No abstract

Sustainability, circular economy and alternative production systems are urgent imperatives for humanity and animal husbandry. Unless wasted, agri-food by-products can offer a promising source of high value. We evaluated the effect of rice bran (RB), corncob (CC), potato peels (PP), solid biogas residues (BR), and olive-oil processing residuals (OR), as alternative substrates to wheat bran (WB as control), on the growth and nutritional value of Tenebrio molitor during its breeding for animal feeds and/or human consumption. Innovation-wise, we further investigated the substrate supplementation (0, 10, 20%) with post-distillation residues of Mediterranean aromatic-medicinal plants (MAPs: lavender, Greek oregano, rosemary, olive; 1:1:1:1 ratio). Tenebrio molitor larvae (TML) were reared in all the studied substrates, and TML and diets’ proximate and fatty acid compositions as well as total phenol and flavonoid content and antioxidant potential were assessed using standard procedures. After statistical analysis of correlations, we observed that CC promoted oviposition and progeny survival; larval weight and dry matter were positively affected mainly by dietary energy and fat content; number of TML and/or larval weight increased using 10% MAPs inclusion in WB, RB and OR or RB, OR, BR and PP, respectively, which did not affect protein content; TML fatty acid composition decreased the content of saturated ones and increased that of mono-unsaturated ones; MAPs residues had an apparent favorable impact on total phenolic content and antioxidant activity of each substrate, with RB displaying the highest capacity and content. These findings indicate that alternative substrates can be exploited and their enrichment with natural phenolics is able to influence T. molitor growth, offering highly beneficial and nutritional value.

Industrial production of Tenebrio molitor larvae (TML), a promising source of protein for food, requires safety, fast growth, maturation, and high survival. Probiotics, enhance host growth and protect against pathogens and diseases. This study evaluates the effects of three probiotic bacteria immobilized on the diet of mealworms, on growth performance, nutritional value, and microbial load of T. molitor larvae. The bacteria employed were Bacillus subtilis, Bacillus toyonensis and Enterococcus faecalis, all presenting probiotic properties. The highest larvae weight and length gain and shorter time to pupation were observed in the E. faecalis series. Following probiotic administration, the crude protein content increased, and crude fat was reduced. The highest protein values were observed in E. faecalis series, the highest dry matter content when B. toyonensis and B. subtilis were employed, and the lowest fat content in B. subtilis series. Fatty acid analysis showed significantly decreased content of palmitic and myristic acid and increased levels of stearic acid in all treatments. Microbial load analysis showed a decrease in Enterobacteriaceae by 46 and 99% in B. subtilis and B. toyonensis series, while coliforms and endospores were significantly reduced in all probiotic series. Addition of probiotic bacteria in T. molitor larvae diet resulted in a significant improvement in terms of growth enhancement, nutritional fortification, and microbial load reduction. In conclusion, probiotic bacteria in TML diet result in the faster production of nutritious and safe insects, to cover insect food market demands.