The gas composition in the headspace (H2 and O2) was analyzed every hour for the first 6 h and then every 24 h for 5 days on a PerkinElmer® Clarus® 580 gas chromatograph (PerkinElmer Inc., USA) that was equipped with a thermal conductivity detector (TCD) and an Elite-GC GS Molesieve column
(30 m 0.53 mm).