Biodegradazione dei residui di cuoio

A model system is described that has great potential as a tool for use in studies of the biodegradation of solid leather waste. Untanned collagenous waste is shown to be readily degraded and provides an excellent substrate for biogas production. Collagen tanned with chromium(III) or mimosa extract was found to be completely resistant to anaerobic degradation. This can be reversed: in the case of chromium(III) this is achieved by simple heat denaturation, when the presence of chromium(III) bound to denatured collagen has no significant effect on gas production. In contrast, heat denaturation of mimosa tanned collagen did not bring about an increase in biodegradation. Mimosa and three other condensed tannins, quebracho, gambier and myrica esculenta were also shown to have a direct inhibitory effect on biogas production. However, the concentration of each tannin required to bring about complete inhibition varied. Quebracho and mimosa were the most effective inhibitors of gas production, followed by gambier and myrica. It is proposed that this difference in inhibitory efficiency can be explained in part by the patterns of hydroxylation in the A-rings of the flavonoid structural units, but inhibition appears not to be influenced by the structure of the B-rings.