Disintegration evaluation of bioplastic elaborated with polysaccharides from plant biomass

Author(s)

Mateus Manabu Abe

• Document type: Master's Dissertation
• Press: Rio Claro. 2022-06-23.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências. Rio Claro
• Defense date: 2022-03-10
• Advisor: Michel Brienzo

Abstract

Since 1950, the growing demand for plastic resins has increased the production of this material. This increase is due to the different applications of these materials, with advantages due to low cost, mechanical properties, water vapor barrier, chemical inertness and reduced or lack of biodegradation. Even with all the clear advantages of using synthetic plastics, the accumulation of this material represents a wide variety of problems such as outbreaks of disease proliferation, animal strangulation, damage to the fishing economy, causes of liver protein anomalies, the modifier of the physical-chemical biological soil profile, in addition to many other social and environmental impacts. Therefore, the development of biomaterials such as bioplastics from renewable and/or biodegradable sources is important to mitigate the environmental problems of plastics, at least in a few areas of the use of synthetic plastics. In this context, this study aimed to evaluate the addition of xylan in starch bioplastic’s to verify biodegradation and possible ecotoxic effects. The bioplastics were prepared with 10, 15, and 25% (w/w) of xylan, in 5% (w/v) total polysaccharides including starch, dried at 30 °C. The bioplastic resulted in a continuous and homogeneous plastic matrix without cracks. The bioplastic was buried to evaluate the biodegradation showing disintegration after 13 days. The time period for composting and disintegration in the soil was short compared to plastics from petroleum. In general, the bioplastic did not negatively influence the germination and tissue development of seeds of Cucumis sativus, with 100% of seed germination. A positive influence was observed on the root and hypocotyl growth but with a temporary inhibition of C. sativus tissue exposed to 10-days biodegradation soil washing. The optical and photoprotective properties and the solubility in food simulants (waxy and acidic foods) of bioplastics were also analyzed. Also, employing Thermogravimetric Analysis, Dynamic Mechanical Analysis, Differential Scanning Calorimetry Analysis, Scanning Electron Microscopy, the thermal resistance, mechanical resistance, crystallinity, and morphology of bioplastics were performed, respectively. The highest tensile strength was with the composition 15/25% (w/w) of xylan/starch (2.99 MPa). All bioplastic compositions resulted in homogeneous and bubble-free materials, and there was no difference in transparency at 600 nm (except for the bioplastic with alpha-cellulose and hemicellulose), however, between 200- 400 nm of the wavelength of light, the bioplastics with higher concentrations of xylan reduced transmittance, probably due to the presence of lignin. The bioplastic with 25% xylan showed a small photoprotective capacity against the yeast Saccharomyces cerevisiae when exposed to UVC light. Solubility increases in acid simulants with plastics with higher xylan concentration (25% w/w), however, in fatty food simulants, the solubility of bioplastic with 25% (w/w) xylan was negligible. In general, the addition of xylan, alpha-cellulose, and holocellulose reduced the thermal resistance in relation to the pure starch-based bioplastic, as well as reduced crystallinity with higher concentrations of xylan, except for the addition of alpha-cellulose and holocellulose. (AU)

• FAPESP's process: 19/16853-9 - Biodegradation evaluation of films made with plant biomass polysaccharides
• Grantee: Mateus Manabu Abe
• Support Opportunities: Scholarships in Brazil - Master