Fast chemical treatments for ligno-cellulosic yeast carriers’ production from brewers´ spent grains

Abstract

Caustic (NaOH) and acid-caustic (HCl + NaOH) treatments have both been previously proposed to prepare ligno-cellulosic yeast carriers from Brewers´ Spent Grains (BSG) [1]. However, these treatments are time consuming (more than 24 h). Base-treated carriers are more hydrophobic if compared to acid-base treated, enhancing adhesion in one hand, but more floatable and easily washed out from the reactor in the other hand [2]. Thus, a balance between hydrophilic (cellulose) and hydrophobic (lignin) composition in carriers obtained from BSG must be idealized. The aim of this study was to idealize a fast and simple treatment on ligno-cellulosic substrate from BSG. Two types of BSG have been used in this work: dried BSG settle as pellets for animal nutrition and fresh BSG, directly from the beer industry. Both pelleted and fresh BSG were subjected to a series of proposed chemical treatments, as well as to treatments suggested in the literature [1] (Table 1 summarizes the conditions used). Carriers were assessed for cellulose content through high performance liquid chromatography (HPLC) (Varian, Metacarb 67H Column 300 x 6.5 mm). Briefly, approximately 0.5 g of each dried carrier was digested with sulfuric acid. The digested material was settled in glass flasks with water, autoclaved and filtered. Then, the solids were held separately for lignin content determination, while the liquid was settled in vials for sugars assessment.