Sustainable Valorisation of British Sheep Wool as a Cost-Effective Protein Source for the Cultivation of Marine Yeast

Purpose
The use of peptone in microbial growth and fermentation media incurs significant costs, which makes synthesis of microbial products expensive. This research evaluated valorisation of wool hydrolysate as a nitrogen source for yeast growth in cost effective and environmentally friendly way.

Method
The hydrolysis of four different British wool types was conducted using a variety of agents, such as acids (H2SO4, HCl, H3PO4), alkalis (NaOH and KOH), and deionised water. The findings demonstrated that optimal hydrolysis was achieved using 15% solid loading and 0.2 M KOH for 30 min under pressurized condition (15 psi). Hydrolysis using low KOH concentration in contrast to other studies, along with the valorisation of different wool types for their potential as protein sources for microbial growth, distinguishes this research. The hydrolysate underwent neutralization through two methods, including concentrated HCl and membrane dialysis. Hydrolysate’s amino acid profile was determined to assess its viability as a nitrogen source. Subsequently, the neutralized hydrolysate was employed as a replacement for peptone and yeast extract in YPD medium to investigate its effects on the cultivation of the marine yeast Wickerhamomyces anomalus M15.

Results
The results showed that media supplemented with acid‑neutralised wool hydrolysate, used in place of yeast extract and peptone, supported yeast growth at levels comparable to commercial YPD medium, achieving up to 84% of the biomass obtained in the control. Among the tested concentrations of hydrolysate, 8% (v/v) proved optimal, yielding a biomass concentration of 5.72 g/L after 72 h of incubation, compared to 6.52 g/L in the YPD control.

Conclusion
This study illustrates that waste wool hydrolysate can serve as an effective substitute for peptone and yeast extract in fermentation media, achieving comparable yeast growth.