Effect of extrusion conditions and hydrolysis with fiber-degrading enzymes on the production of C5 and C6 sugars from brewers’ spent grain for bioethanol production

Document Type: Research Paper

Authors

Centro de Biotecnología FEMSA, Escuela de Ingeniería y Ciencias, Tecnológico de Monterrey, Avenida Eugenio Garza Sada 2501 Sur, CP 64849, Monterrey, Nuevo León, México.

Abstract

The bioconversion of brewers’ spent grain into bioethanol was investigated in the present study using thermoplastic extrusion and the use of fiber degrading enzymes. The extrusion conditions i.e. tempering moisture, screws speed, and temperature of last zone of the barrel were taken into account in order to optimize the yield of C5 and C6 sugars during the subsequent enzymatic hydrolysis step of the fibers. The most important variable that affected the sugar yield was the extrusion temperature, followed by the screws speed. The best extrusion conditions were 20% tempering moisture, 200 rpm and 50 °C. No enzymatic and yeast inhibitors were detected in any of the enzymatically-treated fiber hydrolyzates. The fermentation resulted in 5.43 mL bioethanol per 100g of extruded brewers’ spent grain (dry weight basis). The only sugar consumed was glucose. The free amino nitrogen amount quantified in the hydrolyzates was as low as >20 mg L-1, negatively affecting sugars consumption during the fermentation and consequently the ethanol yield.

Graphical Abstract

Effect of extrusion conditions and hydrolysis with fiber-degrading enzymes on the production of C5 and C6 sugars from brewers’ spent grain for bioethanol production

Keywords


Aliyu, S., Bala, M., 2011. Brewer`s spent grain: a review of its potentials and applications. Afr. J. Biotechnol. 10(3), 324-331.

Celus, I., Brijs, K., Delcour, J.A., 2006. The effects of malting and mashing on barley protein extractability. J. Cereal Sci. 44(2), 203-211.

Dowe, N., McMillan, J., 2008. SSF Experimental protocols- Lignocellulosic biomass hydrolysis and fermentation. Laboratory Analytical Procedure (LAP). National Renewable Energy Laboratory. Golden, Colorado.

Faulds, C.B., Collins, S., Robertson, J.A., Treimo, J., Eijsink, V.G.H., Hinz, S.W.A., Schols, H.A., Buchert, J., Waldron, K.W., 2009. Protease-induced solubilisation of carbohydrates from brewers’ spent grain. J. Cereal Sci. 50(3), 332-336.

Forssell, P., Kontkanen, H., Schols, H. A., Hinz, S., Eijsink, V. G. H., Treimo, J., Robertson, J. A., Waldron, K. W., Faulds, C. B., Buchert, J., 2008. Hydrolysis of brewer’s spent grain by carbohydrate degrading enzymes. J. Inst. Brew. 114(4), 306-314.

Heredia-Olea, E., Pérez-Carrillo, E., Serna-Saldívar, S. O., 2013. Production
 of ethanol from sweet sorghum bagasse pretreated with different chemical and physical processes and saccharified with fiber degrading enzymes. Bioresour. Technol. 134, 386-390.

Karunanithy, C., Muthukumarappan, K. 2010. Effect of extruder parameters and moisture content of switchgrass, prairie cord grass on sugar recovery from enzymatic hydrolysis. Appl. Biochem. Biotechnol. 162 (6), 17585-1803.

Karunanithy, C., Muthukumarappan, K., Gibbons, W.R., 2013. Effects of extruder screw speed, temperature, and enzyme levels on sugar recovery from different biomasses. ISRN Biotechnol.  Article ID 942810.

Lie. S., 1973. The EBC-ninhydrin method for determination of free amino nitrogen. J. Inst. Brew. 79(1), 37-41.

Lin, Z., Liu, L., Li, R., Shi, J. 2012., Screw extrusion pretreatments to enhance the hydrolysis of lignocellulosic biomass. J. Microb. Biochem. Technol. 12, 5.

Moscicki, L., 2011. Extrusion-cooking techniques, applications, theory and sustainability. ed. WILEY-VCH Verlag and Co. KGaA, Weinheim, Germany.

Mussatto, S. I., Dragone, G., Roberto, I. C., 2006. Brewers’ spent grain: generation, characteristics and potential applications. J. Cereal Sci. 43(1), 1-14.

Mussatto, S.I., Fernandes, M., Milagres, A.M.F., Roberto, I.C., 2008. Effect of hemicellulose and lignin on enzymatic hydrolysis of cellulose from brewers’ spent grain. Enzyme Microb. Technol. 43(2), 124-129.

Pandey, A., 2011. Biofuels: alternative feedstocks and conversion processes. ed. Academic Press, Kidlington, Oxford; Burlington, MA.

Reddy, N., Yang, Y., 2005. Biofibers from agricultural byproducts for industrial applications. Trends Biotechnol. 23(1), 22-27.

Sluiter, A., Ruiz, R., Scarlata, C., Sluiter, J., Templeton, D. 2008a. Determination of extractives in biomass. Laboratory Analytical Procedure (LAP). National Renewable Energy Laboratory. Golden, Colorado.

Sluiter, A., Hames, B., Ruiz, R., Scarlata, C., Sluiter, J., Templeton, D., Crocker, D. 2008b. Determination of structural carbohydrates and lignin in biomass. Laboratory Analytical Procedure (LAP). National Renewable Energy Laboratory. Golden, Colorado.

Scheper, T., 2007. Biofuels. Advances in Biochemical Engineering/Biothecnology. ed. Springer, London.

Shindo, S., Tachibana, T., 2006. Production of bioethanol from spent grain –a by-product of beer production. Technical quarterly-Master Brewers Association of the Americas. 43(3), 189-193.

Thomas, K. C., Ingledew, W. M., 1990. Fuel alcohol production: effects of free amino nitrogen on fermentation of very-high-gravity wheat mashes. Appl. Environ. Microbiol. 56 (7), 2046-2050.

White, J.S., Yohannan, B.K., Walker, G.M., 2008. Bioconversion of brewer’s spent grain to bioethanol. FEMS Yeast Res. 8(7), 1175-1184.