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Toward a circular bioeconomy: extracting cellulose from grape stalks
* 1, 2 , 3, 4 , 5 , 6 , 6, 7
1  Universidade Católica Portuguesa, Centro de Investigação em Ciência e Tecnologias das Artes (CITAR)
2  Centro de Biotecnologia e Química Fina (CBQF), Porto, Portugal
3  Universidade Católica Portuguesa, Centro de Biotecnologia e Química Fina (CBQF), Porto,
4  Portugal & Collaborative Laboratory Towards Circular Economy (CECOLAB), Oliveira do Hospital
5  Universidade Católica Portuguesa, Centro de Biotecnologia e Química Fina (CBQF), Porto, Portugal
6  Universidade Católica Portuguesa, Centro de Investigação em Ciência e Tecnologia das Artes (CITAR), Porto, Portugal.
7  Tecnologia das Artes (CITAR) & Centro de Biotecnologia e Química Fina (CBQF), Porto, Portugal
Academic Editor: Chi-Fai Chau

Abstract:

Inspired by the principles of circular economy, harvest waste is being engineered to be reintroduced into the economical chain to manufacture new added-value materials, such as cellulose. In this regard, the purpose of this study was to assess the extraction of cellulose from micronized stalks of vines and characterize the effects of the granulometric fractions (500, 300, 250, 150 µm, and Retain (>150 µm). The cellulose collected from different fractions of micronized stalks vines underwent acid hydrolysis (acid sulfuric), alkaline hydrolysis (NaOH), and finally bleached (H2O2 adjusted pH to 11.5 with NaOH). The efficiency of the fiber bleaching of cellulose from each granulometric fraction (500, 300, 250, 150 µm and Retain (>150 µm)) for each fraction was evaluated from the color through a colorimeter (CM 700d Konica Minolta). Moreover, the extraction of cellulose fibers was assessed by Fourier transform infrared (FTIR), to evaluate the efficiency to remove lignin and hemicellulose. The size and shape m)) were measured by Dino-lite® (AM7915MZT) microcopy. As results obtained from this study, the colorimeter readings, displayed a final yellow color of the fiber, demonstrating that the bleaching process was insufficient and that multiple bleaching processes might be required. According to the FTIR data, the stretching and deformation vibrations of the C-H group in the glucose unit are responsible for the intense bands at 2988 cm-1 and 1394 cm-1. Moreover, the signal at 1066 cm-1 is attributed to the functions of the -C-O- group of secondary alcohols and ethers found in the cellulose chain backbone. Although lignin and hemicellulose were successfully removed according to the FTIR. Direct measurements reveal linear cellulose fibers with lengths between 0,100 and 6 mm long. The granulometric fractions obtained from the micronation of stalks vines (harvest waste) are intended to understand the influence of extraction procedures on the produced fibers. As a result, distinct cellulose yields were achieved for each fraction, including fractions 500, 300, 250, 150 µm, and retain, with values of 21.98, 12.70, 7.20, 5.74, and 3.11 %, respectively. In sum, we were able to extract cellulose from the stalk vine using this approach, although the last step still needs to be optimized for better whitening.

Keywords: acid hydrolysis, alkaline hydrolysis, color; fiber and size.
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