Samples for analysis of sulfur containing AA (Met and Cys) were subjected to performic acid
oxidation before acid hydrolysis.
A separate portion of the samples was oxidized with performic acid
and then hydrolyzed with 6 N HCl in order to obtain reliable cysteine and methionine values .
The FAME was epoxidized at low temperature, with performic acid
generated in situ, using benzene as a diluent for the organic phase, to minimize epoxy ring opening (31).
Activity of performic acid
against spore-forming bacteria(a) Lot 1 Lot 2 Bacillus subtilis(b) 0/30 growth 0/30 growth B.
was used in oxidizing amino acids and neutralized with sodium citrate dihydrate, and then hydrolyzed with 6 N HC1 for 24 h at 110[degrees]C to be liberated from the protein.
During this step, the hydrogen peroxide reacts with the formic acid to form performic acid
Cysteine and methionine were analyzed after performic acid
oxidation and determined as cysteic acid and methionine sulfone, respectively.
Methionine were determined as methionine sulfone acid after cold performic acid
oxidation and a 24-h hydrolysis with 7.
5 g sample was weighed into a 100 ml flat bottomed flask, 1 ml of Norleucine standard solution, 5 ml of performic acid
in ice bath.
As a consequence, in situ prepared performic acid
could not be produced in the reaction pathway of the epoxidation.
Methionine and cysteine were determined on samples that had been oxidized in performic acid
prior to acid hydrolysis according to the method of Moore (1963).
Cystine was determined as cysteic acid and methionine as methionine sulfone after preoxidation with performic acid
and pre-column derivation using phenylisothiocyanate (L-8800 Hitachi Automatic Amino Acid Analyzer, Tokyo, Japan).