Monday, April 30, 2007

Strategies for integral use of the main brewery by-product

Solange I. Mussatto, Marcela Fernandes, and InÍs C. Roberto. Department of Biotechnology,, Engineering School of Lorena, University of S„o Paulo, Estrada Municipal do Campinho s/n, Lorena, 12602-810, Brazil

The main brewery by-product is brewer’s spent grain (BSG), a material composed by the barley malt residue obtained after the wort manufacture. Recently, BSG has been employed as raw material for xylose-to-xylitol bioconversion. In this process, the BSG hemicellulose is hydrolyzed generating a hydrolysate rich in xylose, which is fermented by yeasts to xylitol. Nevertheless, the obtained solid residue is rich in cellulose and lignin, and can be also used. In the present work, this residue was submitted to the following treatments: T1) Alkaline hydrolysis using a 2% w/v NaOH solution in a solid:liquid ratio of 1:20 g:g, at 120oC for 90 min; T2) Enzymatic hydrolysis using the Celluclast 1.5L (Novozymes) extract in the ratio of 45 FPU/g dry matter, 8% w/v substrate concentration, at 45oC, 100 rpm for 96 h; T3) A sequence of the treatments 1 and 2 was employed. By alkaline hydrolysis (T1), a liquor rich in phenolic compounds, mainly ferulic (145.3 mg/l) and p-coumaric (138.8 mg/l) acids was produced, and a pulp containing 90.5% w/w cellulose (residual solid material) was also generated. The enzymatic hydrolysis (T2) was not able to attack the material structure probably due to the high lignin content present (49.2% w/w). However, the enzymatic hydrolysis use after the alkaline procedure (T3) easily degraded the cellulose pulp producing a liquor with 59.3 g/l glucose. Several strategies can be thus employed for integral use of BSG, which make possible the BSG reuse in the food, cosmetics, pulp and paper industries. Acknowledgements: Capes, Fapesp,  CNPq, Novozymes.