J. Dong (1), S. HU (1), J. Yu (1), H. Yin (1), S. Huang (1), J. Liu
(1), S. Huang (1); (1) State Key Laboratory of Biological Fermentation
Engineering of Beer, Tsingtao Brewery Co. Ltd., Qingdao, China
Poster
The hydrolysis of malt starch could be hindered by the cell wall
polysaccharide and protein. In this paper, the effects of glucanase,
xylanase individually and in combination, as well as proteinase on
starch degradation during the course of small-scale, emulated commercial
mashing were investigated. Gairdner was mashed and assayed at five time
points during mashing for levels of alpha-amylase, beta-amylase, and
limit dextrinase and soluble starch content in the supernatant of mash
with the addition of barley glucanase (Megazyme), xylanase (Shearzyme
500L, Novozyme), glucanase-xylanase mixture (Ultraflo Max, Novozyme),
proteinase (Neutrase 0.8L, Novozyme) or no addition. Compared to the
control, the activities of alpha-amylase, beta-amylase, and limit
dextrinase were improved to different extents when individual glucanase,
proteinase, or glucanase-xylanase mixtures were added to the mash. The
greatest increase was found in the activities of beta-amylase and limit
dextrinase with the addition of proteinase during mashing. These results
indicated that lots of inactive limit dextrinase and beta-amylase
forms, which were inhibited by proteinaceous inhibitor, existed in the
mash and were released by proteinase. Moreover, the pattern of soluble
starch content in the supernatant of mash during mashing showed that the
soluble starch content was improved to different extents between 5 and
55 min because of the accelerated release of starch by cell wall
hydrolysis. Then, the soluble starch contents were decreased at 115 min
with the addition of four enzymes, because there were more
starch-degrading enzymes in the mash, especially with addition of
proteinase. Finally, the wort sugar content was greatly increased
because of the accelerated release of starch and starch-degrading
enzymes. Fermentable sugars were improved greatly by proteinase because
of high level of limit dextrinase in the mash. Compared to the
individual glucanase and xylanase, the glucanase-xylanase mixture had a
greater impact on the starch-degrading enzymes and wort sugars,
suggesting the access of glucanase to the cell wall was hindered by the
xylan. These results offered a comprehensive understanding of the
correlation between cell wall-derived polysaccharides, protein, and
starch during mashing.
Shumin Hu, born in 1984, received a Ph.D. degree in fermentation
engineering from Shandong University in Jinan, China. She joined in the
State Key Laboratory of Biological Fermentation Engineering of Beer,
Tsingtao Brewery in 2011 as a post-doctoral researcher, working in
barley starch degradation.
