Repurposing Onion Peel Waste as a Cost-Effective and Sustainable Substrate for Xanthan Production

This study investigates the potential of onion peel waste as a sustainable and cost-effective alternative substrate for xanthan gum production using Xanthomonas campestris NCIM 2961. The results demonstrate that onion peel-based medium consistently produced higher xanthan gum yields compared to the standard medium, achieving a maximum yield of 5.21 gL-1 at optimal conditions (pH 7.0, 30°C, 100 rpm agitation, and a 48 h incubation period), without supplements or pretreatments. FT-IR confirmed the chemical identity and purity of xanthan gum derived from the onion peel-based medium, closely matching commercial food-grade xanthan gum. Utilizing onion peels as a carbon substrate can contribute to waste management in India, a major onion producer, generating tons of onion peel waste every year. This would also align with sustainable development and circular economic goals. However, large-scale production of xanthan gum may be challenging due to factors like variable peel composition, inhibitory compounds, microbial contaminants, and extraction limitations. Future efforts focused on refining pretreatment and purification techniques, engineering Xanthomonas strains for improved waste utilization, and optimizing fermentation conditions using response surface methodology could further boost production efficiency. These findings highlight the viability of onion peel waste as a standalone substrate for cost-effective and sustainable xanthan gum production.