Brewer's spent grain standardization and upstream processes for enzymatic hydrolysate production

摘要

JUSTIFICATION: An important way to re-use agro-industrial wastes and to produce added value productsconsists in the production of hydrolysates. The selection of an ideal agro-biotech waste depends upon severalfactors, mainly related with cost and availability of the substrate material. We used brewer's spent grain(BSG) as solid substrate. The BSG is the residue left after separation of the wort during brewing process isrich in fiber and protein.OBJECTIVE: The main objectives were to standardize the BSG used as raw material and to define thefermentation upstream processes for enzymatic hydrolysis by Bacillus cereus.METHODOLOGY: The composition characterization, granulometry assay, size reduction analysis and themicrobiological stability of different lots and varieties (78%, 93% and 100% Pilsner) of BSG provided by alocal company (Antares S.A., Argentina) were carried out. Simple pre-treatments of the substrate were alsodefined in order to eliminate interference (polyphenols) and standardize the substrate accordingly. After thatthe fermentation substrate (FS) was hydrolysate in submerged fermentation with Bacillus cereus.Antagonistic and synergistic effects were evaluated by combinations of strains as inoculum.RESULTS: The initial microflora was predominantly termophilic aerobic bacteria. Drying was the betteralternative for BSG preservation. BSG showed small variations in composition. The water, lipids and ashcontents differed significatively with the BSG varieties. The raw material was dried at 60°C for 24-48 h andsieved. BSG retained above mesh No10 was ground, then polyphenols were extracted with an alcohol: watersolution 30:70 for 60 min in an orbital shaker at 50 rpm and finally sterilized in autoclave for 10 min at121°C. Synergistic effects were observed inoculating B. cereus with both Pseudomonas strains.IMPLICATIONS: The production of hydrolysates could also add value to BSG, a low value by-product ofbeer production. This methodology could be applied on a large scale and extended to other agro industrialwastes.