Technical Review: The Chonkus Cyanobacterium as a High-Density, Fast-Settling Bioproduction Chassis

Abstract

A recently described cyanobacterium nicknamed Chonkus (UTEX 3222, Cyanobacterium aponinum) was isolated from CO₂-rich volcanic seeps off Vulcano Island, Italy. Peer-reviewed work reports rapid growth to very high culture densities and unusually fast sinking behaviour. These traits could reduce harvesting energy and open new options for high-density photobioreactors and solid-liquid separation strategies. This review synthesises the primary literature and authoritative summaries, evaluates engineering implications for industrial photobioreactors, and identifies key knowledge gaps relevant to Nellie’s bioengineered carbon removal systems.

1. Origin and taxonomic assignment

Chonkus derives from shallow marine sites where volcanic seeps deliver near-continuous CO₂, driving low pH conditions in Baia di Levante, Vulcano, Sicily. The strain is catalogued as UTEX B-3222 and taxonomically placed within Cyanobacterium aponinum. The UTEX entry records the collection site conditions and recommended artificial seawater medium for culture. These details suggest innate tolerance to high dissolved inorganic carbon, variable salinity, and warm surface waters.

2. Key reported phenotypes

The primary paper by Schubert et al. reports two traits of direct process interest. First, robust high-density growth under laboratory conditions compared with model cyanobacteria. Second, rapid settling relative to other fast-growing strains, which the authors quantified as accelerated sedimentation in static assays. Public summaries emphasise large cell or colony size and high intracellular carbon storage, with images showing dense, cohesive pellets after short quiescent periods.

Several institutional and media explainers are consistent with the paper. They note fast growth in CO₂-rich conditions, tolerance to variable pH and salinity, and a tendency to form dense aggregates that sink quickly. While secondary sources are not substitutes for the article, they help clarify potential use-cases and have been cross-checked against the peer-reviewed text.

3. Engineering relevance

3.1 Harvesting and dewatering

Rapid sedimentation is uncommon in planktonic cyanobacteria. If maintained at scale, Chonkus could enable gravity thickening, lamella settlers, or low-g centrifugation instead of energy-intensive dissolved air flotation or high-g disk stacks. The potential to operate photobioreactors at higher optical densities with periodic quiescent settling would alter downstream energy balances and capital choices. Validation requires size distribution, floc strength, and hindered settling kinetics under relevant ionic strength and shear, since shear in loop reactors often disrupts flocs.

3.2 High-density growth

The reported high-density cultures suggest advantages for land use and reactor footprint. In closed photobioreactors, light path and mixing become limiting at high optical density, so maintaining productivity requires either short path reactors, strong internal circulation, or light dilution strategies. If Chonkus maintains photosynthetic efficiency at higher densities than common strains, geometric productivity could improve. Comparative areal productivity data across light spectra and temperatures are needed to quantify this advantage.

3.3 Gas transfer and pH control

Chonkus’ native environment is CO₂-rich and acidic. In industrial media, elevated CO₂ delivery depresses pH and increases dissolved inorganic carbon availability, improving Rubisco kinetics. The trade-off is increased inorganic carbon stripping if gas transfer is not optimised. Process design should pair mass transfer coefficients with buffering and pH control to exploit the strain’s tolerance without incurring excessive CO₂ losses.

3.4 Compatibility with downstream valorisation

Reports highlight conspicuous intracellular carbon storage. The biochemical form of this storage matters. If carbon is in glycogen or storage polysaccharides, hydrothermal and catalytic routes will differ from lipid-rich strains. If cells are larger and more carbon dense, pyrolysis mass yields and char quality may shift. Bench tests should quantify elemental C, H, N, S, O, ash, and H/C_\text{org} at typical harvest moisture to model char yield and stability in Nellie’s pyrolysis units.

4. Cultivation options and control strategies

4.1 Suspension growth with triggered settling

A logical mode is standard suspension growth with mixing strong enough to prevent continuous sedimentation, followed by periodic quiescent phases for gravity separation. Control variables include superficial velocity, mixing Reynolds number, and cycle timing to balance light exposure with settle-and-harvest efficiency. This approach suits tubular or flat-panel photobioreactors with side-stream settlers.

4.2 Biofilm or attached growth

Chonkus’ cohesive behaviour suggests potential for biofilm or trickle-bed modes. However, attached growth changes light fields and mass transfer. Bench studies should compare surface attachment tendencies on hydrophilic and hydrophobic carriers, including whether fast settling translates into strong biofilm formation. If biofilm is viable, hydraulic shear and backwash cycles must be tuned to avoid sloughing losses.

4.3 Open systems and risk

Given Chonkus was isolated from natural seawater, open raceways might appear attractive. In practice, contamination pressure, predators, and weather variability argue for enclosed systems until more data are available. The strain’s robust growth in high CO₂ environments does not guarantee competitiveness in open ponds at ambient conditions.

5. Data gaps and experimental plan for Nellie

• Kinetics under industrial light and temperature. Replicate laboratory growth curves under Nellie-relevant photon flux densities, diel cycles, and temperatures. Compare to a well-characterised fast cyanobacterium as control. Track biomass concentration, specific growth rate, photosynthetic efficiency, and pigment content.

• Sedimentation and rheology. Measure isokinetic settling rates, floc strength versus shear, and sludge rheology at target harvest densities. Determine whether lamella settlers or inclined plate clarifiers will meet throughput. Quantify how nutrient levels and ionic strength affect settling.

• Gas transfer and carbon use efficiency. In flat-panel and short-path reactors, map k_\text{La}, pH, and dissolved inorganic carbon under high CO₂ sparging. Optimise CO₂ utilisation by coupling gas composition, superficial velocity, and residence time to minimise stripping.

• Biomass composition and downstream fits. Perform proximate and ultimate analysis, carbohydrate and storage polymer assays, and then pyrolyse wet and dried biomass to compare char yield and H/C_\text{org}. This will establish whether Chonkus improves carbon retention or energy integration in pyrolysis versus current strains.

• Genetic tools and stability. Confirm availability of transformation or genome tools for UTEX 3222. The AEM paper discusses genomics and biochemical composition. If engineering is planned, tool availability will influence timelines.

6. Opportunities and constraints for policy audiences

• Potential energy savings in harvesting: If rapid settling at scale is confirmed, process energy for separation could fall significantly. That would improve net energy balance and operating costs for algal bioproduction facilities. The magnitude depends on actual settling velocities and achievable thickening without polymer aids.

• Land and water footprint: High-density growth offers better land productivity. If productivity scales with culture density, facilities could be more compact, which supports brownfield siting near CO₂ sources. Confirmation requires year-round areal productivity data.

• Responsible deployment: Open water release is not advised. The discovery team itself highlights the need for safeguards and controlled systems. Enclosed photobioreactors with well-defined containment are compatible with UK environmental protection principles while enabling rigorous study.

7. Conclusions

Chonkus combines two rare and industrially attractive traits. It grows to high density and it sinks quickly. Together these traits could reduce harvesting costs and reshape reactor operations if reproduced outside the laboratory. The strain’s origin in CO₂-rich, low-pH volcanic seeps aligns with industrial conditions that feed elevated CO₂ into reactors. The engineering case is not yet proven at scale. The next step is a focused bench-to-pilot programme that quantifies growth and settling under industrial conditions, characterises biomass for downstream thermal conversion, and establishes whether the advantages outweigh control challenges. On current evidence, Chonkus merits near-term laboratory evaluation within Nellie’s photobioreactor platform.

References

1. Schubert, M. G. et al. Cyanobacteria newly isolated from marine volcanic seeps display rapid sinking and robust high-density growth. Applied and Environmental Microbiology 90(11), e00841-24, 2024.

2. Wyss Institute. Newly discovered cyanobacteria could help sequester carbon from oceans and factories. News release, 29 Oct 2024.

3. UTEX Culture Collection of Algae. UTEX B-3222 Cyanobacterium aponinum entry. Accessed Oct 2025.

4. Science News. Meet Chonkus, the mutant cyanobacteria that could help fight climate change. 7 Nov 2024.

5. ScienceDaily. Cyanobacteria newly isolated from marine volcanic seeps display rapid sinking and robust, high-density growth. 29 Oct 2024.

6. EcoWatch. Newly discovered bacteria Chonkus offers potential for carbon capture. 5 Nov 2024.

7. Interesting Engineering. New CO₂-hungry algae found, could eat carbon in oceans. 29 Oct 2024.

8. SynBioBeta. Meet Chonkus: the algae that eats carbon and sinks like a rock. 29 Oct 2024.