Valorization of horse chestnut burs to produce simultaneously valuable compounds under a green integrated biorefinery approach

11 pages, 5 figures, 6 tablesA biorefinery scheme for the valorization of horse chestnut biowastes (a municipal solid waste) into added value bioactive compounds is proposed in this work. The bur fraction of horse chestnut was evaluated as a novel and cheap renewable feedstock to obtain valuable compounds suitable for their use in industrial applications. The integrated valorization scheme comprised an initial hydroethanolic extraction of antioxidant compounds (optimized through surface response methodology), the alkaline delignification of the exhausted solid to obtain a lignin-enriched fraction, and the enzymatic digestibility of the remaining cellulose fraction to produce fermentable sugars. In addition, the structural characterization of the extract by FT-IR and TGA was performed, and the analysis by UPLC-DAD-ESI-MS allowed the tentative identification of eleven antioxidant phenolic compounds. The application of this multiproduct valorization approach led to the production of 13 kg antioxidant extracted compounds, 33.2 kg lignin and 14.5 kg glucose per each 100 kg of horse chestnut burs, which demonstrates the great potential of this residue as a biorefinery substrateThis work was funded by the Ministry of Science, Innovation and Universities (RTI2018-094482-J-I00). G.E., A.M.-M. and T.A.L-C. belong to the Galician Competitive Research Group GRC-ED431C 2017/29 and the CRETUS Strategic Partnership (ED431E 2018/01). These programs are co-funded by FEDER (EU). Beatriz Gullón and Gemma Eibes would like to express their gratitude to the Ministry of Science, Innovation and Universities for financial support (Grant reference RYC2018-026177-I and RYC2018-024846-I). Abel Muñiz-Mouro thanks the Programa de axudas á etapa predoutoral da Xunta de GaliciaPeer reviewe

Laccase Activity as an Essential Factor in the Oligomerization of Rutin

The enzyme-mediated polymerization of bioactive phenolic compounds, such as the flavonoid rutin, has gained interest due to the enhanced physico-chemical and biological properties of the products, which increases their potential application as a nutraceutical. In this work, the influence of enzyme activity on rutin oligomerization was evaluated in reactions with low (1000 U/L) and high (10,000 U/L) initial laccase activities. For both reactions, high molecular weight oligomer fractions showed better properties compared to lower weight oligomers. Products of the reaction with low laccase activity exhibited thermal stability and antioxidant potential similar to control reaction, but led to higher inhibitory activity of xanthine oxidase and apparent aqueous solubility. Oligomers obtained in the reaction with high laccase activity showed better apparent aqueous solubility but decreased biological activities and stability. Their low antioxidant activity was correlated with a decreased phenolic content, which could be attributed to the formation of several bonds between rutin molecules