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PRODUCTION OF BEER USING IMMOBILIZED YEAST ENCODING α‐ACETOLACTATE DECARBOXYLASE
Author(s) -
Kronlöf J.,
Linko M.
Publication year - 1992
Publication title -
journal of the institute of brewing
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.523
H-Index - 51
eISSN - 2050-0416
pISSN - 0046-9750
DOI - 10.1002/j.2050-0416.1992.tb01133.x
Subject(s) - brewing , diacetyl , acetoin , yeast , fermentation , chemistry , valine , bioreactor , food science , yeast extract , chromatography , biochemistry , butanediol , leucine , amino acid , organic chemistry
Genetically modified brewer's yeast encoding α‐acetolactate decarboxylase (α‐ALDC) was tested in immobilized yeast bioreactors for main fermentation of beer. The α‐ALDC enzyme produced by the transformant catalyzes the direct conversion of α‐acetolactate to acetoin without formation of diacetyl. The long lagering period required for beer maturation in conventional brewing can thus be shortened or even omitted. Three different packed bed bioreactors were employed, with volumes of 1.6 dm 3 , 5 dm 3 and 25 dm 3 . The 5 dm 3 column had a slightly conical geometry in contrast to the others which had cylindrical shapes. Sintered glass beads were chosen as the carrier material on the basis of experiments with the parent strain. The brewing performance of the transformant compared well with that of the parent strain in the immobilized system. Fermentation, utilization of amino acids (including isoleucine, valine and leucine) and flavour formation were practically identical with both strains, the only difference being a marked decrease in the formation of diacetyl by the transformant. Small differences were, however, observed in the long‐term biochemical stability. By using yeast encoding α‐ALDC in the immobilized yeast system the total (primary and secondary) fermentation time could be reduced to approximately 2–6 days, compared with 3–6 weeks in a conventional batch process.