Biodegradation of Films Based on Natural and Synthetic Biopolymers Using an Aquatic System from Active Sludge
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ORIGINAL PAPER
Biodegradation of Films Based on Natural and Synthetic Biopolymers Using an Aquatic System from Active Sludge Jeannine Bonilla1,2 · Renan B. Paiano3 · Rodrigo V. Lourenço1 · Ana Mônica Q. B. Bittante1 · Paulo J. A. Sobral1,2 Accepted: 4 November 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The biodegradability of natural gelatin (GEL) and sodium caseinate (SCas) and synthetic poly(vinyl alcohol) (PVA) and poly(lactic acid) (PLA) biopolymers films, were studied in an aquatic system following OECD 301D guidelines. Biodegradation was determined measuring the dissolved oxygen (DO) over 28 days with closed respirometers. Elementary compositions and changes in physicochemical parameters were analyzed. The results demonstrated that carbon (46 to 60%) and oxygen (31 to 44%) were the most important elements in the composition of all films. Moreover, GEL and SCas films were completely biodegraded (100%) on day 1, showing a DO increased (GEL up to 42.5 mg O 2/l and SCas up to 34.6 mg O 2/l) as a consequence of the biodegradation time. This is in stark contrast to PVA and PLA films, who presented an inverse behavior (PLA up to 1.1 mg O2/l and PVA up to 0.5 mg O 2/l), which in fact cannot be classified as “readily biodegradable” according to the results of in this study because they required more time to biodegrade than the rules defined for this aquatic system. PLA film showed a more opaque and whitish color, a clear increase in EM values (day 7 = 85.7 ± 2.0 MPa), Tg temperature (day 28 = 56.8 ± 0.0 °C) and crystallinity (Day 28 = 49.3 ± 0.6%) over the effects of biodegradation times. FTIR analysis showed changes in the intensity of the typical bands of the PLA samples, and the presence of Pseudomonas, was later observed on their surface by SEM studies. Keywords Gelatin · Sodium caseinate · Poly(vinyl alcohol) · Poly(lactic acid) · OECD guidelines
Introduction Plastic pollution is spreading throughout the world’s oceans by prevailing winds and surface currents. It is estimated that almost 6.4 million tons of waste (with plastics accounting for 62%) is introduced into marine environments annually [1]. Plastics are differentiated according to their origins, structural arrangements, physical properties and potentials for environmental degradation. In general, all polymers are * Jeannine Bonilla [email protected] 1
Faculty of Animal Science and Food Engineering, University of São Paulo, Av. Duque de Caxias Norte, 225, Pirassununga, SP 13635‑900, Brazil
2
Food Research Center (FoRC), University of São Paulo, Rua do Lago, 250, Semi‑industrial building, block C, São Paulo 05508‑080, Brazil
3
Department of Animal Reproduction, School of Veterinary Medicine and Animal Sciences, University of São Paulo, São Paulo, Brazil
degradable on different time scales, whereas biodegradable polymers are considered to degrade in a few months up to 2 years [2]. According to Moura et al. [3], important information concerning a polymer’s final fate in the environment
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