# Enzymatic Activity in the Anaerobic Co-Digestion of Cavitated Coffee Waste and Sewage Sludge
## 3 Results
### Enzyme Activity of Feedstock and Digestate  
Enzyme activity, such as that of \(\beta\)-Glu, PAC, PAL, PR and URE, in the feedstocks and digestate was observed depending on the experimental variants used. In the study, higher enzymatic activity of PAC, PAL, PR and URE was observed in the feedstock than in digestate, while the activity of \(\beta\)-Glu was at a higher level in the digestate (Figure 6).  
The obtained results indicate that the activity of \(\beta\)-Glu was highest in D + R1 (3.34 mg pNP/g TS/h) and lowest in F + R2--2.08 mg pNP/g TS/h. Figure 6 shows the enzyme activity for the feedstock and digestate for the individual experiments. The activity of \(\beta\)-Glu was highest in D + R3 and lowest in F + R2. The addition of CW to SS resulted in a decrease in the activity of this enzyme of approx. 18% compared to F + R0. In turn, the use of 20 min HCD and 30 min HCD reduced the \(\beta\)-Glu activity by approx. 28% and 18%, respectively, compared to F + R0. Furthermore, increases in the \(\beta\)-Glu activity in D + R1, D + R2 and D + R3 by approx. 18%, 8% and 24%, respectively, were observed for the investigated variants with added CW.  
The PAC activities of the feedstock ranged from 9.50 mg pNP/g TS/h (F + R0) to 12.24 mg pNP/g TS/h (F + R1), while in the digestate, these ranged from 0.787 mg pNP/g TS/h (D + R1) to 1.14 mg pNP/g TS/h (D + R3). The highest increase in this enzyme was observed in F + R1, which was higher by 29% compared to that in F + R0. Moreover, the use of HCD for 20 min and 30 min caused an increase in the activity of this enzyme by approx. 16% and 15%, respectively, compared to that in F + R0. In the digestate of D + R2 and D + R3, increased PAC activity by approx. 15% and 22%, respectively, was observed compared to D + R0. Alkaline phosphatase in the feedstock ranged from 7.9 mg pNP/g TS/h (F + R1) to 11.19 mg pNP/g TS/h (F + R3). In the digestate, the PAL activity significantly decreased on average by approx. 80% compared to the feedstock (Figure 6). Among the digestates, the lowest PAL activity was observed in D + R1 (1.56 mg pNP/g TS/h) while the highest was in D + S3 (2.38 mg pNP/g TS/h).  
The PR activity in the digestate and feedstock ranged around a similar level (Figure 6). The average PR activity in the feedstock was approx. 68.30 mg tyr/g TS/2 h, while for the digestate, it was approx. 53.26 mg tyr/g TS/2 h. The applied HCD increased the PR activity in the feedstock by approx. 11.5% and 15%, respectively, compared to that in F + S0.  
Moreover, the used HCD caused an increase in the activity of this enzyme by approx. 3% (for F + R2) and 4.5% (for F + R3) compared to F + R1.  
In the samples from the feedstock, the URE activity was in the range from 8.24 mg N/g TS/2 h (F + R1) to approx. 14.45 (for F + R2 and F + R3). Compared to F + R0, a significant decrease in the URE activity of approx. 38% was observed only in F + R1. The activity of URE in the digestate was in the range from 1.47 mg N/g TS/2 h (D + R0) to 3.32 mg N/g TS/2 h (D + R3). Over 75% of the URE activity of the feedstock was increased in F + R2 and F + R3 after using HCD, compared to F + R1 (Figure 6).