latexes\u2019 are favored as they can be biocompatible, robust, inexpensive, easy to handle, and potentially implemented on an industrial scale19<\/a>,20<\/a>,21<\/a>,22<\/a>,23<\/a>,24<\/a>,25<\/a>,26<\/a><\/sup>.<\/p>\n\n\n\n

Cell immobilization using latex polymers is greatly influenced by latex formulation and the film formation process. Emulsion polymerization is a heterogeneous process used to produce synthetic rubbers, adhesive coatings, sealants, concrete additives, paper and textile coatings, and latex paints27<\/a><\/sup>. It has several advantages over other polymerization techniques such as its high reaction rate and monomer conversion efficiency and ease of control over the products27<\/a>,28<\/a><\/sup>. Monomer selection depends on the desired properties of the resulting polymeric film and with mixed monomers systems (i.e., copolymerization) the polymer properties can be altered by selection of different monomer ratios which form the resulting polymeric material29<\/a><\/sup>. Butyl acrylate and styrene are amongst the most common monomers for acrylic latexes30<\/a><\/sup>, and are used here. In addition, coalescing agents (e.g., Texanol) are typically used to promote uniform film formation, in which they can alter the properties of the polymeric latex, allowing the creation of a robust and ‘continuous’ (coalesced) coating. In our initial proof-of-concept study, high surface area and highly macroporous 3D biocomposites were fabricated using commercial latex-based paints applied to loofah sponge31<\/a><\/sup>. Over prolonged and continuous operation (eight weeks) the biocomposites displayed a limited capacity to retain the cyanobacteria on the loofah scaffolds due to cell outgrowth which weakened the structural integrity of the latex. In the current study, we aimed to develop a range of acrylic latex polymers of known chemical composition for continuous use for carbon capture applications that were not compromised by polymer failure. In so doing, we have demonstrated capacity to design the polymer matrix element of the lichen mimic, enabling improved biological performance with substantially enhanced mechanical resilience compared with proof-of-concept biocomposites. Further optimization will accelerate the deployment of biocomposites for carbon capture applications, particularly if paired with cyanobacteria that are metabolically engineered for enhanced CO2<\/sub> fixation.<\/p>\n\n\n\n

Results<\/h3>\n\n\n\n

Toxicity and adhesion screening<\/h3>\n\n\n\n

Nine latexes with three polymer formulations (H\u2014\u2018Hard\u2019, N\u2014\u2018Normal\u2019, S\u2014\u2018Soft\u2019) and three levels of Texanol (0, 4, 12% v\/v) were tested for toxicity and adhesion with two cyanobacteria strains. Latex type significantly influenced cell growth for S. elongatus<\/em> PCC 7942 (Scheirer-Ray-Hare test, Latex: DF\u2009=\u20092, H\u2009=\u200923.157, P<\/em>\u2009=\u2009\u2009<\u20090.001) and CCAP 1479\/1A (Two-way ANOVA, Latex: DF\u2009=\u20092, F\u2009=\u2009103.93, P<\/em>\u2009=\u2009\u2009<\u20090.001)  (Fig. 1<\/a>a). There was no significant effect of Texanol concentration on S. elongatus<\/em> PCC 7942 growth; only the N-latexes were non-toxic (Fig. 1<\/a>a), with 0 N and 4 N supporting increased growth of 26 and 35% respectively (Mann\u2013Whitney U, 0 N vs. 4 N: W\u2009=\u200913.50, P<\/em>\u2009=\u20090.245; 0 N vs. control: W\u2009=\u200925.0, P<\/em>\u2009=\u20090.061; 4 N vs. control: W\u2009=\u200925.0, P<\/em>\u2009=\u20090.061), and 12 N sustaining growth that was comparable to the biotic controls (Mann\u2013Whitney U, 12 N vs. control: W\u2009=\u200917.0, P<\/em>\u2009=\u20090.885). For S. elongatus<\/em> CCAP 1479\/1A, latex blend and Texanol concentration were both significant factors, with a significant interaction between the two (Two-way ANOVA, Latex: DF\u2009=\u20092, F\u2009=\u2009103.93, P<\/em>\u2009=\u2009\u2009<\u20090.001, Texanol: DF\u2009=\u20092, F\u2009=\u20095.96, P<\/em>\u2009=\u20090.01, Latex*Texanol: DF\u2009=\u20094, F\u2009=\u20093.41, P<\/em>\u2009=\u20090.03). The 0 N and all \u2018soft\u2019 latexes enhanced growth (Fig. 1<\/a>a). There was a trend of improved growth as the styrene composition decreased.<\/p>\n\n\n\n

\"figure<\/a>
Figure 1<\/strong><\/figcaption><\/figure><\/div>\n\n\n\n

In most cases, cell viability decreased as the Texanol concentration increased; however, there was no significant correlation for either strain (CCAP 1479\/1A: DF\u2009=\u200925, r\u2009=\u2009\u2212\u20090.208, P<\/em>\u2009=\u20090.299; PCC 7942: DF\u2009=\u200925, r\u2009=\u2009\u2212\u20090.127, P<\/em>\u2009=\u20090.527). Figure 1<\/a>b presents the relationship between cell growth and glass transition temperature (Tg). There were strong negative correlations between the Texanol concentration and Tg values (H-latex: DF\u2009=\u20097, r\u2009=\u2009\u2212\u20090.989, P<\/em>\u2009=\u2009\u2009<\u20090.001; N-latex: DF\u2009=\u20097, r\u2009=\u2009\u2212\u20090.964, P<\/em>\u2009=\u2009\u2009<\u20090.001; S-latex: DF\u2009=\u20097, r\u2009=\u2009-0.946, P<\/em>\u2009=\u2009\u2009<\u20090.001). The data indicate an optimal Tg for S. elongatus<\/em> PCC 7942 growth of approximately 17 \u00b0C (Fig. 1<\/a>b), whereas S. elongatus<\/em> CCAP 1479\/1A favored a Tg of below 0 \u00b0C (Fig. 1<\/a>b). There was a strong negative correlation between Tg and toxicity data for S. elongatus<\/em>CCAP 1479\/1A only (DF\u2009=\u200925, r\u2009=\u2009\u2212\u20090.857, P<\/em>\u2009=\u2009\u2009<\u20090.001).<\/p>\n\n\n\n

All latexes had good adhesive affinity, with none releasing more than 1% of cells after 72 h (Fig. 1<\/a>c). There were no significant differences between latexes for either S. elongatus<\/em> strain (PCC 7942: Scheirer-Ray-Hare test, Latex\u2009*\u2009Texanol, DF\u2009=\u20094, H\u2009=\u20090.903; P<\/em>\u2009=\u20090.924; CCAP 1479\/1A: Scheirer-Ray-Hare test, Latex\u2009*\u2009Texanol, DF\u2009=\u20094, H\u2009=\u20093.277, P<\/em>\u2009=\u20090.513). More cells were released as the Texanol concentration increased (Fig. 1<\/a>c). There was a stronger negative correlation between Texanol concentration and cell adhesion affinity for S. elongatus<\/em> CCAP 1479\/1A (DF\u2009=\u200925, r\u2009=\u2009\u2212\u20090.428, P<\/em>\u2009=\u20090.026) than for S. elongatus<\/em> PCC 7942 (DF\u2009=\u200925, r\u2009=\u2009\u2212\u20090.660, P<\/em>\u2009=\u2009\u2009<\u20090.001)  (Fig. 1<\/a>d). Furthermore, there was no statistical relationship between Tg and cell adhesion for either strain (PCC 7942: DF\u2009=\u200925, r\u2009=\u20090.301, P<\/em>\u2009=\u20090.127; CCAP 1479\/1A: DF\u2009=\u200925, r\u2009=\u20090.287, P<\/em>\u2009=\u20090.147).<\/p>\n\n\n\n

For both strains the \u2018hard\u2019 latex polymers performed poorly. In contrast, 4 N and 12 N were the best performing for S. elongatus<\/em> PCC 7942, while 4S and 12S were best for CCAP 1479\/1A (Fig. 1<\/a>e); although clearly there is scope to further optimize the polymer matrix. These polymers were taken forward for semi-batch net CO2<\/sub> absorption tests.<\/p>\n\n\n\n

Photosynthetic responses to latex polymers<\/h3>\n\n\n\n

Photophysiology was monitored over seven days using cells suspended in the aqueous latex formulations. In general, both the apparent rate of photosynthesis (PS) and the maximum PSII quantum yield (Fv<\/sub>\/Fm<\/sub>) decreased over time, although the decreases were not uniform and several of the PS datasets displayed a bi-phasic response indicating partial, albeit short-lived recovery of PS activity (Figs. 2<\/a>a and 3<\/a>b). The biphasic response was less pronounced for Fv<\/sub>\/Fm<\/sub> (Figs. 2<\/a>b and 3<\/a>b).<\/p>\n\n\n\n

\"figure<\/a>
Figure 2<\/strong><\/figcaption><\/figure><\/div>\n\n\n\n
\"figure<\/a>
Figure 3<\/strong><\/figcaption><\/figure><\/div>\n\n\n\n

For S. elongatus<\/em> PCC 7942, latex formulation and Texanol concentration did not interact to affect PS over time (GLM, Latex\u2009*\u2009Texanol\u2009*\u2009Time, DF\u2009=\u200928, F\u2009=\u20091.49, P<\/em>\u2009=\u20090.07), although the formulation was a significant factor (GLM, Latex\u2009*\u2009Time, DF\u2009=\u200914, F\u2009=\u20093.14, P<\/em>\u2009=\u2009\u2009<\u20090.001)  (Fig. 2<\/a>a). Texanol concentration did not have a significant effect over time (GLM, Texanol\u2009*\u2009Time, DF\u2009=\u200914, F\u2009=\u20091.63, P<\/em>\u2009=\u20090.078). There were significant interactions affecting Fv<\/sub>\/Fm<\/sub> (GLM, Latex\u2009*\u2009Texanol\u2009*\u2009Time, DF\u2009=\u200928, F\u2009=\u20094.54, P<\/em>\u2009=\u2009\u2009<\u20090.001). An interaction between latex formulation and Texanol concentration had a significant effect on Fv<\/sub>\/Fm<\/sub> (GLM, Latex\u2009*\u2009Texanol, DF\u2009=\u20094, F\u2009=\u2009180.42, P<\/em>\u2009=\u2009\u2009<\u20090.001). Each parameter also influenced Fv<\/sub>\/Fm<\/sub> over time (GLM, Latex\u2009*\u2009Time, DF\u2009=\u200914, F\u2009=\u20099.91, P<\/em>\u2009=\u2009\u2009<\u20090.001 and Texanol\u2009*\u2009Time, DF\u2009=\u200914, F\u2009=\u200910.71, P<\/em>\u2009=\u2009\u2009<\u20090.001). The 12H latex supported the lowest mean PS and Fv<\/sub>\/Fm<\/sub> values (Fig. 2<\/a>b), indicating that the polymer was more toxic.<\/p>\n\n\n\n

There were significant differences in PS for\u00a0S. elongatus<\/em>\u00a0CCAP 1479\/1A (GLM, Latex\u2009*\u2009Texanol\u2009*\u2009Time, DF\u2009=\u200928, F\u2009=\u20092.75,\u00a0P<\/em>\u2009=\u2009\u2009<\u20090.001), with latex formulation but not Texanol concentration as significant factors (GLM, Latex\u2009*\u2009Time, DF\u2009=\u200914; F\u2009=\u20096.38;\u00a0P<\/em>\u2009=\u2009\u2009<\u20090.001; GLM, Texanol\u2009*\u2009Time, DF\u2009=\u200914, F\u2009=\u20091.26,\u00a0P<\/em>\u2009=\u20090.239). The 0S and 4S \u2018soft\u2019 polymers supported slightly higher PS performance levels than the suspension controls (Mann\u2013Whitney U, 0S vs. control, W\u2009=\u2009686.0,\u00a0P<\/em>\u2009=\u20090.044, 4S vs. control, W\u2009=\u2009713,\u00a0P<\/em>\u2009=\u20090.01) and supported improved Fv<\/sub>\/Fm<\/sub>\u00a0performance (Mann\u2013Whitney U, 0S vs. control, W\u2009=\u2009794.0,\u00a0P<\/em>\u2009=\u2009\u2009<\u20090.001, Mann\u2013Whitney U, 4S vs. control, W\u2009=\u2009815.0,\u00a0P<\/em>\u2009=\u2009\u2009<\u20090.001) \u00a0(Fig.\u00a03<\/a>a) indicating more efficient photon transport into photosystem II. For the Fv<\/sub>\/Fm<\/sub>\u00a0values of CCAP 1479\/1A cells, there were significant differences between latexes over time (GLM, Latex\u2009*\u2009Texanol\u2009*\u2009Time, DF\u2009=\u200928, F\u2009=\u20096.00,\u00a0P<\/em>\u2009=\u2009\u2009<\u20090.001) \u00a0(Fig.\u00a03<\/a>b).<\/p>\n\n\n\n

<\/p>\n\n\n\n

…<\/p>\n\n\n\n

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you may read the full article under https:\/\/www.nature.com\/articles\/s41598-022-21686-3<\/a><\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"

Abstract Carbon capture and storage is required to meet Paris Agreement targets. Photosynthesis is nature\u2019s carbon capture technology. Drawing inspiration from lichen, we engineered 3D photosynthetic cyanobacterial biocomposites (i.e., lichen mimics) using acrylic latex polymers applied to loofah sponge. Biocomposites had CO2 uptake rates of 1.57\u2009\u00b1\u20090.08 g CO2 g\u22121biomass d\u22121. Uptake rates were based on the dry biomass at […]<\/p>\n","protected":false},"author":59,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_seopress_robots_primary_cat":"none","nova_meta_subtitle":"Photosynthesis is nature\u2019s carbon capture technology; however, its capacity to reverse anthropogenic carbon enrichment within a meaningful timescale is equivocal","footnotes":""},"categories":[5571],"tags":[10744,10416,10743],"supplier":[1582,9285],"class_list":["post-119046","post","type-post","status-publish","format-standard","hentry","category-co2-based","tag-carboncapture","tag-circulareconomy","tag-useco2","supplier-chulalongkorn-university","supplier-northumbria-university"],"_links":{"self":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts\/119046","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/users\/59"}],"replies":[{"embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/comments?post=119046"}],"version-history":[{"count":0,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts\/119046\/revisions"}],"wp:attachment":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/media?parent=119046"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/categories?post=119046"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/tags?post=119046"},{"taxonomy":"supplier","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/supplier?post=119046"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}