Stabilization of Natural Fiber Collagen Using Vegetable Tannins: An Effective Enzyme Assisted Process

ABSTRACT

Leather making involves conversion of a putrefiable skin or hide protein (collagen) into nonputrescible material. Environmental concerns have forced the leather industry to develop tanning systems based on natural products. Vegetable tanning is one of the oldest methods of tanning. However, there is limitation in the usage of vegetable tanning materials because of its high organic load in the effluent generated, which is difficult to degrade and leads to high biological and chemical oxygen demand. In this investigation an attempt has been made to design an eco-friendly tanning process of protein fibers using proteolytic enzymes to improve the exhaustion of vegetable tannins by increased uptake of vegetable tannins. The enzymatic treatment of the protein fibers brought in an exhaustion of 97% in the case of the optimized experimental process, compared to 85% in conventional vegetable tanning process. The enzyme treatment before tanning showed slight improvement in hydrothermal stability. Physical and tactile evaluation of leathers was slightly better than conventionally tanned leathers. Surface color values illustrated the variation in color or shade between control and optimized experimental leather was negligible. Experimental leathers showed opened-up fiber structure well coated by vegetable tannins, indicating that the enzymatic tanning process did not bring about any major change on the fiber structure of the leathers. The enzymatic process also benefits from reduction in total solids and chemical oxygen demand (COD) loads by 76% and 25%, respectively from the identified streams.

KEYWORDS:

• Leather
• skin protein
• Acacia mollisima
• acid protease
• enzyme assisted vegetable tanning
• total solids
• chemical oxygen demand
• spent tan liquor