Effect of a milling pre-treatment on the enzymatic hydrolysis of carbohydrates in brewer’s spent grain

• Published in: Bioresource technology 2012-07, Vol.116, p.155-160
• Main Authors: Niemi, Piritta, Faulds, Craig B., Sibakov, Juhani, Holopainen, Ulla, Poutanen, Kaisa, Buchert, Johanna
• Format: Article
• Language: English
• Subjects: Biotechnology - methods; Brewer’s spent grain; Byproducts; Carbohydrate Metabolism; Carbohydrates; Carbohydrates - chemistry; Edible Grain - metabolism; Enzymatic hydrolysis; Enzymes - metabolism; Foods; Grains; Hydrolysis; Industrial Waste - analysis; Microscopy; Milling; Particle Size; Particle size distribution; Pre-treatment; Solubility; Time Factors; Waste Products - analysis
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2012.04.043

► BSG has the potential to be a valuable source of food, chemicals and energy. ► The overall enzymatic release of BSG carbohydrates was improved 2-fold by milling. ► The choice of the milling technique affected the particle size and hydrolysis yield. ► Initial hydrolysis rate increased with milling improving the overall solubilisation. ► Milling affected the solubility of cellulose more than that of arabinoxylan. Millions of tonnes of brewer’s spent grain (BSG) are annually produced worldwide as a by-product of the brewing industry. BSG has the potential to be a valuable source of food, chemicals and energy if cost-efficient fractionation methods can be developed. A 2-fold improvement in carbohydrate solubilisation could be achieved through the introduction of a milling step prior to enzymatic hydrolysis. Course and fine milled fractions were characterized by particle size distribution and light microscopy. Fine milling decreased particle size down to the micron level and this in turn improved the carbohydrate solubility yield by a multi-enzyme mixture from 23% up to 45%. Carbohydrate solubilisation could be further increased through the supplementation of this enzyme preparation with additional cellulases. The physical degradation caused by the milling also liberated soluble carbohydrates without the requirement of any enzymatic treatment.