Green composites made of polyhydroxybutyrate and long-chain fatty acid esterified microcrystalline cellulose from pineapple leaf

PLOS ONE RESEARCH ARTICLE Green composites made of polyhydroxybutyrate and long-chain fatty acid esterified microcrystalline cellulose from pineapple leaf Pitchanun Sinsukudomchai1, Duangdao Aht-Ong2,3, Kohsuke Honda4, Suchada Chanprateep Napathorn ID1,4* a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 1 Department of Microbiology, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok, Thailand, 2 Department of Materials Science, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok, Thailand, 3 Center of Excellence on Petrochemical and Materials Technology, Chulalongkorn University, Bangkok, Thailand, 4 International Center for Biotechnology, Osaka University, Suita, Osaka, Japan * Abstract OPEN ACCESS Citation: Sinsukudomchai P, Aht-Ong D, Honda K, Napathorn SC (2023) Green composites made of polyhydroxybutyrate and long-chain fatty acid esterified microcrystalline cellulose from pineapple leaf. PLoS ONE 18(3): e0282311. https://doi.org/ 10.1371/journal.pone.0282311 Editor: Martin Koller, Karl-Franzens-Universitat Graz, AUSTRIA Received: February 20, 2022 Accepted: February 14, 2023 Published: March 3, 2023 Copyright: © 2023 Sinsukudomchai et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its supporting data file. Funding: This research was supported by the 90th Anniversary of Chulalongkorn University Fund (Ratchadapiseksomphot Endowment Fund) to SCN and PS. There was no additional external funding received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. Pineapple leaf fibres are an abundant agricultural waste product that contains 26.9% cellulose. The objective of this study was to prepare fully degradable green biocomposites made of polyhydroxybutyrate (PHB) and microcrystalline cellulose from pineapple leaf fibres (PALF-MCC). To improve compatibility with PHB, the PALF-MCC was surface modified using lauroyl chloride as an esterifying agent. The influence of the esterified PALF-MCC laurate content and changes in the film surface morphology on biocomposite properties was studied. The thermal properties obtained by differential scanning calorimetry revealed a decrease in crystallinity for all biocomposites, with 100 wt% PHB displaying the highest values, whereas 100 wt% esterified PALF-MCC laurate showed no crystallinity. The addition of esterified PALF-MCC laurate increased the degradation temperature. The maximum tensile strength and elongation at break were exhibited when adding 5% of PALF-MCC. The results demonstrated that adding esterified PALF-MCC laurate as a filler in the biocomposite film could retain a pleasant value of tensile strength and elastic modulus whereas a slight increase in elongation can help to enhance flexibility. For soil burial testing, PHB/ esterified PALF-MCC laurate films with 5–20% (w/w) PALF-MCC laurate ester had higher degradation than films consisting of 100% PHB or 100% esterified PALF-MCC laurate. PHB and esterified PALF-MCC laurate derived from pineapple agricultural wastes are particularly suitable for the production of relatively low-cost biocomposite films that are 100% compostable in soil. Introduction Petroleum-based plastics have been a major source of innovation-driven technologies due to their unique properties, including low price; therefore, they remain a promising material for PLOS ONE | https://doi.org/10.1371/journal.pone.0282311 March 3, 2023 1 / 26 PLOS ONE Abbreviations: CDW, cell dry weight; DSC, differential scanning calorimetry; GPC, gel permeation chromatography; PALF, pineapple leaf fibres; PALF-MCC, pineapple leaf fibresmicrocrystalline cellulose; MW, weight-average molecular weight; ΔHC, enthalpy of crystallization; ΔHM, enthalpy of fusion; MN, the number-average molecular weight; PHB, poly(3-hydroxybutyrate; Tc, crystallization temperature; Td, degradation temperature; Tg, glass transition temperature; TGA, thermal gravimetric analysis; Tm, melting temperature; XC (%), percent of crystallinity. Green composites made of polyhydroxybutyrate and esterified microcrystalline cellulose from pineapple leaf future technologies. However, their high usage volume has resulted in the unrelenting rise in plastic and microplastic pollution, which calls for global policies and legislation [1, 2]. Over the past two decades, bioplastics have increasingly been promoted as a solution to the problems of conventional plastics. Nevertheless, it has also been reported that there is no distinction between conventional, nonbiodegradable plastics and biodegradable plastics, and they have been considered the most polluting single-use plastics [3]. Notably, biodegradable properties depend on the plastic properties including chemical structure and crystallinity and the environmental conditions, such as humidity, temperature, and other conditions [4]. Nowadays, biodegradable plastic products can be disintegrated or composted only in particular environments such as in industrial composting facilities rather than in natural environments [5]. To realize the potential environmental benefits of using bioplastics instead of conventional plastics, there is a need for the development of truly biodegradable polymers as well as biodegradability testing and standards, and factual information on the features, suitable usage, disposal, and restrictions of biodegradable plastics and their applications to be provided to relevant customers. Among a wide range of bioplastics, polyhydroxyalkanoates (PHAs) are one of the most well-known types of biodegradable polymers with great potential to alleviate conventional plastic pollution [6]. PHAs exhibit industrial compostability, home compostability and biodegradability in open natural ecosystems. However, the production cost and mechanical properties of PHAs remain controversial. To reduce the cost of PHAs, one of our interests is to develop biocomposites of poly(3-hydroxybutyrate) (PHB) and natural fibres derived from agricultural waste [7]. Recently, biocomposites between PHB and other natural polymers, such as natural rubber, starch, wood and cellulose, have also been investigated [8–12]. As a research prototype, PHB produced from soil-isolated Cupriavidus necator strain A-04 was used as a major matrix material [13–15]. Regarding natural fibre resources, the agricultural sector has played an important role in the Thai economy. Pineapple is an important economic crop of Thailand and Asian countries such as the Philippines, Taiwan, and Malaysia. Currently, Thailand is one of the world’s greatest pineapple exporters. During the pa (...truncated)