Drying enhances immunoactivity of spent brewer's yeast cell wall β-d-glucans

Due to immunological activity, microbial cell wall polysaccharides are defined as 'biological response modifiers' (BRM). Cell walls of spent brewer's yeast also have some BRM activity. However, up to date there is no consensus on the use of spent brewer's yeast d-glucan as specific BRM in humans or animals. The aim of this paper is to demonstrate the potential of spent brewer's yeast β-d-glucans as BRM, and drying as an efficient pretreatment to increase β-d-glucan's immunogenic activity. Our results revealed that drying does not change spent brewer's yeast biomass carbohydrate content as well as the chemical structure of purified β-d-glucan. However, drying increased purified β-d-glucan TNF-α induction activity in the murine macrophage model. We presume drying pretreatment enhances purity of extracted β-d-glucan. This is corroborated with FT-IR analyses of the β-d-glucan spectra. Based on our results, we suggest that dry spent brewer's yeast biomass can be used as a cheap source for high-quality β-d-glucan extraction. Drying in combination with carboxylmethylation (CM), endows spent brewer's yeast β-d-glucan with the immunoactivity similar or exceeding that of a well-characterized fungal BRM pleuran.