Plastics Biodegradation by Mealworms

Research History

  1. Feasibility studies on biodegradation of polystyrene and polyethylene. From 2011 to 2015. Dr. Wei-Min Wu collaborated with Professor Jun Yang, Beijing University to conducted feasibility studies of biodegradation of polystyrene (PS) and polyethylene (PE) with yellow mealworms (larvae of Tenebrio monitor) and bacteria isolated from PE film-eating Indian meal moth larve in Professor Yang’s Laboratory.
  2. Ubiquity of PS degradation by T. molitor larvae. In 2014-2017, Drs. Wu, Criddle and Ms. Brandon started research on biodegradation of PS foam at Y2E2 laboratory. Dr. Shawshank Yang, a postdoc from HIT, China jointed the team in 2016. We collaborated with universities in USA, UK and China. We tested yellow mealworms from five different sources in the USA, six sources from China and one source from the UK for their abilities to biodegrade polystyrene (PS). After Feb. 2017, we worked with Beta Hatch, a Seattle-based mealworm production company to test PS degradation and growth on PS-bran by 11 different mealworm strains obtained from US sources. We then carried out a global survey and confirmed that yellow mealworms can survive by consuming polystyrene (PS) foam.
  3. Identification of T. molitor subspecies or strains for PS degradation. We collected mealworm samples from 12 different sources and fed them different diets. We also carried out mealworm taxonomic identification In collaboration with Professor Eric Benbow (Michigan State University) and Professor Christine J. Puicard (IUPUL).
  4. Verification of biodegradation of polyethylene (PE). We tested biodegradation of polyethylene (PE) by T. molitor larvae. The results demonstrated that PE can be degraded by mealworms via gut microbial mealworms in a short detention time (12-15 hrs). This is the first evidence that mealworms are capable of degrading polyethylene.
  5. Identification of PS biodegradation in Tenebrio obscurus（dark mealworms). We determined that dark mealworms (larvae of Tenebrio obscurus) belong to a different species of Tenebrio, and that they also have the capacity to biodegrade PS. This work was conducted in both Tonjing University, China and Stanford University. Again, the degradation was found to be gut-microbe dependent.
  6. Effect of co-diet and temperature on PS-degradation by mealworms. We tested the effects of different ratios of added food (soy protein, bran) on PS and PE degradation with various feeding strategies and examined the impact of temperatures (20, 25, and 30 oC). Feeding of food along with plastic significantly enhanced biodegradation and survival rates for both yellow and dark mealworms.
  7. Antibiotics assays. We tested the effect of antibiotics (gentamicin) on PS-degradation ability of yellow mealworms from five sources as well as dark mealworms. Addition of antibiotics severely inhibited PS depolymerization in both yellow and dark mealworms due to suppression of microbial activity in the gut.
  8. Characterization of gut microbial communities. We collaborated with Professor Eric Benbow Michigan State University to analyze shifts in gut microflora in12 strains of yellow mealworms, and in a strain of black mealworm before and after feeding PS. Microbial communities were monitored for the whole mealworm and for the gut alone. Jizhong Zhou (U. Oklahoma), Mark Eric Benbow (Michigan State University), and Yalei Zhang (Tongji U.) analyzed the gut microbial communities before and after feeding of PS and PE Shifts in the gut microbiome of dark mealworms was also evaluated.
  9. Toxicity assays. We carried out toxicity assays to determine whether biomass of the yellow mealworms fed PS has any toxicity or negative effect on the growth of shrimp. We also collaborated with Professor Xiouyang Li, Eastern China Normal University to test the toxicity of mealworm biomass fed with. No bioaccumulation or toxicity was observed when mealworms were fed PS foam and were then used as food source for Pacific white leg shrimp.
  10. Fate of flame retardant hexabromocyclododecane (HBCD) in polystyrene foam. HBCB is widely used flame retardant in polystyrene foam. We tested the fate of two levels of HBCD in PS foam (0.24 versus 0.0008 mg/g) after ingestion by yellow mealworms. HBCD did not biodegrade in the gut, but was egested with the mealworm frass. As the PS degraded, HBCD accumulated in the frass. A small fraction of HBCD (0.27%) was adsorbed in the mealworm body but this fraction decreased when feeding stopped. No evidence of higher trophic level bioaccumulation or toxicity was observed with L. vannamei (Pacific whiteleg shrimp) fed mealworm biomass grown with PS containing HBCD.
  11. Utilization of frass as raw material for biochar production. We collaborated with Dr. Shanshan Yang, our former visiting scholar (2017-2018) to produce biochar.
  12. Feasibility of biodegradation of other plastics. We examined the eating behavior of mealworms with other widely used plastics, including polypropylene (PP), polyvinyl chloride (PVC), polyester (PET) and polyurethane (PUR) and we assessed the feasibility of biodegradation.
  13. Education course program. We developed and taught a laboratory course for undergraduates. Four visiting students participated in the course in 2018 and two in 2019.

Major Findings and Achievements

  1. We and our collaborators Dr. J. Yang et al first time demonstrated that PS can be depolymerized and degraded to CO2 in short detention time (12-15 hrs) in mealworm but.
  2. Further studies indicated that polystyrene (PS) biodegrades in yellow mealworms (Tenebrio molitor) and dark mealworms (Tenebrio obscure from diverse sources, including the US, UK, and China;
  3. Supplemental nutrition, such soy protein or bran, increases PS and PE biodegradation rates;
  4. Optimal PS removal occurs at 25°C using a bran feed that has 6-11% (w/w) PS
  5. Co-degradation of PE and PS foam was observed. Mealworms preferred PE and exhibited a higher consumption rate compared to PS.
  6. All seven PS foams tested degraded, with low density foams degrading most rapidly.
  7. All common microplastics (PE, PP, PVC, PS and PET) were consumed by mealworms.
  8. A second generation of mealworms fed bran and PS has high rates of PS biodegradation
  9. Gut microbial community shifts after the diet switched from bran to PS or PE
  10. Broad microbial communities with PS/PE degradation are present in mealworms gut and can be enhanced by feeding PS or PE plus proper nutrition;
  11. Antibiotics inhibited PS-degrading activities of yellow mealworms and dark mealworms, confirming microbe-dependent PS biodegradation
  12. HBCD in PS foam was not degraded and was egested along with frass.
  13. No detectable acute toxicity was observed when mealworms fed PS foam were fed to shrimp.
  14. Mealworm frass can pyrolyzed to produce high quality biochar for soil conditioning and environmental remediation.

Publications

  1. Brandon, Anja Malawi; Sahar El Abbadi; Uwakmfon Ibekwe; YeoMyoung Cho; Wei-Min Wu; Craig S. Criddle.2019. The fate of hexabromocyclododecane (HBCD), a common flame retardant, in polystyrene-degrading mealworms: elevated HBCD levels in egested polymer but no bioaccumulation. Environmental Science & Technology. DOI: http://dx.doi.org/10.1021/acs.est.9b06501
  2. Yang, Shan-Shan, Yi-di, Chen, Ye Zhang, Hui-Min Zhou, Xin-Yu Ji, Lei He, De-Feng Xing, Nan-qi Ren, Shih-Hsin Ho, Wei-Min Wu. 2019. A novel clean production approach to utilize crop waste residues as co-diet for mealworm (Tenebrio molitor) biomass production with biochar as by product for heavy metal removal. Environmental Pollution. 252, 1142-1153. DOI. 10.1016/j.envpol.2019.06.28.
  3. Peng, Bo-Yu; Yiming Su, Zhibin Chen, Jiabin Chen, Xuefei Zhou, Mark Eric Benbow, Craig S. Criddle, Wei-Min Wu, and Yalei Zhang. 2019. Biodegradation of polystyrene by dark (Tenebrio obscurus) and yellow (Tenebrio molitor) mealworms (Coleoptera: Tenebrionidae). Environmental Science & Technology. 53 (9), 5256–5265. DOI: 10.1021/acs.est.8b06963.
  4. Yang, Shan-Shan; Yi-di Chen; Jin-Hao Kang; Ting-Rong Xie; Lei He; De-Feng Xing; Nan-Qi Ren; Shih-Hsin Ho; Wei-Min Wu. 2019. Generation of high-efficient biochar for dye adsorption using frass of yellow mealworms (larvae of Tenebrio molitor Linnaeus) fed with wheat straw for insect biomass production. Journal of Cleaner Production. 227, 33-47. doi.org/10.1016/j.jclepro.2019.04.005.
  5. Yang Shan-Shan, Wei-Min Wu, Anja M. Brandon, Han-Qing Fan, Joseph P. Receveur, Yiran Li, Zhi-Yue Wang, Rui Fan, Rebecca L. McClellan, Shu-Hong Gao, Daliang Ning, Debra H. Phillips, Bo-Yu Peng, Hongtao Wang, Shen-Yang Cai, Ping Li, Wei-Wei Cai, Ling-Yun Ding, Jun Yang, Min Zheng, Jie Ren, Ya-Lei Zhang, Jie Gao, Defeng Xing, Nan-Qi Ren, Robert M. Waymouth, Jizhong Zhou, Hu-Chun Tao, Christine J. Picard, Mark Eric Benbow, Craig S. Criddle. 2018. Ubiquity of polystyrene digestion and biodegradation within yellow mealworms, larvae of Tenebrio molitor Linnaeus (Coleoptera: Tenebrionidae). Chemosphere. 212, 262-271.
  6. Brandon, Anja Malawi, Shu-Hong Gao, Renmao Tian, Daliang Ning, Shan-Shan Yang, Jizhong Zhou, Wei-Min Wu, Craig S. Criddle. 2018. Biodegradation of polyethylene and plastic mixtures in mealworms (larvae of Tenebrio molitor) and effects on the gut microbiome. Environmental Science and Technology. 52, 6526−6533.
  7. Yang, Shan-Shan, Anja Malawi Brandon, James Christopher Andrew Flanagan, Jun Yang, Daliang Ning, Shen-Yang Cai, Han-Qing Fan, Zhi-Yue Wang, Jie Ren, Eric Benbow, Nan-Qi Ren, Robert M. Waymouth, Jizhong Zhou, Craig S. Criddle, Wei-Min Wu. 2018. Biodegradation of polystyrene wastes in yellow mealworms (larvae of Tenebrio molitor Linnaeus): factors affecting biodegradation rates and the ability of polystyrene-fed larvae to complete their life cycle. Chemosphere. 191,979-989.
  8. Yang, Y., J. Yang, W.-M. Wu, J. Zhao, Y.-L Song, L.-C. Gao, R.F Yang, L. Jiang. 2015. Biodegradation and mineralization of polystyrene by plastic-eating mealworms. 1. Chemical and physical characterization and isotopic tests. Environmental Science and Technology. 49: 12080-12086.
  9. Yang, Y., J. Yang, W.-M. Wu, J. Zhao, Y.-L. Song, L.-C. Gao, R.-F. Yang, L. Jiang. 2015. Biodegradation and mineralization of polystyrene by plastic-eating mealworms. 2. role of gut Microorganisms. Environmental Science and Technology. 49: 12087-12093.
  10. Yang, J., Y. Yang, W.-M Wu, J. Zhao，L. Jiang. 2014. Evidence of polyethylene biodegradation by bacterial strains from the guts of plastic-eating waxworms. Environmental Science & Technology. 48 (23), 13776–13784.