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Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
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Target Concepts:
Gene/Protein
Disease
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Query: UMLS:C0847097 (
acidity
)
15,165
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
The effect of various sourdoughs and additives on bread firmness and staling was studied. Compared to the bread produced with Saccharomyces cerevisiae 141, the chemical acidification of dough fermented by S. cerevisiae 141 or the use of sourdoughs increased the volume of the breads. Only sourdough fermentation was effective in delaying starch retrogradation. The effect depended on the level of acidification and on the lactic acid bacteria strain. The effect of sourdough made of S. cerevisiae 141-Lactobacillus sanfranciscensis 57-Lactobacillus plantarum 13 was improved when fungal alpha-amylase or amylolytic strains such as L. amylovorus CNBL1008 or engineered L. sanfranciscensis
CB1
Amy were added. When pentosans or pentosans, endoxylanase enzyme, and L. hilgardii S32 were added to the same sourdough, a greater delay of the bread firmness and staling was found. When pentosans were in part hydrolyzed by the endoxylanase enzyme, the bread also had the highest titratable
acidity
, due to the fermentation of pentoses by L. hilgardii S32. The addition of the bacterial protease to the sourdough increased the bread firmness and staling.
...
PMID:Combined effect of sourdough lactic acid bacteria and additives on bread firmness and staling. 1089 63
This manuscript probes the steric and electronic attributes that lead to "frustrated Lewis pair" (FLP)-type catalysis of imine hydrogenation by borenium ions. Hydride abstraction from (I
t
Bu)HB(C
6
F
5
)
2
2
prompts intramolecular C-H bond activation to give (CHN)
2
(
t
Bu) (CMe
2
CH
2
)CB(C
6
F
5
)
2
3
, defining an upper limit of Lewis
acidity
for FLP hydrogenation catalysis. A series of seven N-heterocyclic carbene-borane (NHC-borane) adducts ((R'
CNR
)
2
C)(HBC
8
H
14
) (R' = H, R = dipp
4a
, Mes
5a
, Me
8a
; R = Me R' = Me
9a
, Cl,
10a
) and ((HC)
2
(NMe)(NR)C)(HBC
8
H
14
) (R =
t
Bu,
6a
, Ph
7a
) are prepared and converted to corresponding borenium salts. These species are evaluated as catalysts for metal-free imine hydrogenation at room temperature. Systematic tuning of the carbene donor for the hydrogenation of archetypal substrate
N
-benzylidene-
tert
-butylamine achieves the highest reported turn-over frequencies for FLP-catalyzed hydrogenation at amongst the lowest reported catalyst loadings. The most active NHC-borenium catalyst of this series, derived from
10a
, is readily isolable, crystallographically characterized and shown to be effective in the hydrogenation catalysis of functional group-containing imines and N-heterocycles.
...
PMID:A family of N-heterocyclic carbene-stabilized borenium ions for metal-free imine hydrogenation catalysis. 2944 20
