Optimization of enzyme-assisted phenolic reactions applied to thermal stabilization of collagen using response surface methodology

Vegetable tannins used in tanning of hides and skins are limited by surface reactions as well as large molecular weights, reducing penetration into the skin and lowering the thermal stability or tanning effect. Investigation into the utilization of small phenolic compounds such as catechin to improve penetration with subsequent in situ enzyme-catalysed polymerization may provide a novel and alternative tanning agent. In this study, catechin was oxidized by enzymatic catalysis using laccase, with the polymerization confirmed by FT-IR and UHPLC. Tanning experiments were undertaken to measure the effect of laccase-catalysed polymerization of catechin in the thermal stabilization of collagen, i.e., the change in shrinkage temperature between the treated and untreated sample of hide powder (ΔTs). A factorial design was subsequently used to study process parameters that may affect enzymatic reactions: temperature, substrate concentration, enzyme concentration and incubation period. The statistically significant variables were found to be temperature and incubation period, and were thus chosen to be studied further for process optimization using response surface methodology. Maximum ΔTs can be obtained for a temperature of 34.6°C and incubation period of 25 hours. This study demonstrates that the stabilization of collagen (ΔTs) is increased with the use of enzyme-assisted polymerization.