Extraction and characterization of xylan from walnut shell

U skladu s povećanjem količine otpadne biljne biomase, znanstvenici, ali i stručnjaci iz različitih grana industrije, uočili su potencijal iskorištavanja agro-industrijskog otpada kao izvora različitih visokovrijednih sastojaka. Cilj ovoga rada je izdvajanje ksilana iz ljuske oraha, kao i njegova karakterizacija u svrhu ispitivanja potencijala za daljnju upotrebu. U tu svrhu praćen je utjecaj delignifikacije (2 h i 4 h) te vremena i koncentracije lužine (2 M i 4 M) tijekom alkalne ekstrakcije. Primjenjenim postupcima izdvojene su tri frakcije (topljiva i netopljiva hemiceluloza te celulozni ostatak) u kojima je primjenom tekućinske kromatografije visoke djelotvornosti (HPLC) uz prethodnu PMP-derivatizaciju određen monomerni sastav. Gotovo 53 % suhe tvari sirovine čine strukturni polisaharidi, u čijem sastavu dominiraju ksiloza i glukoza, odnosno ukupni glukan i ukupni ksilan. Udjel ukupnog ksilana u ljusci oraha iznosi 19,9 %, što je 38 % polisaharidne suhe tvari. Iskorištenje ksilana u topljivoj i netopljivoj hemiceluloznoj frakciji, izraženo kao postotak inicijalno prisutnog ksilana u originalnom uzorku, iznosi oko 100 % u svim uzorcima. Prethodnom delignifikacijom uzoraka poboljšana je ekstrakcija ksilana, dok koncentracija lužine te vrijeme trajanja alkalne ekstrakcije nisu imali značajan utjecaj na ekstrakciju ksilana. Ljuska oraha je dobar izvor ksilana, koji se većim dijelom odvaja u topljivoj hemiceluloznoj frakciji.In accordance with the rising amount of vegetable biomass waste, scientists and experts from different branches of industry have noticed the potential for agro-industrial waste utilization and its use as a secondary raw material. The aim of this study was the extraction of xylan from walnut shell, as well as its characterization in order to examine its potential for further utilization. For this purpose, the effect of previous delignification (2 h and 4 h), time and alkaline concentration (2 M and 4 M) was observed during alkaline extraction. Three fractions were isolated using different extraction conditions (the soluble and the insoluble hemicellulose and the cellulose residue) in which it was determined monomeric composition using high performance liquid chromatography (HPLC) with previous PMP derivatization. Almost 53 % of the dry matter of the raw material (walnut shell) is composed of structural polysaccharides, whose composition is dominated by xylose and glucose (total glucan and total xylan). The share of xylan in walnut shell is 19,9 %, which is around 38 % of the carbohydrate portion of structural polysaccharides. The utilization of xylan in the soluble and the insoluble hemicellulose fraction expressed as % of the initially present xylan in the raw material is approximately 100 % in all samples. Previous delignification of the samples improved the xylan extraction, while alkaline concentration and duration of alkaline extraction did not have a significant effect on xylan extraction. Walnut shell is a good source of xylan, which is mostly separated in a soluble hemicellulose fraction