Biodegradation of caffeine by whole cells of tea-derived fungi Aspergillus sydowii, Aspergillus niger and optimization for caffeine degradation

Table 4 Comparison of the kinetic parameters for caffeine degradation in different substrate concentrations (30 °C, 15 d, pH 7.0)^a

Substrate concentration (mg/L)	Fungal dry mass (g)	C_caffeine,f (mg/L)	C_{theophylline,f} (mg/L)	C_{3-methylxanthine,f} (mg/L)	Q_caffeine (mg/L d)	Q_theophylline (mg/L d)	Y_{theophylline/caffeine}	% of caffeine degraded
600	0.22 ± 0.02^A	3.7 ± 0.8^A	262.6 ± 20.7^A	115.8 ± 10.1^A	39.8 ± 0.5^A	17.5 ± 1.4^A	0.44 ± 0.04^A	99.3 ± 0.1^A
1200	0.22 ± 0.03^A	105.0 ± 16.9^B	549.4 ± 29.3^B	178.7 ± 10.8^B	73.0 ± 1.1^B	36.6 ± 2.0^B	0.50 ± 0.03^B	91.3 ± 1.4^B
1800	0.23 ± 0.02^A	668.2 ± 37.3^C	643.8 ± 25.3^C	191.2 ± 4.5^B	75.5 ± 2.5^B	42.9 ± 1.7^C	0.57 ± 0.01^C	62.9 ± 2.1^C

^aAll kinetic parameters were calculated according to Sirisansaneeyakul and others (2013) [34]
All data are presented as mean ± SD, ^A-Cp < 0.05 in the same column
Concentrations of caffeine, theophylline and 3-methylxanthine determined by HPLC
C_caffeine,f the final caffeine concentration (mg/L), C_{theophylline,f} the final theophylline concentration (mg/L), C_{3-methylxanthine,f} the final 3-methylxanthine concentration (mg/L), Q_caffeine the volumetric rate of caffeine degradation (mg/L d), Q_theophylline the volumetric rate of theophylline production (mg/L d), Y_{theophylline/caffeine} theophyline yield on caffeine (mg/mg)

ISSN: 1471-2180