Enzymatic-Based Hydrolysis of Digested Potato Peel Wastes by Amylase Producing Fungi to Improve Biogas Generation

Potato peel wastes are generated in high quantities from potato processing industries. They are pollutants to the environment, and they release greenhouse gases into the atmosphere. The present study assessed the potentiality of hydrolyzing potato wastes by amylase-producing fungi to improve biogas generation from potato peels through the anaerobic digestion process. Different fungal isolates were screened for amylase production on potato wastes, and the highest amylase producer was selected for optimizing the efficacy of producing amylases in high quantities to efficiently allow the conversion of potato organic matter into fermentable sugars that are utilized for the anaerobic digestion process. The best amylase producers were those derived from Rhizopus stolonifer (32.61 +/- 0.89 U/mL). The highest cumulative methane yield from hydrolyzed potato peel was 65.23 +/- 3.9 mL CH4/g and the methane production rate was 0.39 mL CH4/h, whereas the highest biogas yield from unhydrolyzed potato wastes was 41.32 +/- 2.15 mL CH4/g and the biogas production rate was 0.25 mL CH4/h. Furthermore, it was found that the two combined sequential stages of anaerobic digestion (biogas production) followed by biodiesel production (enzymatic esterification) were the most effective, recording 72.36 +/- 1.85 mL CH4/g and 64.82% biodiesel of the total analytes. However, one-pot fermentation revealed that biogas yield was 22.83 +/- 2.8 mL CH4/g and the biodiesel extracted was 23.67% of the total analytes. The insights of the current paper may increase the feasibility of potato peel-based biorefinery through the biological hydrolysis strategy of potato wastes using eco-friendly enzymes.

Automated summary

This study assessed the potential of using amylase-producing fungi to hydrolyze potato wastes for improved biogas generation. The highest amylase producer was selected to optimize the conversion of potato organic matter into fermentable sugars for anaerobic digestion. The best amylase producers were derived from Rhizopus stolonifer, resulting in the highest methane yield and production rate. The combination of anaerobic digestion and biodiesel production proved to be the most effective, while one-pot fermentation yielded lower results. The findings contribute to the feasibility of potato peel-based biorefineries using environmentally friendly enzymes.