Impact of Processed Food (Canteen and Oil Wastes) on the Development of Black Soldier Fly (Hermetia illucens) Larvae and Their Gut Microbiome Functions

Thomas Klammsteiner; Andreas Walter; Tajda Bogataj; Carina D Heussler; Blaž Stres; Florian M Steiner; Birgit C Schlick-Steiner; Heribert Insam

doi:10.3389/fmicb.2021.619112

Impact of Processed Food (Canteen and Oil Wastes) on the Development of Black Soldier Fly (Hermetia illucens) Larvae and Their Gut Microbiome Functions

Front Microbiol. 2021 Jan 21:12:619112. doi: 10.3389/fmicb.2021.619112. eCollection 2021.

Authors

Thomas Klammsteiner¹, Andreas Walter², Tajda Bogataj¹, Carina D Heussler^{1

3}, Blaž Stres^{4

5

6}, Florian M Steiner³, Birgit C Schlick-Steiner³, Heribert Insam¹

Affiliations

¹ Department of Microbiology, University of Innsbruck, Innsbruck, Austria.
² Department of Biotechnology and Food Engineering, MCI - The Entrepreneurial School, Innsbruck, Austria.
³ Department of Ecology, University of Innsbruck, Innsbruck, Austria.
⁴ Department of Animal Science, University of Ljubljana, Ljubljana, Slovenia.
⁵ Institute of Sanitary Engineering, University of Ljubljana, Ljubljana, Slovenia.
⁶ Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.

Abstract

Canteens represent an essential food supply hub for educational institutions, companies, and business parks. Many people in these locations rely on a guaranteed service with consistent quality. It is an ongoing challenge to satisfy the demand for sufficient serving numbers, portion sizes, and menu variations to cover food intolerances and different palates of customers. However, overestimating this demand or fluctuating quality of dishes leads to an inevitable loss of unconsumed food due to leftovers. In this study, the food waste fraction of canteen leftovers was identified as an optimal diet for black soldier fly (Hermetia illucens) larvae based on 50% higher consumption and 15% higher waste reduction indices compared with control chicken feed diet. Although the digestibility of food waste was nearly twice as high, the conversion efficiency of ingested and digested chicken feed remains unparalleled (17.9 ± 0.6 and 37.5 ± 0.9 in CFD and 7.9 ± 0.9 and 9.6 ± 1.0 in FWD, respectively). The oil separator waste fraction, however, inhibited biomass gain by at least 85% and ultimately led to a larval mortality of up to 96%. In addition to monitoring larval development, we characterized physicochemical properties of pre- and post-process food waste substrates. High-throughput amplicon sequencing identified Firmicutes, Proteobacteria, and Bacteroidota as the most abundant phyla, and Morganella, Acinetobacter, and certain Lactobacillales species were identified as indicator species. By using metagenome imputation, we additionally gained insights into the functional spectrum of gut microbial communities. We anticipate that the results will contribute to the development of decentralized waste-management sites that make use of larvae to process food waste as it has become common practice for biogas plants.

Keywords: 16S amplicon sequencing; animal feedstuff; circular economy; growth parameters; metabolism; microbial communities; oil waste; waste valorization.