The studies on waste biodegradation by Tenebrio molitor

Abstract

Abstract.As cities are growing in size with a rise in the population, the amount of plastic waste generated is increasing and becoming unmanageable. The treatment and disposal of plastic waste is an urgent need of our present and future. It has been proved recently that mealworms, the larvae of Tenebrio molitor Linnaeus, are able eat styrofoam, a common polystyrene product. Polystyrene is one of the most widely used plastics, the scale of its production being several million tons per year. Tenebrio molitor is one of the largest pests found in stored-grain products. The insect is indigenous to Europe, but is currently cosmopolitan in distribution. The styrofoam is efficiently degraded in the larval gut by microorganisms. We have used the larvae of T. molitor to biodegrade three types of food packaging plastics: polystyrene (PS), polyvinyl chloride (PVC) and polylactide (PLA). PVC is a thermoplastic made of 57% chlorine (derived from industrial grade salt) and 43% carbon (derived predominantly from oil /gas via ethylene). It is the world's third-most widely produced synthetic plastic polymer, which is not biodegradable easily. On the other hand, PLA is an easily biodegradable and bioactive thermoplastic aliphatic polyester derived from corn and tapioca starch or sugarcane. Three groups of larvae were fed selected types of polymers as an only food, while a control population was fed on oatmeal. The mass loss, dry matter content and biochemical composition of mealworms were assessed in the performed laboratory experiments. The protein concentration in homogenates of the larvae was determined by the Bradford method. To determine the level of hydrolized carbohydrates we used anthrone method. The classical sulfo-phospho-vanillin assay (SPVA) was used to quantitate total lipids in mealworms. The results allowed to compare the decomposition efficiency of selected polymer materials by mealworms and to recognize the mechanism of decomposition contributing to the future use of these animals for the treatment and disposal of plastic waste.

Ubiquity of polystyrene digestion and biodegradation within yellow mealworms, larvae of Tenebrio molitor Linnaeus (Coleoptera: Tenebrionidae)

“…Marshall School students (Duluth MN, USA) reported 33 mg PS 100 worms −1 d −1 , within the range of previous tests; a team at the University of Queensland, St. Lucia, Australia, reported that local mealworms consumed PS at a rate of 13 mg PS 100 worms −1 d −1 ; a team in Bandar Lampung, Indonesia, reported that PS foam feeds supported mealworm growth, and the feed had no significant effect on larvaemortality (Nukmal et al, 2018); and students reported formation of beetles from larvae when fed PS plus bran, confirming prior reports (Yang et al, 2015a. Mealworms were also observed consuming PE, an observation now documented in the peer-reviewed literature , as well as other plastics, including PVC and PLA, as reported by an academic team in Poland (Boźek et al, 2017). Fig.…”

“…Other academic researchers have reported mealworm consumption of PVC and PLA (Boźek et al, 2017). Chewing of plastic into small fragments increases the surface area of the ingested plastic and thus likely enhances enzymatic depolymerization, but depolymerization of the ingested plastic was not completed in the 14-18 h transit time through the mealworm gut.…”

Biodegradation of Different Types of Plastics by Tenebrio molitor Insect

“…The results of PS shown a higher degree of utilization compared to the studies of [16], where the reduction was only 9.0%, and [20,41], where the reduction was 31.0% and 39.1%, respectively. Mealworms from three Chinese regions of Guangzhou, Tai'an, Shenzhen utilized 57.5%, 34.4%, and 52.4% of PS, respectively [19].…”

Feed Parameters Influencing the Breeding of Mealworms (Tenebrio molitor)

“…For this reason, it was not possible to compare the results with other authors [16,17,[31][32][33][34], who have currently focused mainly on the biodegradation of plastics in various insect species. The studies [35] on waste biodegradation by Tenebrio molitor) described the weight loss of groups of larvae in individual types of plastics after 21 days from −15% to −19%. There were also losses in this work.…”