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

KOTLAR CATALINA; BELAGARDI MARIELA ; AGÜERO MARÍA VICTORIA; ROURA SARA INES

Atenas

Congreso; International Congress on Engineering and Food ICEF 11; 2011

JUSTIFICATION: An important way to re-use agro-industrial wastes and to produce added value products consists in the production of hydrolysates. The selection of an ideal agro-biotech waste depends upon several factors, 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 is rich in fiber and protein. OBJECTIVE: The main objectives were to standardize the BSG used as raw material and to define the fermentation upstream processes for enzymatic hydrolysis by Bacillus cereus. METHODOLOGY: The composition characterization, granulometry assay, size reduction analysis and the microbiological stability of different lots and varieties (78%, 93% and 100% Pilsner) of BSG provided by a local company (Antares S.A., Argentina) were carried out. Simple pre-treatments of the substrate were also defined in order to eliminate interference (polyphenols) and standardize the substrate accordingly. After that the 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 better alternative for BSG preservation. BSG showed small variations in composition. The water, lipids and ash contents differed significatively with the BSG varieties. The raw material was dried at 60ºC for 24-48 h and sieved. BSG retained above mesh Nº10 was ground, then polyphenols were extracted with an alcohol: water solution 30:70 for 60 min in an orbital shaker at 50 rpm and finally sterilized in autoclave for 10 min at 121ºC. 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 of beer production. This methodology could be applied on a large scale and extended to other agro industrial wastes.