Possibilities for discriminating between Tenebrio molitor larvae fed with plastic and conventional substrates

The rapid increase in the global population is driving up the demand for high-quality biological proteins and contributing to rising plastic production and plastic waste. Research indicates that certain larvae may break down plastic, which is resistant to biodegradation, due to bacteria and enzymes in their gut. This study aims to identify a measurement method suitable for industrial use to detect plastic consumption by larvae, which were fed three distinct diets: a mixture of flour and carrot (control), white Styrofoam (wPs), and grey Styrofoam (gPS) enriched with activated carbon. In addition to Styrofoam (polystyrene (PS)), the second two groups were given a mix of flour and carrots. The measurements were conducted using near-infrared spectroscopy, and the data were analysed using Matlab2019a software. A variety of classification algorithms were employed to separate the three groups following pretreatment of the spectra. The linear support vector machine (SVM) model demonstrated an 88% accuracy rate in separating the three groups. Larvae fed on polystyrene-free feed were accurately identified, while larvae fed on two types of polystyrene were less well differentiated. The classification methods were also tested for two groups: larvae fed with polystyrene-containing and polystyrene-free feed. The results indicate that the linear SVM was 92% efficient. At the same time, the quadratic SVM and cubic SVM demonstrated 100% efficiency. The results show that the appropriate model can be employed to differentiate between larvae that consume polystyrene and those that consume plastic-free diets. The underlying mechanism responsible for this separation, whether it be undegraded microplastics in the larval gut or other substances accumulated from polystyrene, requires further investigation.