Uptake of heavy metals and arsenic in black soldier

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Research Article Received: 18 May 2017

Revised: 27 July 2017

Accepted article published: 27 September 2017

Published online in Wiley Online Library:

(wileyonlinelibrary.com) DOI 10.1002/jsfa.8702

Uptake of heavy metals and arsenic in black soldier fly (Hermetia illucens) larvae grown on seaweed-enriched media Irene Biancarosa,a,b Nina S Liland,a Daan Biemans,c Pedro Araujo,a Christian G Bruckner,d Rune Waagbø,a,b Bente E Torstensen,a† Erik-Jan Locka and Heidi Amlunda* Abstract BACKGROUND: The black soldier fly (Hermetia illucens) is one of the most promising insect species for use in animal feed. However, studies investigating feed and food safety aspects of using black soldier fly as feed are scarce. In this study, we fed black soldier fly larvae feeding media enriched with seaweed, which contains naturally high concentrations of heavy metals and arsenic. The aim of this study was to investigate the potential transfer of such undesirable substances from the feeding media to the larvae. RESULTS: The larvae accumulated cadmium, lead, mercury and arsenic. Concentrations of these elements in the larvae increased when more seaweed was added to the feeding media. The highest retention was seen for cadmium (up to 93%) and the lowest for total arsenic (up to 22%). When seaweed inclusion exceeded 20% in the media, this resulted in larval concentrations of cadmium and total arsenic above the current European Union maximum levels for these elements in complete feed. CONCLUSION: Our results confirm that insect larvae can accumulate heavy metals and arsenic when present in the feeding media. A broader understanding of the occurrence of these undesirable substances in processed larvae products is needed to assess feed and food safety. © 2017 Society of Chemical Industry Keywords: contaminants; macroalgae; insect larvae; heavy metals; arsenic; seaweed

INTRODUCTION Research on insects has increased significantly over the past few years for a wide range of purposes. Among the insect species, there has been an increasing interest in rearing the black soldier fly (Hermetia illucens, L.; BSF). The larvae of this species can be used for biodegradation of organic waste1,2 and are a promising feed source for animal nutrition, being rich in both protein (∼400 g kg−1 dry weight, DW) and lipid (>300 g kg−1 DW).3,4 They also contain essential amino and fatty acids, and micronutrients.3,4 Previous studies indicated that BSF larvae are beneficial dietary ingredients for swine,5 poultry6 and some fish species such as channel catfish (Ictalurus punctatus), blue tilapia (Oreochromis aureus), Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss).7–10 These studies, among others, have revealed high potential for the use of BSF larvae as both whole and processed larvae meal. BSF larvae are scavengers and can easily grow on a wide range of substrates11–13 – an ability that can be favourable for rearing purposes. Several substrates for rearing BSF larvae have been tested, e.g. livestock manure,11–13 food waste12 and fish offal.14 However, such media are not suitable substrates for rearing BSF larvae in the European Union (EU), where their use as feed is currently forbidden.15 The European insect industry is using plant-based feeding media for rearing BSF larvae, such as vegetable and fruit J Sci Food Agric (2017)

residues, wheat bran, grass and brewery by-products, hay and powder made from plants.16 Besides these materials, insect producers in Europe have recently shown great interest in using other media for rearing insect larvae.16 Among resources that could be used as rearing substrates for farming insects are marine macroalgae or seaweed. Seaweeds are listed as authorized feed materials for food-producing animals17 and could therefore be used as substrate for insects. Seaweeds are traditionally eaten in most Asian countries, whereas their utilization in Europe has been mostly limited to the industrial production of thickeners (e.g. alginates, agar).18 Moreover, natural stocks of seaweeds along European



Correspondence to: H Amlund, National Institute of Nutrition and Seafood Research, Strandgaten 229, PO Box 2029 Nordnes, 5817 Bergen, Norway. E-mail: [email protected]

† Present address: NOFIMA, Kjerreidviken 16, NO-5141, Fyllingsdalen, Norway a National Institute of Nutrition and Seafood Research, Nordnes, Bergen, Norway b Department of Biology, University of Bergen, Bergen, Norway c Protix Biosystems BV, 5107 NC Dongen, The Netherlands d Norwegian Institute of Bioeconomy Research, Bodø, Norway

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© 2017 Society of Chemical Industry

www.soci.org coastlines are highly available and underexploited.19 Seaweeds are rich in minerals, vitamins, protein and marine nutrients such as omega-3 fatty acids, e.g. eicosapentaenoic acid (EPA).20 There is currently a global demand for feed ingredients containing such nutrients. Seaweeds, however, are not optimal as a feed ingredient for certain animals, including carnivorous fish, owing to its high content of water, salt and complex polysaccharides.21 Insect larvae can accumulate essential nutrients when fed seaweed-enriched media.22 Hence one can tailor the composition of insects towards a desired nutrient profile to be used in feed. Seaweeds can accumulate elements from the surrounding environment, especially heavy metals such as cadmium (Cd), lead (Pb) and mercury (Hg) and the metalloid arsenic (As).23 The presence of these undesirable substances in seaweeds highly depend on species as well as on seasonal and geographical variations.24 A survey conducted in Norway showed levels of Cd, Pb and Hg in brown algae species ranging from 0.5 to 3.4, from 0.08 to 0.2 and from 95

>95

>95

82

76

51 ± 5

5.6

4.8 ± 0.0

2.6

1.6

1.7

1.8

1.4 ± 0.3

95

>95

9.2 ± 1.2

7.1

6.8

6.4

89

102

1.5

36.6 ± 0.5 35.6

135 ± 7 2.2 ± 0.2

30.7 ± 0.3

BA80

BA90

BA100a

23.1 ± 0.8

P-value n.a.

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