Upvaluing animal biomass : structural fibrous proteins for engineering biobased material and bioactive compounds

RESULTS
We investigated the extraction of fibrillar collagen from cattle bone (Bos taurus, type-1 collagen) factoring several parameters:

• age factor (young adult, i.e. 4 years old, and full adult, i.e. 7 years old) and anatomy factor (femur and tibia) to study collagen extractability according to variability in source material;
• drying-method factor (high-temperature or low-temperature) to study collagen assembly once extracted from the bone.
We found that bone age is negatively correlated with collagen extraction yield and positively correlated with minerals content (calcium and phosphorous) and proteoglycans content, which is important for collagen fibril assembly in vivo and probably ex vivo too. From an anatomical point of view, the tibia gave the highest yields and tibia collagen showed better stability in colloidal dispersion (zeta potential). Regardless of bone age and bone anatomy, the extracted collagen is able to self-assemble into 3-dimensional structures (fibrils or microcapsules). Circular dichroism studies led at the SOLEIL synchrotron facility enabled analysis of the denaturation-renaturation balance of collagen extracted under a temperature gradient.
The thermodynamic parameters related to changes in protein secondary structure were thereby determined.

We learned that collagen from an adult-cow tibia has the most denaturation-resistant structure.

FUTURE OUTLOOK
As a corollary of this finding, we conducted a review of the literature on potential applications for structural fibrous collagen, elastin and keratin proteins from animal byproducts. Published in Trends in Food Science & Technology, our paper is the very first publication by a French research institute on the use of animal biomass waste to recover valuable structural fibrous proteins.