Waste hop stem in the beer industry upcycled into cellulose nanofibers

The TEMPO-mediated oxidation produced cellulose nanofibers from waste hop stems. Credit: Yokohama National UniversityThree quarters of the hop plant biomass used in beer-making ends in landfills. A group of Japanese researchers have developed a method that "upcycles" the waste hop into cellulose nanofibers. The technique was described in a paper published in the journal ACS Agricultural Science & Technology, June 11.Craft beer-making has seen a surge in popularity over the last few years. There are many styles of beer that use more hops than traditional commercial beer. Hops are a traditional preservative for beer. They also impart floral and citrus aromas and flavors. In 2019, hop production reached a new record.Beer making is limited to the hop flower. After harvest, the stems and leaves of hop plants, which account for about 75% of the biomass, are usually burned or thrown in a landfill. The technique will reduce the amount of waste from hop cultivation and the land footprint, while also reducing the use of petroleum feedstocks.Researchers have created a method that recycles these products using hop stems to extract CNFs. CNFs have been gaining popularity since the 2000s because of their exceptional properties. They are light, strong, and stable. CNFs will be an excellent plant-derived material for reducing petroleum-based plastics in various industrial applications, such as the automotive, housing and food industries."This project would be a great success if we could reduce our dependence on oil while simultaneously radically reducing the amount of agricultural waste from the beer sector," stated Izuru Kamura, an associate professor at the Graduate School of Engineering Science of Yokohama National University.CNFs were successfully extracted from wood, agro-industrial wastes like banana stems, grapefruit peels and pineapple leaves.Kawamura said that until now, there had not been an attempt to isolate CNFs in hop stems.Cell wall structures are composed of cellulose microfibrils or very short and thin fibers in a matrix of lignin, hemicellulose, and lignin. The chemical compositions and amounts of cellulose, hempicellulose, or lignin will vary depending on where they came from.CNFs are generally extracted from wood pulp through a series of purification and refinement using chemicals or enzymes. CNFs were previously obtained by using 2,2,6,6-tetramethylpiperidine-1–oxyl radical (also known as 'TEMPO') to pre-treat cellulose from wood, followed by gentle mechanical disintegration with water.Researchers used the TEMPO method, but also decreased the pretreatments for removing lignin from hop stems. This is what was considered lignocellulose fibers before the TEMPO step. CNFs could be obtained even without pretreatments at a median length of 2 nanometers. They were able to determine that hop stems had a similar amount of cellulose to wood by using chemical composition analysis.This means that this method could not only replace petroleum but could also be used to produce CNFs from hop waste."You could even shout 'three cheers!' for CNFs from hops.The team plans to prepare emulsions that are stabilized with hop stem-derived CNFs as a next step and show the industry their feasibility. They should result in a significant decrease in conventional synthetic surfactants if they are successful.Look into more Banana extract may be the key to making ice cream cream creamier and lasts longerMore information: Norikokanai et.al, Upcycling Waste Hop Stems into Cellulose Nanofibers. Isolation and Structural Characterization. ACS Agricultural Science & Technology (2021). Noriko Kanai and colleagues, Upcycling Waste Hop Stems into Nanofibers of Cellulose: Isolation & Structural Characterization. (2021). DOI: 10.1021/acsagscitech.1c00041Provided by Yokohama National University