There is growing interest on the utilization of animal by-products and wastes based on sustainability and recycling of natural biomaterials. Animal by-products and wastes mainly refer to skin, bones, and tendons that contain proteins and other macromolecules[1]. Animal raw hides represent a remarkable portion of the weight of sheep (11.0–11.7%), which are abundant sources of epithelial tissue that contains a high concentration of collagen[2]. As the primary ingredients to produce leather products, these raw materials undergo trimming to achieve uniform shapes before commencing the tanning process, which may generate considerable proteinaceous waste[3]. Reportedly, one ton of wet salted hides/skins yields approximately 200kg finished leather along with 350 kg non-tanned solid waste, 250 kg tanned solid waste, and 200 kg wastewater loss[4]. Hence, there remains a considerable of lamb trimming wastes of tannery for the collagen recycle. Plant-based enzymes including papain and bromelain have been utilized for extracting gelatin or collagen from un-tanned bovine trimming waste. Given the potential of ficin enzyme for collagen hydrolysis[5], harnessing this enzyme to extract collagen from discarded sheep trimming waste could be beneficial. In addition, with aided ultrasound, entangled collagen fibrils can be opened then separated, contributing to post-treatment with acids or enzymes as well as reduced extraction periods. 

Based on aided ultrasound technology, the aim of this research is to design a sustainable method for extracting collagen from untreated tannery trimming waste using ficin enzyme derived from ficin leaves. The structural and biochemical characteristics of the extracted collagen from this green method and conventional methods (acetic acid) will be fully discussed.

A simple and effective method for the extraction of collagen from untanned tannery trimming waste using acetic acid and ficin enzyme obtained from ficin leaves was developed in this study. Although acetic acid and ficin enzyme both are effective for the extraction of collagen but enzymatic hydrolysis can extract more collagen than the acid hydrolysis method. Collagen obtained from the enzymatic hydrolysis process maintained its predominant triple helix structure and had amorphousness which was confirmed by the FTIR and XRD analysis. However, the collagen obtained from enzymatic hydrolysis was thermally less stable compared to the collagen obtained by acid hydrolysis. Hence, it can be concluded that ficin enzyme- assisted hydrolysis method can aid in the implementation of circular economy approach in the leather industry by extracting collagen from the trimming waste in an environment-friendly way.