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Beverage-carton hydropulping reject secondary resource

The aluminium-polymer-rich reject remaining after paper recovery by hydropulping discarded liquid beverage cartons, with residual cellulosic fibres and mixed plastics. This process-defined secondary resource is distinct from intact beverage cans, pharmaceutical blisters, aluminium as an element and purified polyethylene. The selected industrial-origin sample does not define a universal reject composition or inherit a criticality list.

Microbial & Biochemical Mechanisms (1)

Culture-derived acid leaching in staged carton-reject processing

bioleaching Microbial

Associated Organisms: Acidithiobacillus thiooxidans (NCBITaxon:930), Acidithiobacillus caldus (NCBITaxon:33059)

Sulfur-oxidizing mixed cultures supplied acidic supernatant for aluminium dissolution in a separate laboratory leaching stage. Enzymatic fibre removal, acid leaching, sodium-hydroxide precipitation and polymer density separation are distinct operations. Comparable reagent-acid performance prevents assigning a special leaching benefit to live cells or microbial metabolites. Aluminium precipitation is a subsequent chemical operation.

Experimental Context & Analytical Limits:
About 25 kg of reject was supplied by a German paper recycler after hydropulping. Large caps were removed, the material dried at 60 degrees C for up to 48 hours, shredded below 11 mm and homogenized. FTIR and SEM-EDX identified layered Al, predominantly PE, other plastics and residual fibres. Small-scale enzyme pretreatment used 1 g feed in 100 mL, 0.5 M citrate buffer at pH 4.8, 2.5-7.5% v/v Cellic CTec3, 50 degrees C and 150 rpm for 24 hours. This commercial enzyme mixture is not a live microbial culture, and its producing strain is not assigned. The supplement identifies DSM 504 and DSM 9466 for acid generation in a 2 L vessel with 1.8 L working volume, 6% w/v sulfur, 30 degrees C, 250 rpm and 60 L/h air, followed by partial medium replacement and a second cycle. Centrifuged supernatant is described as cell-free 1.4 M sulfuric acid; the supplement estimates total acidity from sulfate and pH rather than establishing reagent purity. Leaching used 100 mL in 250 mL flasks, 1.0, 2.5 or 5.0% w/v reject, room temperature and 150 rpm, in triplicate, with a commercial 1.4 M acid comparator only at the highest loading. Aluminium was measured by the chromazurol-S Spectroquant assay. The integrated trial used 50 g/L reject in a 2 L bottle: four days of enzyme treatment at 50 degrees C and 170 rpm, washing, then 1 L biogenic acid at 30 degrees C and 170 rpm for about a week.
Curated Evidence Points:
Methods 2.5 and 2.8, Results 3.3-3.4 and Figures 4-5 support aluminium dissolution from this prepared reject. The authors describe near-complete flask leaching by seven days and integrated leaching by seven to eight days. Figure 4a contains variation with loading and uncertainty, so these descriptions are approximate outcomes rather than an exact 100% yield for every replicate. Figure 4a's commercial-acid comparison is similar; the evidence supports acid substitution, not microbial necessity during the leaching stage or a universal advantage over chemical treatment.
A separate direct-culture arm used source-labelled A. ferrooxidans DSM 583, also called newly classified A. ferridurans in Methods 2.5. Its pre-grown iron-containing medium, initial acidification to pH 1.4, added sulfur and reagent-medium blanks differ from the spent-acid comparison. The authors report at most about 88% leaching at 10 g/L after 14 days, falling to about 20% at 25 g/L. Figure 4b shows a nonzero chemical blank. Figure 4g and Figure S2 show polymer oxidation-associated spectra and discoloration. These results limit extrapolation across loadings and methods; they do not establish a persulfate or Fenton pathway, which is proposed without a pathway-specific intervention. No taxon CURIE is assigned to this disputed direct-culture stock.
After leaching, NaOH addition to pH 6.5 in the methods produced a filtered precipitate described as Al(OH)3. The abstract instead says pH 6.4. Reported near-100% precipitation follows residual-solution Al non-detection, without a stated detection limit, crystalline-phase confirmation, product purity or whole-feed isolated Al yield. This is chemical precipitation downstream of microbial acid production, not demonstrated microbial aluminium biomineralization.
Enzyme and acid processing, repeated washing, drying, density separation and extrusion all contribute to the recovered polymer fraction. Figure 3 supports fibre removal with some lignin-rich remains; no enzyme-producing organism or enzyme-free glucose baseline is established here. Figure 6 retains visible impurities despite similar processed-film rheology. Figure 2's starting 79/11/11% component labels sum to 101%, so they are not an exact mass balance. The abstract's stirred-tank description of the integrated trial differs from the bottle-and-shaking methods. An industrial feed supplier and 1 L laboratory treatment do not establish industrial deployment or verified environmental and economic savings.
Context_only Source: dsm504
The live collection corroborates the upstream DSM 504 species label.
Context_only Source: dsm9466
The live collection corroborates upstream DSM 9466 as A. caldus C-SH12.
Partial Source: dsm583
The current catalogue retains A. ferrooxidans for DSM 583, unlike the paper's reclassification statement. Neither label independently authenticates the experimental stock or resolves its genomic identity.
The species CURIE does not identify DSM 504 or prove its individual role.
Context_only Source: ncbi_caldus
The species CURIE does not identify DSM 9466 or prove its individual role.

Sources & References

  1. kremser2022_cartons: Kremser, Gerl, Benedito Borrás, Ramírez Espinosa, Monje Martínez, Guebitz and Pellis (2022). Bioleaching/enzyme-based recycling of aluminium and polyethylene from beverage cartons packaging waste. Resources, Conservation and Recycling 185:106444. DOI 10.1016/j.resconrec.2022.106444; published journal version, Sections 2-3, Figures 1-6, supplementary acid-production methods, Table S1 and Figures S1-S2.
    https://doi.org/10.1016/j.resconrec.2022.106444 (accessed 2026-10-11)
  2. dsm504: DSMZ catalogue DSM 504, Acidithiobacillus thiooxidans.
    https://www.dsmz.de/collection/catalogue/details/culture/DSM-504 (accessed 2026-10-11)
  3. dsm9466: DSMZ catalogue DSM 9466, Acidithiobacillus caldus, strain C-SH12.
    https://www.dsmz.de/collection/catalogue/details/culture/DSM-9466 (accessed 2026-10-11)
  4. dsm583: DSMZ catalogue DSM 583, Acidithiobacillus ferrooxidans. The live collection label differs from the paper's statement that this strain was newly classified as A. ferridurans; no experimental stock is silently reassigned.
    https://www.dsmz.de/collection/catalogue/details/culture/DSM-583 (accessed 2026-10-11)
  5. ncbi_thiooxidans: NCBI Taxonomy 930, Acidithiobacillus thiooxidans, species identifier.
    https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=930&mode=Info (accessed 2026-10-11)
  6. ncbi_caldus: NCBI Taxonomy 33059, Acidithiobacillus caldus, species identifier.
    https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=33059&mode=Info (accessed 2026-10-11)

Curation History

Timestamp Curator Action Summary
2026-10-11T15:35:11.845370Z Codex (GPT-6; Codex) CREATE Created the process-defined carton reject resource and staged acid-leaching observation, retaining chemical-acid equivalence, poorer direct-culture outcomes, disputed DSM 583 nomenclature, precipitation-assay limitations and laboratory-scale boundaries.

Record source: data/records/beverage-carton-hydropulping-reject.yaml