Fate of polychlorobiphenyls in Tenebrio molitor larvae: consequences for further use as food and feed

Abstract

This study explored the ability of Tenebrio molitor, one of the most widely bred and traded insect species in Europe, to bioaccumulate polychlorobiphenyls (PCBs) from their feeding substrate. T. molitor larvae were reared for 20 days in a temperature- and humidity-controlled incubator and fed with wheat bran artificially contaminated with PCBs at a concentration of 0.67, 4.0 or 24.4 μg/kg. The larvae PCB content was then measured based on an analysis by GC-MS and GC-μECD. Whatever the level, a bran contamination by PCBs did not affect the body weight of larvae indicating a high tolerance to PCBs. The bioaccumulation factors (BAF; concentration of PCBs in larvae / concentration of PCBs in wheat bran) obtained with fresh larvae ranged between 0.4 and 1.0 and were significantly higher with the highest contamination level for PCBs 153 and 180. Although there is no bioaccumulation of PCBs in T. molitor larvae during rearing, PCBs can be transferred from the diet to the larvae. This study highlights the significant impact of the drying process which induces an increase of the PCB concentration in larvae by a factor of almost 3. This demonstrates the importance of considering the quality of the substrates used for farming insects as food and feed in terms of content in chemical contaminants including persistent organic pollutants like PCBs.