engleski

Brewer’s spent grain bioprocessing by Trametes versicolor: production of lignocellulose-degrading enzymes

Brewer's spent grain (BSG) is a widespread by-product of the brewing industry. In this work two different BSG (BSG 1 and BSG 2) were used as substrates for the growth of Trametes versicolor under solid-state conditions. The enzymatic activities of hydrolytic (xylanase, invertase, cellulase, and β-glucosidase) and lignolytic enzymes (laccase, manganese peroxidase, and lignin peroxidase) and the chemical composition (total protein content, total polyphenol content, and total reducing sugar content) of BSG during the 15-day fermentation were measured. The maximum volumetric activities of the hydrolytic enzymes and the days on which they were obtained were as follows: a) xylanase: BSG 1 (day 15: V.A. = 511 U/mL), BSG2 (day 14: V.A. = 497 U/mL) ; b) invertase: BSG 1 (day 15: V.A. = 186 U/mL) ; BSG 2 (day 12: V.A. = 179 U/mL), c) β-glucosidase: BSG 1 (day 12: V.A. = 4.34 U/mL), BSG 2 (day 11: V.A. = 3.75 U/mL), and d) cellulase: BSG 1 (day 10: V.A. = 0.074 FPU/mL), BSG 2 (day 11: V.A. = 0.064 FPU/mL). The maximum volumetric activities of lignolytic enzymes and the days on which they were obtained were as follows: a) laccase: BSG 1 (day 9: V.A. = 173 U/L), BSG 2 (day 12: V.A. = 349 U/L) ; Manganese peroxidase: BSG 1 (day 9: V.A. = 110 U/L), BSG2 (day 6: V.A. = 3.71 U/L). It was shown that Trametes versicolor do not produce lignin peroxidase under investigated process conditions. Biologically processed BSG subjected to a 15-day SSF treatment resulted in an increase in total protein content by 1.10- and 1.15-fold (for BSG 1 and BSG 2, respectively), total polyphenolic compound content by 3.80- and 1.64-fold (for BSG 1 and BSG 2, respectively) and total sugar content by 7.20-fold for BSG1, while BSG2 showed a decrease in total sugar content by 1.06-fold.

brewers'spent grain; solid-state fermentation; enzyme production

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