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Lignin Impact on Fibre Degradation: 1—Quinone Methide Intermediates Formedfrom Lignin During In Vitro Fermentation ofCorn Stover*
Author(s) -
Sewalt Vincent J H,
Glasser Wolfgang G,
Fontenot Joseph P,
Allen Vivien G
Publication year - 1996
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/(sici)1097-0010(199606)71:2<195::aid-jsfa568>3.0.co;2-#
Subject(s) - lignin , quinone methide , fermentation , degradation (telecommunications) , chemistry , stover , in vitro , food science , quinone , organic chemistry , biochemistry , biology , agronomy , crop , computer science , telecommunications
Experiments were conducted to determine whether formation of quinone methide intermediates from lignin occurs during ruminal fermentation of corn stover, as indicated by nucleophilic addition reaction with sulphur‐containing reducing agents. Corn stover leaf and stem fractions harvested at full maturity were incubated in buffered ruminal fluid without reducing agents or with (NH 4 ) 2 SO 4 (S‐control), Na 2 S.9H 2 O, cysteine‐HCl (cysHCl), or cysHCl plus Na 2 S.9H 2 O; and in only buffer with or without cysHCl plus Na 2 S.9H 2 O. Mixed reducing agents (cysHCl plus Na 2 S.9H 2 O) enhanced ( P< 0.001) in vitro fibre degradation after 48 h, tended to increase solubilisation of fibre ( P =0.07) and dry matter ( P =0.06) in buffer alone, and elevated ( P< 0.001) S‐content of residual fibre. In vitro incorporation of S into the undegraded fibre was determined for corn stover fractions of varying lignin compositions that were harvested at two maturities (early dent and full maturity) in 2 years. Extent of fibre degradation was correlated with extent of S‐incorporation ( r =‐0.54, P< 0.001), and with lignin methoxyl content ( r =‐0.84, P< 0.001). The negative association of lignin methoxyl content with digestibility is explained by the relative likelihood of quinone methide intermediate formation from guaiacyl and syringyl units in lignin.