Potato peel as feedstock for bioethanol production: A comparison of acidic and enzymatic hydrolysis

• The use of potato peels as medium for amylase production by Bacillus was investigated.
• Amylase production at fermenter scale was improved by 6-fold compared to flasks scale.
• Enzymatic hydrolysis of potato peels liberates higher reducing sugar than acidic one.
• Amylase UEB-S released higher fermentable sugars than Termamyl 120L.
• Potato peels features a high potential for ethanol production.

Biofuels are of increasing interest as alternatives to the petroleum-based fuels. In particular, second and third generation advanced biofuels, that could be produced from renewable materials such as agricultural residues appear to be more competitive. In this context, this work has focused on the potential of the potato peel use (PPW), a zero value waste, as feedstock for bioethanol production. First, an economical medium for amylase production from Bacillus sp. UEB-S (amylase UEB-S) was formulated using potato peel (10 g L−1) as a carbon source and soy flour (20 g L−1) as a nitrogen source. Amylase production reached 15 U/mL at flask scale and increased to 87 U/mL at fermenter scale. A comparative study between acidic and enzymatic hydrolysis of PPW was investigated. It showed that a combined enzymatic treatment using amylase UEB-S and Amyloglucosidase under optimal conditions gave significant yields of reducing sugars (69 g L−1) and ethanol (21 g L−1). These results are highly interesting and demonstrate the possibility of substituting commercial enzyme by an onsite produced enzyme as well as the potential of PPW as bioethanol feedstock.