Microbial activity has the potential to enhance the corrosion of high-level radioactive waste disposal canisters, which, in the proposed Swiss deep geological repository, will be embedded in bentonite and placed in the Opalinus Clay (OPA) rock formation. A total of 12 stainless steel cylindrical vessels (referred to as modules) containing bentonite were deployed in an anoxic borehole in OPA for up to 5.5 years. Carbon steel coupons were embedded in the bentonite. Individual modules were retrieved after 1, 1.5, 2.5, and 5.5 years. Enumeration of aerobic and anaerobic heterotrophs and sulfate-reducing bacteria (SRB) revealed microbial growth for 1.5 years followed by a decline or stagnation in microbial viability. It was surprising to observe the growth of aerobic heterotrophs followed by their persistent viability in bentonite, despite the nominally anoxic conditions. In contrast, SRB numbers remained at very low levels. DNA-based amplicon sequencing confirmed the persistence of aerobes and the relatively low contribution of anaerobes to the bentonite microbiome. Bentonite dry density, in situ exposure time, and bioavailable trapped oxygen are observed to shape the bentonite microbial community in the clay.
Background Edible insects have a low ecological footprint and could serve as an alternative dietary iron source. However, chitin, a major component of insects, avidly binds iron and might inhibit iron absorption. Objectives We aimed to measure fractional iron absorption (FIA) from Tenebrio molitor–based test meals with and without dechitinization, and to assess the effect of native and low chitin T. molitor on FIA from iron-fortified maize porridge. Methods We measured iron absorption in young females with low iron stores (n = 21) from 1) labeled (54FeSO4) fortified maize porridge (maize alone); 2) intrinsically labeled (57Fe added during rearing) T. molitor larvae with native chitin content (NC) added to maize alone; and 3) dechitinized intrinsically labeled (57Fe) T. molitor larvae with low chitin content (LC) added to maize alone. We determined FIA using erythrocyte isotope incorporation and measured in vitro iron dialyzability from the 3 meals. Results NC and LC T. molitor had similar mean ± SD iron content (12.0 ± 0.1 mg/100 g). Geometric mean (95% CI) FIAs from the 3 test meals were 1) maize alone: 5.8% (3.2%, 10.8%); 2) maize + NC T. molitor: 5.3% (2.5%, 11.3%) and 4.1% (1.9%, 8.7%); and 3) maize + LC T. molitor: 4.6% (2.0%, 10.3%) and 4.0% (1.8%, 9.2%), for extrinsic and intrinsic labels, respectively. FIA from NC and LC T. molitor did not significantly differ, and both were lower (P < 0.005) than FIA from the labeled maize porridge in the 3 meals, which did not significantly differ. The slopes of the relations between FIA and serum ferritin in the different meals and from the intrinsic and extrinsic labels did not significantly differ. Conclusions T. molitor biomass does not strongly affect iron absorption when added to maize porridge. Our data suggest T. molitor iron is absorbed from the common nonheme iron pool. Native T. molitor is high in iron which is moderately well absorbed, suggesting it could be a valuable dietary iron source. This trial was registered at clinicaltrials.gov as NCT04510831.
Objectives Iron deficiency is estimated to affect up to 1.5–2 billion people worldwide. Edible insects can be a rich source of iron and may have a smaller environmental food print than other animal source foods. Mealworm (Tenebrio molitor) larvae are recognized as an edible insect, but iron bioavailability in humans has not been investigated. Chitin, a major component of insect biomass, is a known iron binder. Our primary objective was to measure fractional iron absorption (FIA) from T.molitor with and without chitin in young women. Secondly, we aimed to assess the effect of the presence of mealworm biomass on iron absorption from iron present in low-phytate maize porridge. Methods Non-anemic females (18–45 years, body weight < 65 kg) were recruited and FIA was measured as erythrocyte incorporation of stable isotopes tracers in red blood cells 14 days after test meal administration. Using a randomized cross over design, three different meals were administered to each subject, consisting of A) a low phytate refined maize porridge with 54FeSO4; B) intrinsically labelled (57Fe) T.molitor with native chitin and extrinsic 58FeSO4; C) intrinsically labelled (57Fe) T.molitor with reduced chitin and extrinsic 58FeSO4. Results Median serum ferritin concentration in the participating subjects (n = 21) was 22.7 µg/L. Iron content in T.molitor larvae was FIA from meals B (58Fe, 5.28%) and C (58Fe, 4.55%) in which mealworm biomass was given in combination with maize porridge did not significantly differ to FIA from maize porridge fed alone (5.84%). In case of intrinsic labelling, FIA from meals B (57Fe, 4.11%) and C (57Fe, 4.03%) were significantly lower compared to maize meal A (P < 0.001). Conclusions FIA from T.molitor was similar to low-phytate containing maize. Presence of mealworm biomass did not enhance or inhibit the FIA of iron present in the maize meal. Furthermore, a chitin reduction process did not show any discernible effect on FIA. T.molitor larvae could be a viable source of iron in the human diet, but iron absorption may be similar to plant-based foods. The study was registered at clinicaltrials.gov as NCT04510831. Funding Sources Coop Research Program, World Food System Center, ETH Zurich, Switzerland.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.