Overview
Truzzi et al. tested whether black soldier fly prepupae grown on coffee-silverskin substrates enriched with microalgae could remain chemically suitable as feed or food biomass. The study measured cadmium (Cd), lead (Pb), total mercury (Hg), total arsenic (As), and nickel (Ni) in substrate ingredients, formulated growth substrates, prepupae, and frass. Coffee silverskin had low Cd, Pb, total As, and total Hg, while black soldier fly prepupae bioaccumulated Cd, Pb, and total Hg but remained within the EU undesirable-substance limits evaluated by the authors.
Key numbers
- Experimental design: nine growth substrates were tested, each with five replicate groups of 150 larvae. The control substrate was 100% coffee silverskin; the other substrates added 5%, 10%, 20%, or 25% Schizochytrium sp. or Isochrysis sp.
- Coffee silverskin ingredient concentrations, dry weight: Cd 0.053 +/- 0.008 mg/kg, Pb 0.032 +/- 0.002 mg/kg, total Hg 0.027 +/- 0.001 mg/kg, total As 0.147 +/- 0.006 mg/kg, and Ni 3.5 +/- 0.2 mg/kg.
- Microalgae ingredient concentrations, dry weight: Schizochytrium sp. had Cd 0.0025 +/- 0.0002 mg/kg, Pb 0.065 +/- 0.003 mg/kg, total Hg 0.009 +/- 0.002 mg/kg, total As 0.184 +/- 0.002 mg/kg, and Ni 3.6 +/- 0.1 mg/kg. Isochrysis sp. had Cd 0.0020 +/- 0.0005 mg/kg, Pb 0.084 +/- 0.009 mg/kg, total Hg 0.0016 +/- 0.0004 mg/kg, total As 0.153 +/- 0.001 mg/kg, and Ni 1.18 +/- 0.03 mg/kg.
- Growth-substrate concentrations, dry weight: Cd ranged from 0.037 to 0.050 mg/kg, Pb from 0.032 to 0.045 mg/kg, total Hg from 0.020 to 0.027 mg/kg, and total As from 0.139 to 0.154 mg/kg.
- Prepupae concentrations, dry weight: Cd ranged from 0.19 to 0.24 mg/kg, Pb from 0.063 to 0.075 mg/kg, total Hg from 0.029 to 0.112 mg/kg, and total As from 0.123 to 0.138 mg/kg.
- Prepupae concentrations, wet weight, from the abstract: Cd 0.072 to 0.084 mg/kg, Pb 0.018 to 0.026 mg/kg, total Hg 0.010 to 0.032 mg/kg, total As 0.036 to 0.047 mg/kg, and Ni 0.18 to 0.76 mg/kg.
- Bioaccumulation: Cd BAF was greater than 1 for all groups, with mean +/- SD 5.6 +/- 0.8; Pb BAF ranged from 1.6 to 2.3, mean 1.9 +/- 0.3; total Hg BAF was greater than 1 for all groups and ranged from 1.4 to 4.5. Total As BAF was near 1, ranging from 0.82 to 0.99.
Methods (brief)
The authors analyzed coffee silverskin, microalgae, formulated substrates, black soldier fly prepupae, and frass. Cd, Pb, Ni, and As were measured by graphite furnace atomic absorption spectrometry after nitric acid and hydrogen peroxide microwave digestion. Total Hg was measured by thermal decomposition amalgamation atomic absorption spectrometry using a direct mercury analyzer. Analytical quality control used DORM-2 dogfish muscle certified reference material.
Related evidence
Update history
The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.