Fig. 5
From: 3-Methylxanthine production through biodegradation of theobromine by Aspergillus sydowii PT-2
Effects of pH (a) and metal ions (b) on theobromine degradation and 3-methylxanthine production in A. sydowii PT-2 culture, respectively. The pH in the inoculated mediums was adjusted by phosphate buffer. Metal ions were added into the culture solution at a concentration of 2 mM. The culture solution without extra addition was defined as the control. The reaction (pH 6.0) was carried out at 30 °C for 5 days on an incubator shaker (130 rpm). Data are presented as mean value ± SD of three biological replications. The lowercase letters indicated a significant difference at p < 0.05 level by using Tukey’s multiple comparison test for one-way ANOVA. The different letters show significant differences