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Cellulose-Based Upcycling of Brewer´s Spent Grains: Extraction and Acetylation

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Abstract

As the main byproduct of beer production, huge amounts of brewer´s spent grain (BSG) are generated annually worldwide. BSG is being currently underutilized since they are mostly devoted to animal feeding. Nevertheless, BSG offers a wide range of upcycling possibilities due to its lignocellulosic nature. In this work, we have addressed the extraction of cellulose and its further conversion into cellulose acetate, a biodegradable polymer with potential industrial application, especially as food contact material. The effectiveness of both processes, cellulose extraction and acetate synthesis were monitored by performing a comprehensive physicochemical characterization of the products. The influence of reaction time (1–5 h) on acetylation extent and acetate properties was also assessed. The results reflected that the process effectively removed hemicelluloses and lignin from BSG, and yielded a cellulose pulp with 63% crystallinity and 351 °C maximum degradation temperature. However, around 28% of the cellulose was solubilized, with acid pretreatment as the most aggressive step (above 19% disappearance). Acetylation extent was practically not affected by reaction time, and cellulose acetate with degree of substitution approximately 2.60 was obtained already after 1 h. Infrared spectra and X-ray diffractograms were similar for all acetate samples. Nevertheless, the thermogravimetric analysis evidenced that at least 3 h were needed to obtain a product with high thermal stability. This work addressed for the first time the acetylation of cellulose isolated from BSG, and may serve as basis for the manufacturing of a biobased plastic with application in sectors such as food packaging.

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Acknowledgements

The authors gratefully acknowledge the Provincial Council of Jaén (Spain) for funding this research (Grant number 2022/4090). L. Camacho-Núñez also acknowledges the cooperation between the University of Jaén and Andaltec I + D + i for the economic support received during the experimental phase of the study. We also thank the technical and human support provided by Centro de Instrumentación Científico-Técnica (CICT; University of Jaén) and Andaltec I + D + i laboratory staff, as well as M. José de la Mata (Autonomous University of Madrid) for performing the simultaneous TGA-DSC measurements.

Funding

This research was funded by the Provincial Council of Jaén (Spain) under Grant number 2022/4090.

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Authors and Affiliations

  1. Department of Chemical, Environmental and Materials Engineering. Campus Las Lagunillas, University of Jaén, 23071, Jaén, Spain

    Leticia Camacho-Núñez & M. Dolores La Rubia

  2. Andaltec I+D+i, Plastic Technological Centre. Ampliación Polígono Industrial Cañada de la Fuente, C/Vilches 34, 23600, Martos, Jaén, Spain

    Leticia Camacho-Núñez, Sofía Jurado-Contreras, Francisco Javier Navas-Martos & José Antonio Rodríguez-Liébana

  3. University Institute for Research in Olive Grove and Olive Oil (INUO), Campus Las Lagunillas, University of Jaén, 23071, Jaén, Spain

    M. Dolores La Rubia

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  1. Leticia Camacho-Núñez
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  2. Sofía Jurado-Contreras
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  3. M. Dolores La Rubia
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LCN: Methodology, Investigation, Writing‒Original Draft. SJC: Conceptualization, Methodology, Investigation, Writing‒Review and Editing. MDLR: Conceptualization, Resources, Writing‒Review and Editing, Supervision. FJNM: Conceptualization, Resources, Writing‒Review and Editing, Funding acquisition. JARL: Conceptualization, Resources, Writing‒Review and Editing, Supervision, Project administration, Funding acquisition.

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Correspondence to José Antonio Rodríguez-Liébana.

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Camacho-Núñez, L., Jurado-Contreras, S., La Rubia, M.D. et al. Cellulose-Based Upcycling of Brewer´s Spent Grains: Extraction and Acetylation. J Polym Environ (2023). https://doi.org/10.1007/s10924-023-03137-w

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