Valorization of sunflower meal toward the production of emerging prebiotics

Abstract

Recently, there is an increasing interest in utilizing biomass and waste potential for development of new products and materials. The example of this is sunflower meal, by-product of sunflower seed oil industry, that is currently used as a cheap component of animal feed owing to a poor protein content. The major drawback for their application is high content of complex carbohydrates (15.27% hemicellulose, 12.54% cellulose and 5.88% lignin). Therefore, extraction and enzymatic transformation of carbohydrates (primarily xylan) represent an attractive valorization approach. Since xylan extraction from the plant cell wall is highly restricted by lignin presence, different alkaline extraction methods have been proposed. This work is focused on xylan extraction using ethanol extraction and subsequent delignification approach. The ethanol extraction step yielded fraction rich in simple sugars, polyphenols (predominantly chlorogenic acid) and colorants that proved to have great prebiotic potential for application in skin products enabling proliferation of beneficial skin commensal and suppressing the pathogen one. Introduction of additional delignification step enabled high xylan yields (91.35%). This fraction was subjected to the enzymatic treatment using commercial xylanase (ROHALASE® SEP-VISCO) to obtain xylo-oligosaccharides (XOS), compounds that comprise of 2–10 xylose residues linked via β-1,4-glycosidic bonds with high prebiotic activity and excellent application properties (high temperature and pH stability, good sweetening power and low caloric value) for food industry. As result of the sunflower meal xylan treatment under optimum reaction conditions (60°C, pH6 and enzyme concentration of 0.5% per substrate), XOS with a polymerization degree of 2–6 were produced (with predominance of XOS2), without xylose generation. The prebiotic activity of the obtained XOS fraction was confirmed by fermentation with beneficial microbial cultures and pathogenic gut microbiota representative. Therefore, it was shown that significant portion of meal can be converted to added-value functional ingredients, while remaining product retains higher protein content.