At 0.05–0.25 g/g VSS, the influence of ZVSI
was inappreciable (p > 0.05), but the degradation efficiency of solubilized
products at 0.50 and 1.00 g/g VSS significantly increased in
comparison with the ZVSI-free (p = 0.019 and 0.003, respectively),
and reached up to 48.3 ± 0.3% and 52.6 ± 0.4% (versus 45.2 ± 0.5%
in the ZVSI-free) at the end of test, respectively.